Experimental Determination of Organized Fluctuating Fluid Forces acting on the Finite Circular Cylinders with Different Aspect Ratios

不同长径比有限圆柱上有组织脉动流体力的实验测定

• 批准号: 05650183
• 负责人: TANAKA Shuji
• 金额: $ 1.28万
• 依托单位: Toyota Technological Institute
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 1994
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05650183/
• 关键词: Finite Circular Cylinder; Organized Sturucture; Fluctuating Fluid Force; Aspect Ratio; Conditional Sampling; Turbulent Wake; Strouhal Number; 組織性; 後流

The organized fluctuating fluid forces acting on finite circular cylinders with aspect ratios of 1 to 12 located on the ground plate in a uniform flow have been determined experimentally. The fluctuating pressures on the cylinder surface were processed using the conditional sampling technique, for which the filtered fluctuating velocity signals with well defined frequencies at which the clear organized behaviors can be confirmed in the analysis with FFT.The local and global organized fluctuating fluid forces have been obtained from these results, and the influences of aspect ratios on the details of the organized fluctuating fluid forces have been discussed. The results obtained from the present research project can be summarized as follows :(1) The aerodynamic characteristics of the finite circular cylinders are severely affected by the aspect ratios, but the general characteristics can be classified in two cases. The first is the case for the cylinders with large aspect ratios as high as more than 7 or 8, which can be called "high aspect ratio cylinder", and the other is the case for the cylinders with low aspect ratios smaller than 7 or 8, which can be called "low aspect ratio cylinder".(2) In the case of high aspect ratio cylinders, many noticeable organized fluctuating fluid forces have been confirmed. The three organized fluctuations with different frequencies and different natures on the side wall appears as well as two organized fluctuations on the top.(3) In the case of low aspect ratio cylinders, only a single noticeable organized fluctuating fluid force have been detected on the side wall and the top. On the side wall of the cylinders a fluctuation corresponding to the Karman's vortex street appears with Strouhal numbers from 0.15 to 0.21. For the cylinders with aspect ratios of 2 or 3, a organized fluctuation corresponding to the Karman's vortex street can be also detected on the top surfaces.

本文用实验方法确定了均匀流中作用在底板上的长径比为1 ~ 12的有限长圆柱上的有组织脉动流动力。采用条件采样技术对圆柱表面脉动压力进行处理，得到具有明确频率的脉动速度信号，在此频率下，通过FFT分析，可以确定其具有清晰的有组织行为，并由此得到局部和全局有组织的脉动流体力。并讨论了纵横比对有组织脉动流体力细节的影响。研究结果表明：（1）展弦比对有限长圆柱的气动特性有很大影响，但一般情况下可分为两种情况。第一种是具有高达7或8以上的大展弦比的气缸的情况，其可以被称为“大展弦比气缸”，另一种是具有小于7或8的低展弦比的气缸的情况，其可以被称为“低展弦比气缸”。(2)在大展弦比圆柱体的情况下，许多明显的有组织的波动流体力已被证实。侧壁出现三个不同频率、不同性质的有组织波动，顶部出现两个有组织波动。(3)在低展弦比圆柱体的情况下，仅在侧壁和顶部上检测到单个明显的有组织的波动流体力。在圆柱体的侧壁上出现了对应于卡门涡街的波动，Strouhal数从0.15到0.21。对于展弦比为2或3的圆柱体，在顶面上也可以检测到对应于卡门涡街的有组织的波动。