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1
Ross, Molly, and Hitesh Bindra. "Statistical Mechanics-Based Surrogates for Scalar Transport in Channel Flow." Fluids 6, no. 2 (2021): 79. http://dx.doi.org/10.3390/fluids6020079.
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Thermal hydraulics, in certain components of nuclear reactor systems, involve complex flow scenarios, such as flows assisted by free jets and stratified flows leading to turbulent mixing and thermal fluctuations. These complex flow patterns and thermal fluctuations can be extremely critical from a reactor safety standpoint. The component-level lumped approximations (0D) or one-dimensional approximations (1D) models for such components and subsystems in safety analysis codes cannot capture the physics accurately, and may introduce a large degree of modeling uncertainty. On the other hand, high-fidelity computational fluid dynamics codes, which provide numerical solutions to the Navier–Stokes equations, are accurate but computationally intensive, and thus cannot be used for system-wide analysis. An alternate way to improve reactor safety analysis is by building reduced-order emulators from computational fluid dynamics (CFD) codes to improve system scale models. One of the key challenges in developing a reduced-order emulator is to preserve turbulent mixing and thermal fluctuations across different-length scales or time-scales. This paper presents the development of a reduced-order, non-linear, “Markovian” statistical surrogate for turbulent mixing and scalar transport. The method and its implementation are demonstrated on a canonical problem of differentially heated channel flow, and high-resolution direct numerical simulations (DNS) data are used for emulator or surrogate development. This statistical surrogate model relies on Kramers–Moyal expansion and emulates the turbulent velocity signal with a high degree of accuracy.
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Yang, Yuanlong, Baozhi Sun, Yanjun Li, Liu Yang, and Lusong Zheng. "Computational fluid dynamics investigation of thermal–hydraulic characteristics for a steam generator with and without tube support plates." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 227, no. 12 (2013): 2897–911. http://dx.doi.org/10.1177/0954406213479740.
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A three-dimensional computational fluid dynamics model with the thermal phase change model is used to investigate the thermal–hydraulic characteristics of a steam generator with and without quatrefoil tube support plates. The two types of modeled designs are a unit pipe with and one without tube support plates. The computational fluid dynamics simulations capture the boiling phenomena, vortex and recirculation distributions, and the periodic characteristics of the circumferential wall temperature in the regions surrounding the tube support plates. The cross-flow energy responsible for flow-induced vibration damage in the region of the U-bend tubes is obtained with the aid of these localized thermal–hydraulic distributions. A comparison between the key parameters of the unit pipe models with and without tube support plates clearly reveals the influence of tube support plates in guiding flow behavior and alleviating flow-induced vibration damage for a steam generator’s U-bend tube bundle. Therefore, this computational fluid dynamics model can provide technical support for optimizing tube support plate design and improving the thermal–hydraulic characteristics of steam generator.
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Salter, H. E., C. T. Ta, S. K. Ouki, and S. C. Williams. "Three-dimensional computational fluid dynamic modelling of a facultative lagoon." Water Science and Technology 42, no. 10-11 (2000): 335–42. http://dx.doi.org/10.2166/wst.2000.0674.
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A series of facultative lagoons operated by Thames Water treating industrial wastewater in Thailand were found to be performing poorly, particularly with respect to the removal of biological oxygen demand (BOD). A review of the design parameters for the site found that all the lagoons are of a sufficient area for the flow and BOD load. However, observations of the lagoons suggested that there may be significant hydraulic short-circuiting. Computational fluid dynamics (CFD) modelling was therefore carried out on one of the lagoons to establish the hydraulic regime. Two consecutive simulations were carried out, both with and without baffles; the first to establish steady flow conditions, and the second using a chemical species transport model to obtain the residence time distribution (RTD). The results of the modelling indicate that the lagoons do currently suffer from significant short-circuiting, and large dead-zones are present. The installation of baffles in the CFD model improved the plug-flow characteristics of the lagoons, substantially reducing the short-circuiting and the size of the dead-zones. It has therefore been concluded that the installation of baffles in the lagoons will lead to an improvement in their performance, by increasing the retention time of the system.
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Wang, Yan, Song Du, Huai Gong Zhu, He Xu Ma, and Shao Qing Zuo. "CFD Simulation of Hydraulics of Dividing Wall Sieve Trays." Advanced Materials Research 476-478 (February 2012): 1345–50. http://dx.doi.org/10.4028/www.scientific.net/amr.476-478.1345.
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A 3D two-phase flow computational fluid dynamics (CFD) model containing gas mal-distribution is developed in the Eulerian framework to predict the hydraulics of a dividing wall sieve tray. Variable and position dependent gas superficial velocity is used in the calculation. Using water-air system, simulations of flow patterns and hydraulics of a commercial- scale 1.2m diameter sieve tray are carried out using this model to testify its precision. Then, the same simulations of a dividing wall sieve tray with equal diameter are carried out. The results show that there are two backflow regions on a dividing wall tray, one is in the segmental area, and the other is in the region nearby junction of dividing wall and outlet weir. In the segmental area of trays with equal diameter, the area of backflow region of dividing wall trays is basically equal to that of conventional trays.
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Li, Xiaoqin, Xuelin Tang, Min Zhu, and Xiaoyan Shi. "1D-3D coupling investigation of hydraulic transient for power-supply failure of centrifugal pump-pipe system." Journal of Hydroinformatics 21, no. 5 (2019): 708–26. http://dx.doi.org/10.2166/hydro.2019.122.
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Abstract In the pumping station, the main feedwater system and the reactor system of nuclear power plant, power-supply failure causes strong hydraulic transients. One-dimensional method of characteristics (1D-MOC) is used to calculate the transient process in the pipeline system while three-dimensional (3D) computational fluid dynamics is employed to analyze the turbulent flows inside the pump and to obtain the performance parameters of the pump, and the data exchanges on the boundary conditions of the shared interface between 1D and 3D domains are updated based on the MpCCI platform. Based on the equation of motion of the pump motion parts, the relationship between the external characteristics and the internal flow field in the pump is further investigated because the dynamic behavior of the pump and the detailed fluid field evolutions inside the pump are captured during the transition process, and the transient flow rate, rotating speed, and pressure inside the impeller are comprehensively investigated. Meanwhile, compared with the data gained by experiment and traditional 1D-MOC, the relative errors of rotating speed and the flow rate obtained by 1D-3D coupling method are smaller than those by 1D-MOC. Furthermore, the influences of the main coupling parameters and coupling modes on the calculation results are analyzed, and the cause of the deviation is further explained.
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Yan, Guanxi, Zi Li, Thierry Bore, Sergio Andres Galindo Torres, Alexander Scheuermann, and Ling Li. "Discovery of Dynamic Two-Phase Flow in Porous Media Using Two-Dimensional Multiphase Lattice Boltzmann Simulation." Energies 14, no. 13 (2021): 4044. http://dx.doi.org/10.3390/en14134044.
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The dynamic two-phase flow in porous media was theoretically developed based on mass, momentum conservation, and fundamental constitutive relationships for simulating immiscible fluid-fluid retention behavior and seepage in the natural geomaterial. The simulation of transient two-phase flow seepage is, therefore, dependent on both the hydraulic boundaries applied and the immiscible fluid-fluid retention behavior experimentally measured. Many previous studies manifested the velocity-dependent capillary pressure–saturation relationship (Pc-S) and relative permeability (Kr-S). However, those works were experimentally conducted on a continuum scale. To discover the dynamic effects from the microscale, the Computational Fluid Dynamic (CFD) is usually adopted as a novel method. Compared to the conventional CFD methods solving Naiver–Stokes (NS) equations incorporated with the fluid phase separation schemes, the two-phase Lattice Boltzmann Method (LBM) can generate the immiscible fluid-fluid interface using the fluid-fluid/solid interactions at a microscale. Therefore, the Shan–Chen multiphase multicomponent LBM was conducted in this study to simulate the transient two-phase flow in porous media. The simulation outputs demonstrate a preferential flow path in porous media after the non-wetting phase fluid is injected until, finally, the void space is fully occupied by the non-wetting phase fluid. In addition, the inter-relationships for each pair of continuum state variables for a Representative Elementary Volume (REV) of porous media were analyzed for further exploring the dynamic nonequilibrium effects. On one hand, the simulating outcomes reconfirmed previous findings that the dynamic effects are dependent on both the transient seepage velocity and interfacial area dynamics. Nevertheless, in comparison to many previous experimental studies showing the various distances between the parallelly dynamic and static Pc-S relationships by applying various constant flux boundary conditions, this study is the first contribution showing the Pc-S striking into the nonequilibrium condition to yield dynamic nonequilibrium effects and finally returning to the equilibrium static Pc-S by applying various pressure boundary conditions. On the other hand, the flow regimes and relative permeability were discussed with this simulating results in regards to the appropriateness of neglecting inertial effects (both accelerating and convective) in multiphase hydrodynamics for a highly pervious porous media. Based on those research findings, the two-phase LBM can be demonstrated to be a powerful tool for investigating dynamic nonequilibrium effects for transient multiphase flow in porous media from the microscale to the REV scale. Finally, future investigations were proposed with discussions on the limitations of this numerical modeling method.
