论文标题
最终边界对倾斜圆柱体的唤醒动力学的影响
End boundary effects on wakes dynamics of inclined circular cylinders
论文作者
论文摘要
我们执行直接的数值模拟，以表征具有不均匀终端边界条件的长倾斜圆柱的三维唤醒动力学。三个雷诺数，$ \ rey = 100 $，200和300被认为揭示了内在的次要不稳定性的作用以及外在端边界在塑造三维流中的作用。在$ \ rey = 100 $时，通过诱导倾斜的涡旋脱落，在整个气缸跨度中感觉到末端边界效应，这与尾流相比，这与平行的脱落相比，这与较强的跨度流相关。考虑到组合的倾斜角度和倾斜角度，斜面的斜体脱落数与直缸平行脱落的数量有关。在$ \ rey = 200 $时，固有的二次不稳定性导致大规模涡流位错，从而排除了末端边界对进一步跨度的传播。然而，对于倾斜的情况，在上游端边界的有限跨度内仍观察到倾斜的脱落。从余弦法的角度来看，倾斜的涡旋与$ \ rey = 200 $的二维流有关。沿着跨度更进一步，倾斜的涡旋会随着小规模涡流的形成而破坏了稳定，流动过渡到典型的模式A*唤醒。在$ \ rey = 300 $时，末端边界附近的高度三维流动会产生沿圆柱跨度传播的干扰，从而为倾斜角度较低的病例造成了涡流位错。对于高倾斜角，在圆柱跨度上再次观察到倾斜的涡旋脱落，并且不会因固有或外在原因的涡流位错而破坏。
We perform direct numerical simulations to characterize the three-dimensional wake dynamics of long inclined circular cylinders with inhomogeneous end boundary conditions. Three Reynolds numbers, $\Rey=100$, 200 and 300 are considered to reveal the roles of the intrinsic secondary instabilities and the extrinsic end boundary effects in shaping the three-dimensional flows. At $\Rey=100$, the end boundary effects are felt over the entire cylinder span by inducing oblique vortex shedding, which is associated with stronger spanwise flow in the wake than a parallel shedding. The Strouhal number of the oblique shedding is related to that of the parallel shedding of straight cylinder by the cosine law, considering the combined inclination angle and oblique angle. At $\Rey=200$, the intrinsic secondary instability results in large-scale vortex dislocation, precluding the propagation of the end boundary effects towards further span. Nevertheless, for the inclined cases, oblique shedding is still observed within limited span from the upstream end boundary. The oblique vortices are related to the two-dimensional flow at $\Rey=200$ from the viewpoint of cosine law. Further along the span, the oblique vortices destabilizes with the formation of small-scale vortices, and the flow transitions to the typical mode A* wake. At $\Rey=300$, the highly three-dimensional flow near the end boundary creates disturbances that travel along the cylinder span, creating vortex dislocations for cases with low inclination angles. For high inclination angle, oblique vortex shedding is again observed over the cylinder span, and is not disrupted by vortex dislocations of either intrinsic or extrinsic causes.
