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Journal articles on the topic 'Mesh Velocities'
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1
Löhner, Rainald, and Chi Yang. "Improved ALE mesh velocities for moving bodies." Communications in Numerical Methods in Engineering 12, no. 10 (1996): 599–608. http://dx.doi.org/10.1002/(sici)1099-0887(199610)12:10<599::aid-cnm1>3.0.co;2-q.
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Bakosi, Jozsef, Jacob Waltz, and Nathaniel Morgan. "Improved ALE mesh velocities for complex flows." International Journal for Numerical Methods in Fluids 85, no. 11 (2017): 662–71. http://dx.doi.org/10.1002/fld.4403.
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Bam, Campbell, Daniel N. Wilke, and Schalk Kok. "A generic strategy to obtain semi‐analytical mesh sensitivities/velocities for tetrahedral mesh generators." International Journal for Numerical Methods in Engineering 122, no. 18 (2021): 4944–65. http://dx.doi.org/10.1002/nme.6752.
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Morente, J. A., G. Gimenez, J. A. Porti, and M. Khalladi. "Group and phase velocities in the TLM-symmetrical-condensed node mesh." IEEE Transactions on Microwave Theory and Techniques 42, no. 3 (1994): 514–17. http://dx.doi.org/10.1109/22.277448.
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Vera Duarte, Luis Emilio, Faustino Moreno Gamboa, and José Rafael Eugenio López. "Proposal for improving of paddy rice drying process in dryers inclined pools." Scientia et Technica 26, no. 2 (2021): 146–51. http://dx.doi.org/10.22517/23447214.24554.
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The operation of inclined type dryers for paddy rice is studied to improve their operation and efficiency, considering the variables of drying time, humidity distribution in the rice layer after drying and air velocities within the plenum. Simulating the distribution and velocities of the air flow before crossing the rice layer, the outlet ducts to the plenum are relocated and dampers are placed to distribute the flow evenly. On the other hand, it is proposed to replace the flat-type mesh with a zigzag-type mesh. To verify the proposed modifications, a scale model was built to determine the humidity and drying time variation inside the rice layer, obtaining more uniform moisture percentages within the rice layer and a decrease in drying time.
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Guan, Gong Shun, Bao Jun Bang, and Rui Tao Niu. "Investigation into Damage of AL-Mesh Bumper under Hypervelocity AL-Spheres Impact." Key Engineering Materials 488-489 (September 2011): 202–5. http://dx.doi.org/10.4028/www.scientific.net/kem.488-489.202.
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The aluminum mesh/plate bumper was designed by improving on AL-Whipple shield, and a series of hypervelocity impact tests were practiced with a two-stage light gas gun facility at Harbin Institute of Technology. Impact velocities of Al-spheres were varied between 3.5km/s and 5km/s. The diameters of projectiles were 3.97mm and 6.35mm respectively. The hypervelocity impact characteristics of 5052 aluminum alloy mesh bumper were studied through hypervelocity impact on aluminum mesh/plate bumpers. The fragmentation and dispersal of hypervelocity particle against mesh bumpers varying with material and specification were analyzed. It was found that the mesh wall position, diameter of wire and separation distance arrangement and mesh opening had high influence on the hypervelocity impact characteristic of aluminum mesh/plate shields. At similar impact velocity, hypervelocity impact characteristics comparison with aluminum sheet bumpers of equal areal mass was thrust. The optimized design idea of aluminum mesh/plate bumpers was suggested.
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Guan, Gong Shun, and Rui Tao Niu. "Numerical Simulation of Hypervelocity Impact on Mesh Bumper Causing Fragmentation and Ejection." Key Engineering Materials 525-526 (November 2012): 401–4. http://dx.doi.org/10.4028/www.scientific.net/kem.525-526.401.
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In order to study the fragmentation of projectile and ejection of debris clouds caused by hypervelocity impacting mesh bumper, simulation of aluminum sphere projectile hypervelocity normal impacting aluminum mesh bumper was practiced with SPH arithmetic of LS-DYNA soft. The diameter of projectile was 4mm. Impact velocities of aluminum spheres were varied between 2.2km/s and 6.2km/s. The impact angle was 0°. The relationship between the debris clouds characteristic of projectile and the impact position on aluminum mesh bumper was studied. The effect on fragmentation of projectile from different combination mode of aluminum mesh bumper was analyzed. The results showed that the morphologies of the debris cloud varied with the impact position when a projectile impacted the mesh bumper. The debris clouds as palpus was found, and some local kinetic energy concentrated appeared in the debris clouds. Debris clouds distribution was more uniform when projectile impacted wire across point on the mesh bumper. Debris clouds had more diffuse area and less residual kinetic energy when mesh bumper was combined with interleaving mode. Mesh bumper combined with interleaving mode was helpful in enhancing the protection performance of shields.
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Hu, Zhicheng, and Zhihui Liu. "Heat Conduction Simulation of 2D Moving Heat Source Problems Using a Moving Mesh Method." Advances in Mathematical Physics 2020 (February 11, 2020): 1–16. http://dx.doi.org/10.1155/2020/6067854.
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This paper focuses on efficiently numerical investigation of two-dimensional heat conduction problems of material subjected to multiple moving Gaussian point heat sources. All heat sources are imposed on the inside of material and assumed to move along some specified straight lines or curves with time-dependent velocities. A simple but efficient moving mesh method, which continuously adjusts the two-dimensional mesh dimension by dimension upon the one-dimensional moving mesh partial differential equation with an appropriate monitor function of the temperature field, has been developed. The physical model problem is then solved on this adaptive moving mesh. Numerical experiments are presented to exhibit the capability of the proposed moving mesh algorithm to efficiently and accurately simulate the moving heat source problems. The transient heat conduction phenomena due to various parameters of the moving heat sources, including the number of heat sources and the types of motion, are well simulated and investigated.
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Fahad Anwer, Syed, Syed Mohammed Yahya, Mohammad Athar Khan, and Saif Masood. "On the Thrust Generation from an Elliptic Airfoil in Plunging and Translating Motion at Low Reynolds Numbers." Advanced Science, Engineering and Medicine 12, no. 10 (2020): 1261–71. http://dx.doi.org/10.1166/asem.2020.2711.
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In this paper, numerical simulation elliptic airfoil model, which mimics the biological locomotion, is studied. Elliptic airfoil undergoes a combined plunging and translating at low Reynolds number is simulated by using body fitted coordinate system. The moving mesh in the physical domain is mapped to a regular fixed mesh in the computational domain through a time dependent transformation between the physical and computational co-ordinates. The governing equations of laminar incompressible flow are transformed in the computational plane by incorporating the time dependent transformation, which naturally accounts for the mesh velocities. The transformed equations are discretized on the structured, collocated, o-type elliptic grid using the finite difference methodology. The unsteady equations are marched in time by using a semi-implicit pressure correction (projection) scheme. Along with the time marching of the governing equations, utilizing the mesh velocities and the forward Eulertime integration also moves the mesh points. The effect of Reynolds number (Re) is investigated on the flapping flight propulsion is investigated. It is found that there exists a critical Reynolds number (Rec) for every frequency after which there exists a thrust force. The effect of Rec is related to transformation of neutral wake to thrust generating wake. It is also found that the optimal frequency corresponds to a reduced frequency parameter of 0.7 where a lock in exists. It is also found that this Stc is independent of Re and the mode of vortex shedding is same at Re = 100 and 200 for Stc = 0.7. Further, it is shown that the mode of vortex shedding present is always helpful in thrust generation.