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Ghidaoui, Mohamed S., Ming Zhao, Duncan A. McInnis, and David H. Axworthy. "A Review of Water Hammer Theory and Practice." Applied Mechanics Reviews 58, no. 1 (2005): 49–76. http://dx.doi.org/10.1115/1.1828050.
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Hydraulic transients in closed conduits have been a subject of both theoretical study and intense practical interest for more than one hundred years. While straightforward in terms of the one-dimensional nature of pipe networks, the full description of transient fluid flows pose interesting problems in fluid dynamics. For example, the response of the turbulence structure and strength to transient waves in pipes and the loss of flow axisymmetry in pipes due to hydrodynamic instabilities are currently not understood. Yet, such understanding is important for modeling energy dissipation and water quality in transient pipe flows. This paper presents an overview of both historic developments and present day research and practice in the field of hydraulic transients. In particular, the paper discusses mass and momentum equations for one-dimensional Flows, wavespeed, numerical solutions for one-dimensional problems, wall shear stress models; two-dimensional mass and momentum equations, turbulence models, numerical solutions for two-dimensional problems, boundary conditions, transient analysis software, and future practical and research needs in water hammer. The presentation emphasizes the assumptions and restrictions involved in various governing equations so as to illuminate the range of applicability as well as the limitations of these equations. Understanding the limitations of current models is essential for (i) interpreting their results, (ii) judging the reliability of the data obtained from them, (iii) minimizing misuse of water-hammer models in both research and practice, and (iv) delineating the contribution of physical processes from the contribution of numerical artifacts to the results of waterhammer models. There are 134 refrences cited in this review article.
8
Gülich, J. F. "Impact of three-dimensional phenomena on the design of rotodynamic pumps." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 213, no. 1 (1999): 59–70. http://dx.doi.org/10.1243/0954406991522185.
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Three-dimensional Navier—Stokes calculations are expected to be increasingly applied in the future for performance improvement of rotodynamic pumps. Frequently such an optimization process involves a preliminary design—based on one-dimensional methods and empirical data—which is subsequently optimized by computational fluid dynamics (CFD). Employing an empirical database is not only necessary in order to provide a good starting point for the CFD analysis but also to ensure that the design has a good chance of fulfilling part load requirements, since recirculating flows at the impeller inlet and outlet are not easily handled by CFD programs. CFD calculations provide the specific work input to the fluid and information on losses and reveal the complex three-dimensional flow patterns. The designer is faced with the task of interpreting such data and drawing conclusions for the optimization of the impeller. It is the purpose of the present contribution to analyse and describe the impact of various geometric parameters and flow features on the velocity distribution in the impeller and their influence on performance and part load characteristics. Criteria are also provided to select the parameters for the preliminary design. Hydraulic impeller losses calculated by CFD programs may often be misleading if the non-uniformity of the flow distribution at the impeller outlet is ignored. Procedures to quantify such mixing losses in the diffuser or volute downstream of the impeller are discussed.
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Wilson, Jonathan P. "Modeling 400 Million Years of Plant Hydraulics." Paleontological Society Papers 19 (October 2013): 175–94. http://dx.doi.org/10.1017/s1089332600002734.
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Mathematical models of fluid flow thorough plant stems permit quantitative assessment of plant ecology using anatomy alone, allowing extinct and extant plants to be measured against one another. Through this process, a series of patterns and observations about plant ecology and evolution can be made. First, many plants evolved high rates of water transport through the evolution of a diverse suite of anatomical adaptations over the last four hundred million years. Second, adaptations to increase hydraulic supply to leaves tend to precede, in evolutionary time, adaptations to increase the safety margin of plant water transport. Third, anatomical breakthroughs in water transport function tend to occur in step with ecological breakthroughs, including the appearance of leaves during the Devonian, the evolution of high leaf areas in early seed plants during the Carboniferous, and the early radiation of flowering plants during the Cretaceous. Quantitative assessment of plant function not only opens up the plant fossil record to ecological comparison, but also provides data that can be used to model fluxes and dynamics of past ecosystems that are rooted in individual plant anatomy.
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Zhu, Hong Jun, Bo Shi Qiu, Qing Kun Jia, and Xiao Lu Yang. "Simulation Analysis of Hydraulic Jet Pump." Advanced Materials Research 204-210 (February 2011): 293–96. http://dx.doi.org/10.4028/www.scientific.net/amr.204-210.293.
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Hydraulic jet pump is one of the mixing-reaction equipments using high-speed jet for work force to deliver energy and mass of fluid. Many factors affect the efficiency of this pump, and the mechanism is very complex. The present work aims to study the influence of different hydraulic structures on the efficiency. Based on computational fluid dynamics, two-dimensional oil flow in hydraulic jet pump with different structural parameters (area ratio, throat length and spray distance) was simulated. Calculation results show that: area ratio determines the suction capacity, throat length determines the mixing efficiency, and spray distance determines the outlet pressure. Since numerical simulation method can reduce experimental expenses and design cycle, our approach may provide some references for safe design and engineering practice of hydraulic jet pump.
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Filimonov, Sergey, Alexander Dekterev, and Andrey Minakov. "Computational modelling of flow in a microporous environment of a natural reservoir with consideration of the topological structure." E3S Web of Conferences 219 (2020): 01007. http://dx.doi.org/10.1051/e3sconf/202021901007.
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The article presents the initial stage of developing a hybrid mathematical model for describing the recovery of oil from a natural sand reservoir. The hybrid model means that part of the computational domain (microchannel structure in the space between particles) is calculated by one- dimensional models is based on the hydraulic circuit theory, and another part (large cracks and caverns) is calculated by computational fluid dynamics methods (CFD). The article also describes a unique algorithm for building a network model based on preliminary CFD calculation. The last section of the article presentation compares of results of calculation CFD and network models.
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He, Cheng, Jiri Marsalek, and Quintin Rochfort. "Numerical Modelling of Enhancing Suspended Solids Removal in a CSO Facility." Water Quality Research Journal 39, no. 4 (2004): 457–65. http://dx.doi.org/10.2166/wqrj.2004.057.
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Abstract One of the most common methods of combined sewer overflow (CSO) treatment is by conventional settling, the efficiency of which depends on the properties of solid particles and the characteristics of the flow transporting these solids. Since the geometry and hydraulics of CSO facilities are often very complex, traditional design methods based on many simplifying assumptions may not predict well the actual operational performance. Therefore, there is a growing need for new tools assisting engineers in design or operation of CSO storage and treatment facilities. In a study of such a CSO facility, a commercial computational fluid dynamics (CFD) model (FLUENT) was used to investigate flow and sediment behaviour, and to explore the ways of optimizing the overall facility performance by adding flow conditioning baffles to improve particle settling. A two-stage approach was adopted; flow patterns were simulated first by means of a volume of fluid (VOF) model and subsequently formed a basis for simulating particle transport by the discrete phase (DP) model. The simulation results for water surface, flow fields in different structure configurations, and particle capture rates in three parallel CSO storage/treatment tanks are presented for various flow conditions.
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McBain, Geordie Drummond. "Three ways to compute multiport inertance." ANZIAM Journal 60 (August 26, 2019): C140—C155. http://dx.doi.org/10.21914/anziamj.v60i0.14058.
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The immediate impulse-response of a confined incompressible fluid is characterized by inertance. For a vessel with one inlet and outlet, this is a single quantity; for multiple ports the generalization is a singular reciprocal inertance matrix which acts on the port-impulses to give the corresponding inflows. The reciprocal inertance coefficients are defined by the boundary fluxes of potential flows. Green's identity converts these coefficients to domain integrals of kinetic energy. For a system discretized with finite elements, a third method is proposed for computing reciprocal inertance coefficients which requires only the stiffness matrix and the solution vectors and no numerical differentiation.
