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Journal articles on the topic 'Realizable k-epsilon'
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1
Devade, Kiran Dattatraya, Ashok T. Pise, and Atul R. Urade. "Numerical Analysis of Flow Behavior in Vortex Tube for Different Gases." Mechanical Engineering Research 7, no. 2 (November 28, 2017): 18. http://dx.doi.org/10.5539/mer.v7n2p18.
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The vortex tube is an energy separation device that separates compressed gas stream into a low and a high temperature stream. Present work reports the flow behavior inside the vortex tube for different commonly used fluids with varied properties like Air, He, N2, CO2 and NH3. Flow behavior investigation for three-dimensional short straight-diverging vortex tube is done with CFD code (ANSYS 16.0). Different turbulent models, standard k-epsilon, Realizable k-epsilon and RNG k-epsilon are tested. Realizable k-epsilon model was then used for analysis. Flow behavior of gases with varied multi-atomic number is analyzed and compared with literature. The effect on temperature for N2 is found to be better, followed by He, CO2, Air and NH3. Energy separation for N2 is 46 % higher than all other gases. Energy separation and flow behavior inside vortex tube is analyzed and compared with literature.
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Liu, Lai Guo, Xiao Jun Zhang, and Song Lin Nie. "CFD Flow Model and its Effects on the Calculations of High Pressure Sprays." Applied Mechanics and Materials 553 (May 2014): 174–79. http://dx.doi.org/10.4028/www.scientific.net/amm.553.174.
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The computational fluid dynamics (CFD) model has been used to investigate the two-phase flow phenomena such as high-pressure water jet. High-pressure water jet is a new technology and develops rapidly due to its advantages in recent years. In this research, the effects of different models on the macroscopic parameters of jet propagation characteristics of high pressure water jet have been investigated numerically through the CFD technique. The simulations of the water jet with three kinds of k-ε models (i.e., standard, RNG, and realizable k-ε models) have been compared under the same conditions. It may be concluded that, the results calculated by the realizable k-epsilon model agree well with the experiment data and the realizable k-epsilon model would be utilized in the latter simulation. The agreement of the predicted data and experimental data are quite reasonable, it demonstrates that the CFD technique can be successfully applied to high-pressure water jet.
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Phapatarinan, Satapan, Eakarach Bumrungthaichaichan, and Santi Wattananusorn. "A suitable k-epsilon model for CFD simulation of pump-around jet mixing tank with moderate jet reynolds number." MATEC Web of Conferences 192 (2018): 03010. http://dx.doi.org/10.1051/matecconf/201819203010.
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This paper presents the appropriate turbulence model for predicting the overall mixing time inside an open 45° inclined side entry pump-around jet mixing tank with moderate jet Reynolds number of about 17,515. The model was carefully developed by using appropriate hexahedral grid arrangement and proper numerical methods. The two different k-epsilon turbulence models, including realizable k-epsilon model and low Reynolds number k-epsilon model, were simulated. The overall mixing times predicted by these turbulence models were compared with the previous data reported by Patwardhan (Chem. Eng. Sci. 57 (2002) 1307-1318). The results revealed that the low Reynolds number k-epsilon model was a suitable model for predicting the overall mixing time of jet mixing tank with moderate jet Reynolds number.
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Bacak, Aykut, and Ali Pinarbasi. "Numerical Investigation of Acoustics Performance of Low- Pressure Ducted Axial Fan by Using Different Turbulence Models." ITM Web of Conferences 22 (2018): 01004. http://dx.doi.org/10.1051/itmconf/20182201004.
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In this article, capacity and acoustics parameters of low pressure ducted axial fan is numerically investigated with Realizable k-epsilon, k-w SST and DES turbulence models by using computational fluid dynamics software. One slice of six bladed axial fan operating at 3000 RPM is simulated periodically as low pressure ducted axial ventilation fan. Simulations are run for operating point on the performance curve for each turbulence models. Investigation of acoustics parameters are obtained Ffowcs-Williams Hawkings acoustic model to calculate sound pressure levels for related frequencies. Numerical results are compared with the experimental results provided from blade manufacturer company.
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Guo, Bao Dong, Pei Qing Liu, Qiu Lin Qu, and Yue Li Cui. "Turbulence Models Performance Assessment for Pressure Prediction during Cylinder Water Entry." Applied Mechanics and Materials 224 (November 2012): 225–29. http://dx.doi.org/10.4028/www.scientific.net/amm.224.225.
