附属小圆柱对主圆柱绕流影响的数值模拟

从小马赫数下的可压缩Navier-Stokes方程出发,采用覆盖网格分区算法,对在主圆柱尾流场的适当位置放置附属小圆柱时的流动特性及其对主圆柱绕流问题的影响进行了详细的数值模拟研究.根据模拟结果,主要探讨在小雷诺数范围内,附属小圆柱位置、个数、大小以及雷诺数变化等因素对主圆柱绕流的流场结构及其非定常演化过程的影响.计算结果表明,在小雷诺数范围内,无论附属小圆柱的个数如何,都存在最佳抑制区域.当附属小圆柱放在这个区域时,涡街被完全抑制,整个流场达到准定常状态;同时,阻力系数也显著下降.在一定程度上,随着小圆柱直径的增加,主圆柱涡脱落更易被抑制.另外,相对于单个附加小圆柱而言,使用两个附加小圆柱能使主圆柱涡脱落的抑制提高到更高的雷诺数. 

Numerical study of flow around a main cylinder by controlled satellite cylinders

Vortex shedding behind circular cylinder, when placing single or multiple secondary, much smaller cylinders in the near wake of the main cylinder, was numerically investigated using overlapping grids in conjunction with a domain decomposition method for the compressible Navier-Stokes equations. The efforts of the present study were paid toward the influences of Reynolds number, the locations and the number of the secondary cylinders, upon the flowfield structures and their evolution for low Reynolds number. The existing of an optimal suppressive region over the vortex flow fields at low Reynolds number was discovered, regardless of the number of the small cylinders. When controlling cylinders are located at the optimal position, vortex street is completely suppressed and the flow achieves a quasi-stationary state; at the same time, substantial reduction of the net drag coefficient is noticed. In a way, vortex shedding suppression is comparatively easier for a larger controlling cylinder. It is also found that the vortex street suppression by two controlling cylinders can sustain to higher Reynolds numbers by comparing with a single cylinder.