 
 References A. Asai. Bubble dynamics in boiling under high heat flux pulse heating. J. Heat Transf., 113(4):973979, 1991. doi:10.1115/1.2911230. A. Asai. Three-dimensional calculation of bubble growth and drop ejection in a bubble jet printer. J. Fluids Eng., 114(4):638641, 1992. doi:10.1115/1.2910079. G. K. Batchelor. An introduction to fluid dynamics. Cambridge University Press, 1967. doi:10.1017/CBO9780511800955. J. D. Beasley. Model for fluid ejection and refill in an impulse drive jet. Soc. Photogr. Sci. Eng., 21(2):7882, 1977. F. Dorfler and F. Bullo. Kron reduction of graphs with applications to electrical networks. IEEE T. Circuits I, 60(1):150163, 2013. doi:10.1109/tcsi.2012.2215780. A. Ern and J.-L. Guermond. Theory and practice of finite elements. Springer, 2004. doi:10.1007/978-1-4757-4355-5. K. Foster and G. A. Parker. Fluidics: Components and circuits. Wiley, 1970. URL https://www.worldcat.org/title/fluidics-components-and-circuits/oclc/138528. C. Geuzaine and J.-F. Remacle. Gmsh: A 3-D finite element mesh generator with built-in pre- and post-processing facilities. Int. J. Numer. Meth. Eng., 79(11): 13091331, 2009. doi:10.1002/nme.2579. G. Geymonat and D. Chenais. Introduction, pages xixii. Birkhauser, 1996. doi:10.1007/978-1-4612-2436-5. T. Gustafsson and G. McBain. kinnala/scikit-fem 0.1.17, Nov. 2018. O. Heaviside. Some remarks on the Volta force and seat of electro-motive forces questions, and on impressed force and potential in condenser circuits. J. Soc. Tele.-Eng. Electric., 14(57): 269296, 1885. doi:10.1049/jste-3.1885.0014. H. E. Koenig, Y. Tokad, and H. K. Kesavan. Analysis of discrete physical systems. McGrawHill, 1967. URL https://trove.nla.gov.au/work/21368152?selectedversion=NBD2690879. M. Krizek and P. Neittaanmaki. Superconvergence phenomenon in the finite element method arising from averaging gradients. Numer. Math., 45(1):105116, 1984. doi:10.1007/bf01379664. H. Lamb. Hydrodynamics. Cambridge University Press, 6th edition, 1932. URL https://www.cambridge.org/au/academic/subjects/mathematics/fluid-dynamics-and-solid-mechanics/hydrodynamics-6th-edition. G. D. McBain and S. G. Mallinson. Impulsively generated incompressible two-phase flow and the Asai thermal ink-jet model. In 21st Australasian Fluid Mechanics Conference, 2018. URL https://people.eng.unimelb.edu.au/imarusic/proceedings/21/Contribution_616_final.pdf. K. W. Oh, K. Lee, B. Ahn, and E. P. Furlani. Design of pressure-driven microfluidic networks using electric circuit analogy. Lab Chip, 12(3):515545, 2012. doi:10.1039/c2lc20799k. H. F. Olson. Elements of acoustical engineering. Van Nostrand, 1948. doi:10.1002/sce.3730320378. R. S. Sanford. Physical networks. Prentice-Hall, 1965. URL https://trove.nla.gov.au/work/8815056?q&versionId=10200776. V. L. Streeter. Steady flow in pipes and conduits. In H. Rouse, editor, Engineering Hydraulics: Proceedings of the Fourth Hydraulics Conference, chapter 6, pages 387443. Wiley, 1950. URL https://trove.nla.gov.au/work/17727563.
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Broecker, Tabea, Katharina Teuber, Vahid Sobhi Gollo, Gunnar Nützmann, Jörg Lewandowski, and Reinhard Hinkelmann. "Integral Flow Modelling Approach for Surface Water-Groundwater Interactions along a Rippled Streambed." Water 11, no. 7 (2019): 1517. http://dx.doi.org/10.3390/w11071517.
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Exchange processes of surface and groundwater are important for the management of water quantity and quality as well as for the ecological functioning. In contrast to most numerical simulations using coupled models to investigate these processes, we present a novel integral formulation for the sediment-water-interface. The computational fluid dynamics (CFD) model OpenFOAM was used to solve an extended version of the three-dimensional Navier–Stokes equations which is also applicable in non-Darcy-flow layers. Simulations were conducted to determine the influence of ripple morphologies and surface hydraulics on the flow processes within the hyporheic zone for a sandy and for a gravel sediment. In- and outflowing exchange fluxes along a ripple were determined for each case. The results indicate that larger grain size diameters, as well as ripple distances, increased hyporheic exchange fluxes significantly. For higher ripple dimensions, no clear relationship to hyporheic exchange was found. Larger ripple lengths decreased the hyporheic exchange fluxes due to less turbulence between the ripples. For all cases with sand, non-Darcy-flow was observed at an upper layer of the ripple, whereas for gravel non-Darcy-flow was recognized nearly down to the bottom boundary. Moreover, the sediment grain sizes influenced also the surface water flow significantly.
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Gupta, Nikita, Nishant Bhardwaj, Gulam Muhammad Khan, and Vivek Dave. "Global Trends of Computational Fluid Dynamics to Resolve Real World Problems in the Contemporary Era." Current Biochemical Engineering 6, no. 3 (2020): 136–55. http://dx.doi.org/10.2174/2212711906999200601121232.
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Background: Computational fluid dynamics (CFD) came into existence with great success, thereby replacing the traditional methods used to simulate the problems related to the flow of fluid. First CFD utilitarian was introduced to the world in 1957, which was developed by a team at Los Alamos National Lab. For tremendous performance and to meet the expected results with ease for modern process conditions, engineers are now more inclined towards the use of simulation software rather than traditional methods. Hence, in the current scenario with the advancement of computer technologies, “CFD is recognized as an excellent tool for engineers to resolve real-world problems.” Introduction: CFD is defined as a branch of fluid dynamics which involves the use of numerical analysis and data structure to solve complications related to the flow of fluids (gasses or liquids). CFD is based on three major principles that are mass conservation, Newton's second law, and energy conservation. CFD has extended to a number of applications at an alarming rate in every field such as in aerospace, sports, food industry, engineering, hydraulics, HVAC (Heating, Ventilating, and Air conditioning), automotive, environmental, power generation, biomedical, pharmaceutical, and many more. Hence, a number of software like ANSYS, Open Foam, SimScale, Gerris, Auto desk simulation, Code_Saturne, etc, are beneficial in order to execute the operations, and to find the solution of realworld problems within a fraction of seconds. Methods: CFD analysis involves three major steps; pre-processing, solution, and post-processing. Preprocessing deals with defining model goals, identification of domain, designing, and creating the grid. Solution involves setting up the numerical model, computing, and monitoring the solution; whereas, post-processing includes results of the examination and revision of the model. Results: The review includes current challenges about the computational fluid dynamics. It is relevant in different areas of engineering to find answers for the problems occurring globally with the aid of a number of simulation-based software hereby, making the world free from complex problems in order to have a non-complicated scenario. Conclusion: Computational fluid dynamics are relevant in each, and every kind of problem related to the fluid flow, either existing in the human body or anywhere. In the contemporary era, there are enormous numbers of simulation-based software, which provide excellent results with just one click, thereby resolving the problems within microseconds. Hence, we cannot imagine our present and upcoming future without CFD, which has ultimately made the execution of work easier, leaving behind non-complicating scenarios. Lastly, we can conclude that “CFD is a faster, smarter, and lighter way in designing process.”
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Cao, Zheng, Jianqiang Deng, Linkun Zhao, and Lin Lu. "Numerical Research of Pump-as-Turbine Performance with Synergy Analysis." Processes 9, no. 6 (2021): 1031. http://dx.doi.org/10.3390/pr9061031.
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The wide use of pumps and turbines has significant value in energy conservation and utilization. In this work, a three-dimensional Computational Fluid Dynamics (CFD) model and a one-dimensional theoretical model of a Pump as Turbine (PAT) were established. On this basis, the correlation between pressure and velocity was quantitatively investigated by a proposed sensitivity index (SPV). A synergy field analysis was then applied to evaluate the flow characteristics of a pump and PAT, providing a perspective from the mechanism of the energy transfer enhancement for hydraulic devices. Moreover, the hydraulic and synergy performances of PAT were studied under various operating conditions. The results show that the minimum SPV is obtained in the impeller. With increasing flow rate, the SPV of the PAT generally increases, and the synergy angle of the impeller surface increases as well. A strong disordered synergy field is observed in regions of the blade leading edge, trailing edge, and volute tongue. The variations in efficiency and head with flow rate showed similar trends, respectively, with the synergy angle of the outlet and the mid-plane. This study provides an analytical method for quantitative evaluation of flow synergy characteristics, and it supplies a basis for further design improvement of the pump and PAT.
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Ahmad, Muhammad, Usman Ghani, Naveed Anjum, Ghufran Ahmed Pasha, Muhammad Kaleem Ullah, and Afzal Ahmed. "Investigating the Flow Hydrodynamics in a Compound Channel with Layered Vegetated Floodplains." Civil Engineering Journal 6, no. 5 (2020): 860–76. http://dx.doi.org/10.28991/cej-2020-03091513.
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In natural rivers, vegetation grows on floodplains, generating complex velocity field within the compound channel. The efficient modelling of the flow hydraulics in a compound channel with vegetated floodplains is necessary to understand and determine the natural processes in rivers and streams. As the three dimensional (3D) flow features are difficult to capture through experimental investigation; therefore, the present numerical study was carried out to investigate the complex 3D flow structures with the vertically layered vegetation placed over the floodplains in a symmetric trapezoidal compound channel. The simulations were conducted using a Computational Fluid Dynamics (CFD) code FLUENT, whereas a Reynolds Averaged Navier-Stokes (RANS) technique based on Reynolds stress model (RSM) was implemented for turbulence closure. The numerical model successfully replicated the flow behavior and showed a good agreement with the experimental data. The present study concluded the presence of quite-S shaped velocity profile in the layered vegetated floodplains when the short vegetation was submerged during high flows or floods, whereas the velocity profile was uniform or almost logarithmic during low floods or when both short and tall vegetation remained emergent. The lateral exchange of mass and momentum was promoted due to the flow separation and instability along the junction of the floodplains and main channel. The flow velocities were significantly reduced in the floodplains due to resistance offered by the vegetation, which consequently resulted in an increased percentage i.e. 67-73%, of passing discharge through the main channel. In general, the spatial distribution of mean flow and turbulence characteristics was considerably affected near the floodplain and main channel interfaces. Moreover, this study indicated a positive flow response for the sediment deposition as well as for the nourishment of the aquatic organisms in the riparian environment.