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Numerical simulations of two-dimensional cylinder free droping into water are presented based on volume of fluid (VOF) method and dynamic mesh technique. Solutions with a time-accurate finite-volume method (FVM) were generated based on the unsteady compressible ensemble averaged Navier-Stokes equations for the air and the unsteady incompressible ensemble averaged Navier-Stokes equations for the water. Computed pressure histories of the cylinder were compared with experimentally measured values. The performance of various turbulence models for pressure prediction was assessed. The results indicate that Realizable k-epsilon model with Enhanced Wall Treatment is the best choice for engineering practice.
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Xu, Benliang, Zuchao Zhu, Zhe Lin, Dongrui Wang, and Guangfei Ma. "Numerical and experimental research on the erosion of solid-liquid two-phase flow in transport butterfly valve based on DEM method." Industrial Lubrication and Tribology 73, no. 4 (May 10, 2021): 606–13. http://dx.doi.org/10.1108/ilt-12-2020-0454.
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Purpose The purpose of this paper is to analyze the mechanism of particle erosion in butterfly valve pipelines under hydraulic transportation conditions. The results will affect the sealing and safety of butterfly valve pipelines and hopefully serve as reference for the anti-erosion design of butterfly valve pipelines. Design/methodology/approach Through the discrete element method (DEM) simulation that considers the force between particles, the detached eddy simulation (DES) turbulence model based on realizable k-epsilon is used to simulate the solid-liquid two-phase flow-induced erosion condition when the butterfly valve is fully opened. The simulation is verified by building an experimental system correctness. The solid-liquid two-phase flow characteristics, particle distribution and erosion characteristics of the butterfly valve pipeline under transportation conditions are studied. Findings The addition of particles may enhance the high-speed area behind the valve. It first increases and then decreases with increasing particle size. With increasing particle size, the low-velocity particles change from being uniformly distributed in flow channel to first gathering in the front of the valve and, then, to gathering in lower part of it. Fluid stagnation at the left arc-shaped flange leads to the appearance of two high-speed belts in the channel. With increasing fluid velocity, high-speed belts gradually cover the entire valve surface by focusing on the upper and lower ends, resulting in the overall aggravation of erosion. Originality/value Considering the complexity of solid-liquid two-phase flow, this is the first time that the DEM method with added inter-particle forces and the DES turbulence model based on realizable k-epsilon has been used to study the flow characteristics and erosion mechanism of butterfly valves under fully open transportation conditions.
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Şumnu, Ahmet, İbrahim Halil Güzelbey, and Orkun Öğücü. "Aerodynamic Shape Optimization of a Missile Using a Multiobjective Genetic Algorithm." International Journal of Aerospace Engineering 2020 (June 8, 2020): 1–17. http://dx.doi.org/10.1155/2020/1528435.
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The aim of this paper is to demonstrate the effects of the shape optimization on the missile performance at supersonic speeds. The N1G missile model shape variation, which decreased its aerodynamic drag and increased its aerodynamic lift at supersonic flow under determined constraints, was numerically investigated. Missile geometry was selected from a literature study for optimization in terms of aerodynamics. Missile aerodynamic coefficient prediction was performed to verify and compare with existing experimental results at supersonic Mach numbers using SST k-omega, realizable k-epsilon, and Spalart-Allmaras turbulence models. In the optimization process, the missile body and fin design parameters need to be estimated to design optimum missile geometry. Lift and drag coefficients were considered objective function. Input and output parameters were collected to obtain design points. Multiobjective Genetic Algorithm (MOGA) was used to optimize missile geometry. The front part of the body, the main body, and tailfins were improved to find an optimum missile model at supersonic speeds. The optimization results showed that a lift-to-drag coefficient ratio, which determines the performance of a missile, was improved about 11-17 percent at supersonic Mach numbers.
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Kumar, Aishvarya, Ali Ghobadian, and Jamshid M. Nouri. "Assessment of Cavitation Models for Compressible Flows Inside a Nozzle." Fluids 5, no. 3 (August 13, 2020): 134. http://dx.doi.org/10.3390/fluids5030134.
