全风向角下小间距双方柱绕流的大涡模拟

Large-Eddy Simulation of Flow Past Two Close Square Cylinders at Various Incidences

摘要:

采用大涡模拟方法研究了间距比（P/B）为1.5（P为柱心间距，B为方柱边长）、风向角α 为 0°~90°等条件下双方柱在均匀来流作用下的气动力、流态划分、表面风压和流场特性。研究发现：小间距双方柱流动干扰效应显著，下游柱平均气动力随风向角的变化规律与上游柱和单方柱差异较大，且可能受更大的升力绝对值。将小间距比双方柱绕流分为前角分离流态（α = 0°~10°）、分离泡流态（α = 20°~30°）、附着流流态（α = 40°~60°）及间隙侧分离泡流态（α = 70°~90°）四种模式。附着流流态和间隙侧分离泡流态的间隙区出现较强的负压。尾流负压区的强度随风向角先增强后减弱，在α = 50°附近达到峰值。前角分离流态时双柱具有一个整体的尾流回流区，而在其他流态下上下游方柱均有独立的回流区。

Abstract:

Large-eddy simulation was applied in the investigation of uniform flow past two square cylinders at a spacing ratio of P/B = 1.5 （P is the center distance of two cylinders and B is the side length of the cylinder） and an incidence angle of α = 0°to 90°. The aerodynamic forces， flow patterns， surface pressures， and flow fields were analyzed. The flow interference is significant for two square cylinders at a small spacing ratio. The variation of mean aerodynamic forces on the downstream cylinder is quite different from that on the upstream cylinder or a single square cylinder. In addition， a larger absolute value of lift force might occur at the downstream cylinder. The leading-edge separation mode （α = 0° to 10°）， separation-bubble mode （α = 20° to 30°）， attached-flow mode （α = 40° to 60°）， and gap-side separation-bubble mode （α = 70° to 90°） are summarized from the flow around two close square cylinders. A strong negative pressure is observed at the gap region for the attached-flow mode and gap-side separation-bubble mode. The strength of negative pressure in the near weak rises with incidence， reaches the maximum around α = 50°， and declines afterward. A single recirculation zone is observed in the weak of two cylinders at the lead-edge separation mode. However， two recirculation zones are recognized for the other three modes.