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Klemp, Joseph B., Richard Rotunno, and William C. Skamarock. "On the dynamics of gravity currents in a channel." Journal of Fluid Mechanics 269 (June 25, 1994): 169–98. http://dx.doi.org/10.1017/s0022112094001527.
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We attempt to clarify the factors that regulate the propagation and structure of gravity currents through evaluation of idealized theoretical models along with two-dimensional numerical model simulations. In particular, we seek to reconcile research based on hydraulic theory for gravity currents evolving from a known initial state with analyses of gravity currents that are assumed to be at steady state, and to compare these approaches with both numerical simulations and laboratory experiments. The time-dependent shallow-water solution for a gravity current propagating in a channel of finite depth reveals that the flow must remain subcritical behind the leading edge of the current (in a framework relative to the head). This constraint requires that hf/d ≤ 0.347, where hf is the height of the front and d is the channel depth. Thus, in the lock-exchange problem, inviscid solutions corresponding to hf/d = 0.5 are unphysical, and the actual currents have depth ratios of less than one half near their leading edge and require dissipation or are not steady. We evaluate the relevance of Benjamin's (1968) well-known formula for the propagation of steady gravity currents and clarify discrepancies with other theoretical and observed results. From two-dimensional simulations with a frictionless lower surface, we find that Benjamin's idealized flow-force balance provides a good description of the gravity-current propagation. Including surface friction reduces the propagation speed because it produces dissipation within the cold pool. Although shallow-water theory over-estimates the propagation speed of the leading edge of cold fluid in the ‘dam-break’ problem, this discrepancy appears to arise from the lack of mixing across the current interface rather than from deficiencies in Benjamin's front condition. If an opposing flow restricts the propagation of a gravity current away from its source, we show that the propagation of the current relative to the free stream may be faster than predicted by Benjamin's formula. However, in these situations the front propagation remains dependent upon the specific source conditions and cannot be generalized.
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Guyonvarch, Estelle, Elham Ramin, Murat Kulahci, and Benedek G. Plósz. "Quantifying the sources of uncertainty when calculating the limiting flux in secondary settling tanks using iCFD." Water Science and Technology 81, no. 2 (2020): 241–52. http://dx.doi.org/10.2166/wst.2020.090.
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Abstract Solids-flux theory (SFT) and state-point analysis (SPA) are used for the design, operation and control of secondary settling tanks (SSTs). The objectives of this study were to assess uncertainties, propagating from flow and solids loading boundary conditions as well as compression settling behaviour to the calculation of the limiting flux (JL) and the limiting solids concentration (XL). The interpreted computational fluid dynamics (iCFD) simulation model was used to predict one-dimensional local concentrations and limiting solids fluxes as a function of loading and design boundary conditions. A two-level fractional factorial design of experiments was used to infer the relative significance of factors unaccounted for in conventional SPA. To move away from using semi-arbitrary safety factors, a systematic approach was proposed to calculate the maximum SST capacity by employing a factor of 23% and a regression meta-model to correct values of JL and XL, respectively – critical for abating hydraulic effects under wet-weather flow conditions.
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Freile, Ramiro, and Mark Kimber. "Influence of molten salt-(FLiNaK) thermophysical properties on a heated tube using CFD RANS turbulence modeling of an experimental testbed." EPJ Nuclear Sciences & Technologies 5 (2019): 16. http://dx.doi.org/10.1051/epjn/2019027.
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In a liquid fuel molten salt reactor (MSR) a key factor to consider upon its design is the strong coupling between different physics present such as neutronics, thermo-mechanics and thermal-hydraulics. Focusing in the thermal-hydraulics aspect, it is required that the heat transfer is well characterized. For this purpose, turbulent models used for FLiNaK flow must be valid, and its thermophysical properties must be accurately described. In the literature, there are several expressions for each material property, with differences that can be significant. The goal of this study is to demonstrate and quantify the impact that the uncertainty in thermophysical properties has on key metrics of thermal hydraulic importance for MSRs, in particular on the heat transfer coefficient. In order to achieve this, computational fluid dynamics (CFD) simulations using the RANS k-ω SST model were compared to published experiment data on molten salt. Various correlations for FLiNaK’s material properties were used. It was observed that the uncertainty in FLiNaK’s thermophysical properties lead to a significant variance in the heat coefficient. Motivated by this, additional CFD simulations were done to obtain sensitivity coefficients for each thermophysical property. With this information, the effect of the variation of each one of the material properties on the heat transfer coefficient was quantified performing a one factor at a time approach (OAT). The results of this sensitivity analysis showed that the most critical thermophysical properties of FLiNaK towards the determination of the heat transfer coefficient are the viscosity and the thermal conductivity. More specifically the dimensionless sensitivity coefficient, which is defined as the percent variation of the heat transfer with respect to the percent variation of the respective property, was −0.51 and 0.67 respectively. According to the different correlations, the maximum percent variations for these properties is 18% and 26% respectively, which yields a variation in the predicted heat transfer coefficient as high as 9% and 17% for the viscosity and thermal conductivity, respectively. It was also demonstrated that the Nusselt number trends found from the simulations were captured much better using the Sieder Tate correlation than the Dittus Boelter correlation. Future work accommodating additional turbulence models and higher fidelity physics will help to determine whether the Sieder Tate expression truly captures the physics of interest or whether the agreement seen in the current work is simply reflective of the single turbulence model employed.
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Didenko, Denis V., Dmitry Ye Baluyev, Oleg L. Nikanorov, et al. "Development of a methodological approach for the computational investigation of the coolant flow in the process of the sodium cooled reactor cooldown." Nuclear Energy and Technology 7, no. 1 (2021): 61–66. http://dx.doi.org/10.3897/nucet.7.65442.
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A methodological approach has been developed for the computational investigation of the thermal-hydraulic processes taking place in a sodium cooled fast neutron reactor based on a Russian computational fluid dynamics code, FlowVision. The approach takes into account the integral layout of the reactor primary circuit equipment and the peculiarities of heat exchange in the liquid metal coolant, and makes it possible to model, using well-defined simplifications, the heat and mass exchange in the process of the coolant flowing through the reactor core, and the reactor heat-exchange equipment. Specifically, the methodological approach can be used for justification of safety during the reactor cooldown, as well as for other computational studies which require simulation of the integral reactor core and heat-exchange equipment. The paper presents a brief overview of the methodological approaches developed earlier to study the liquid metal cooled reactor cooldown processes. General principles of these approaches, as well as their advantages and drawbacks have been identified. A three-dimensional computational model of an advanced reactor has been developed, including one heat-exchange loop (a fourth part of the reactor). It has been demonstrated that the FlowVision gap model can be applied to model the space between the reactor core fuel assemblies (interwrapper space), and a porous skeleton model can be used to model the reactor’s heat-exchange equipment. It has been shown that the developed methodological approach is applicable to solving problems of the coolant flow in different operating modes of liquid metal cooled reactor facilities.
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Bousbia-Salah, Anis, Fabio Moretti, and Francesco D’auria. "State-of-the-art and needs for jet instability and direct contact condensation model improvements." Nuclear Technology and Radiation Protection 22, no. 1 (2007): 58–66. http://dx.doi.org/10.2298/ntrp0701058b.
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There is a common understanding among thermal-hydraulic experts that the system analysis codes have currently reached an acceptable degree of maturity. Reliable application, however, is still limited to the validated domain. There is a growing need for qualified codes in assessing the safety of the existing reactors and for developing advanced reactor systems. Under conditions involving multi-phase flow simulations, the use of classical methods, mainly based upon the one dimensional approach, is not appropriate at all. The use of new computational models, such as the direct numerical simulation, large-eddy simulation or other advanced computational fluid dynamics methods, seems to be more suitable for more complex events. For this purpose, the European Commission financed NURESIM Integrated Project (as a part of the FP6 programme), was adopted to provide the initial step towards a Common European Standard Software Platform for Modeling, recording and recovering computer data for nuclear reactor simulations. Some of the studies carried out at the University of Pisa within the framework of the NURESIM project are presented in this paper. They mainly concern the investigation of two critical phenomena connected with jet instabilities and direct contact condensation that occur during emergency core cooling. Through these examples, the state-of-the-art and the need for model improvements and validation against new experimental data for the sake of getting a better understanding and more accurate predictions are discussed.
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Danchuk, S., and C. S. Willson. "NUMERICAL MODELING OF OIL SPILLS IN THE INLAND WATERWAYS OF THE LOWER MISSISSIPPI RIVER DELTA." International Oil Spill Conference Proceedings 2008, no. 1 (2008): 887–91. http://dx.doi.org/10.7901/2169-3358-2008-1-887.