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This study assessed two cavitation models for compressible cavitating flows within a single hole nozzle. The models evaluated were SS (Schnerr and Sauer) and ZGB (Zwart-Gerber-Belamri) using realizable k-epsilon turbulent model, which was found to be the most appropriate model to use for this flow. The liquid compressibility was modeled using the Tait equation, and the vapor compressibility was modeled using the ideal gas law. Compressible flow simulation results showed that the SS model failed to capture the flow physics with a weak agreement with experimental data, while the ZGB model predicted the flow much better. Modeling vapor compressibility improved the distribution of the cavitating vapor across the nozzle with an increase in vapor volume compared to that of the incompressible assumption, particularly in the core region which resulted in a much better quantitative and qualitative agreement with the experimental data. The results also showed the prediction of a normal shockwave downstream of the cavitation region where the local flow transforms from supersonic to subsonic because of an increase in the local pressure.
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Stepanov, Borivoj, Ivan Pesenjanski, and Momcilo Spasojevic. "Scandinavian baffle boiler design revisited." Thermal Science 19, no. 1 (2015): 305–16. http://dx.doi.org/10.2298/tsci130508070s.
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The aim of this paper is to examine whether the use of baffles in a combustion chamber, one of the well-known low-cost methods for the boiler performance improvement, can be enhanced. Modern day tools like computational fluid dynamics were not present at the time when these measures were invented, developed and successfully applied. The objective of this study is to determine the influence of location and length of a baffle in a furnace, for different mass flows, on gas residence time. The numerical simulations have been performed of a simple Scandinavian stove like furnace. The isothermal model is used, while air is used as a medium and turbulence is modeled by realizable k-epsilon model. The Lagrange particle tracking is used for the residence time distribution determination. The statistical analysis yielded the average residence time. The results of the computational fluid dynamics studies for different baffle positions, dimensions and flow rates show from up to 17% decrease to up to 13 % increase of residence time. The conclusion is that vertical position of the baffle is the most important factor, followed by the length of the baffle, while the least important showed to be the mass flow.
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Lam, Soo Poey, Abdul Wahab Abas, Saparudin Ariffin, and Woon Kiow Lee. "Numerical Analysis of Single Phase Flow Pressure Drop in a Horizontal Rifled Tube." Applied Mechanics and Materials 110-116 (October 2011): 4398–405. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.4398.
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Numerical analysis by using Fluent® has been carried out to investigate the pressure drop of single phase flow in a 2 meter long of rifled tube and smooth tube which is placed horizontally. The rifled tube or also known as spiral internally ribbed tube that is used in this investigation has an outside diameter 45.0 mm and inside equivalent diameter1 of 33.1 mm while the smooth tube has an outside diameter 45.0 mm and inside diameter 34.1 mm. The working fluid that is used in this investigation is water. In this numerical analysis, realizable k-epsilon model has been chosen to solve the fully developed turbulence flow in both the tubes. The result of the pressure drop which is obtained from simulation shows that the pressure drop in rifled tube is about 1.69-1.77 times much higher than pressure drop in smooth tube. The high pressure drop in rifled tube comparing to smooth tube is due to the helical rib in the rifled tube which causes swirling effect near the wall. A correlation has been proposed for the single phase friction factor of the rifled tube.
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Samiran, N. Afzanizam, A. A. Wahab, Mohd Sofian, and N. Rosly. "Simulation Study on the Performance of Vertical Axis Wind Turbine." Applied Mechanics and Materials 465-466 (December 2013): 270–74. http://dx.doi.org/10.4028/www.scientific.net/amm.465-466.270.
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The present study considered the design improvement of Savonius rotor, in order to increase the efficiency of output power. An investigation was conducted to study the effect of geometrical configuration on the performance of the rotor in terms of coefficient of torque, coefficient of power and power output. Modification of conventional geometry has been designed by combining the effect of number of blades and shielding method. CFD simulation was conducted to analyze the flow characteristic and calculate the torque coefficient of all the rotor configurations. The continuity and Reynolds Averaged Navier-Stokes (RANS) equations and realizable k-ε epsilon turbulence model are numerically solved by commercial software Ansys-Fluent 14.0. The results obtained by transient and steady method for the conventional two bladed Savonius rotor are in agreement with those obtained experimentally by other authors and this indicates that the methods can be successfully applied for such analysis. The modified 3 and 4 bladed rotors with hybrid shielding method gave the highest maximum power coefficient which 0.37 at TSR 0.5 and output power exceed 4 watts with rotor dimensions of 0.2m width and 0.2m height. This blade configuration also is the best configuration by several percentages compared to the other model from the previous study
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Bajracharya, Tri Ratna, Rajendra Shrestha, and Ashesh Babu Timilsina. "Numerical modelling of the sand particle flow in pelton turbine injector." Journal of Engineering Issues and Solutions 1, no. 1 (May 1, 2021): 88–105. http://dx.doi.org/10.3126/joeis.v1i1.36821.
