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Analysis of flow over backward facing step with transition

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Frontiers of Structural and Civil Engineering 2015年第1期9卷 71-81页

作者： Dwarikanath RATHA Arindam SARkAR Civil Engineering Department Thapar University Patiala Punjab 147001 India School of Infrastructure Indian Institute of Technology Bhubaneswar 751013 India

The present study deals with the study of the velocity distribution and the separation phenomenon of flow of air over a two dimensional backward facing step. The flow of air over a backward facing step has been investigated numerically using FLUENT. Flow simulation has been carried out in a backward facing step having an expansion ratio （ratio of the height before and after the step） of 1：1.94 and the results obtained are compared with the published experimental results. Comparison of flow characteristics between steps with three different transitions is made. The variation ofreattachment length for all the three cases are analyzed for wide range of Reynolds number ranging from 100 to 7000 which covers the laminar, transition and turbulent flow of air. Simulation of the flow over steps with expansion ratios of 1：1.24, 1：1.38, 1：1.47, 1：1.53, 1：1.94, 1：2.20 are also carried out to examine the effect of different expansion ratios on the reattachment length. It is found that the primary reattachment length increases with increase in the expansion ratio. The primary reattachment length at the bottom wall downstream of the step is minimum for the step with round edged transition and maximum for the step with a vertical drop transition.

关键词： Reattachment length backward facing step transition flow separation k-ε model

COMPARISON OF k-ε AND k-ω TURBULENCE modelS FOR SIMULATION OF SHALLOW RECIRCULATING FLOWS IN AN OPEN CHANNEL

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Journal of Hydrodynamics 1998年第2期10卷 74-86页

作者： Zhang, Yifan Li, C.W. Nanjing Hydraulic Research Inst Nanjing China

The paper describes the comparison of commonly used k-ε and k-ω turbulence models for simulating the recirculating flows behind a sudden expansion in a straight open channel. The depth-average numerical model and the quasi three-dimensional multilayer model are presented respectively. The governing equations are split into three parts in the finite difference approach: advection, dispersion and propagation. Comparison of the results computed with the k-ε and k-ω models shows that the two turbulence models have strong robustness in simulating the reattachment length of the recirculating flows. The computed results are found in good agreement with the measured data.

关键词： turbulence k-ω modek k-ε model finite difference channel expansion

WAVE INTERACTION WITH PERFORATED CAISSON BREAkWATERS

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Journal of Hydrodynamics 2003年第6期15卷 106-107页

作者： Ph. D. Candidate:Chen Xue-fengState key Laboratory of Offshore and Coastal Engineering, Dalian University of Technology, Dalian116024, China, e-mail: cxfeng @ student, dlut. *** State key Laboratory of Offshore and Coastal Engineering Dalian University of Technology Dalian 116024 China

The reflection coefficient of perforated caissons and the total horizontalforces acting on them were experimentally and numerically analyzed and discussed when wavepropagates normally. To consider the viscosity effect of fluid and nonlinear action of waves onstructures, the VOF (Volume Of Fluid) method combined with the k-ε turbulence model was used tosimulate the interaction between waves and structures. Governing equations were solved with thefinite difference method. Through 2D experimental study in the wave flume, the empiricalrelationship between the reflection coefficient of perforated caissons and the main affectingfactors were obtained from the experimental data using the least square method. Also the correlationbetween the ratio of the total horizontal force acting on perforated caisson and the force actingon solid caisson and the main affecting factors were regressed from the experimental data.

关键词： regular wave irregular wave single―layer perforated caisson double―layerperforated caisson reflection coefficient total horizontal force volume Of fluid (VOF) method k-ε model

Optimal convergence rates for three-dimensional turbulent flow equations

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Applied Mathematics and Mechanics(English Edition) 2013年第5期34卷 637-656页

作者：边东芬郭柏灵 The Graduate School of China Academy of Engineering Physics Institute of Applied Physics and Computational Mathematics

In this paper, the convergence turbulent flow equations are considered. By rates of solutions to the three-dimensional combining the LP-Lq estimate for the linearized equations and an elaborate energy method, the convergence rates are obtained in various norms for the solution to the equilibrium state in the whole space when the initial perturbation of the equilibrium state is small in the H3-framework. More precisely, the optimal convergence rates of the solutions and their first-order derivatives in the L2-norm are obtained when the LP-norm of the perturbation is bounded for some p ε [1, 6）.

