不同倒角半径柱体绕流数值模拟及水动力特性分析
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摘要
为研究倒角半径变化对柱体绕流水动力特性的影响,本文使用Fluent软件,采用大涡模拟对雷诺数Re=3 900下的6种不同倒角半径的三维柱体进行了研究。在模型验证基础上,分析了由方柱渐变到圆柱过程中后方流场速度的时均特性及瞬时涡脱落变化规律,给出了不同倒角半径下的升、阻力系数值及无量纲涡脱频率St数。分析结果表明:平均阻力系数随倒角半径的增加而降低,在倒角半径为0.2D时下降速率最大,相较方柱降幅达到50%;升力系数均方根在倒角半径为0.1D~0.2D时变化最显著,减小约93%; St数随倒角半径增加而增大,在倒角半径为0.4D时可达到最大值;回流区长度随倒角半径的增加呈先增大后减小的趋势,其长度在倒角半径为0.2D时达到最大;尾涡宽度在倒角半径为0.0D最大,后随倒角半径增加逐渐下降,且当倒角半径大于0.2D以后变化不大。本文研究结果可为柱体绕流研究及相关工程应用提供参考。
In order to study the influence of the change of rounded radius on the dynamic characteristics of the flow around the cylinder,by using Fluent software and the method of Large Eddy,we simulated the three-dimensional flow around cylinder with 6 different rounded radius under the Reynolds number of 3 900. Based on the model verification,the time-averaged characteristics of the velocity field at the rear and the characteristic of the instantaneous vortex shedding were analyzed. Besides,lift coefficient,drag coefficient and St number were given when the cylinder changed to square column. The results show that with the increase of the rounded radius,the average drag force decreases,especially at 0.2 D,when the drag force decreases by 50% relative to the square. The root-mean-square lift coefficient decreases most significantly from 0.1 D to 0.2 D,during which the reduction was made by near 93%.The St numbers increase with the increase of the rounded radius,and reach the maximum at 0. 4 D. The length of the reflow zone increases at first and reaches the longest length when the rounded radius is 0.2 D,but decreases after then. Tail vortex width reaches the highest at 0.0 D and gradually decreases then,but changes slowly after the rounded radius of 0.2 D. This paper would provide a reference for the research on the flow around the cylinder and related engineering application.
In order to study the influence of the change of rounded radius on the dynamic characteristics of the flow around the cylinder,by using Fluent software and the method of Large Eddy,we simulated the three-dimensional flow around cylinder with 6 different rounded radius under the Reynolds number of 3 900. Based on the model verification,the time-averaged characteristics of the velocity field at the rear and the characteristic of the instantaneous vortex shedding were analyzed. Besides,lift coefficient,drag coefficient and St number were given when the cylinder changed to square column. The results show that with the increase of the rounded radius,the average drag force decreases,especially at 0.2 D,when the drag force decreases by 50% relative to the square. The root-mean-square lift coefficient decreases most significantly from 0.1 D to 0.2 D,during which the reduction was made by near 93%.The St numbers increase with the increase of the rounded radius,and reach the maximum at 0. 4 D. The length of the reflow zone increases at first and reaches the longest length when the rounded radius is 0.2 D,but decreases after then. Tail vortex width reaches the highest at 0.0 D and gradually decreases then,but changes slowly after the rounded radius of 0.2 D. This paper would provide a reference for the research on the flow around the cylinder and related engineering application.
引文
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[14]贾晓荷.单圆柱及双圆柱绕流的大涡模拟[D].上海:上海交通大学,2008.(JIA Xiaohe. Large eddy simulation of flow around one and two circular cylinders[D]. Shanghai:Shanghai Jiao Tong University,2008.(in Chinese))
[15] WORNOM S,OUVRARD H,SALVTTI M V,et al. Variational multiscale large-eddy simulations of the flow past a circular cylinder:Reynolds number effects[J]. Computers&Fluids,2011,47(1):44-50.
