流体绕多个钝体不稳定分离流动数值仿真

Numerical simulation for unstable separated flow past multi blunts

采用离散涡方法对绕多个钝体不稳定、分离流动进行了数值仿真。数值试验结果表明，在来流对称的条件下，绕双圆柱流动是双稳态的，这和实验是一致的。绕多个钝体的流动更为复杂，前排对后排的流动存在很大的影响，尤其在前排不仅是一个物体的情况下。计算中还包括了物体的不同截面形状。这些计算结果将有助于各种换热器、海洋平台、建筑群布置等正确设计，改变以往仅按平均、稳定流动的设计。

The applicability of the vortex method to unstable separated flow is assessed by computing the flow past the multiˉblunts.In the vortex method,since no computational mesh is needed,there is no any limit of number,shape or relative position of the multiˉblunts.The typical results were obtained for flow past the twoˉcylinders,threeˉcylinders and threeˉsquares under high Re Number,such as 1×10 7. For each numerical testing,a long time series was calculated in order to obtain the consequential process of development.Instantaneous streamlines pattern and distributions of discrete vortices are presented as well as the unsteady lift and drag forces effected the multi blunts. The numerical testing demonstrated the unstable characteristics of massively separated flow past the multi blunts.The flow past the two cylinders is in by equilibrium status.It means that even the zero incidence,uniform inlet flow past the symmetrical two cylinders,the flow is asymmetrical.The unsteasdy lift and drag forces affected the two cylinders respectively are also different.The three cylinders that are located on the triangle is similar with the construction type of Shanghai TV Tower.The flow past the three cylinders was also simulated numerically for different directions of wind.The flow around the back cylinder is more complicated than that around the front cylinders.This result is reasonable since the back cylinder is under the effects of wake of the flow past front cylinders.The computation for flow past the multi squares is to simulate the wind past the set of buildings.The vortices are held up between the buildings,if the set of buildings is under a poor design.This phenomena is not suitable in view of the environment engineering.This research is also helpful to improve the design for power engineering,ocean engineering and high building.