水流绕过二维方形障碍物的湍流数值模拟
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第l6卷6期 2008年l2月
应用基础与工程科学学报
JOURNAL OF BASIC SCIENCE AND ENGINEERING Vo1.16,No.6
Deeember 2008
文章编号:1005-0930(2008)06-0879-12 CLC number:TV133 Document code:A Numerical Prediction of Turbulent Flow past a 2D Surface—mounted Rib
LIU Baicang ,MA Jun ,HUANG Shehua , QIAN Zhongdong ,CHEN Wenxue (1.School of Municipal and Environmental Engineefing,Harbin Institute of Technology,Harbin 150090,China; 2.State Key Laboratory of Water Resource&Hydropower Eng.meering,Wuhan University,Wuhan 430072,China; 3.Department of Hydraulics Research,IWHR,Bering 100038,China)
Abstract:A numerical study was performed for investigating the turbulent flow over a surface—mounted two—dimensional rib using Hybrid Finite Analytic Method(HFAM). The Boussinesq approximation had been used for modehng of the Reynolds stress.A two—equation k-e model with two—layer model was employed.The validity of the numerical method was tested by comparison the numerical predictions with experimental results and numerical simulation results available in literatures,and a good agreement was obtained.The simulation results showed that the two—layer model was suit for modeling the turbulent flow over a square rib and was more accurate than wall function method.Numerical simulation results indicated that upstream of the rib.the length of vo ̄ex I almost had no change with varying rib lengths under the same rib height and flow conditions(Re=1.4×10 ,H=1.0),downstream of the rib.if L/H≥4 the length of vo ̄ex 11 keeps almost unchanged for the varying lengths Keywords:hybdd finite analytic method;two-layer model;turbulent flow;wall function method;surface-mounted rib
Inhomogeneity and anisotropy is the main characteristic of turbulent flow.It’s especially evident in turbulent flow past a SUrface-mounted rib.It was showed that standard k-e model could not simulate turbulent flow over a square rib very well due to its strong shear and strong anisotropy ,so it was very impo ̄ant to study turbulent model that could simulate turbulent flow over a square rib. In order to solve the complicated separation flow,a k-e two—layer model is introduced by Chen and Pate1 E ].The basic idea of this method is that the whole computational domain is
Manuscript received:2007-03-28;Revised:2008-03-26 Foundation item:This work is partially supported by Natural Science Foundation of China(No.59709007);Supported by State Key Laboratory of Urban Water Resource and Environment(08UWQA04). AuthorBriefIntroduction:Liu Baieang(198l一),Male,PhD.E・mail:baiearIgliu@yahoo.coln.ca 880 应用基础与工程科学学报 Vo1.16 divided into two parts:the standard k-8 two—equation model is employed in the far region of the wall,a simplified model is adopted in the near wall region,and the length scale is introduced to be used to instead of solving the troubling 8 equation.The k-e two-layer model overcomes the unreasonable simplification of wall function method in theory.and doesn’t need set very dense meshes in the wall region to solve oo equation.It has the good quality to capture the reverse pressure gradient and separation flow,SO it is expected to work well with turbulent flow over a square rib. For the resistance of the square rib,a significant separation occurs in the front and behind of the rib.Some experiments were conducted to quantify the flow features.The separation length has been measured in the front and behind of the ribL .The velocity and turbulent intensitv in the separation region were also measured .Benodekar et al used nonlinear k-6 mode1 to conduct a series of calculations.The Ji}. two.1ayer model and Finite Volume Method (FVM)were used to study the turbulent flow over a square rib with diferent L/H ratios。。 . Achraya et al[ with ADV measured the averaged velocity and Reynolds stress in the vortices, and employed k-e mode1 with wall function method to simulate the flow.Their calculated averaged velocity profiles and Reynolds stress are less than the experimental results,because the floW in the viscous sublayer and t}le balance relationship are ignored in the wall function method.The turbulent motion details,i.e.ejections,sweep,wailward interaction motions and outward interaction motions of the rib roughened shear layer were investigated using quadrant analysis[引.Turbulent structures and budgets behind permeable ribs were studied[9。
.It is very
meaningful to investigate turbulent flow over square rib due to its importance. The main purpose of this paper is to simulate turbulent flow over a square rib with two’ layer model using HFAM and analyze the characteristics of turbulent flow over a square by comparing with experimental results and the simulated results available in literatures.