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Pelton turbine is commonly employed high head impulse type turbine. Pelton turbine injector is an integrated part of the Pelton turbine machine which serves the purpose of converting entire pressure energy of water to kinetic energy and also regulates the water flowrate, with partial opening hence governing the power production. Severe erosion in Pelton turbine injector is reported from field setting research studies. Since the jet is atmospheric pressure jet, there is few chances of occurrence of cavitation hence it can be understood that impact of sand particles is the major cause of erosion. Furthermore, with turbine operating in partial flow condition, more erosion is reported in the needle of injector. For a long spear type injector, this study explores the cause of erosion by modeling the motion of the sand particle flow in steady state jet. For numerical modeling of the flow, the realizable k-epsilon model is used and for modeling the particle flow, the Discrete Phase Model (DPM) is used. Three different operating condition of the injector is considered and 77000 particles were injected to the flow domain. It is observed from the numerical simulations that the more sand particle hits the nozzle-needle surface with partial opening of the injector.
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Czetany, Laszlo, and Peter Lang. "Impact of Inlet Boundary Conditions on the Fluid Distribution of Supply Duct." Applied Mechanics and Materials 861 (December 2016): 384–91. http://dx.doi.org/10.4028/www.scientific.net/amm.861.384.
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Ventilation is important to maintain the indoor air quality and other comfort parameters in the occupied zone. The design of ventilation systems is based on one dimensional approach. When the air distribution is modelled in the ventilated space usually CFD simulation is performed and simplified boundary conditions are defined at the locations where the supply air enters the room. However, in some cases it is difficult to predict the duct flow by 1D methods. The flow in the duct system determines the outflow at the air terminal devices. The interaction between the multiple system elements is important, since many different combinations are possible, for instance multiple bends can create a special flow field which also influences the distribution performance of the duct. It is very important to determine this impact, because the room airflow depends on it. In this study the impact of the inlet boundary conditions on the fluid distribution performance of a special supply duct –which is designed to provide uniform distribution– is investigated with CFD. Three different inlet boundary conditions are defined: constant inlet velocity and turbulence parameters estimated from intensity and hydraulic diameter, diffuser after fully developed turbulent pipe flow, diffuser with one bend and a Venturi-tube upstream. In each case, the simulations are performed with the realizable k-epsilon model. The reliability of the results is estimated with the grid convergence index.
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Luan, He, Zhang, Jing, Jin, Geng, and Liu. "Study on the Optimal Wave Energy Absorption Power of a Float in Waves." Journal of Marine Science and Engineering 7, no. 8 (August 13, 2019): 269. http://dx.doi.org/10.3390/jmse7080269.
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The utilization of ocean renewable energy, especially wave energy, is of great significance in ocean engineering. In this study, a three-dimensional numerical wave tank was established to simulate the wave-float interaction based on the Reynolds-averaged Navier–Stokes equations and the Realizable K-Epsilon Two-Layer turbulence model was applied. Firstly, convergence studies with respect to the mesh and time step were carried out and confirmed by the published analytical and numerical data. Then, the resonance condition of a particular float was solved by both numerical and analytical methods. The numerical and the analytical results are mutually verified in good agreements, which verify the reliability of the analytical process. Furthermore, a wave energy converter (WEC) consisting of a single float without damping constant was adopted, and its hydrodynamic performance in different wave conditions was investigated. It was found that the damping factor can affect the motion response of the float and the wave force it receives. Under a certain wavelength condition, the WEC resonates with the wave, at which the wave force on the float, displacement of the float and other parameters reach a maximum value. Finally, the influence of linear damping constant on the power take-off (PTO) was studied. The results show that the damping factor does not affect the wave number turning point of the optimal damping constant.