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Kuprat, Andrew, Denise George, Eldon Linnebur, Harold Trease, and R. Kent Smith. "Moving Adaptive Unstructured 3-D Meshes in Semiconductor Process Modeling Applications." VLSI Design 6, no. 1-4 (1998): 373–78. http://dx.doi.org/10.1155/1998/15828.
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The next generation of semiconductor process and device modeling codes will require 3-D mesh capabilities including moving volume and surface grids, adaptive mesh refinement and adaptive mesh smoothing. To illustrate the value of these techniques, a time dependent process simulation model was constructed using analytic functions to return time dependent dopant concentration and time dependent SiO2 volume and surface velocities. Adaptive mesh refinement and adaptive mesh smoothing techniques were used to resolve the moving boron dopant diffusion front in the Si substrate. The adaptive mesh smoothing technique involves minimizing the L2 norm of the gradient of the error between the true dopant concentration and the piecewise linear approximation over the tetrahedral mesh thus assuring that the mesh is optimal for representing evolving solution gradients. Also implemented is constrained boundary smoothing, wherein the moving SiO2/Si interface is represented by moving nodes that correctly track the interface motion, and which use their remaining degrees of freedom to minimize the aforementioned error norm. Thus, optimal tetrahedral shape and alignment is obtained even in the neighborhood of a moving boundary. If desired, a topological “reconnection” step maintains a Delaunay mesh at all times. The combination of adaptive refinement, adaptive smoothing, and mesh reconnection gives excellent front tracking, feature resolution, and grid quality for finite volume/finite element computation.
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Zhang, Xiang Hui, and Jun Li. "Effects of Clothing Ventilative Designs on Thermal Insulation under Varying Wind Conditions." Advanced Materials Research 332-334 (September 2011): 1927–30. http://dx.doi.org/10.4028/www.scientific.net/amr.332-334.1927.
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This paper reports on an experimental investigation of the effects of clothing ventilative designs on thermal comfort measured in terms of thermal insulation. Eight T-shirts with varying areas and locations of mesh fabric were designed and produced for testing on a dry thermal manikin. Clothing thermal insulation of T-shirts was measured under three wind velocities: 0.5, 1 and 2m/s. The results showed that, the areas and locations of ventilation panels affect the total thermal insulation. The T-shirts with larger area of mesh fabric are preferable in terms of releasing more body heat. Among various designs tested, mesh fabrics applied at two vertical side seams can most effectively release heat and moisture from the body. Clothing insulation is also greatly affected by wind.
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Sokołowski, P., and P. G. Kossakowski. "Estimation of the Modulus Fir Wood Reinforced With PBO Fiber Mesh." Archives of Civil Engineering 64, no. 4 (2018): 105–21. http://dx.doi.org/10.2478/ace-2018-0047.
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AbstractThis paper presents the results of preliminary tests for estimating the modulus of elasticity of wooden beams from firs reinforced with PBO fiber mesh. The tests were carried out in the Materials Strength Laboratory at the Kielce University of Technology in Kielce, Poland with PN-EN 408: 2004. The wooden elements were subjected to a four-point bending test with the aim of estimating the elastic modulus when bending, assuming the loading velocities of the loading forces of 5 mm / min. The obtained results show a significant increase in the load-bearing capacity of beams reinforced with PBO mesh.
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Viré, A., J. Xiang, and C. C. Pain. "An immersed-shell method for modelling fluid–structure interactions." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 373, no. 2035 (2015): 20140085. http://dx.doi.org/10.1098/rsta.2014.0085.
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The paper presents a novel method for numerically modelling fluid–structure interactions. The method consists of solving the fluid-dynamics equations on an extended domain, where the computational mesh covers both fluid and solid structures. The fluid and solid velocities are relaxed to one another through a penalty force. The latter acts on a thin shell surrounding the solid structures. Additionally, the shell is represented on the extended domain by a non-zero shell-concentration field, which is obtained by conservatively mapping the shell mesh onto the extended mesh. The paper outlines the theory underpinning this novel method, referred to as the immersed-shell approach. It also shows how the coupling between a fluid- and a structural-dynamics solver is achieved. At this stage, results are shown for cases of fundamental interest.
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Titov, Pavel A. "Simulation of 3D Wave Fields in Inhomogeneous Domain with Complex Topography Using the Lebedev Scheme." Vestnik NSU. Series: Information Technologies 18, no. 4 (2020): 66–85. http://dx.doi.org/10.25205/1818-7900-2020-18-4-66-85.
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Numerical simulation is widely used in the study of wave fields in various media. One of the methods is to divide the domain of interest into elementary volumes and build a finite-difference scheme for numerical implementation. The work assumes that the domain can have a significant curvature of the surface, therefore, the technology of generating a mesh of curved cubes is used. This mesh provides good consistency between the discrete and physical models of the domain. A parallel algorithm is proposed for the numerical solution of a 3D linear system of elasticity theory, expressed via displacement velocities and stresses, using a curvilinear mesh and an explicit difference scheme based on the Lebedev scheme. The simulation results are presented. The calculations were carried out using the resources of the SSCC SB RAS.
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Kim, B. H., G. P. Peterson, and K. D. Kihm. "Analytical and Experimental Investigation of Entrainment in Capillary Pumped Wicking Structures." Journal of Energy Resources Technology 115, no. 4 (1993): 278–86. http://dx.doi.org/10.1115/1.2906433.
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Analytical and experimental investigations were conducted to identify and better understand the parameters that govern the entrainment of liquid droplets in high-velocity gas streams flowing over capillary wicking structures. Using a flow visualization technique, two modes of entrainment were identified and described for high-velocity gas flows over an intermittently interrupted liquid surface. These two modes, roll-wave entrainment and stripping entrainment, were found to correspond to the lower and upper critical gas velocities, respectively. Measurements of the critical gas velocities and the droplet size distribution (Sauter mean diameter) of the entrained sprays were made as a function of the capillary pore size for three different mesh sizes and were compared with several analytical models developed in previous investigations. The flow visualization results indicate that the upper critical velocity is insensitive to variations in the capillary pumping rate provided the capillary pores are properly primed. The experimental results also indicate that the critical velocity for a given mesh is strongly influenced by the mesh dimensions, but that the previously developed criteria for estimating the critical velocity results in an underestimation of the upper critical velocity for all but very small pore sizes. Finally, to resolve this problem a new analytical model for predicting the critical velocity was developed and shown to be accurate for a wide range of capillary pore sizes.
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Kim, A. Ram, Shawn Keshmiri, Weizhang Huang, and Gonzalo Garcia. "Guidance of Multi-Agent Fixed-Wing Aircraft Using a Moving Mesh Method." Unmanned Systems 04, no. 03 (2016): 227–44. http://dx.doi.org/10.1142/s2301385016500084.
