Grid criteria for numerical simulation of hypersonic aerothermodynamics in transition regime

2019 ◽  
Vol 881 ◽  
pp. 585-601 ◽  
Author(s):  
Xiang Ren ◽  
Junya Yuan ◽  
Bijiao He ◽  
Mingxing Zhang ◽  
Guobiao Cai
Keyword(s):  
Numerical Simulation ◽  
Heat Flux ◽  
Direct Simulation Monte Carlo ◽  
Viscosity Coefficient ◽  
Grid Size ◽  
Navier Stokes ◽  
Transition Flow ◽  
Simulation Accuracy ◽  
Transition Flow Regime ◽  
Cfd Method

Grid is an important factor in numerical simulation of hypersonic aerothermodynamics. This paper introduces three criteria for determining grid size in the transition flow regime when using the computational fluid dynamics (CFD) method or the direct simulation Monte Carlo (DSMC) method. The numerical relationship between these three criteria sizes is deduced according to the one-dimensional fluid theory. Then, the relationship is verified using the CFD method to simulate the flow around a two-dimensional cylinder. At the same time, the dependence of simulation accuracy on grid size in the CFD and DSMC methods is studied and the mechanism is given. The result shows that the simulation accuracy of heat flux especially depends on the normal grid size next to surfaces, where the $Re_{\mathit{cell},w}$ criterion and the $\unicode[STIX]{x1D706}_{w}$ criterion based on local parameters are applicable and equivalent, while the $Re_{\mathit{cell},\infty }$ criterion based on the free-stream parameter is only applicable under the assumption of constant viscosity coefficient and constant temperature wall conditions. On the other hand, the trend of the heat flux changing with grid size obtained by CFD and DSMC is exactly the opposite. Therefore, the grid size must be strictly satisfied with the grid criteria when comparing CFD with DSMC and even the hybrid DSMC with Navier–Stokes method.

Numerical Simulation of Gas Flow Pattern in Cyclone Spray Scrubber

2011 ◽  
Vol 233-235 ◽  
pp. 701-706
Author(s):  
Bing Tao Zhao ◽  
Yi Xin Zhang ◽  
Kai Bin Xiong
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Flow Pattern ◽  
Gas Flow ◽  
Stokes Equations ◽  
Tangential Velocity ◽  
Navier Stokes ◽  
Computational Domain ◽  
Spray Scrubber ◽  
Cfd Method

The numerical simulation of the fluid flow is presented by CFD technique to characterize the flow pattern of cyclone spray scrubber. In this process, the Reynolds-averaged Navier-Stokes equations with the Reynolds stress turbulence model (RSM) for fluid flow are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the fluid computational domain. According to the computational results, the tangential velocity, axial velocity and turbulence intensity of the gas flow are addressed in the different flowrate. The results indicate that the CFD method can effectively reveal the mechanism of gas flow in the cyclone spray scrubber.

Numerical Simulation of Ship Motions in Regular and Irregular Waves

2019 ◽  
Vol 53 (1) ◽  
pp. 97-106
Author(s):  
Bao-Ji Zhang ◽  
Jie Liu ◽  
Ning Xu ◽  
Lei Niu ◽  
Wen-Xuan She
Keyword(s):  
Numerical Simulation ◽  
Wave Length ◽  
Simulation Method ◽  
Irregular Waves ◽  
Navier Stokes ◽  
Ship Motions ◽  
Vof Model ◽  
Split Operator ◽  
Strip Theory ◽  
Cfd Method

AbstractA numerical simulation method is presented in this study to predict ship resistance and motion responses in regular and irregular waves. The unsteady RANS (Reynolds Average Navier-Stokes) method is selected as the governing equation, and a volume of fluid (VoF) model is used to capture the free surface, combining the k-ε equations. A finite volume method (FVM) is utilized to discretize both the RANS equations and VoF transport equation. The pressure implicit split operator (PISO) method is set as the velocity-pressure coupling equation. The overset mesh technique is utilized to simulate ship motions in waves. A DTMB5415 ship is selected as a case study to predict its pitch and heave responses in regular and irregular waves at different wave length and wave steepness. The ship is free to move in the pitch and heave directions. The CFD (Computational Fluid Dynamics) results are found to be in good agreement with the strip theory and experimental data. It can be found that the CFD method presented in this study can provide a theoretical basis and technical support for green design and manufacture of ships.