[16]战庆亮,周志勇,葛耀君. Re=3900圆柱绕流的三维大涡模拟[J].哈尔滨工业大学学报,2015,47(12):75-79.(ZHAN Qingliang,ZHOU Zhiyong,GE Yaojun. 3-Dimensional large eddy simulation of circular cylinder at Re=3900[J]. Journal of Harbin Institute of Technology,2015,47(12):75-79.(in Chinese))
[17] HUNT J C R,WRAY A A,MOIN P. Eddies,streams and convergence zones in turbulent flows[R].Center for Turbulence Research Report CTR-S88,1988:193-208.
[2] ZHANG WEI,SAMTANEY RAVI. Low-Re flow past an isolated cylinder with rounded corners[J]. Computers and Fluids,2016,136:384-401.
[3] TAMURA T,MIYAGI T. The effect of turbulence on aerodynamic forces on a square cylinder with various corner shapes[J].Journal of Wind Engineering and Industrial Aerodynamics,1999,83:135-145.
[4] CARASSALE LUIGI,FREDA ANDREA,MARRE-BRUNENGHI MICHELA. Experimental investigation on the aerodynamic behavior of square cylinders with rounded corners[J].Journal of Fluids and Structures,2014,44:195-204.
[5] HU J C,ZHOU Y,DALTON C. Effects of the corner radius on the near wake of a square prism[J]. Experiments in Fluids,2006,40:106-118.
[6] TAMURA T,MIYAGI T,KITAGISHI T. Numerical prediction of unsteady pressures on a square cylinder with various corner shapes[J]. Journal of Wind Engineering and Industrial Aerodynamics,1998,74-76:531-542.
[7] LYSENKO D A,ERTESVaG I S,RIAN K E. Large-eddy simulation of the flow over a circular cylinder at reynolds number 3900using the Open FOAM Toolbox[J]. Flow Turbulence Combust,2012,89:491-518.
[8] LOURENCO L M,SHIT C. Characteristics of the plan turbulent near wake of a circular cylinder:A partical image velocimetry study[R]. Private Communication,1993.
[9] ONG L,WALLACE J. The velocity field of the turbulent very near wake of a circular cylinder[J].Experiments in Fluids,1996,20:441-453.
[10] KRAVCHENKO A G,MOIN P. Numerical studies of flow over a circular cylinder at Re D=3900[J].Physics of Fluids,2000,12(2):403-417.
[11]端木玉,万德成.不同长细比圆柱绕流的大涡模拟[J].水动力学研究与进展(A辑),2016,31(3):295-302.(DUAN Muyu,WAN Decheng. Large eddy simulation of flow around the cylinders with different aspects[J]. Journal of Hydrodynamics,A,2016,31(3):295-302.(in Chinese))
[12] SMAGORINSKY J. General circulation experiments with the primitive equations[J].Month Weather Review. 1963,91(3):99-164.
[13]端木玉,万德成.雷诺数为3900时三维圆柱绕流的大涡模拟[J].海洋工程,2016,34(6):11-20.(DUAN Muyu,WAN Decheng. Large-eddy simulation of the flow past a cylinder with Re=3900[J]. The Ocean Engineering,2016,34(6):11-20.(in Chinese))
[14]贾晓荷.单圆柱及双圆柱绕流的大涡模拟[D].上海:上海交通大学,2008.(JIA Xiaohe. Large eddy simulation of flow around one and two circular cylinders[D]. Shanghai:Shanghai Jiao Tong University,2008.(in Chinese))
[15] WORNOM S,OUVRARD H,SALVTTI M V,et al. Variational multiscale large-eddy simulations of the flow past a circular cylinder:Reynolds number effects[J]. Computers&Fluids,2011,47(1):44-50.
[16]战庆亮,周志勇,葛耀君. Re=3900圆柱绕流的三维大涡模拟[J].哈尔滨工业大学学报,2015,47(12):75-79.(ZHAN Qingliang,ZHOU Zhiyong,GE Yaojun. 3-Dimensional large eddy simulation of circular cylinder at Re=3900[J]. Journal of Harbin Institute of Technology,2015,47(12):75-79.(in Chinese))
[17] HUNT J C R,WRAY A A,MOIN P. Eddies,streams and convergence zones in turbulent flows[R].Center for Turbulence Research Report CTR-S88,1988:193-208.