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This paper presents a novel guidance logic for multi-agent fixed-wing unmanned aerial systems using a moving mesh method. The moving mesh method is originally designed for use in the adaptive numerical solution of partial differential equations, where a high proportion of mesh points are placed in the regions of large solution variations and few points in the rest of the domain. In this work, the positions of the aircraft are considered as mesh nodes connected to form a triangular mesh in two spatial dimensions. The outer aircraft positions are planned with the reference point algorithm. This logic provides the outer agents moving point positions that are relative to a virtual point position with the desired heading angle and velocity. The inner agents, or interior mesh nodes, are moved with a moving mesh technique to keep the whole mesh as uniform as possible. The moving mesh technique has built-in mechanisms to keep the mesh as uniform as possible and prevent nodes from crossing over or tangling. This property can be seen as an automatic internal collision avoidance mechanism. It also has explicit formulas for nodal velocities, making the technique easy to implement on computer. The mesh nodes are replaced by unmanned aerial systems with nonlinear six degrees of freedom dynamics. The centralized moving mesh guidance is complimented by a decentralized nonlinear predictive controller to control each aircraft. To validate flexibility and coherency of agents and formation, the moving point concept is used in the simulation to follow an arbitrary, linear, sinewave-like, or curvature shaped flight segments. Robustness of the algorithm is also verified where agents were affected by external wind.
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Ha, Soyoung, Chris Snyder, William C. Skamarock, Jeffrey Anderson, and Nancy Collins. "Ensemble Kalman Filter Data Assimilation for the Model for Prediction Across Scales (MPAS)." Monthly Weather Review 145, no. 11 (2017): 4673–92. http://dx.doi.org/10.1175/mwr-d-17-0145.1.
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A global atmospheric analysis and forecast system is constructed based on the atmospheric component of the Model for Prediction Across Scales (MPAS-A) and the Data Assimilation Research Testbed (DART) ensemble Kalman filter. The system is constructed using the unstructured MPAS-A Voronoi (nominally hexagonal) mesh and thus facilitates multiscale analysis and forecasting without the need for developing new covariance models at different scales. Cycling experiments with the assimilation of real observations show that the global ensemble system is robust and reliable throughout a one-month period for both quasi-uniform and variable-resolution meshes. The variable-mesh assimilation system consistently provides higher-quality analyses than those from the coarse uniform mesh, in addition to the benefits of the higher-resolution forecasts, which leads to substantial improvements in 5-day forecasts. Using the fractions skill score, the spatial scale for skillful precipitation forecasts is evaluated over the high-resolution area of the variable-resolution mesh. Skill decreases more rapidly at smaller scales, but the variable mesh consistently outperforms the coarse uniform mesh in precipitation forecasts at all times and thresholds. Use of incremental analysis updates (IAU) greatly decreases high-frequency noise overall and improves the quality of EnKF analyses, particularly in the tropics. Important aspects of the system design related to the unstructured Voronoi mesh are also investigated, including algorithms for handling the C-grid staggered horizontal velocities.
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Kysela, Bohuš, Jiří Konfršt, Ivan Fořt, and Zdeněk Chára. "CFD Simulation of the Discharge Flow from Standard Rushton Impeller." International Journal of Chemical Engineering 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/706149.
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The radial discharge jet from the standard Rushton turbine was investigated by the CFD calculations and compared with results from the Laser Doppler Anemometry (LDA) measurements. The Large Eddy Simulation (LES) approach was employed with Sliding Mesh (SM) model of the impeller motion. The obtained velocity profiles of the mean ensemble-averaged velocity and r.m.s. values of the fluctuating velocity were compared in several distances from the impeller blades. The calculated values of mean ensemble-averaged velocities are rather in good agreement with the measured ones as well as the derived power number from calculations. However, the values of fluctuating velocities are obviously lower from LES calculations than from LDA measurements.
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Tacutu, Laurentiu, Ilinca Nastase, Florin Bode, Angel Dogeanu, and Cristiana Croitoru. "Local and general ventilation system for an operating room with surgeons and patient." E3S Web of Conferences 111 (2019): 06081. http://dx.doi.org/10.1051/e3sconf/201911106081.
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The aim of this study is to determine how the air flow from a unidirectional air flow (UAF) system and a local ventilation system will interact with each other. The study analyzes the air circulation near the operating table at different air flow velocities from both systems. The air flow velocities correspond to the usual range of velocities recommended by norms and guidelines. The research was approached by numerical and experimental studies. The thermal plume of the occupants (patient and surgeon) were measured by Particle Image Velocimetry (PIV) and thermography (IR). The results of the measurements were compared with the results from the numerical case. A mesh independence study was carried out for the numerical case. The study showed that velocities ≥0.2 m/s from the UAF, depending on the height of the room, can overcome the thermal plume generated by a human subject with a moderate activity (100÷120W). The velocities from the local ventilation system need to be higher with at least one step, in accordance with the distance from the ventilation system to the operating wound, in order to avoid disturbances generated from the UAF system.
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Hübner, Madeleine K., Diana N. Michler-Kozma, and Friederike Gabel. "Microplastic concentrations at the water surface are reduced by decreasing flow velocities caused by a reservoir." Fundamental and Applied Limnology / Archiv für Hydrobiologie 194, no. 1 (2020): 49–56. http://dx.doi.org/10.1127/fal/2020/1307.
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Microplastic particles are found globally in all kinds of water bodies posing a serious threat to aquatic organisms and ecosystems. However, plastic concentrations are not homogeneously distributed and can decrease along a river course. Thus, potential sinks need to exist. Dams and reservoirs are proposed to be such potential sinks for microplastics. We investigated plastic concentrations at the water surface upstream and downstream of a reservoir inundated by a wastewater treatment plant effluent by filtering water with a net with 200 μm mesh size. We sampled at flow velocities ranging from 6 cm s –1 to 35 cm s –1 . Upstream of the reservoir significantly higher concentrations of microplastics (19.9 ± 7.3 particles per m –3) than downstream (3.4 ± 2.2 particles per m–3) were identified. Furthermore, the plastic concentrations increased with increasing flow velocities. Hence, reservoirs can be sinks of microplastics as decreased flow velocities may lead to an increased sedimentation or decreased erosion potential. Consequently, flow velocities are critical when identifying plastic loads. Single time or single spot measurements may not well represent plastic loads if flow velocities vary considerably in time or space.
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Prakash, Sujata, and C. Ross Ethier. "Requirements for Mesh Resolution in 3D Computational Hemodynamics." Journal of Biomechanical Engineering 123, no. 2 (2000): 134–44. http://dx.doi.org/10.1115/1.1351807.
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Computational techniques are widely used for studying large artery hemodynamics. Current trends favor analyzing flow in more anatomically realistic arteries. A significant obstacle to such analyses is generation of computational meshes that accurately resolve both the complex geometry and the physiologically relevant flow features. Here we examine, for a single arterial geometry, how velocity and wall shear stress patterns depend on mesh characteristics. A well-validated Navier-Stokes solver was used to simulate flow in an anatomically realistic human right coronary artery (RCA) using unstructured high-order tetrahedral finite element meshes. Velocities, wall shear stresses (WSS), and wall shear stress gradients were computed on a conventional “high-resolution” mesh series (60,000 to 160,000 velocity nodes) generated with a commercial meshing package. Similar calculations were then performed in a series of meshes generated through an adaptive mesh refinement (AMR) methodology. Mesh-independent velocity fields were not very difficult to obtain for both the conventional and adaptive mesh series. However, wall shear stress fields, and, in particular, wall shear stress gradient fields, were much more difficult to accurately resolve. The conventional (nonadaptive) mesh series did not show a consistent trend towards mesh-independence of WSS results. For the adaptive series, it required approximately 190,000 velocity nodes to reach an r.m.s. error in normalized WSS of less than 10 percent. Achieving mesh-independence in computed WSS fields requires a surprisingly large number of nodes, and is best approached through a systematic solution-adaptive mesh refinement technique. Calculations of WSS, and particularly WSS gradients, show appreciable errors even on meshes that appear to produce mesh-independent velocity fields.
