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The Investigation of Rayleigh-Taylor Mixing with a Premixed Layer by BHR Turbulence model

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Advances in Applied Mathematics and Mechanics 2022年第5期14卷 1017-1039页

作者： Yang Song Lili Wang Pei Wang Institute of Applied Physics and Computational Mathematics Beijing 100094China

The Rayleigh-Taylor mixing with a premixed layer is investigated in the present study.ABHR-II Turbulence model is employed to simulate the Rayleigh-Taylor mixing with different premixed layers.The implementation of the BHR-II model is described in detail and validated in canonical problems.Afterwards,the classic Rayleigh-Taylor instability(RTI)with a premixed layer is studied.Effects of density ratio,layer thickness and density profiles on the late time behaviour of classic RTI are analysed,and the results are also compared with ILES data.It turns out that the premixed layer delays the transition time of turbulent mixing.The late time behaviours of different premixed cases show a similar trend with the similarity of their distributions of turbulent kinetic energy.It is also shown that the premixed layer has little effect on the tilted angle in the canonical tilted rig case while the temporal evolution of the turbulent mixing at the early beginning is distinctly influenced by the premixed layer.

关键词： Turbulence model Rayleigh-Taylor instability premixed layer

A dual-eddy EMMS-based Turbulence model for laminar-turbulent transition prediction

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Particuology 2021年第5期19卷 285-298页

作者： Shuyu Guo Limin Wang State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China School of Chemical Engineering University of Chinese Academy of SciencesBeijing 100049China Innovation Academy for Green Manufacture Chinese Academy of SciencesBeijing 100190China

turbulence is a century-old physics problem,and the prediction of laminar-turbulent transition remains a major challenge in computational fluid dynamics(CFD).This paper proposes a new conceptual multiscale-structure flow system consisting of a nonturbulent part and two types of turbulent eddies with different properties.The stability criterion for turbulent transition flows,based on the principle of compromise-in-competition between viscosity and inertia,is used to obtain model closure.The multiscale-structure concept and stability criterion are the characteristics of the dual-eddy energy-minimization multiscale(EMMS)-based Turbulence model.The solved heterogeneous structure parameters and energy dissipation rate are analyzed,which reveal the laminar-turbulent transition process.To validate the dual-eddy EMMS-based Turbulence model,three benchmark problems,namely,the transitional flows over the flat plate boundary layer with zero pressure gradient,NACA0012,and Aerospatiale-A airfoils,were simulated.The simulation was performed by combining the optimized results from the proposed model with the equations of the well-known κ-ω shear stress transfer(SST)Turbulence model.The numerical results show that the dual-eddy EMMS-based Turbulence model improves the prediction in the laminar-turbulent transition process.This demonstrates the soundness of using the multiscale-structure concept in turbulent flows to establish the turbulence transition model by considering the principle of compromise-in-competition between viscosity and inertia.

关键词： Turbulent flows Laminar-turbulent transition EMMS Turbulence model Multiscale structure

Effect of Time Step Size and Turbulence model on the Open Water Hydrodynamic Performance Prediction of Contra-Rotating Propellers

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China Ocean Engineering 2013年第2期27卷 193-204页

作者：王展智熊鹰 College of Naval Architecture and Power Naval University of Engineering

A growing interest has been devoted to the contra-rotating propellers （CRPs） due to their high propulsive efficiency, torque balance, low fuel consumption, low cavitations, low noise performance and low hull vibration. Compared with the single-screw system, it is more difficult for the open water performance prediction because forward and aft propellers interact with each other and generate a more complicated flow field around the CRPs system. The current work focuses on the open water performance prediction of contra-rotating propellers by RANS and sliding mesh method considering the effect of computational time step size and Turbulence model. The validation study has been performed on two sets of contra-rotating propellers developed by David W Taylor Naval Ship R ＆ D center. Compared with the experimental data, it shows that RANS with sliding mesh method and SST k-ω Turbulence model has a good precision in the open water performance prediction of contra-rotating propellers, and small time step size can improve the level of accuracy for CRPs with the same blade number of forward and aft propellers, while a relatively large time step size is a better choice for CRPs with different blade numbers.

关键词： contra-rotating propeller open water performance RANS time step size Turbulence model

Extension of the KDO turbulence/transition model to account for roughness

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Advances in Aerodynamics 2022年第1期4卷 25-38页

作者： Chunfei Fang Jinglei Xu State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development Sinopec Research Institute of Petroleum EngineeringBeijing100029China School of Energy and Power Engineering Beihang UniversityBeijing100191China Hangzhou Innovation Institute Yuhang Beihang UniversityHangzhou311100China

Wall roughness significantly influences both laminar-turbulent transition process and fully developed turbulence.A wall roughness extension for the KDO turbulence/transition model is developed.The roughness effect is introduced via the modification of the k andνt boundary conditions.The wall is considered to be lifted to a higher position.The difference between the original position and the higher position,named as equivalent roughness height,is linked to the actual roughness height.The ratio between the two heights is determined by reasoning.With such a roughness extension,the predictions of the KDO RANS model agree well with the measurements of turbulent boundary layer with a sand grain surface,while the KDO transition model yields accurate cross-flow transition predictions of flow past a 6:1 spheroid.