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Pratyaksa, Md Ranasandhya Amy. "SIMULASI NUMERIK PENGARUH VARIASI RASIO PANJANG LEADING EDGE TERHADAP KARAKTERISTIK AERODINAMIKA PADA MOBIL PICK UP." Otopro 15, no. 2 (May 16, 2020): 45. http://dx.doi.org/10.26740/otopro.v15n2.p45-53.
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The aerodynamic style influences fuel consumption due to drag and the stability of the vehicle speed due to the force lift. Varying the geometry of the leading edge is estimated to have an effect on aerodynamics. This study uses a car pickup model with dimensions like the actual size. Geometry Leading Edge can be modified so that in the variation of the ratio of length leading edge of the vehicle's overall length ( ): ; and . The research method used is a 2-D numerical simulation underconditions steady and unsteady using software ANSYS FLUENT 2019 R3. The mesh using Hybrid model, its triangular and rectangular shape. The viscous model used by k-epsilon Realizable with variation Reynolds Number 7.15 x 104; 2.6 x 106; 3.26 x 106 and 3.91 x 106. The result data analyzed are coefficient lift (CL), coefficient drag (CD), velocity contour, velocity streamline, and pressure contour. From the simulation results, varying ratio of the length of leading edge can affect aerodynamic characteristics of the car. The greater leading edge ratio can delay separation above the car. In addition, the momentum deficit behind the vehicle is also getting smaller. Variation of the length ratio of leading edge is the best variation, having a coefficient drag (CD) of 0.72 with a percentage decrease of 4% and a coefficient lift (CL) of 0.07 with a reduction percentage of 36.36% of the standard variation. CD and CL values go down making fuel consumption more efficient and the car more stable.
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Lvov, Vladislav, and Leonid Chitalov. "Semi-Autogenous Wet Grinding Modeling with CFD-DEM." Minerals 11, no. 5 (May 1, 2021): 485. http://dx.doi.org/10.3390/min11050485.
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The paper highlights the features of constructing a model of a wet semi-autogenous grinding mill based on the discrete element method and computational fluid dynamics. The model was built using Rocky DEM (v. 4.4.2, ESSS, Brazil) and Ansys Fluent (v. 2020 R2, Ansys, Inc., United States) software. A list of assumptions and boundary conditions necessary for modeling the process of wet semi-autogenous grinding by the finite element method is presented. The created model makes it possible to determine the energy-coarseness ratios of the semi-autogenous grinding (SAG) process under given conditions. To create the model in Rocky DEM the following models were used: The Linear Spring Rolling Limit rolling model, the Hysteretic Linear Spring model of the normal interaction forces and the Linear Spring Coulomb Limit for tangential forces. When constructing multiphase in Ansys Fluent, the Euler model was used with the primary phase in the form of a pulp with a given viscosity and density, and secondary phases in the form of air, crushing bodies and ore particles. The resistance of the solid phase to air and water was described by the Schiller–Naumann model, and viscosity by the realizable k-epsilon model with a dispersed multiphase turbulence model. The results of the work methods for material interaction coefficients determination were developed. A method for calculating the efficiency of the semi-autogenous grinding process based on the results of numerical simulation by the discrete element method is proposed.
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Uddin, Ghulam Moeen, Sajawal Gul Niazi, Syed Muhammad Arafat, Muhammad Sajid Kamran, Muhammad Farooq, Nasir Hayat, Sher Afghan Malik, et al. "Neural networks assisted computational aero-acoustic analysis of an isolated tire." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 234, no. 10-11 (May 4, 2020): 2561–77. http://dx.doi.org/10.1177/0954407020915104.
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The computational aero-acoustic study of an isolated passenger car tire is carried out to understand the effect of dimensions of longitudinal tire grooves and operational parameters (velocity and temperature) on tire noise. The computational fluid dynamics and acoustic models are used to obtain aero-acoustic tire noise at near-field and far-field receivers around the tire and artificial neural networks-based regression are used to study the highly non-linear and interactive causal relationships in the system. Unsteady Reynolds-Averaged Navier-Stokes based realizable k-epsilon model is used to solve the flow field in the computational domain. The Ffowcs Williams and Hawkings model is used to obtain aero-acoustic tire noise at far-field positions. Spectral analysis is used to convert the output time domain to frequency domain and to obtain A-weighted sound pressure level. Artificial neural network–based response surface regression is conducted to understand casual relationships between A-weighted sound pressure level and control variables (Groove depth, Groove width, Temperature and velocity). Maximum A-weighted sound pressure level is observed in the wake region of the tire model. The interaction study indicates that ∼10% reduction in the aero-acoustic emissions is possible by selecting appropriate combinations of groove width and groove depth. The interaction of velocity with width is found to be most significant with respect to A-weighted sound pressure level at all receivers surrounding the tire. The interaction of operational parameters, that is, velocity and temperature are found to be significant with respect to A-weighted sound pressure level at wake and front receivers. Therefore, the regional speed limits and seasonal temperatures need to be considered while designing the tire to achieve minimum aero-acoustic emissions.