The planar Couette flow with slip and jump boundary conditions in a microchannel

2016 ◽  
Vol 22 (4) ◽  
Author(s):  
Mohamed Hssikou ◽  
Jamal Baliti ◽  
Mohammed Alaoui
Keyword(s):  
Heat Flux ◽  
Boundary Conditions ◽  
Direct Simulation Monte Carlo ◽  
Ideal Gas ◽  
Navier Stokes ◽  
Heat Conducting ◽  
Direct Simulation ◽  
Dilute Gas ◽  
Viscous Heat ◽  
Simulation Monte Carlo

AbstractThe steady state of a dilute gas enclosed within a rectangular cavity, whose upper and lower sides are in relative motion, is considered in the slip and early transition regimes. The DSMC (Direct simulation Monte Carlo) method is used to solve the Boltzmann equation for analysing a Newtonian viscous heat conducting ideal gas with the slip and jump boundary conditions (SJBC) in the vicinity of horizontal walls. The numerical results are compared with the Navier–Stokes solutions, with and without SJBC, through the velocity, temperature, and normal heat flux profiles. The parallel heat flux and shear stress are also evaluated as a function of rarefaction degree; estimated by the Knudsen number

CFD Study of Propeller Cavitation With Hull-Propeller Interaction

2019 ◽  
Author(s):  
Chang Wei Kang ◽  
Xiuqing Xing
Keyword(s):  
Free Surface ◽  
Flow Field ◽  
High Performance ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Simulation Accuracy ◽  
Eddy Simulation ◽  
Marine Industry ◽  
Propeller Blades ◽  
Cfd Method

Abstract Propeller cavitation is the root cause for noise, hull vibration, as well as erosion on the propeller blades and appendages. Although it is a common practice for marine industry to predict the propeller cavitation by model tests, numerical simulation of propeller performance and the hull-propeller interaction has become feasible with the advancement of high performance computing. In this study, numerical studies of the flow field details around the ship hull with a rotating propeller are performed using Computational Fluid Dynamics (CFD) method by solving the unsteady Reynolds Averaged Navier-Stokes (RANS) equations. The numerical model is developed with commercial software package STAR-CCM+ for the cavitation prediction by considering the hull/propeller interactions and the free surface. Rotating propeller is modeled with an overset mesh, while κ-ω turbulence model is chosen instead of large eddy simulation (LES) or detached eddy simulation (DES) for higher computational efficiency while maintaining satisfied simulation accuracy. Cavitation bubble growth and collapse are estimated using Schnerr-Sauer cavitation model based on Rayleigh-Plesset equation. Simulation results suggest that the model developed in this study is capable to capture the flow field details under the effect of hull-propeller interactions and the free surface. This includes the cavitation emerging position, extinction position, as well as the cavitation patterns on the blade surface at various angular positions. The cavitation induced pressure oscillations on the hull at 1st to 3rd harmonics of Blade Passing Frequency (BPF) are also analyzed. The pressure fluctuation result can provide pressure load information for hull vibration evaluations in future.

scholarly journals Pumping Speed Measurement and Analysis for the Turbo Booster Pump

2004 ◽  
Vol 10 (1) ◽  
pp. 1-13 ◽  
Author(s):  
R. Y. Jou ◽  
S. C. Tzeng ◽  
J. H. Liou
Keyword(s):  
Rarefied Gas ◽  
High Vacuum ◽  
Direct Simulation Monte Carlo ◽  
Transitional Flow ◽  
Transition Flow ◽  
Dsmc Method ◽  
Dsmc Simulation ◽  
Computational Fluid Dynamics Cfd ◽  
Booster Pump ◽  
Cfd Method