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ABSTRACT The demand for fossil fuels is driving the rapid expansion of the petroleum industry'S infrastructure. Louisiana'S wetlands are the most industrialized in the world. The oil industry has infiltrated every part of the Lower Mississippi River Delta (LMRD) from the fixed facilities and transport vessels traveling along inland waterways, the pipelines and canals running through the wetlands, and the offshore platforms along the Gulf of Mexico coastline. An oil spill could seriously damage the coastal wetlands that are already rapidly degrading, pollute the water supply, destroy wildlife habitat, and impact other natural economic and social resources. Additionally, proposed coastal restoration initiatives such as freshwater diversions could provide a conduit for spills to travel from the river to open wetland areas. Current inland oil fate and transport models cannot automatically be applied in the deltaic environment because they do not represent the high degree of minerals and fines in suspension, the unique characteristics of the shorelines, or the potential flow into the wetland areas. Thus, a three- dimensional oil fate and transport model was developed to investigate the behavior of oil spilled in the unique environment of the LMRD, assess the vulnerability at specific locations such as freshwater diversions from the river, and provide information for contingency and remediation plans. Simulations of the hydrodynamics of the LMRD were generated using the U.S. Army Corps of Engineers Adaptive Hydraulics (ADH) modeling code. The model simulates the physical and chemical processes affecting the fate of a surface oil spill including slick advection and spreading, the vertical transport of dissolved and emulsified parcels, evaporation, dissolution, adsorption, sedimentation, re-suspension and degradation. The model estimates the distribution of oil in the surface slick, water column, sediments and atmosphere. Almost seventy percent of the Mississippi River'S sediment load is comprised of finer materials. The model is unique in using empirical predictions to describe oil'S interactions with fine suspended material and muddy shorelines. Hypothetical spills representative of the type and location of spills commonly occurring in the region were simulated to investigate the sensitivity of the system to the unique parameters. This model was developed to take advantage of the latest advances in computational fluid dynamics and weathering algorithms, while focusing on the complex hydraulics and sediment characteristics local to the Lower Mississippi River Delta.
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Peng, Song Jiang, Cheng Zhou, and Cun Gui Yu. "The Numerical Simulation of Three-Dimensional Dynamic-Mesh Flow Field of a Hydraulic Buffer." Advanced Materials Research 588-589 (November 2012): 1264–68. http://dx.doi.org/10.4028/www.scientific.net/amr.588-589.1264.
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In order to study the dynamic changes of the internal flow field physical quantities in the hydraulic buffer of a special equipment, based on the Computational Fluid Dynamics (CFD), a three-dimensional incompressible and viscous model under unsteady condition is created. The model keeps the control rod of varying diameter and non-working chamber cover, simulates the turbulent in the flow field of the hydraulic buffer of the special equipment with dynamic meshing technology. From the results, the distributions of velocity in flow field and pressure in chamber are got. It shows that there are negative pressure areas in the non-working chamber and that will lead to cavitation. The results give us a great reference to improve the structure of hydraulic buffer.
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Borghi, M., G. Cantore, M. Milani, and R. Paoluzzi. "Analysis of hydraulic components using computational fluid dynamics models." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 212, no. 7 (1998): 619–29. http://dx.doi.org/10.1243/0954406981521583.
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This paper presents some results obtained during the computational fluid dynamics (CFD) analysis of internal flows inside a hydraulic component, using a scaling technique applied to numerical pre- and post-processing. The main aim of the work is to demonstrate the reduction of computational work needed for a complete analysis of component behaviour over a wide range of operating conditions. This result is achieved through the adoption of a methodology aimed at giving the highest level of generality to a non-dimensional solution, thereby overcoming the two major limitations encountered in the use of CFD in fluid power design: computer resources and time. In the case study, the technique was applied to a hydraulic distributor and computations were performed with a commercial computational fluid dynamics code. The key factor of this technique is the evaluation, for a given distributor opening, of the Reynolds number of the flow in the metering region. Provided that this number is high enough to ensure that the discharge coefficient has reached its asymptotic value, the characterization of the flow by a single non-dimensional numerical run can be shown. The theoretical contents of the analysis of the re-scaling technique, which focuses on the engineering information necessary in component design, are described in detail. The bases for its subsequent application to actual cases are then outlined. Finally, a fairly close correlation between numerical results and experimental data is presented.
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Amirante, Riccardo, Luciano Andrea Catalano, and Paolo Tamburrano. "The importance of a full 3D fluid dynamic analysis to evaluate the flow forces in a hydraulic directional proportional valve." Engineering Computations 31, no. 5 (2014): 898–922. http://dx.doi.org/10.1108/ec-09-2012-0221.
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Purpose – The purpose of this paper is to present a full 3D Computational Fluid Dynamics (CFD) analysis of the flow field through hydraulic directional proportional valves, in order to accurately predict the flow forces acting on the spool and to overcome the limitations of two-dimensional (2D) and simplified three-dimensional (3D) models. Design/methodology/approach – A full 3D CAD representation is proposed as a general approach to reproduce the geometry of an existing valve in full detail; then, unstructured computational grids, which identify peculiar positions of the spool travel, are generated by means of the mesh generation tool Gambit. The computational grids are imported into the commercial CFD code Fluent, where the flow equations are solved assuming that the flow is steady and incompressible. To validate the proposed computational procedure, the predicted flow rates and flow forces are compared with the corresponding experimental data. Findings – The superposition between numerical and experimental curves demonstrates that the proposed full 3D numerical analysis is more effective than the simplified 3D flow model that was previously proposed by the same authors. Practical implications – The presented full 3D fluid dynamic analysis can be employed for the fluid-dynamic design optimization of the sliding spool and, more generally, of the internal profiles of the valve, with the objective of reducing the flow forces and thus the required control force. Originality/value – The paper proposes a new computational strategy that is capable of recognizing all 3D geometrical details of a hydraulic directional proportional valve and that provides a significant improvement with respect to 2D and partially 3D approaches.
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Wang, Kuiyang, Jinhua Tang, and Guoqing Li. "Research on Parametric Design of Hydraulic Retarder Based on Multi-Field Coupling of Heat, Fluid and Solid." Open Mechanical Engineering Journal 9, no. 1 (2015): 58–64. http://dx.doi.org/10.2174/1874155x01509010058.
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In order to optimize the design method and improve the performance of hydraulic retarder, the numerical simulation of multi-field coupling of heat, fluid and solid is carried out to hydraulic retarder, based on the numerical computation and algorithm of heat-fluid coupling and fluid-solid coupling. The computation models of heat-fluid coupling and fluid-solid coupling of hydraulic retarder are created. The three dimensional model of hydraulic retarder is established based on CATIA software, and the whole flow passage model of hydraulic retarder is extracted on the basis of the three dimensional model established. Based on the CFD calculation and the finite element numerical simulation, the temperature field, stress field, deformation and stress state are analysised to hydraulic retarder in the state of whole filling when the rotate speed is 1600 r/min. In consideration of rotating centrifugal force, thermal stress and air exciting vibration force of blade surface, by using the sequential coupling method, the flow field characteristics of hydraulic retarder and dynamic characteristics of blade structure are analysised and researched based on multi-field coupling of heat, fluid and solid. These provide the theoretical foundation and references for parametric design of hydraulic retarder.
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Zhang, Jun, Wei Wang, Hong Mei Tang, Xian Hua Li, and Chun Bao Fu. "Analysis of Pipeline Dynamic Flow Signal Coupling in Hydraulic System." Applied Mechanics and Materials 397-400 (September 2013): 2161–66. http://dx.doi.org/10.4028/www.scientific.net/amm.397-400.2161.
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The dynamic measurement of the high pressure side flow in hydraulic system is still one of the important and difficult problems in hydraulic test technique. In order to solve the dynamic coupling mechanism between main and bypass oil-way fluid flow signals in the bypass flow measurement method, hydraulic system software was used to analysis the problem in this paper, the dynamic coupling relationship between main and bypass oil-way fluid flow signals were obtained. Finally verify the feasibility of the bypass flow measurement method.
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Rotunno, Richard, and George H. Bryan. "Numerical Simulations of Two-Layer Flow past Topography. Part I: The Leeside Hydraulic Jump." Journal of the Atmospheric Sciences 75, no. 4 (2018): 1231–41. http://dx.doi.org/10.1175/jas-d-17-0306.1.
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Abstract Laboratory observations of the leeside hydraulic jump indicate it consists of a statistically stationary turbulent motion in an overturning wave. From the point of view of the shallow-water equations (SWE), the hydraulic jump is a discontinuity in fluid-layer depth and velocity at which kinetic energy is dissipated. To provide a deeper understanding of the leeside hydraulic jump, three-dimensional numerical solutions of the Navier–Stokes equations (NSE) are carried out alongside SWE solutions for nearly identical physical initial-value problems. Starting from a constant-height layer flowing over a two-dimensional obstacle at constant speed, it is demonstrated that the SWE solutions form a leeside discontinuity owing to the collision of upstream-moving characteristic curves launched from the obstacle. Consistent with the SWE solution, the NSE solution indicates the leeside hydraulic jump begins as a steepening of the initially horizontal density interface. Subsequently, the NSE solution indicates overturning of the density interface and a transition to turbulence. Analysis of the initial-value problem in these solutions shows that the tendency to form either the leeside height–velocity discontinuity in the SWE or the overturning density interface in the exact NSE is a feature of the inviscid, nonturbulent fluid dynamics. Dissipative turbulent processes associated with the leeside hydraulic jump are a consequence of the inviscid fluid dynamics that initiate and maintain the locally unstable conditions.