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Bonan, Bertrand, Nancy K. Nichols, Michael J. Baines, and Dale Partridge. "Data assimilation for moving mesh methods with an application to ice sheet modelling." Nonlinear Processes in Geophysics 24, no. 3 (2017): 515–34. http://dx.doi.org/10.5194/npg-24-515-2017.
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Abstract. We develop data assimilation techniques for non-linear dynamical systems modelled by moving mesh methods. Such techniques are valuable for explicitly tracking interfaces and boundaries in evolving systems. The unique aspect of these assimilation techniques is that both the states of the system and the positions of the mesh points are updated simultaneously using physical observations. Covariances between states and mesh points are generated either by a correlation structure function in a variational context or by ensemble methods. The application of the techniques is demonstrated on a one-dimensional model of a grounded shallow ice sheet. It is shown, using observations of surface elevation and/or surface ice velocities, that the techniques predict the evolution of the ice sheet margin and the ice thickness accurately and efficiently. This approach also allows the straightforward assimilation of observations of the position of the ice sheet margin.
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Liebold, Frank, Ali A. Heravi, Oliver Mosig, Manfred Curbach, Viktor Mechtcherine, and Hans-Gerd Maas. "Crack Propagation Velocity Determination by High-speed Camera Image Sequence Processing." Materials 13, no. 19 (2020): 4415. http://dx.doi.org/10.3390/ma13194415.
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The determination of crack propagation velocities can provide valuable information for a better understanding of damage processes of concrete. The spatio-temporal analysis of crack patterns developing at a speed of several hundred meters per second is a rather challenging task. In the paper, a photogrammetric procedure for the determination of crack propagation velocities in concrete specimens using high-speed camera image sequences is presented. A cascaded image sequence processing which starts with the computation of displacement vector fields for a dense pattern of points on the specimen’s surface between consecutive time steps of the image sequence chain has been developed. These surface points are triangulated into a mesh, and as representations of cracks, discontinuities in the displacement vector fields are found by a deformation analysis applied to all triangles of the mesh. Connected components of the deformed triangles are computed using region-growing techniques. Then, the crack tips are determined using the principal component analysis. The tips are tracked in the image sequence and the velocities between the time stamps of the images are derived. A major advantage of this method as compared to the established techniques is in the fact that it allows spatio-temporally resolved, full-field measurements rather than point-wise measurements. Furthermore, information on the crack width can be obtained simultaneously. To validate the experimentation, the authors processed image sequences of tests on four compact-tension specimens performed on a split-Hopkinson tension bar. The images were taken by a high-speed camera at a frame rate of 160,000 images per second. By applying the developed image sequence processing procedure to these datasets, crack propagation velocities of about 800 m/s were determined with a precision in the order of 50 m/s.
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Kooij, S. A., A. M. Moqaddam, T. C. de Goede, et al. "Sprays from droplets impacting a mesh." Journal of Fluid Mechanics 871 (May 22, 2019): 489–509. http://dx.doi.org/10.1017/jfm.2019.289.
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In liquid spray applications, the sprays are often created by the formation and destabilization of a liquid sheet or jet. The disadvantage of such atomization processes is that the breakup is often highly irregular, causing a broad distribution of droplet sizes. As these sizes are controlled by the ligament corrugation and size, a monodisperse spray should consist of ligaments that are both smooth and of equal size. A straightforward way of creating smooth and equally sized ligaments is by droplet impact on a mesh. In this work we show that this approach does however not produce monodisperse droplets, but instead the droplet size distribution is very broad, with a large number of small satellite drops. We demonstrate that the fragmentation is controlled by a jet instability, where initial perturbations caused by the injection process result in long-wavelength disturbances that determine the final ligament breakup. During destabilization the crests of these disturbances are connected by thin ligaments which are the leading cause of the large number of small droplets. A secondary coalescence process, due to small relative velocities between droplets, partly masks this effect by reducing the amount of small droplets. Of the many parameters in this system, we describe the effect of varying the mesh size, mesh rigidity, impact velocity and wetting properties, keeping the liquid properties the same by focusing on water droplets only. We further perform lattice Boltzmann modelling of the impact process that reproduces key features seen in the experimental data.
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Grau, Arno, Michael Haeusler, and Wälti Schmitt. "Micro-straining as advanced treatment of wastewater applied to the main wastewater treatment plant in Wiesbaden." Water Science and Technology 29, no. 12 (1994): 237–45. http://dx.doi.org/10.2166/wst.1994.0618.
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Micro-straining as an advance treatment of wastewater has been evaluated in a half as well as full technical unit. Mesh dimensions of 10, 20 and 40 μ have been used, straining velocities between 10 to 35 m/h have been measured and suspended solids retention of 75 – 85 % could be achieved. The investment and operational costs are lower than those of other systems, e.g. sand filtration.
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Su, Wen Yi, and Yu Ren Wu. "Design Optimization of a Rocker-Joint Silent Chain and Sprocket Drive Based on the Mesh Performance Indices." Applied Mechanics and Materials 197 (September 2012): 104–9. http://dx.doi.org/10.4028/www.scientific.net/amm.197.104.
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Improvement on noise, vibration and wear in silent chain drives is always an important research subject. However, design methods revealed in public are few because the silent chain shapes are variable and complex. A feasible design procedure is extremely required for improving transmission performance of chain drives. Therefore, a novel design optimization procedure for the rocker-joint silent (RJS) chain and sprocket drive is proposed in this paper. The mathematical models of geometry generation, tooth contact analysis and impact velocities at different mesh stages and chain raise amount in the RJS chain drive have been established. Besides, impact velocities and raise amount which may produce ill effects in the chine drive are incorporated as a multi-objective function to carry out the global minimization trying to find out the optimal design parameters for RJS chain drives. The single-objective optimization trends have also been verified with the previous references.
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Naves, Juan, Jose Anta, Joaquín Suárez, and Jerónimo Puertas. "Development and Calibration of a New Dripper-Based Rainfall Simulator for Large-Scale Sediment Wash-Off Studies." Water 12, no. 1 (2020): 152. http://dx.doi.org/10.3390/w12010152.