This study applies testing apparatus and a computational approach to examine a newly designed spiral-grooved turbo booster pump (TBP), which has both volume type and momentum transfer type vacuum pump functions, and is capable of operating at optimum discharge under pressures from approximately 1000 Pa to a high vacuum. Transitional flow pumping speed is increased by a well-designed connecting element. Pumping performance is predicted and examined via two computational approaches, namely the computational fluid dynamics (CFD) method and the direct simulation Monte Carlo (DSMC) method. In CFD analysis, comparisons of measured and calculated inlet pressure in the slip and continuum flow demonstrate the accuracy of the calculation. Meanwhile, in transition flow, the continuum model of CFD is unsuitable for calculating such rarefied gas. The pumping characteristics for a full 3D model on a rotating frame in transition and molecular regimes thus are simulated using the DSMC method and then confirmed experimentally. However, when the Knudsen number is in the range 0.5 < Kn < 0.1, neither CFD computation nor DSMC simulation is suitable for analyzing the pumping speed of the turbo booster pump. In this situation, the experimental approach is the most appropriate and effective method for analyzing pumping speed. Moreover, the developed pump is tested using assessment systems constructed according to ISO and JVIS-005 standards, respectively. Comparisons are also made with other turbo pumps. The compared results show that the turbo booster pump presented here has good foreline performance.

CFD/Monte Carlo Simulation of Collision-Dominated Gas-Particle Flows Over Bodies

2002 ◽  
Author(s):  
Aleksei N. Volkov ◽  
Yury M. Tsirkunov
Keyword(s):  
Monte Carlo ◽  
Gas Flow ◽  
Stokes Equations ◽  
Particle Interaction ◽  
Direct Simulation Monte Carlo ◽  
Navier Stokes ◽  
Dsmc Method ◽  
Carrier Gas ◽  
Cfd Method ◽  
Energy Equations

An efficient algorithm of numerical simulation of two-way coupled viscous flows of a dusty gas with collisions between particles is described. The flow of a carrier gas which is treated as a continuum is simulated by solving the modified Navier-Stokes equations using a CFD-method. The reverse effect of particles on a gas flow is modelled by the source terms entered into the momentum and energy equations. A dispersed phase is treated as a discrete set of particles which move in the carrier gas and can collide with each other. The particle drag force, the Magnus lift force, the damping torque and the heat exchange are taken into account in gas-particle interaction. Particles are assumed to collide inelastically and frictionally. A modified majorant frequency scheme of the Direct Simulation Monte Carlo (DSMC) method is proposed for computations of flow fields of a collisional “gas” of particles. The developed combined CFD / DSMC method is applied to the study of the supersonic gas-particle flow over a blunt body.

Numerical Simulation and Experiment Research on Aerodynamic Characteristics of a Multi-Blade Centrifugal Fan

2011 ◽  
Vol 317-319 ◽  
pp. 2157-2161
Author(s):  
Yong Chao Zhang ◽  
Qing Guang Chen ◽  
Yong Jian Zhang ◽  
Xiang Xing Jia
Keyword(s):  
Numerical Simulation ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Internal Flow ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Computational Domain ◽  
Centrifugal Fan ◽  
Cfd Method

The full flow field model of a widely used multi-blade centrifugal fan was built, and unstructured grids were used to discrete the computational domain. The moving reference frame is adopted to transfer data between the interfaces of the rotating field and the stationary field. Pressure boundary conditions are specified to the inlet and the outlet. The SIMPLE algorithm in conjunction with the RNG k-ε turbulent model was used to solve the three-dimensional Navier-Stokes equations. The steady and unsteady numerical simulations of the inner flow in the fan at different working conditions were presented using the CFD method. The numerical simulation results were validated by contrasting to the experiment results. The results displayed the characteristics of the velocity field, pressure field, pressure fluctuation at two monitoring points in the centrifugal fan. The results can provide basis for optimizing the fan design and the internal flow, and have important value of engineering applications in the increase of the overall performance in operation.

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