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Alex, J., S. G. E. Rönner-Holm, M. Hunze, and N. C. Holm. "A combined hydraulic and biological SBR model." Water Science and Technology 64, no. 5 (2011): 1025–31. http://dx.doi.org/10.2166/wst.2011.472.
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A sequencing batch reactor (SBR) model was developed consisting of six continuous stirred tank reactors which describe the hydraulic flow patterns occurring in different SBR phases. The model was developed using the results of computational fluid dynamics (CFD) simulation studies of an SBR reactor under a selection of dynamic operational phases. Based on the CFD results, the model structure was refined and a simplified ‘driver’ model to allow one to mimic the flow pattern driven by the external operational conditions (influent, aeration, mixing) was derived. The resulting model allows the modeling of biological processes, settlement and hydraulic conditions of cylindrical SBRs.
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Mu, Dong Jie, and Chang Chun Li. "Numerical Simulation of Fluid Transients in Servo-Controlled Hydraulic Piping." Advanced Materials Research 383-390 (November 2011): 2262–68. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.2262.
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His analytical model is carried out based on the one-dimensional fluid transient theory. In view of the micro-compression of the fluid can change its momentum in the transient process, an improved fluid dynamic model of pipeline is proposed. The characteristic method and the finite difference method are adopted for this simulation. In this paper, The fluid transients of the pipes after servo valve shut down are analyzed. The correctness of the simulation is approved by the comparison of calculation data with experiment data .The results showed that these models give more reasonable descriptions for water hammer and flow oscillation during servo valve starting process and could provide guidance for designs and experiments of the hydraulic pipe system
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Cao, M., K. W. Wang, L. DeVries, et al. "Steady State Hydraulic Valve Fluid Field Estimator Based on Non-Dimensional Artificial Neural Network (NDANN)." Journal of Computing and Information Science in Engineering 4, no. 3 (2004): 257–70. http://dx.doi.org/10.1115/1.1765119.
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An automatic transmission (AT) hydraulic control system includes many spool-type valves that have highly asymmetric flow geometry. A simplified flow field model based on a lumped geometry is computationally efficient. However, it often fails to account for asymmetric flow characteristics, leading to an inaccurate analysis. An accurate analysis of their flow fields typically requires using the computational fluid dynamics (CFD) technique, which is numerically inefficient and time consuming. In this paper, a new hydraulic valve fluid field model is developed based on non-dimensional artificial neural networks (NDANNs) to provide an accurate and numerically efficient tool in AT control system design applications. A grow-and-trim procedure is proposed to identify critical non-dimensional inputs and optimize the network architecture. A hydraulic valve testing bench is designed and built to provide data for neural network model development. NDANN-based fluid force and flow rate estimators are established based on the experimental data. The NDANN models provide more accurate predictions of flow force and flow rates under broad operating conditions (such as different pressure drops and valve openings) compared with conventional lumped flow field models. Because of its non-dimensional characteristic, the NDANN fluid field estimator also exhibits good input-output scalability, which allows the NDANN model to estimate the fluid force and flow rate even when the operating condition parameter or design geometry parameters are outside the range of the training data. That is, although the operating/geometry parameter values are outside the range of the training sets, the non-dimensional values of the specific operating/geometry parameters are still within the training range. This feature makes the new model a potential candidate as a system design tool.
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Montaseri, H., K. Tavakoli, S. Evangelista, and P. Omidvar. "Sediment transport and bed evolution in a 180∘ curved channel with lateral intake: Numerical simulations using Eulerian and Discrete Phase models." International Journal of Modern Physics C 31, no. 08 (2020): 2050113. http://dx.doi.org/10.1142/s0129183120501132.
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Lateral intakes are hydraulic structures used for domestic, agricultural and industrial water conveyance, characterized by a very complex three-dimensional morphodynamic behavior: since streamlines near the lateral intake are deflected, some vortices form, pressure gradient, shear and centrifugal forces at the intake generate flow separation and a secondary movement, responsible for local scour and sediment deposition. On the other side, the modeling of flows, besides the sediment transport, in curved channels implies some more complications in comparison with straight channels. In this research, this complex process has been investigated experimentally and numerically, with the mechanism of sediment transport, bed topography evolution, flow pattern and their interactions. Experiments were performed in the Laboratory of Tarbiat Modares University, Iran, where a U-shaped channel with a lateral intake was installed and dry sediment was injected at constant rate into a steady flow. Due to the spiral flow, the bed topography changes significantly and the bed forms in turn affect the sediment entering the intake. Different from the previous works on this topic which were mainly based on laboratory experiments, here, Computational Fluid Dynamics (CFD) numerical simulations with FLUENT software were also performed, specifically with the two-phase Eulerian Model (EM) and Discrete Phase Model (DPM), at the aim of evaluating their performance in reproducing the observed physical processes. This software is used for a large variety of CFD problems, but not much for simulating sediment transport phenomena and bed topography evolution. The comparison of the results obtained through the two models against the laboratory experimental data proved a good performance of both the models in reproducing the main features of the flow, for example, the longitudinal and vertical streamlines and the mechanism of particles movement. However, the EM reveals a better performance than DPM in the prediction of the secondary flows and, consequently, of the bed topography evolution, whereas the DPM well depicts the particles pattern, predicts the location of trapped particles and determines the percentage of sediment entering the intake. The numerical models so calibrated and validated were applied to other cases with different positions of the intake in the bend. The results show that mechanism of sediment entrance into the intake varies in different position. If the intake is installed in the second half of the bend, the sediment accumulates along the inner bank of the bend and enters the intake from downstream edge of intake; on the other side, if it is placed in the first half of the bend, the sediment accumulates along both the inner and the outer bends and, therefore, more sediment enters the intake. Also the results of the simulations performed with the DPM model for different positions of the lateral intake show that for all discharge ratios, the position of 120∘ is the one which guarantees the minimum ratio of sediment diverted to the intake (Gr).
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Wei, Wei, Hongchao Jian, Qingdong Yan, Xiaomei Luo, and Xuhong Wu. "Nonlinear modeling and stability analysis of a pilot-operated valve-control hydraulic system." Advances in Mechanical Engineering 10, no. 11 (2018): 168781401881066. http://dx.doi.org/10.1177/1687814018810660.
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A nonlinear dynamic model is developed to analyze the stability of a pilot-operated valve-control hydraulic system. The dynamic model includes motion of the valve spool and fluid dynamics in the system. Characteristics such as pressure flow across the valve port and orifices, pressure, and flow rate in valve chambers are taken into consideration. Bifurcation analysis is proposed and examined by numerical simulation results when the feedback orifice diameter changes. The effects of different system parameters such as pilot-operating pressure, spring stiffness, and overlap of inlet port on the stability border of the system are studied by two-dimensional bifurcation analyses. The study identifies that bifurcation can occur in the system and lead to sustained self-excited vibration with parameters in certain region of the parameter space. It suggests that the vibration can be effectively predicted and prevented by selecting system parameters from the asymptotic stable parameter region.
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Taft, Kimberly J., Alfred H. Stammers, Clinton C. Jones, Melinda S. Dickes, Michelle L. Pierce, and Daniel J. Beck. "Cardioplegia flow dynamics in an in vitro model." Perfusion 14, no. 5 (1999): 341–49. http://dx.doi.org/10.1177/026765919901400505.
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The flow of fluids in extracorporeal circuits does not conform to conventional Poiseuille mechanics which confounds calculating cardioplegia (CP) flow distribution. The purpose of this study was to quantify CP flow dynamics in a model simulating coronary atherosclerosis across varying sized restrictions. An in vitro preparation was designed to assess hydraulic fluid movement across paired restrictions of 51, 81 and 98% lumen reductions. Volume data were obtained at variable flow, temperature, viscosity and pressure conditions. CP delivered through 14- and 18-gauge (GA) conduits at 8°C and 100 mmHg infusion pressure revealed that both four to one and crystalloid CP solutions had significantly less total percentage flow through the 14-GA conduit, p < 0.0001 and p < 0.001, respectively. Overall, 4:1 CP exhibited the most favorable fluid dynamics at 8°C in that it delivered the highest percentages of total CP flow through the smaller lumen conduit. At both 8°C and 37°C delivery, blood CP resulted in the least homogeneous fluid distribution at all delivery parameters. The results in relation to blood viscosity indicate that, although the 8°C blood CP had a significantly greater viscosity than 37°C blood CP, it did not produce an effect in fluid distribution. These data show that increasing the cardioplegic solution hematocrit causes an inhomogeneous fluid distribution regardless of delivery temperature or infusion pressure.
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Wang, Yu, Junrui Chai, Zengguang Xu, Yuan Qin, and Xin Wang. "Numerical Simulation of the Fluid–Solid Coupling Mechanism of Internal Erosion in Granular Soil." Water 12, no. 1 (2020): 137. http://dx.doi.org/10.3390/w12010137.