关键词： turbulent flow equation k-ε model optimal convergence rate energy estimate

Algebraic-Stress Turbulent model of Planar 2-D Pollutant Transportation in Curvilinear Coordinates

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Engineering Sciences 2005年第3期 70-74页

作者： Wu Xiuguang1, Huang Shichang1, Shen Yongming2, Y k Guo3(1. Zhejiang Institute of Hydraulics & Estuary, Hangzhou 310020 2. State key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024 3. Department of Engineering, University of Aberdeen, Aberdeen AB24 3UE, Uk)

The shallow-water equations and pollutant convective-diffusive equation are transformed into curvilinear coordinate system. The anisotropic algebraic-stress turbulent model is introduced to simulate the turbulence items, and algebraic-stress turbulent model of planar 2-D pollutant convective-diffusive in curvilinear coordinates is build. The meandering channel with measured data of concentration in lab is adopted to validate the model, and the distribution figure of pollutant concentration field calculated through this model and that of the k-ε model, which show the model is superior to k-ε turbulent model in dealing with anisotropy character of flow.

关键词： pollutant curvilinear coordinates anisotropic algebraic-stress turbulent model k-ε model

Drag on a Cylinder with an Apple-Shaped Cross Section

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World Journal of Mechanics 2016年第9期6卷 323-339页

作者： Hirono Matsumoto Yoshihiro kubota Masayuki Ohishi Osamu Mochizuki Graduate School of Biomedical Engineering Toyo University Saitama Japan Faculty of Science and Engineering Toyo University Saitama Japan Daikirika kogyo Inc. Saitama Japan Department of Biomedical Engineering Toyo University Saitama Japan

The drag on a cylinder with an apple-shaped cross section was studied numerically in this paper. This cross section is adopted because the drag on an apple is known to be lower than that of a sphere. Since the hollows of an apple seem to be points of drag reduction, two-dimensional numerical simulations of cylinders with hollows of several shapes are carried out at a Reynolds number of 6.7 × 104 by using the vortex method to check their effects. The cylinder with hollows like those of a real apple attained a 13% reduction in drag compared with a circular cylinder. Other geometrical hollow-shapes, namely, V-shaped and U-shaped grooves, also reduced drag from the circular model, but these effects were less pronounced than those of the apple-shaped cross section. It was concluded that an apple-like hollows were effective for drag reduction of a cylin-der as well as a sphere.

关键词： Drag Reduction Apple Cylinder Vortex Method k-ε model Flow Visualization

Computing Depth-averaged Flows Using Boundary-fitted Coordinates and Staggered Grids

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Tsinghua Science and Technology 2000年第2期5卷 226-230页

作者：洪益平周雪漪陈永灿余常昭 Department of Hydraulic and Hydropower Engineering Tsinghua University Beijing 100084 China

A depth averaged nonlinear k ε model for turbulent flows in complex geometries has been developed in a boundary fitted coordinate system. The SIMPLEC procedure is used to develop an economical discrete method for staggered grids to analyze flows in a 90° bend. This paper describes how to change a program in rectangular coordinate into a boundary fitted coordinate. The results compare well with experimental data for flow in a meandering channel showing the efficiency of the model and the discrete method.

关键词： depth-averaged k-ε model boundary-fitted coordinates staggered grid meandering channel

Aerodynamic Wing Design with CFD for Formula Student Vehicle

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Aerodynamic Wing Design with CFD for Formula Student Vehicle

Analysis of Flow Performances Through Annular Curved Diffusing Duct Using CFD

2020中国汽车工程学会年会暨展览会

作者： Xu Wenzhuo Lu Jiayu Liu Yanbo Zhang Hanwen Mei Hongfei School of Mechanical Engineering Shanghai Jiao Tong University SJTU Racing Team Shanghai Jiao Tong University School of Aeronautics and Astronautics Shanghai Jiao Tong University Teaching development and Student Innovation Center of SEIEE Shanghai Jiao Tong University University of Michigan-Shanghai Jiao Tong University Joint Institute

In this article,a model was constructed based on k-ε turbulence model to simulate the aerodynamic behavior of wing components.A new mesh configuration consisting of three different sizes and density was designed to achieve balance between robust calculation and computational *** process with numerical simulation was presented for aerodynamic design of a Formula Student vehicle,dynamic performances of 8 different configurations for front wing and 5 different configurations for rear wing were evaluated *** were made to maximize downforce while minimizing drag and obtaining good aerodynamic *** the end,a complete set of front wing design with lift coefficient C of-3.21 and rear wing design with lift coefficient of-2.7 at 15 m/s was presented,and a complete simulation model was constructed to evaluate aerodynamic effects on our entire vehicle.

关键词： formula student aerodynamics computational fluid dynamics k-ε model

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Analysis of Flow Performances Through Annular Curved Diffusi...