Flow about a circular cylinder between parallel walls
Flow about a circular cylinder between parallel walls
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DOI：
10.1017/s0022112001004608
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发表时间：
2001-08
影响因子：
3.7
通讯作者：
L. Zovatto;G. Pedrizzetti
中科院分区：
文献类型：
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作者：
L. Zovatto;G. Pedrizzetti
由于壁限制、传入速度剖面中的剪切以及涡量与通道壁分离的影响，围绕放置在通道内的物体的流动与其无界对应物不同。这里使用有限元方法对放置在两个平行壁之间的圆柱体的情况进行数值研究，该有限元方法基于与二维假设一致的雷诺数值的涡量流函数公式。分析了从稳定流到周期性涡旋脱落状态的转变：当物体接近一壁时，转变被延迟，因为圆柱尾流和壁边界层涡度之间的相互作用限制了分离剪切层，减少了其振荡。结果证实了之前对放置在靠近一堵墙的物体的涡流脱落抑制的观察结果。当物体位于通道中心附近时，不稳定的涡旋脱落状态会发生变化，从类似于冯卡门街的模式（有一些差异），到当物体接近一面壁时，会出现单排相同符号的涡旋。提出了导致这种拓扑修改的分离涡动力学。平均阻力系数一旦正确归一化，当圆柱体放置在距一面墙不同距离（小至小于一个圆柱体直径的间隙）时，它们是可比较的。在较小的间隙下，身体的行为类似于表面安装的障碍物。升力由排斥分量加上吸引力分量给出。前者，从文献中众所周知，是由身体后面的尾流的偏差给出的。给出了后者的证据，这是身体前面的剪切力的结果。
The flow about a body placed inside a channel differs from its unbounded counterpart because of the effects of wall confinement, shear in the incoming velocity profile, and separation of vorticity from the channel walls. The case of a circular cylinder placed between two parallel walls is here studied numerically with a finite element method based on the vorticity–streamfunction formulation for values of the Reynolds number consistent with a two-dimensional assumption. The transition from steady flow to a periodic vortex shedding regime has been analysed: transition is delayed as the body approaches one wall because the interaction between the cylinder wake and the wall boundary layer vorticity constrains the separating shear layer, reducing its oscillations. The results confirm previous observations of the inhibition of vortex shedding for a body placed near one wall. The unsteady vortex shedding regime changes, from a pattern similar to the von Kármán street (with some differences) when the body is in about the centre of the channel, to a single row of same-sign vortices as the body approaches one wall. The separated vortex dynamics leading to this topological modification is presented. The mean drag coefficients, once they have been normalized properly, are comparable when the cylinder is placed at different distances from one wall, down to gaps less than one cylinder diameter. At smaller gaps the body behaves similarly to a surface-mounted obstacle. The lift force is given by a repulsive component plus an attractive one. The former, well known from literature, is given by the deviation of the wake behind the body. Evidence of the latter, which is a consequence of the shear in front of the body, is given.