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Rainfall simulators are useful tools for controlling the main variables that govern natural rainfall. In this study, a new drop-forming rainfall simulator, which consists of pressure-compensating dripper grids above a horizontal mesh that breaks and distributes raindrops, was developed to be applied in wash-off experiments in a large-scale physical model of 36 m2. The mesh typology and size, and its distance to drippers, were established through a calibration where rain uniformity and distributions of raindrop sizes and velocities were compared with local natural rainfall. Finally, the rain properties of the final solution were measured for the three rain intensities that the rainfall simulator is able to generate (30, 50 and 80 mm/h), obtaining almost uniform rainfalls with uniformity coefficients of 81%, 89% and 91%, respectively. This, together with the very suitable raindrop size distribution obtained, and the raindrop velocities of around 87.5% of the terminal velocity for the mean raindrop diameter, makes the proposed solution optimal for wash-off studies, where rain properties are key in the detachment of particles. In addition, the flexibility seen in controlling rain characteristics increases the value of the proposed design in that it is adaptable to a wide range of studies.
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Chaudhry, Ahmad Zamir, Guang Pan, and Yao Shi. "Numerical evaluation of the hydrodynamic impact characteristics of the air launched AUV upon water entry." Modern Physics Letters B 34, no. 14 (2020): 2050149. http://dx.doi.org/10.1142/s0217984920501493.
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In this paper, water entry process of air launched AUV is investigated by employing fully coupled finite element method and arbitrary Lagrange–Euler formulation (FEM-ALE) and using penalty coupling technique. Numerical model is established to describe the hydrodynamic characteristics and flow patterns of a high-speed water entry AUV. The effectiveness and accuracy of the numerical simulation are verified quantitatively by the experiments of the earlier study. Selection of suitable advection method and mesh convergence study is carried out during experimental validation process. It is found that appropriate mesh size of impact domain is crucial for numerical simulations and second-order Van Leer advection method is more appropriate for high speed water entry problems. Subsequently, the arbitrary Lagrange–Euler (ALE) algorithm is used to describe the variation laws of the impact load characteristics with water entry velocities, water entry angles and different AUV masses. Dimensionless impact coefficient of AUV at different velocities calculated using ALE method is compared with SPH results. This reveals that ALE method can also simulate the water entry process accurately with less computational cost. This research work can provide beneficial reference information for structure design of AUV and for selection of the water entry parameters.
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Wittbrodt, M. J., and M. J. Pechersky. "A Hydrodynamic Analysis of Fluid Flow Between Meshing Spur Gear Teeth." Journal of Mechanisms, Transmissions, and Automation in Design 111, no. 3 (1989): 395–401. http://dx.doi.org/10.1115/1.3259012.
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A hydrodynamic analysis of the pumping action resulting from the meshing of spur gear teeth was performed. Both compressible (for air) and incompressible (for oil) flow cases were considered. The computed results included the velocity of the fluid at the minimum flow area between the meshing teeth. The pressure and temperature in the mesh region were also computed for the compressible flow case. The velocities were computed as a function of the mesh angle with the pitch line velocity as the normalizing parameter. The calculations required a detailed analysis of the involute geometry to compute the proper mesh region volumes and exit flow areas. For the incompressible calculations with wide face gears, it was found the peak fluid velocity could greatly exceed the pitch line velocity. For the compressible calculations, it was found that sonic conditions could be reached at the minimum flow area leading to the possibility of shock formation downstream of this region. Parametric results for both sets of calculations, including backlash, diametral pitch, and other factors, are presented.
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Tchonkova, Maria. "Solution of two-dimensional vector wave equations via a mixed least squares method." Engineering Computations 32, no. 7 (2015): 1893–907. http://dx.doi.org/10.1108/ec-07-2014-0161.
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Purpose – The purpose of this paper is to present an original mixed least squares method for the numerical solution of vector wave equations. Design/methodology/approach – The proposed approach involves two different types of unknowns: velocities and stresses. The approximate solution to the dynamic elasticity equations is obtained via a minimization of a least squares functional, consisting of two terms: a term, which includes the squared residual of a weak form of the time rate of the constitutive relationships, expressed in terms of velocities and stresses, and a term, which depends on the squared residual of the equations of motion. At each time step the functional is minimized with respect to the velocities and stresses, which for the purpose of this study, are approximated by equal order piece-wise linear polynomial functions. The time discretization is based upon the backward Euler scheme. The displacements are computed from the obtained velocities in terms of a finite difference interpolation. Findings – To test the performance of the method, it has been implemented in original computer codes, using object-oriented logic. One model problem has been solved: propagation of Rayleigh waves. The performed convergence study suggests that the method is convergent for both: velocities and stresses. The obtained results show excellent agreement between the exact and analytical solutions for displacement modes, velocities and stresses. It is observed that this method appears to be stable for the different mesh sizes and time step values. Originality/value – The mixed least squares formulation, described in this paper, serves as a basis for interesting future developments and applications.
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Paulisch, Melanie Cornelia, Marcus Gebhard, David Franzen, et al. "Operando Laboratory X-Ray Imaging of Silver-Based Gas Diffusion Electrodes during Oxygen Reduction Reaction in Highly Alkaline Media." Materials 12, no. 17 (2019): 2686. http://dx.doi.org/10.3390/ma12172686.
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Operando laboratory X-ray radiographies were carried out for imaging of two different silver-based gas diffusion electrodes containing an electroconductive Ni mesh structure, one gas diffusion electrode composed of 95 wt.% Ag and 5 wt.% polytetrafluoroethylene and one composed of 97 wt.% Ag and 3 wt.% polytetrafluoroethylene, under different operating parameters. Thereby, correlations of their electrochemical behavior and the transport of the 30 wt.% NaOH electrolyte through the gas diffusion electrodes were revealed. The work was divided into two parts. In the first step, the microstructure of the gas diffusion electrodes was analyzed ex situ by a combination of focused ion beam technology and synchrotron as well as laboratory X-ray tomography and radiography. In the second step, operando laboratory X-ray radiographies were performed during chronoamperometric measurements at different potentials. The combination of the ex situ microstructural analyses and the operando measurements reveals the impact of the microstructure on the electrolyte transport through the gas diffusion electrodes. Hence, an impact of the Ni mesh structure within the gas diffusion electrode on the droplet formation could be shown. Moreover, it could be observed that increasing overpotentials cause increasing electrolyte transport velocities and faster droplet formation due to electrowetting. In general, higher electrolyte transport velocities were found for the gas diffusion electrode with 97 wt.% Ag in contrast to that with 95 wt.% Ag.
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Sinagra, Marco, Carmelo Nasello, Tullio Tucciarelli, Silvia Barbetta, Christian Massari, and Tommaso Moramarco. "A Self-Contained and Automated Method for Flood Hazard Maps Prediction in Urban Areas." Water 12, no. 5 (2020): 1266. http://dx.doi.org/10.3390/w12051266.
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Water depths and velocities predicted inside urban areas during severe storms are traditionally the final result of a chain of hydrologic and hydraulic models. The use of a single model embedding all the components of the rainfall–runoff transformation, including the flux concentration in the river network, can reduce the subjectivity and, as a consequence, the final uncertainty of the computed water depths and velocities. In the model construction, a crucial issue is the management of the topographic data. The information given by a Digital Elevation Model (DEM) available on a regular grid, as well as all the other elevation data provided by single points or contour lines, allow the creation of a Triangulated Irregular Network (TIN) based unstructured digital terrain model, which provides the spatial discretization for both the hydraulic and the hydrologic models. The procedure is split into four steps: (1) correction of the elevation z* measured in the nodes of a preliminary network connecting the edges with all the DEM cell centers; (2) the selection of a suitable hydrographic network where at least one edge of each node has a strictly descending elevation, (3) the generation of the computational mesh, whose edges include all the edges of the hydrographic network and also other lines following internal boundaries provided by roads or other infrastructures, and (4) the estimation of the elevation of the nodes of the computational mesh. A suitable rainfall–runoff transformation model is finally applied to each cell of the identified computational mesh. The proposed methodology is applied to the Sovara stream basin, in central Italy, for two flood events—one is used for parameter calibration and the other one for validation purpose. The comparison between the simulated and the observed flooded areas for the validation flood event shows a good reconstruction of the urban flooding.