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Internal erosion involves migration and loss of soil particles due to seepage. The process of fluid–solid interaction is a complex multiphase, coupled nonlinear dynamic problem. In this study, we used Particle Flow Code (PFC3D, three-dimensional PFC) software to model solid particles, and we applied computational fluid dynamics (CFD) and the coarse mesh element method to solve the local Navier–Stokes equations. An information-exchange process for the PFC3D and CFD calculations was used to achieve fluid–solid coupling. We developed a numerical model for internal erosion of the soil and conducted relevant experiments to verify the usability of the numerical model. The mechanism of internal erosion was observed by analyzing the evolution of model particle migration, contact force, porosity, particle velocity, and mass-loss measurement. Moreover, we provide some ideas for improving the calculation efficiency of the model. This model can be used to predict the initiation hydraulic gradient and skeleton-deformation hydraulic gradient, which can be used for the design of internal erosion control.
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WOLFF, C. "Closed Loop Controlled ER-Actuator." International Journal of Modern Physics B 10, no. 23n24 (1996): 2867–76. http://dx.doi.org/10.1142/s0217979296001318.
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The results of the investigation regarding the suitability of ERF when applied in hydraulics have shown so far that constructing electrorheological flow resistors for the control of pressure and volume flow is possible in principle. One of the main advantages when using the ER-technology in hydraulic systems can be seen in the high reaction rate of the ER-effect. The investigations presented in this article document the dynamic qualities of ER-fluids by means of a practical exploitation for the control of a cylinder actuator. Due to the particular possibilities for design of ER-control resistors a compact cylinder has resulted which differs considerably from traditional cylinder actuators in its construction and dynamic behaviour.
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Jiang, Shouyan, and Chengbin Du. "Coupled Finite Volume Methods and Extended Finite Element Methods for the Dynamic Crack Propagation Modelling with the Pressurized Crack Surfaces." Shock and Vibration 2017 (2017): 1–16. http://dx.doi.org/10.1155/2017/3751340.
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We model the fluid flow within the crack as one-dimensional flow and assume that the flow is laminar; the fluid is incompressible and accounts for the time-dependent rate of crack opening. Here, we discretise the flow equation by finite volume methods. The extended finite element methods are used for solving solid medium with crack under dynamic loads. Having constructed the approximation of dynamic extended finite element methods, the derivation of governing equation for dynamic extended finite element methods is presented. The implicit time algorithm is elaborated for the time descritisation of dominant equation. In addition, the interaction integral method is given for evaluating stress intensity factors. Then, the coupling model for modelling hydraulic fracture can be established by the extended finite element methods and the finite volume methods. We compare our present numerical results with our experimental results for verifying the proposed model. Finally, we investigate the water pressure distribution along crack surface and the effect of water pressure distribution on the fracture property.
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Ng, Chee Ping, and Melody A. Swartz. "Fibroblast alignment under interstitial fluid flow using a novel 3-D tissue culture model." American Journal of Physiology-Heart and Circulatory Physiology 284, no. 5 (2003): H1771—H1777. http://dx.doi.org/10.1152/ajpheart.01008.2002.
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Interstitial flow is an important component of the microcirculation and interstitial environment, yet its effects on cell organization and tissue architecture are poorly understood, in part due to the lack of in vitro models. To examine the effects of interstitial flow on cell morphology and matrix remodeling, we developed a tissue culture model that physically supports soft tissue cultures and allows microscopic visualization of cells within the three-dimensional matrix. In addition, pressure-flow relationships can be continuously monitored to evaluate the bulk hydraulic resistance as an indicator of changes in the overall matrix integrity. We observed that cells such as human dermal fibroblasts aligned perpendicular to the direction of interstitial flow. In contrast, fibroblasts in static three-dimensional controls remained randomly oriented, whereas cells subjected to fluid shear as a two-dimensional monolayer regressed. Also, the dynamic measurements of hydraulic conductivity suggest reorganization toward a steady state. These primary findings help establish the importance of interstitial flow on the biology of tissue organization and interstitial fluid balance.
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Ferrari, A. "Fluid dynamics of acoustic and hydrodynamic cavitation in hydraulic power systems." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 473, no. 2199 (2017): 20160345. http://dx.doi.org/10.1098/rspa.2016.0345.
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Cavitation is the transition from a liquid to a vapour phase, due to a drop in pressure to the level of the vapour tension of the fluid. Two kinds of cavitation have been reviewed here: acoustic cavitation and hydrodynamic cavitation. As acoustic cavitation in engineering systems is related to the propagation of waves through a region subjected to liquid vaporization, the available expressions of the sound speed are discussed. One of the main effects of hydrodynamic cavitation in the nozzles and orifices of hydraulic power systems is a reduction in flow permeability. Different discharge coefficient formulae are analysed in this paper: the Reynolds number and the cavitation number result to be the key fluid dynamical parameters for liquid and cavitating flows, respectively. The latest advances in the characterization of different cavitation regimes in a nozzle, as the cavitation number reduces, are presented. The physical cause of choked flows is explained, and an analogy between cavitation and supersonic aerodynamic flows is proposed. The main approaches to cavitation modelling in hydraulic power systems are also reviewed: these are divided into homogeneous-mixture and two-phase models. The homogeneous-mixture models are further subdivided into barotropic and baroclinic models. The advantages and disadvantages of an implementation of the complete Rayleigh–Plesset equation are examined.
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Negrini, D., C. Gonano, M. Del Fabbro, and G. Miserocchi. "Transperitoneal fluid dynamics in rabbit liver." Journal of Applied Physiology 69, no. 2 (1990): 625–29. http://dx.doi.org/10.1152/jappl.1990.69.2.625.
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The peritoneal cavity of 18 anesthetized spontaneously breathing supine rabbits was opened through a midline section. One or two hollow capsules (surface area 0.8 cm2) were glued to the exposed liver surface, filled with whole or 25% diluted plasma, and connected to a transducer and a graduated pipette. Various hydraulic pressures (Pcap) were set in the capsule; at each Pcap the liquid flow per unit surface area (V/S) between the Disse's interstitial space and the capsule was measured from the rate of liquid displacement in the pipette. The slope of the V/S vs. Pcap linear regression was utilized to estimate the hydraulic conductivity of the Glissonian-peritoneal membrane and averaged 5.1 x 10(-3) +/- 4.7 x 10(-3) (SD) ml.h-1.cmH2O-1.cm-2 (n = 25). Hydraulic pressure in the Disse's space (Pd) was measured by closing the capsule against the transducer disconnected from the pipette. At portal and hepatic venous pressures of 7.6 +/- 2.9 and 2.6 +/- 1 cmH2O, respectively, Pd was 2.05 +/- 2 cmH2O. Physiologically, Starling pressure gradients cause fluid transfer from the sinusoids to the Disse's space; transperitoneal fluid filtration only occurs through the liver surface that faces the diaphragm, which corresponds to one-fifth of the total hepatic surface.
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Santi, Gian Maria, Daniela Francia, and Francesco Cesari. "Effect of Coriolis Force on Vibration of Annulus Pipe." Applied Sciences 11, no. 3 (2021): 1058. http://dx.doi.org/10.3390/app11031058.
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Annulus pipe conveying fluids have many practical applications, such as hydraulic control lines and aircraft fuel lines. In some applications, these tubes are exposed to high speeds. Normally, this leads to a vibration effect which may be of a catastrophic nature. The phenomenon is not only driven by the centrifugal forces, but an important role is played also by the Coriolis forces. Many theoretical approaches exist for a simple configuration or a complex three-dimensional configuration. Finite element models are tested. This paper provides a numerical technique for solving the dynamics of annulus pipe conveying fluid by means of the mono-dimensional Finite Element Method (FEM). In particular, this paper presents a numerical solution to the equations governing a fluid conveying pipeline segment, where a Coriolis force effect is taken into consideration both for fix and hinge constraint.
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Wang, Shuo, Liaojun Zhang, Guojiang Yin, and Chaonian Guan. "Research on Unsteady Hydraulic Features of a Francis Turbine and a Novel Method for Identifying Pressure Pulsation Transmission Path." Water 11, no. 6 (2019): 1216. http://dx.doi.org/10.3390/w11061216.
Full textAbstract:
It is of significant value to understand the unsteady hydraulic features and pressure pulsation transmission path in the flow channel through a turbine for providing technical support for turbine design and optimization, as well as laying a foundation for analysis of the stability and the coupled vibration of the hydropower house. In this paper, a three-dimensional mechanics–hydraulics–concrete structure coupled numerical model was established to accurately simulate Francis hydraulic machinery, including the high-rotating turbine runner and fixed guide vane, the unsteady flowing water, the structure of the entire flow channel, as well as the dynamic interaction between them. Turbulent hydraulic features of flow condition and pressure pulsation in design operation were explored using the detached eddy simulation (DES) turbulence model. Then, a novel method was proposed to identify the fluid pressure pulsation transmission path based on the time-delayed transfer entropy method and wavelet theory. On basis of time and frequency analysis of pressure calculation results, investigation into identification of pressure pulsation transmission path was performed using the method of traditional transfer entropy and the method adopted in this paper. The pressure pulsation transmission features in the entire flow channel were revealed during operation of the large-scale Francis turbine. The research method and results could not only lay a basis for exploring the structural vibration regularity of the hydropower house but also provide a scientific reference for vibration reduction design of the hydropower house.
