Alternative Control of Fluctuation Frequency in the Wake of a Rectangulay Cylinder near the Critical Shape

矩形柱体临界形状附近尾迹脉动频率的替代控制

基本信息

批准号：
06650209
负责人：
AYUKAWA Kyozo
金额：
$ 1.28万
依托单位：
EHIME UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06650209/
关键词：
Flow around a rectangular cylinder Fluctuating frequency in a wake Control Critical shape Discrete vortex method

项目摘要

Numerical simulation by discrete vortex method was carried out on the alternative control between wholly separated flow and periodically reattached flow, triggered off by suction at a leading edge of a rectangular cylinder near the critical shape in a uniform flow. Experiments were executed after preparing rectangular cylinders with the suction slot at the leading edge connected to a suction device in which suction speed and operating time were controllable, based on the results of the numerical simulation. The main results obtained through the simulation and the experiments are the following.1.In the flow around a cylinder with the critical shape, fluctuation in wholly separated flow appeared in the flow around a cylinder with small side-to-height ratio are superposed on periodically reattached flow appeared in the one with large side-to-height ratio. They appear intermittently in the experiment, while supperposed wave form appears in the simulation.2.In the numerical simulation, the … More flow was transferred to the periodically reattached flow by a single suction which had 0.4-0.7 times speed in the incident flow and 1/30 of fluctuating period in the wholly separated flow for the operating time, and the transferred flow returned to the critical flow after a while. The suction width with a half of the height of cylinder was suitable to the transition. This control was possible in the range of side-height ratio between 3.6 and 4.0 at which the critical shape was realized in the numerical simulation.3.In the experiment, the critical shape was realized at 2.7 of side-height ratio at low Reynolds number and 2.3 at high Reynolds number. The results were similar qualitatively to those of the numerical simulation, but, quantitatively, some differences appeared such as the transition occurred at 0.7-1.0 times of the suction speed higher and for 0.1-0.4 times fluctuating period in the wholly separated flow of operating time longer than the numerical results, and the suitable width for the suction control was below 0.2 times the height.4.We have some problems to be investigated such as the differences above-mentioned and the retarded transition occurred at a few periods after the suction. Less

采用离散涡法对均匀流中矩形圆柱体临界形状附近的前缘吸力触发的完全分离流和周期性再附着流的交替控制进行了数值模拟。前缘处的抽吸槽连接有抽吸速度和操作时间可控的抽吸装置，基于数值模拟的结果，通过模拟和实验获得的主要结果是： 1.在具有临界形状的圆柱绕流中，小边高比的圆柱绕流中出现的完全分离流的脉动叠加在大边高比的圆柱绕流中出现的周期性重新附着流上-高度比。它们在实验中是间歇性出现的，而在模拟中则出现了假设的波形。2.在数值模拟中，流动通过0.4-0.7倍速度的单次吸力转移到周期性重新附着的流动中。运行时间内，入射流量和全分离流量脉动周期为1/30，一段时间后转移流量回到临界流量，吸入宽度为筒体高度的一半，适合过渡。在数值模拟中实现了临界形状的边高比在3.6和4.0之间的范围内，这种控制是可能的。 3.在实验中，在低雷诺数下，在边高比为2.7时实现了临界形状2.3 在高雷诺数下，结果在定性上与数值模拟的结果相似，但在定量上出现了一些差异，例如在0.7-1.0倍吸力速度和0.1-0.4倍波动周期处发生了转变。完全分离流的运行时间比数值结果长，并且吸力控制的合适宽度在0.2倍高度以下。4.我们还有一些问题需要研究，例如差异上述情况和延迟的转变发生在抽吸后的几个时期。