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Gagnon, Louis, Marc J. Richard, and Benoît Lévesque. "SIMULATION OF A ROTATING DEVICE THAT REDUCES THE AERODYNAMIC DRAG OF AN AUTOMOBILE." Transactions of the Canadian Society for Mechanical Engineering 35, no. 2 (2011): 229–49. http://dx.doi.org/10.1139/tcsme-2011-0014.
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A two-dimensional Computational Fluid Dynamics (CFD) analysis of the Ahmed body is performed using the k-omega-SST turbulence model implemented in the OpenFOAM (OF) software. The analysis is then modified to include a rotating paddle wheel which captures energy from the swirl that forms behind the vehicle. The rotating wheel is implemented using a General Grid Interface (GGI) in the mesh. Flow energy is captured by the wheel and the power generated by the wheel reaches 16.1 W at optimal conditions. Overall drag reductions of up to 7.6% are also found as side-effects of the rotating paddle wheel. Computations are run in parallel on a dual core computer. A mesh of 30,000 cells is used. Y+ values on the walls of the vehicle range from 60 to 500. Tests are run at both fixed and variable paddle wheel angular velocities.
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Liu, Jiefeng, Shangxin Yu, Shichang Yang, Yiyi Zhang, Xianhao Fan, and Bing Gao. "Numerical Studies on the Performance of the PCM Mesh-Finned Heat Sink Base on Thermal-Flow Multiphysics Coupling Simulation." Energies 13, no. 18 (2020): 4658. http://dx.doi.org/10.3390/en13184658.
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Operating temperature is an important parameter of thyristors to ensure the stable operation of power electronic devices. Thermal management technology is of great significance for improving the reliability of thyristors. In this study, the performance of a phase change material (PCM) mesh-finned heat sink is investigated for the thermal management of thyristors. A multi-physical coupling model of the PCM mesh-finned heat sink is established to analyze the effects of different power losses, air velocities, heights of fins, and thickness of PCM on the thermal performance of the PCM heat sink. The influence of thermal and flow fields on PCM is considered in this model. Furthermore, the heat sink design is optimized to improve the thermal performance based on the calculation results of thermal network parameters. The results show that the power losses, the air velocity, the height of fins, and the thickness of PCM significantly affect the protection ability of the PCM heat sink. After optimizing the heat sink, the PCM heat sink provides 80 s protection time and 100 s recovery time. The PCM mesh-finned heat sink demonstrated good potential for the thermal management of thyristors.
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Rohr, J. J., E. C. Itsweire, K. N. Helland, and C. W. Van Atta. "An investigation of the growth of turbulence in a uniform-mean-shear flow." Journal of Fluid Mechanics 187 (February 1988): 1–33. http://dx.doi.org/10.1017/s002211208800031x.
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A uniform-mean-gradient shear flow was produced using a ten-layer closed-loop water channel, providing long enough dimensionless flow development times (τ = (x/Ū) (∂ Ū/∂z)) for the turbulence to grow. The rate of growth of the turbulence compares well with similar measurements in wind-tunnel-generated uniform shear flows for which the mean shears and centreline velocities are larger by an order of magnitude. Preliminary investigations were undertaken to study the growth of the turbulent intensity as functions of the mean shear, centreline velocity, and initial disturbance lengthscales. Initial disturbance lengthscales were varied by using grids of different mesh sizes.Turbulent intensities were found to increase nearly linearly with τ. Differences in grid mesh size produce different offsets in the turbulent intensity level, with a larger grid mesh producing a higher positive offset. This offset persists throughout the growth of the turbulent intensity. These observations provide valuable insight in interpreting previous wind-tunnel measurements, in particular the high-shear experiments of Karnik & Tavoularis (1983). Comparison with the theoretical predictions of Tavoularis (1985) allows for an improved universal characterization of evolving turbulence in a uniform mean shear.
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Lee, Ann, Guan H. Yeoh, Victoria Timchenko, and John Reizes. "Numerical Computation and Investigation of the Characteristics of Microscale Synthetic Jets." Modelling and Simulation in Engineering 2011 (2011): 1–8. http://dx.doi.org/10.1155/2011/358940.
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A synthetic jet results from periodic oscillations of a membrane in a cavity. Jet is formed when fluid is alternately sucked into and ejected from a small cavity by the motion of membrane bounding the cavity. A novel moving mesh algorithm to simulate the formation of jet is presented. The governing equations are transformed into the curvilinear coordinate system in which the grid velocities evaluated are then fed into the computation of the flow in the cavity domain thus allowing the conservation equations of mass and momentum to be solved within the stationary computational domain. Numerical solution generated using this moving mesh approach is compared with an experimental result measuring the instantaneous velocity fields obtained by μPIV measurements in the vicinity of synthetic jet orifice 241 μm in diameter issuing into confined geometry. Comparisons between experimental and numerical results on the streamwise component of velocity profiles at the orifice exit and along the centerline of the pulsating jet in microchannel as well as the location of vortex core indicate that there is good agreement, thereby demonstrating that the moving mesh algorithm developed is valid.
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Lindby, T., and J. L. T. Santos. "2-D and 3-D shape optimization using mesh velocities to integrate analytical sensitivities with associative CAD." Structural Optimization 13, no. 4 (1997): 213–22. http://dx.doi.org/10.1007/bf01197449.
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Konovalov, I. A., A. E. Khrobostov, M. A. Legchanov, et al. "Application of the Correlation Velocity Measurements for Hydrodynamic Investigations of Turbulent Coolant Flow in Nuclear Reactor Elements." Devices and Methods of Measurements 11, no. 3 (2020): 196–203. http://dx.doi.org/10.21122/2220-9506-2020-11-3-196-203.
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The method of correlation measurement of the coolant flow rate, widely used for operational diagnostics of nuclear power plants, can be extensively used in research practice. The aim of this work was to apply a correlation method based on the conductometric measurement system with wire-mesh sensors for measuring a coolant flow rate.Insignificant concentration of a salt solution (NaCl or Na2SO4 ) creates a gradient of the conductivity in the flow, which is used as a passive scalar measured by the system. Authors used turbulent pulsations at the interface of two concurrent flows with identical velocities in a square channel as a signal source for the correlation method. The paper presents the methodology of the tests, test facility description, signalto-noise ratio estimation, the results of digital signal processing and comparison of the measured velocities in the model with the flowrate‒averaged velocity determined by the use of flowmeters. The measured velocity values give acceptable agreement for the turbulent flow modes. It was shown that the measurement accuracy drops sharply for low-Reynolds flows.The obtained results were used for flowrate measurements in core-imitator channels of the nuclear reactor test model. The presented paper is an approbation of this approach for its application as part of an test model of a nuclear reactor in order to determine the each duct flow rates in the channels of the core simulator using wire mesh sensors.