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Zhang, J., N. Sinha, M. Ross, and A. E. Tejada-Martínez. "Computational fluid dynamics analysis of the hydraulic (filtration) efficiency of a residential swimming pool." Journal of Water and Health 16, no. 5 (2018): 750–61. http://dx.doi.org/10.2166/wh.2018.110.
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Abstract Hydraulic or filtration efficiency of residential swimming pools, quantified in terms of residence time characteristics, is critical to disinfection and thus important to public health. In this study, a three-dimensional computational fluid dynamics model together with Eulerian and Lagrangian-based techniques are used for investigating the residence time characteristics of a passive tracer and particles in the water, representative of chemicals and pathogens, respectively. The flow pattern in the pool is found to be characterized by dead zone regions where water constituents may be retained for extended periods of times, thereby potentially decreasing the pool hydraulic efficiency. Two return-jet configurations are studied in order to understand the effect of return-jet location and intensity on the hydraulic efficiency of the pool. A two-jet configuration is found to perform on par with a three-jet configuration in removing dissolved constituents but the former is more efficient than the latter in removing or flushing particles. The latter result suggests that return-jet location and associated flow circulation pattern have an important impact on hydraulic efficiency. Thus return-jet configuration should be incorporated as a key parameter in the design of swimming pools complementing current design standards.
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Fuamba, Musandji, Gilles Brosseau, and Éric Mainville. "Determination of head losses in a surge chamber: Robert Bourassa power plant case study." Canadian Journal of Civil Engineering 34, no. 9 (2007): 1038–47. http://dx.doi.org/10.1139/l07-021.
Full textAbstract:
Optimal management of power plant units is achieved when the global efficiency of the units and the minimization of the total hydraulic head losses through the water transportation systems can be combined. Evaluating these hydraulic head losses appears to be very difficult due to the complexity of the flow conditions through the hydraulic structures. A hydraulic energy based method to determine head losses in the surge chamber has been proposed in this paper, as well as a method to manage the opening of units which would optimize the production of electricity. This method was applied to a case study, and successful results have been obtained showing how the head loss varies in the surge chamber.Key words: hydraulic head losses, power plant unit, surge chamber, unit efficiency, three-dimensional flow conditions, turbulent flow models, computational fluid dynamics.
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Zubrilov, G. Yu, V. G. Melnikov, V. A. Zeer, and D. S. Golubtsov. "CALCULATION OF THE HYDRAULIC BOOM LIFTING MECHANISM WHILE LOWERING PROCESS." Russian Automobile and Highway Industry Journal 16, no. 4 (2019): 400–407. http://dx.doi.org/10.26518/2071-7296-2019-4-400-407.
Full textAbstract:
Introduction. The paper considers the throttle regulation providing flow continuity of working fluid for the purpose of cavitations’ prevention. The throttle regulation in a hydraulic actuator of the load-lifting mechanism under the influence of static and dynamic loads taking into account elastic deformations of a hydraulic system while the boom lowering with a load is an important process. The boom lowering is carried out by the working fluid supply in a stocked cavity of a cylinder by the pump of constant productivity; draining of working fluid is made through the one-sided action throttle.Materials and methods. The consumption of working fluid from a piston cavity provided the constant movement speed of the piston without external loading change. Regulation of speed while the boom lowering was carried out by change of effective section of the throttle opening in pressure. The authors used dynamics of hydraulic actuators, mechanisms and machines, resistance of materials and differential equations.Results. The presented technique allowed determining the value of the working fluid pressure and its change in the throttle. Moreover, this technique determined the area of the throttle providing flow continuity while the boom lowering, depending on design features of the kinematic scheme of the loadlifting mechanism, on the mass of the lowered load and technology equipment, on the angular arrow acceleration and on elastic modulus of hydraulic system elements.
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Drtina, P., and M. Sallaberger. "Hydraulic turbines—basic principles and state-of-the-art computational fluid dynamics applications." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 213, no. 1 (1999): 85–102. http://dx.doi.org/10.1243/0954406991522202.
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The present paper discusses the basic principles of hydraulic turbines, with special emphasis on the use of computational fluid dynamics (CFD) as a tool which is being increasingly applied to gain insight into the complex three-dimensional (3D) phenomena occurring in these types of fluid machinery. The basic fluid mechanics is briefly treated for the three main types of hydraulic turbine: Pelton, Francis and axial turbines. From the vast number of applications where CFD has proven to be an important help to the design engineer, two examples have been chosen for a detailed discussion. The first example gives a comparison of experimental data and 3D Euler and 3D Navier-Stokes results for the flow in a Francis runner. The second example highlights the state-of-the-art of predicting the performance of an entire Francis turbine by means of numerical simulation.
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Xie, Chao Yang, Yong Quan Hu, Xing Chen, Ying Chao Ma, Jin Zhou Zhao, and Li Ming Mou. "Fracturing Well Production Dynamic Simulation in Fractured Tight Sandstone Gas Reservoir." Applied Mechanics and Materials 457-458 (October 2013): 410–15. http://dx.doi.org/10.4028/www.scientific.net/amm.457-458.410.
Full textAbstract:
The tight sandstone formation usually has natural fracture, which is the foundation of effective development using hydraulic fracturing. The conventional reservoir productivity simulation method don't adapt to it. In this paper, Warren & Root model was used for describing infinity tight fractured reservoir model with vertical hydraulic fractures. Then, assuming the fracture length and the width does not vary with time and formation pressure, fracture seepage equation was obtained in base of the one-dimensional flow Darcy percolation equation and continuity equation. By Stehfese, a method of numerical inverse transformation, production performance simulation model was established for natural fractured tight sandstone reservoir. Taking for actual example from Daqing oilfield, affection of characteristics of natural fractures and artificial fracture parameters on productivity of natural fractured tight sandstone reservoir were analyzed. Elastic storability ratio has a greater influence than interporosity flow coefficient. It was the core technique for the gas reservoir to effective development by large amount of fluid and low sand ratio.
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Peña-Monferrer, C., C. Gómez-Zarzuela, S. Chiva, R. Miró, G. Verdú, and J. L. Muñoz-Cobo. "On the One-Dimensional Modeling of Vertical Upward Bubbly Flow." Science and Technology of Nuclear Installations 2018 (2018): 1–10. http://dx.doi.org/10.1155/2018/2153019.
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The one-dimensional two-fluid model approach has been traditionally used in thermal-hydraulics codes for the analysis of transients and accidents in water–cooled nuclear power plants. This paper investigates the performance of RELAP5/MOD3 predicting vertical upward bubbly flow at low velocity conditions. For bubbly flow and vertical pipes, this code applies the drift-velocity approach, showing important discrepancies with the experiments compared. Then, we use a classical formulation of the drag coefficient approach to evaluate the performance of both approaches. This is based on the critical Weber criteria and includes several assumptions for the calculation of the interfacial area and bubble size that are evaluated in this work. A more accurate drag coefficient approach is proposed and implemented in RELAP5/MOD3. Instead of using the Weber criteria, the bubble size distribution is directly considered. This allows the calculation of the interfacial area directly from the definition of Sauter mean diameter of a distribution. The results show that only the proposed approach was able to predict all the flow characteristics, in particular the bubble size and interfacial area concentration. Finally, the computational results are analyzed and validated with cross-section area average measurements of void fraction, dispersed phase velocity, bubble size, and interfacial area concentration.
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Shamsuddeen, Mohamed Murshid, Sang-Bum Ma, Sung Kim, et al. "Effect of an Inducer-Type Guide Vane on Hydraulic Losses at the Inter-Stage Flow Passage of a Multistage Centrifugal Pump." Processes 9, no. 3 (2021): 526. http://dx.doi.org/10.3390/pr9030526.
Full textAbstract:
A multistage centrifugal pump was developed for high head and high flow rate applications. A double-suction impeller and a twin-volute were installed at the first stage followed by an impeller, diffuser and return vanes for the next four stages. An initial design feasibility study was conducted using three-dimensional computational fluid dynamics tools to study the performance and the hydraulic losses associated with the design. Substantial losses in head and efficiency were observed at the interface between the first stage volute and the second stage impeller. An inducer-type guide vane (ITGV) was installed at this location to mitigate the losses by reducing the circumferential velocity of the fluid exiting the volute. The ITGV regulated the pre-swirl of the fluid entering the second stage impeller. The pump with and without ITGV is compared at the design flow rate. The pump with ITGV increased the stage head by 63.28% and stage efficiency by 47.17% at the second stage. As a result, the overall performance of the pump increased by 5.78% and 3.94% in head and efficiency, respectively, at the design point. The ITGV has a significant impact on decreasing losses at both design and off-design conditions. An in-depth flow dynamic analysis at the inducer-impeller interface is also presented.