关键词： Transition model Turbulence model Cross-flow transition Wall roughness

Turbulence model performance for ventilation components pressure losses

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Building Simulation 2022年第3期15卷 389-399页

作者： Karsten Tawackolian Martin Kriegel Hermann-Rietschel-Institut EnergyComfort&Health in BuildingsTU BerlinGermany

This study looks to find a suitable Turbulence model for calculating pressure losses of ventilation components.In building ventilation,the most relevant Reynolds number range is between 3×10^(4) and 6×10^(5),depending on the duct dimensions and airflow rates.Pressure loss coefficients can increase considerably for some components at Reynolds numbers below 2×10^(5).An initial survey of popular Turbulence models was conducted for a selected test case of a bend with such a strong Reynolds number dependence.Most of the Turbulence models failed in reproducing this dependence and predicted curve progressions that were too flat and only applicable for higher Reynolds numbers.Viscous effects near walls played an important role in the present simulations.In Turbulence modelling,near-wall damping functions are used to account for this influence.A model that implements near-wall modelling is the lag elliptic blending k-εmodel.This model gave reasonable predictions for pressure loss coefficients at lower Reynolds numbers.Another example is the low Reynolds number k-εTurbulence model of Wilcox(LRN).The modification uses damping functions and was initially developed for simulating profiles such as aircraft wings.It has not been widely used for internal flows such as air duct flows.Based on selected reference cases,the three closure coefficients of the LRN model were adapted in this work to simulate ventilation components.Improved predictions were obtained with new coefficients(LRNM model).This underlined that low Reynolds number effects are relevant in ventilation ductworks and give first insights for suitable Turbulence models for this application.Both the lag elliptic blending model and the modified LRNM model predicted the pressure losses relatively well for the test case where the other tested models failed.

关键词： HVAC ductwork CFD simulation Turbulence model model calibration

Development of the modified k-ε Turbulence model of power-law fluid for engineering applications

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Science China(Technological Sciences) 2012年第1期55卷 276-284页

作者： RO Kyoungchul RYOU HongSun Department of Mechanical Engineering Chung-Ang University

In the present study,a high Reynolds number version of a Turbulence model was proposed by using drag reduction to analyze the turbulent flows of power-law fluid for engineering applications.In order to determine the model constants in the constitu-tive equation,numerical simulation was conducted under the same conditions that were applied to obtain the experiment re-sults and previous Turbulence models.For validation of the modified Turbulence model,numerical simulations were performed for power-law fluids of different viscosities.The results of the modified k-ε Turbulence model showed better agreement with the experimental results than those of the standard k-ε Turbulence model.In addition,computation time and computer resource of the modified k-ε Turbulence model were reduced by about one third as compared to the low Reynolds number model for power-law fluids.

关键词： power-law fluid turbulent flow drag reduction Turbulence model computational fluid dynamics(CFD)

Computational research on film cooling under rotating frame by an anisotropic Turbulence model

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Propulsion and Power Research 2013年第1期2卷 20-29页

作者： Jianqin Zhu Kai Wang Chaoqun Nie National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics School of Energy and Power EngineeringBeihang UniversityBeijing 100191China Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China

A new anisotropic k-o Turbulence model was proposed in this paper.This new model,with the standard k-o model and the standard k-e model was embedded in our three-dimensional(3-D)Navier-Stokes code to compute rotational film cooling.In addition,the theoretical and numerical analysis on the influence of the Coriolis and buoyancy forces induced by the rotation was discussed in detail.Major findings of this study are as follows:⑴The new anisotropic k-o model preformed much better compared to its isotropic counterparts.(2)In the region of 6D-12D downstream the film hole,the numerical results of the new model were much closer to the experimental data than that in the region of 0-6D.(3)The constant density term can be balanced by the pressure gradient and would not influence the velocity and temperature distributions.But the centrifugal buoyancy force and the Coriolis force would change the trajectory of cooling air and temperature distributions.

关键词： Film cooling Turbulence model Rotation Coriolis force Centrifugal force

Numerical Evaluation of Two k-εTurbulence model for Predicting Flow and Solidification in Continuous Casting Slab

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Journal of Iron and Steel Research(International) 2003年第2期10卷 10-16页

作者： LIU He-ping GAN Yong QIU Sheng-tao Central Iron and Steel Research Institute

A steady three-dimensional fluid flow and solidification model was built based on CFD software by high-Reynolds-number and Lam-Bremhorst low-Reynolds-number k-ε model.During the simulation,the fixed-grid enthalpy-porosity technique was used to represent the solidification,and Darcy law was adopted to simulate the flow in mushy region.The prediction for steel flow and solidification was evaluated by the comparison of two Turbulence models.It is found that both Lam-Bremhorst low-Reynolds-number and high-Reynolds-number k-ε models predict the same trend of the steel flow and temperature distribution.However,due to the effect of turbulent flow on heat transfer,the low-Reynolds-number Turbulence model predicts longer penetration depth of molten steel in sub-mold region,less shell growth and higher shell surface temperature at the narrow face compared with standard k-ε model.

关键词： continuous slab caster solidification steel flow Turbulence model numerical simulation

PARAMETER ESTIMATION OF ENGINEERING Turbulence model

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Acta Mechanica Sinica 2001年第4期17卷 302-309页

作者：钱炜棋蔡金狮 China Aerodynamics Research&Development Center Mianyang 621000 China

A parameter estimation algorithm is introduced and used to determine the parameters in the standard k-epsilon two equation Turbulence model (SKE). It can be found from the estimation results that although the parameter estimation method is an effective method to determine model parameters, it is. difficult to obtain a set of parameters for SKE to suit all kinds of separated flow and a modification of the Turbulence model structure should be considered. So, a new nonlinear k-e two-equation model (NNKE) is put forward in this paper and the corresponding parameter estimation technique is applied to determine the model parameters. By implementing the NNKE to solve some engineering turbulent flows, it is shown that NNKE is more accurate and versatile than SKE. Thus, the success of NNKE implies that the parameter estimation technique may have a bright prospect in engineering Turbulence model research.

关键词： Turbulence model parameter estimation k-epsilon two-equation model