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Koutmos, P., and J. J. McGuirk. "Velocity and Turbulence Characteristics of Isothermal Lobed Mixer Flows." Journal of Fluids Engineering 117, no. 4 (1995): 633–38. http://dx.doi.org/10.1115/1.2817315.
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This work describes an experimental and computational study of flows in model multilobed mixers. Laser Velocimetry was used to obtain the velocity and turbulence fields in the downstream mixing duct. Flow development was quantified by examination of the large cross-plane velocities whose direction implied the formation of two streamwise vortices per lobe. A change from coplanar to scarfed geometry increased vortex strength by 25 percent. Vortex cell formation, roll-up and breakdown to fine scale mixing was attained within a distance of 5 lobe heights. The computational investigation of the coplanar configuration adopted a non-aligned mesh to solve the 3-D Reynolds averaged Navier-Stokes equations. The calculations of the lobe and mixing duct flows were coupled to predict the complete mixer. Comparisons between measurements and calculations using a standard k-ε model suggested good qualitative agreement with maximum disagreement of about 20 percent in peak radial velocities.
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Miyamoto, Yoshiaki, Masaki Satoh, Hirofumi Tomita, et al. "Gradient Wind Balance in Tropical Cyclones in High-Resolution Global Experiments." Monthly Weather Review 142, no. 5 (2014): 1908–26. http://dx.doi.org/10.1175/mwr-d-13-00115.1.
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Abstract The degree of gradient wind balance was investigated in a number of tropical cyclones (TCs) simulated under realistic environments. The results of global-scale numerical simulations without cumulus parameterization were used, with a horizontal mesh size of 7 km. On average, azimuthally averaged maximum tangential velocities at 850 (925) hPa in the simulated TCs were 0.72% (1.95%) faster than gradient wind–balanced tangential velocity (GWV) during quasi-steady periods. Of the simulated TCs, 75% satisfied the gradient wind balance at the radius of maximum wind speed (RMW) at 850 and at 925 hPa to within about 4.0%. These results were qualitatively similar to those obtained during the intensification phase. In contrast, averages of the maximum and minimum deviations from the GWV, in all the azimuths at the RMW, achieved up to 40% of the maximum tangential velocity. Azimuthally averaged tangential velocities exceeded the GWV (i.e., supergradient) inside the RMW in the lower troposphere, whereas the velocities were close to or slightly slower than GWV (i.e., subgradient) in the other regions. The tangential velocities at 925 hPa were faster (slower) in the right-hand (left hand) side of the TC motion. When the tangential velocities at the RMW were supergradient, the primary circulation tended to decay rapidly in the vertical direction and slowly in the radial direction, and the eyewall updraft and the RMW were at larger radii. Statistical analyses revealed that the TC with supergradient wind at the RMW at 850 hPa was characterized by stronger intensity, larger RMW, more axisymmetric structure, and an intensity stronger than potential intensity.
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Qian, Peng, and Qianjun Xu. "Development of Embedded Element Technique for Permeability Analysis of Cracked Porous Media." Mathematical Problems in Engineering 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/6713452.
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The widely used approach of mesoscale finite element modeling for permeability analysis is to simulate the matrix and cracks with continuum elements (CE), whereas this process brings technical difficulties in generating a satisfying mesh conformity at the interface. In this work, an alternative method based on embedded element (EE) technique is developed for the prediction of water pressure field and effective permeability in the numerical simulation. Based on the mathematical similarity between elasticity and seepage problems, water pressure can derive from the corresponding displacement through “elastic analogy.” To assess the capability of the EE technique, different cases are simulated and compared with the CE model. The results show that there is a satisfactory agreement in water pressures and velocities between the CE and EE modeling. In the CE model, different factors, such as permeability contrast between matrix and cracks (Kcrack/Kmatrix) and mesh size, are considered. It is obvious to find that results will become stable when Kcrack/Kmatrix reaches 104, and the mesh size has little impact. The effective permeability of 3D porous media with random cracks is evaluated and the results show that the differential method is accurate for 3D permeability analysis when the crack density is not large.
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Hsu, Cheng-Hsing, Jun-Liang Chen, Shan-Chi Yuan, and Kuang-Yuan Kung. "CFD Simulations on the Rotor Dynamics of a Horizontal Axis Wind Turbine Activated from Stationary." Applied Mechanics 2, no. 1 (2021): 147–58. http://dx.doi.org/10.3390/applmech2010009.
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The adaptive dynamic mesh, user-defined functions, and six degrees of freedom (6DOF) solver provided in ANSYS FLUENT 14 are engaged to simulate the activating processes of the rotor of the Grumman WS33 wind system. The rotor is activated from stationary to steady operation driven by a steady or periodic wind flow and its kinematic properties and power generation during the activating processes. The angular velocity and angular acceleration are calculated directly by the post-processed real-time 6DOF solver without presuming a known rotating speed to the computational grid frame. The maximum angular velocity of the rotor is approximately proportional to the driving wind speed, and its maximal angular acceleration is also closely proportional to the square of the driving wind speed. The evolution curves of the normalized rotor angular velocities and accelerations are almost identical due to the self-similarity properties of the rotor angular velocities and accelerations. The angular velocity of the rotor will reach its steady value. One can use these steady angular velocities to predict the mechanical power generations of the rotor. The momentum analysis theory and the blade element momentum method are applied to predicted power generations and reveal good agreements with experimental data in the low wind speed range.
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Han, Wenlong, Yanbin Wang, Jingjing Fan, Yong Li, Xiang Wu, and Yun Yu. "An Experimental Study on Coal Fines Migration during Single Phase Water Flow." Geofluids 2020 (August 14, 2020): 1–13. http://dx.doi.org/10.1155/2020/3974790.
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Coal fines migration and intrusion in coal fractures affect coalbed methane (CBM) wells performance by reducing reservoir permeability and production continuity. Physical simulations are conducted to investigate the permeability variation under different diameter coal fines intrusion at various flow velocities and confining pressures. The results show that the conductivity of fractures is dramatically reduced and hardly recover to its initial condition after coal fines intrusion. The permeability after coal fines intrusion (Pcfi) has no direct correlation with the increase of flooding velocity, while decreases with the increase of confining pressures. The fractures can be totally blocked by coal fines, while penetration also happened during the flooding process, causing permeability fluctuation. The permeability loss rates value for 80-120 mesh coal fines intrusion are generally <60% compared with the initial permeability, including the flow velocity of 2, 3, 4, 6, 8, and 10 mL/min with confining pressure of 6 MPa and the confining pressure of 2, 3, 4, 5, and 6 MPa with flow velocity of 3 mL/min. However, under 120+ mesh coal fines condition, the permeability loss rates are higher than 85% under most flow velocities and confining pressures. When coal fines become smaller, the permeability loss rates decrease to be lower than 45%, and part the coal fines are discharged with the water flow. Thus, coal fines proper dischargement can partly maintain the reservoir permeability during coalbed methane production. The results would be useful in understanding coal fines intrusion behaviors and its controlling strategies during CBM drainage.