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Baek, Seung, and Savas Yavuzkurt. "Effects of Flow Oscillations in the Mainstream on Film Cooling." Inventions 3, no. 4 (October 24, 2018): 73. http://dx.doi.org/10.3390/inventions3040073.
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The objective of this study is to investigate the effects of oscillations in the main flow and the coolant jets on film cooling at various frequencies (0 to 2144 Hz) at low and high average blowing ratios. Numerical simulations are performed using LES Smagorinsky–Lilly turbulence model for calculation of the adiabatic film cooling effectiveness and using the DES Realizable k-epsilon turbulence model for obtaining the Stanton number ratios (St/Sto). Additionally, multi-frequency inlet velocities are applied to the main and coolant flows to explore the effects of multi-frequency unsteady flows and the results are compared to those at single frequencies. The results show that at a low average blowing ratio (M = 0.5) if the oscillation frequency is increased from 0 to 180 Hz, the effectiveness decreases and the Stanton number ratio increases. However, when the frequency goes from 180 to 268 Hz, the effectiveness sharply increases and the Stanton number ratio increases slightly. If the frequency changes from 268 to 1072 Hz, the film cooling effectiveness decreases and the Stanton number ratio increases slightly. If the frequency goes from 1072 to 2144 Hz, the film cooling effectiveness climbs up and the Stanton number ratio decreases. The results show that at high average blowing ratio (M = 1.0) the trends of the film cooling effectiveness are similar to those at low blowing ratio (M = 0.5) except from 0 to 90 Hz. If the frequency goes from 0 to 90 Hz at M = 1.0, the film cooling effectiveness increases and the Stanton number ratio decreases. It can be said that it is important to include the effects of oscillating flows when designing film cooling systems for a gas turbine.
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Teli, Shivanand M., and Channamallikarjun S. Mathpati. "Computational fluid dynamics of rectangular external loop airlift reactor." International Journal of Chemical Reactor Engineering 18, no. 5-6 (July 24, 2020). http://dx.doi.org/10.1515/ijcre-2020-0009.
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AbstractThe novel design of a rectangular external loop airlift reactor is at present the most used large-scale reactor for microalgae culture. It has a unique future for a large surface to volume ratio for exposure of light radiation for photosynthesis reaction. The 3D simulations have been performed in rectangular EL-ALR. The Eulerian–Eulerian approach has been used with a dispersed gas phase for different turbulent models. The performance and applicability of different turbulent model’s i.e., K-epsilon standard, K-epsilon realizable, K-omega, and Reynolds stress model are used and compared with experimental results. All drag forces and non-drag forces (turbulent dispersion, virtual mass, and lift coefficient) are included in the model. The experimental values of overall gas hold-up and average liquid circulation velocity have been compared with simulation and literature results. It is seemed to give good agreements. For the different elevations in the downcomer section, liquid axial velocity, turbulent kinetic energy, and turbulent eddy dissipation experimental have been compared with different turbulent models. The K-epsilon Realizable model gives better prediction with experimental results.
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Atmaca, Mustafa, Berkay Çetin, Cüneyt Ezgi, and Ergin Kosa. "CFD analysis of jet flows ejected from different nozzles." International Journal of Low-Carbon Technologies, March 16, 2021. http://dx.doi.org/10.1093/ijlct/ctab022.
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Abstract Nozzles are widely used to control the rate of flow, speed, direction, mass, shape and pressure of the stream in connection with many different engineering applications. This paper presents the performance predicted by a computational fluid dynamic (CFD) model, which are 3D models that utilize parametric analysis, realizable k-epsilon turbulence models and experimental measurement for a jet. Jet flows are ejected from three different slot nozzles: round-shaped nozzle, rectangular-shaped nozzle and 2D-contoured nozzle. In this numerical study, velocities of free jets have been predicted for different axial distances from the nozzle exit in the range of $0.2\le z/B\le 12$ when center velocity at the nozzle exit. CFD simulation results are compared to experimental results from literature. These results are consistent with the existing experiments.
