摘要
方形截面柱体的圆角化处理是常用的流动控制方法,但其流场作用机理尚未被澄清.采用大涡模拟方法,在雷诺数为2.2×104时,考虑风攻角的影响,对均匀流作用下的标准方柱和圆角方柱的气动性能和流场特性进行了研究,定量分析了圆角化气动措施和风攻角变化对分离泡特性的影响规律,从流场角度澄清了圆角化气动措施对方柱气动性能的影响机理.研究表明:与标准方柱相比,圆角方柱的表面风压、气动力和涡脱强度呈整体下降的趋势,但圆角方柱的斯特劳哈尔数更高;圆角方柱的"分离泡流态"发生在更小的风攻角范围内,分离泡的出现会进一步造成方柱的尾流变窄,涡脱强度减弱;随着风攻角的增大,分离泡的长度会逐渐减小直至消失,分离泡的中心会逐渐向方柱前角(迎风向)和方柱壁面移动;与标准方柱相比,圆角方柱的气流发生初次分离的位置向下游移动,分离后的剪切层更贴近方柱,因而更易发生再附现象;方柱尾流宽度的减小和涡脱强度的减弱是导致圆角方柱气动力减小和斯特劳哈尔数增大的主要原因.
Corner rounding modification is commonly used to improve the aerodynamics of a square cylinder.However,its flow mechanism has not been clarified yet.Aerodynamic performances and flow field characteristics of sharp and rounded-corner square cylinders have been investigated using large eddy simulation(LES)in a uniform flow at the Reynolds number of 2.2×10^4.The e ect of attack angle has been evaluated,and characteristics of the shear layer and the separation bubble have been quantitatively analyzed.The physical mechanism behind the corner modification is discussed as well.Results show that the overall surface pressures,aerodynamic forces and vortex shedding intensity of roundedcorner square cylinders have a downward trend in comparison to sharp-corner cylinders.The“separation bubble”flow pattern occurs in a lower attack angle for rounded-corner cylinders.As the increase of the attack angle,the length of the separation bubble decreases until it disappears.Besides,the separation point of rounded-corner cylinders moves downstream,which leads to a thinner shear layer and a narrower wake and a weaker vortex shedding.All these factors result in a reduced drag coecient and an increased Strouhal number of rounded-corner square cylinders.
作者
杜晓庆
田新新
马文勇
李二东
Du Xiaoqing;Tian Xinxin;Ma Wenyong;Li Erdong(Department of Civil Engineering,Shanghai University,Shanghai 200444,China;Wind Engineering and Aerodynamic Flow Control Research Center,Shanghai University,Shanghai 200444,China;Wind Engineering Research Center,Shijiazhuang Tiedao University,Shijiazhuang 050043,China)
出处
《力学学报》
EI
CSCD
北大核心
2018年第5期1013-1023,共11页
Chinese Journal of Theoretical and Applied Mechanics
基金
国家自然科学基金(51578330)
上海市自然科学基金(14ZR1416000)
河北省自然科学基金(E2017210107)资助项目
关键词
方柱绕流
大涡模拟
圆角化处理
气动性能
流场机理
square cylinder
large eddy simulation
rounded-corner
aerodynamic characteristic
flow mechanism