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Sabah, Cumali, Mark D. Thomson, Fanzhen Meng, Slava Tzanova, and Hartmut G. Roskos. "Terahertz propagation properties of free-standing woven-steel-mesh metamaterials: Pass-bands and signatures of abnormal group velocities." Journal of Applied Physics 110, no. 6 (2011): 064902. http://dx.doi.org/10.1063/1.3638445.
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Correia, V., and S. J. Judd. "Assessment of the colour removal capability of low-pressure dynamically formed membranes." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 211, no. 1 (1997): 1–10. http://dx.doi.org/10.1177/095440899721100101.
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Experimental work undertaken to explore the aptness of low-pressure dynamically formed membranes (DFMs) for colour removal from dyewastes is reported. Hydrous zirconium oxide-polyacrylic acid (Zr-PAA) membranes have been dynamically formed on a composite, ceramic-metal mesh microfiltration (MF) membrane at pressures and cross-flow velocities below 1.5 MPa and 3 m/s respectively. Resulting membranes were assessed on feed steams containing inorganic salts and commercial direct, acid and basic dyes. Membrane performance, expressed as permeate flux and solute rejection, was quantified under various feedwater conditions of salt and dye concentration, dye type and feed temperature.
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Tchonkova, Maria. "Solution of problems in dynamic elasticity via a mixed least squares method." Engineering Computations 32, no. 3 (2015): 687–704. http://dx.doi.org/10.1108/ec-08-2013-0215.
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Purpose – The purpose of this paper is to present an original mixed least squares method for solving problems in dynamic elasticity. Design/methodology/approach – The proposed approach involves two different types of unknowns: velocities and stresses. The approximate solution to the dynamic elasticity equations is obtained via a minimization of a least squares functional, consisting of two terms: a term, which includes the squared residual of a weak form of the time rate of the constitutive relationships, expressed in terms of velocities and stresses, and a term, which depends on the squared residual of the equations of motion. At each time step the functional is minimized with respect to the velocities and stresses, which for the purpose of this study, are approximated by equal order piece-wise linear polynomial functions. The time discretization is based upon the backward Euler scheme. The displacements are computed from the obtained velocities in terms of a finite difference interpolation. The proposed theoretical formulation is given the general three-dimensional case and is tested numerically on the solution of one-dimensional wave equations. Findings – To test the performance of the method, it has been implemented in an original computer code, using object-oriented logic and written from scratch. Two one-dimensional problems from the mathematical physics, with well-known exact analytical solutions, have been solved. The numerical examples include a forced vibrating spring, fixed at its both ends and a rod, vibrating under its own weight, when one of its ends is fixed and the other is traction-free. The performed convergence study suggests that the method is convergent for both: velocities and stresses. The obtained results show excellent agreement between the exact and analytical solutions for displacement modes, velocities and stresses. It is observed that this method appears to be stable for the different mesh sizes and time step values. Originality/value – The mixed least squares formulation, described in this paper, serves as a basis for interesting future developments and applications to two and three-dimensional problems in dynamic elasticity.
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Guo, Kai, Xiongwei Cui, and Minghao Liu. "A Coupled Lattice Boltzmann-Volume Penalization for Flows Past Fixed Solid Obstacles with Local Mesh Refinement." Mathematical Problems in Engineering 2018 (2018): 1–12. http://dx.doi.org/10.1155/2018/6732082.
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A coupled Lattice Boltzmann-Volume Penalization (LBM-VP) with local mesh refinement is presented to simulate flows past obstacles in this article. Based on the finite-difference LBM, the local mesh refinement is incorporated into the LBM to improve computing efficiency. The volume penalization method is introduced into the LBM by an external forcing term. In the LBM-VP method, the processes of interpolating velocities on the boundaries points and distributing the force density to the Eulerian points near the boundaries are unnecessary. Performing the LBM-VP on a certain point, only the variables of this point are needed, which means the whole procedure can be conducted parallelly. As a consequence, the whole computing efficiency can be improved. To verify the presented method, flows past a single circular cylinder, a pair of cylinders in tandem arrangement, and a NACA-0012 are investigated. A good agreement between the present results and the data in the previous literatures is achieved, which demonstrates the accuracy and effectiveness of the present method to solve the flows past obstacle problems.
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Pasipoularides, Ares D., Ming Shu, Michael S. Womack, Ashish Shah, Olaf von Ramm, and Donald D. Glower. "RV functional imaging: 3-D echo-derived dynamic geometry and flow field simulations." American Journal of Physiology-Heart and Circulatory Physiology 284, no. 1 (2003): H56—H65. http://dx.doi.org/10.1152/ajpheart.00577.2002.
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We describe a novel functional imaging approach for quantitative analysis of right ventricular (RV) blood flow patterns in specific experimental animals (or humans) using real-time, three-dimensional (3-D) echocardiography (RT3D). The method is independent of the digital imaging modality used. It comprises three parts. First, a semiautomated segmentation aided by intraluminal contrast medium locates the RV endocardial surface. Second, a geometric scheme for dynamic RV chamber reconstruction applies a time interpolation procedure to the RT3D data to quantify wall geometry and motion at 400 Hz. A volumetric prism method validated the dynamic geometric reconstruction against simultaneous sonomicrometric canine measurements. Finally, the RV endocardial border motion information is used for mesh generation on a computational fluid dynamics solver to simulate development of the early RV diastolic inflow field. Boundary conditions (tessellated endocardial surface nodal velocities) for the solver are directly derived from the endocardial geometry and motion information. The new functional imaging approach may yield important kinematic information on the distribution of instantaneous velocities in the RV diastolic flow field of specific normal or diseased hearts.
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Chen, Zhi, Chang Le Chen, and Li Mei Hao. "Numerical simulation of facet dendritic growth in a forced flow." Canadian Journal of Physics 87, no. 2 (2009): 117–23. http://dx.doi.org/10.1139/p08-124.
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A numerical simulation based on a new regularized phase-field model is developed to describe the silicon solidification in a forced flow. The effect of forced flow, anisotropy, and mesh grid on dendritic growth shape is investigated. These results indicate that crystals grow into an equiaxial facet dendritic without flow and into an asymmetrical facet dendritic with flow, that is, upstream arm growth is promoted, and downstream inhibited, however, there is no such effect on perpendicular arms. It is also found that the asymmetrical growth feature becomes noticeable with increase in the flow velocity. With the increase in the anisotropy value, the tip velocities of upstream and downstream decrease gradually.
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Boe¨r, C. R., and W. D. Webster. "Direct Upper-Bound Solution and Finite Element Approach to Round-To-Square Drawing." Journal of Engineering for Industry 107, no. 3 (1985): 254–60. http://dx.doi.org/10.1115/1.3185995.
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The paper presents a direct comparison between two modeling techniques of metal forming processes, in the present case wire drawing. The two methods have the same basic approach in using the Upper-Bound Theorem but the solution methods are fundamentally different. One method is a direct analytical solution requiring the knowledge of a kinematically admissible velocity field, the other method uses a finite element approach and calculation of the velocities at the nodes of the mesh. Both methods minimize the power required. The theoretical fundamentals of the two methods, the solution approaches and the results are presented and compared. The advantages and disadvantages of both methods are also analysed.