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M.Eng., Harinaldi, Engkos A Kosasih, Damora Rhakasywi, and Rikko Defriadi. "Forced Cooling on a Heated Wall with Impinging Flow Configuration Using Synthetic Jet Actuator Under Combined Wave Excitation." Jurnal Teknologi 58, no. 2 (July 15, 2012). http://dx.doi.org/10.11113/jt.v58.1542.
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This research investigated the forced cooling characterization of an impinging synthetic jet under combined wave excitation. The synthetic jet cooling used an air flowing in a vertical direction into the heated wall. The synthetic jet actuator used two oscilating membranes to push and pull the air from and to the cavity. The main purpose of this synthetic jet was to create vortices pair to come out from nozzle which will accelerate the heat transfer process occurring at the impinged wall. This heat transfer enhancement principles became the basis to simulate an alternative cooling system to substitute the conventional fan cooling in electronic devices application due to its advantage for having a small form factor and low noise. The investigation combined computational and experimental works. The model was simulated to examine the distribution of heat flow on the impinged walls using variation of turbulence model i.e. standard k–epsilon, realizable k–epsilon, standard k–omega and k–omega SST (Shear Stress Transport). Meshing order was elements tri and type pave and the number of grid was 4473 mesh faces to ensure detail discretization and more accurate calculation results. In the experiment the variation of sine and square wave signals were generated with sweep function generators to oscillate the membrane. The frequency of sine wave excitation for the first membrane was kept constant at 80 Hz, meanwhile the second membrane was excitated with varied square wave signals at 80 Hz, 120 Hz, and 160 Hz. Furthermore the velocity amplitude was 0.002 m/s. Some results indicate significant influence of the excitation, and combined waveform to the rate of heat transfer obtained.
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Noume, Hermann Chopkap, Valentin Bomba, Marcel Obounou, Henri Ekobena Fouda, and Flavian Emmanuel Sapnken. "Computational Fluid Dynamics Study of a Nonpremixed Turbulent Flame Using openfoam: Effect of Chemical Mechanisms and Turbulence Models." Journal of Energy Resources Technology 143, no. 11 (February 12, 2021). http://dx.doi.org/10.1115/1.4049740.
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Abstract This article presents a study of the influence of chemical mechanisms and turbulence models on Reynolds-averaged Navier–Stokes (RANS) simulations of the CH4/H2/N2-air turbulent diffusion flame, i.e., the so-called DLR-A flame. The first part of this study is focused on the assessment of the influence of four chemical models on predicted profiles of the DLR-A flame. The chemical mechanisms considered are as follows: (i) a C2 compact skeletal mechanism, which is derived from the GRI3.0 mechanism using an improved multistage reduction method, (ii) a C1 skeletal mechanism containing 41 elementary reactions amongst 16 species, (iii) the global mechanism by Jones and Lindstedt, (iv) and a global scheme consisting of the overall reactions of methane and dihydrogen. RANS numerical results (e.g., velocities, temperature, species, or the heat production rate profiles) obtained running the reactingFOAM solver with the four chemical mechanisms as well as the standard k − ɛ model, the partially stirred reactor (PaSR) combustion model, and the P − 1 radiation model indicate that the C2 skeletal mechanism yields the best agreement with measurements. In the second part of this study, four turbulence models, namely, the standard k − ɛ model, the renormalization group (RNG) k − ɛ model, realizable k − ɛ model, and the k − ω shear stress transport (SST) model, are considered to evaluate their effects on the DLR-A flame simulation results obtained with the C2 skeletal mechanism. Results reveal that the predictions obtained with the standard k − ɛ and the RNG k − ɛ models are in very good agreement with the experimental data. Hence, for simple jet flame with moderately high Reynolds number such as the DLR-A flame, the standard k-epsilon can model the turbulence with a very good accuracy.
