倒角切角对方柱气动性能影响的大涡模拟研究

倒角和切角措施对方柱的气动力及流场影响很大,常作为方柱流动控制的手段,采用大涡模拟方法,以雷诺数22000的方柱为研究对象,考虑了角部措施(角部变化率10%)的影响,对均匀流场下标准方柱、倒角和切角方柱周围流场及气动性能进行了模拟研究。通过将标准方柱大涡模拟结果与相关文献的试验和数值模拟结果对比,验证了该方法及参数取值的有效性;研究分析了倒角和切角措施对方柱风压分布和气动力的影响,并着重从时均流场和瞬态流场角度分析了角部处理措施对方柱气动性能的影响机理。结果表明,倒角和切角措施对方柱表面风压分布和气动力均有一定影响,其中对方柱表面流动分离区的风压系数影响更为显著。采用角部处理措施后,方柱前缘角区的流动分离受到影响,分离剪切层扩散角更小,侧面的分离涡更贴近壁面,从而在方柱侧面形成再附,尾流变窄,旋涡脱落频率成分更为复杂,使得方柱的平均阻力系数更小,气动力脉动强度更弱,旋涡脱落频率更高、强度更弱。

Large eddy simulation for effects of chamfering and corner cut on aerodynamic performance of square cylinder

Due to remarkable effects of chamfering and corner cut measures on aerodynamic force and flow field of a square cylinder,the two measures are commonly taken as means of flow control of square cylinder.Here,the large eddy simulation method was adopted to study aerodynamic performance and flow field of a standard square cylinder,and other two ones with chamfering and corner cut,respectively under the condition of uniform flow field considering Reynolds number for three square cylinders of 22000,and effects of the two measures with angle change ratio of 10%.Firstly,the large eddy simulation results of the standard square cylinder were compared with the test and numerical simulation ones in relevant literatures to verify the correctness of the proposed method and parameter values chosen here.Then,the effects of chamfering and corner cut measures on wind pressure distribution and aerodynamic force of square cylinder were analyzed.The influence mechanism of corner treatment measures on aerodynamic performance of square cylinder was emphatically analyzed from the points of view of time averaged flow field and transient flow one.Results showed that chamfering and corner cut measures have certain effects on wind pressure distribution and aerodynamic force of square cylinder surface,especially,their effects on wind pressure coefficient of flow separation zone on square cylinder surface are more significant;after taking corner treatment measures,the flow separation in the corner area of square cylinder’s front edge is affected,the diffusion angle of the separation shear layer is smaller,and the separation vortex on the side is closer to the wall surface to form reattachment on the side of square cylinder,tail flow is narrower,vortex shedding frequency components are more complex,average drag coefficient is smaller,aerodynamic force fluctuation intensity is weaker,vortex shedding frequencies are higher and intensity is weaker.