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Nowruzi, L., H. Enshaei, J. Lavroff, S. S. Kianejad, and M. R. Davis. "CFD Simulation of Motion Response of a Trimaran in Regular Head Waves." International Journal of Maritime Engineering Part A1 2020 162, A1 (March 1, 2020). http://dx.doi.org/10.3940/rina.ijme.2020.a1.595.
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CFD has proved to be an effective method in solving unsteady Reynolds–Averaged Navier-Stokes (RANS) equations for analysing ships in free surface viscous flow. The research reported in this paper is intended to develop a better understanding of the parameters influencing high-speed trimaran motions responses. Variations of gridding system and time step have been investigated and reliability analysis was performed in solving the RANS equations. Different turbulence models were investigated, and the SST Menter K Omega turbulence model proved a more accurate model than Realizable K-epsilon model. In order to validate the CFD method, the results of the motions response of a highspeed trimaran are compared against a set of experimental and numerical results from a 1.6 m trimaran model tested in various head seas conditions. The results suggest that CFD offers a reliable method for predicting pitch and heave motions of trimarans in regular head waves when compared to traditional low speed strip theory methods. Unlike strip theory, the effect of breaking waves, hull shape above waterline and green seas are considered in CFD application. A wave resonance phenomenon was observed and wave deformation as a result of wave-current-wind interaction in CFD was identified as the main source of discrepancy. The results from this work form the basis for future analysis of trimaran motions in oblique seas for developing a better understanding of the parameters influencing the seakeeping response, as well as passenger comfort.
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Kumar, Aishvarya, Ali Ghobadian, and Jamshid Nouri. "Numerical simulation and experimental validation of cavitating flow in a multi-hole diesel fuel injector." International Journal of Engine Research, February 22, 2021, 146808742199863. http://dx.doi.org/10.1177/1468087421998631.
Full textAbstract:
This study assesses the predictive capability of the ZGB (Zwart-Gerber-Belamri) cavitation model with the RANS (Reynolds Averaged Navier-Stokes), the realizable k-epsilon turbulence model, and compressibility of gas/liquid models for cavitation simulation in a multi-hole fuel injector at different cavitation numbers (CN) for diesel and biodiesel fuels. The prediction results were assessed quantitatively by comparison of predicted velocity profiles with those of measured LDV (Laser Doppler Velocimetry) data. Subsequently, predictions were assessed qualitatively by visual comparison of the predicted void fraction with experimental CCD (Charged Couple Device) recorded images. Both comparisons showed that the model could predict fluid behavior in such a condition with a high level of confidence. Additionally, flow field analysis of numerical results showed the formation of vortices in the injector sac volume. The analysis showed two main types of vortex structures formed. The first kind appeared connecting two adjacent holes and is known as “hole-to-hole” connecting vortices. The second type structure appeared as double “counter-rotating” vortices emerging from the needle wall and entering the injector hole facing it. The use of RANS proved to save significant computational cost and time in predicting the cavitating flow with good accuracy.
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Rentería Peláez, Jorge Luis, Luis Fernando Cardona Sepulveda, and Bernardo Argemiro Herrera Múnera. "Effect of burner angle on the heat transfer of a frit furnace." Revista Facultad de Ingeniería Universidad de Antioquia, February 1, 2021. http://dx.doi.org/10.17533/udea.redin.20210216.
Full textAbstract:
In this work, a numerical analysis was performed about the effect of a flat-flame burner incidence degree on the heat transfer of an industrial scale frit melting furnace, which uses a flat-flame natural gas oxy-combustion burner. The thermal performance of the furnace was evaluated by predicting the temperature distributions, the recirculation of the combustion gases, and the heat flow to the load, using three different geometrical configurations, differing in the inclination of the burner at 0°, 3.5°, 7° with respect to the longitudinal axis. The simulations were carried out using the ANSYS® Fluent software. The Steady Laminar Flamelet (SFM) model, the k-epsilon realizable model, and the discrete ordinates model were used to model combustion, turbulence, and radiation, respectively. The weighted model of the sum of gray gases (WSGGM) was used for the coefficient of absorption of the combustion species. It was observed that the furnace temperature estimated with the simulations is similar to that found in the actual process. Additionally, the simulations showed that for the angle of 7°, the flame collides with the frit, which could generate deposition of frit particles in the internal walls of the furnace; this would affect the emissivity of the refractory material. The 3.5degree angle showed a better distribution of heat flow to the frit and recirculation rate compared to the burner at 0° and 7°.