Experimental Investigations of Suppression of Vortex Shedding from a Circular Cylinder
Other Title
抑制圓柱渦漩剝離之實驗研究
Journal Volume
28
Journal Issue
3
Start Page
249
End Page
254
Date Issued
1996
Author(s)
YEN-CHUNG CHANG
Abstract
渦漩剝離現象，一般成認爲是物體在流場中引致振動、噪音甚至共振破壞的一個主要原因。本研究之主要目的即是探討最近深受囑目之一種新抑制渦漩剝離方法之機構及其效能。此方法係利用一比此物體（在此爲一大圓柱）特性尺寸爲小之結構體（在此爲一小圓柱，或稱控制圓柱）置於尾流近場之適當位置，以抑制渦漩剝離產生之振動。本文針對此種被動式控制法，在不同的雷諾數(35-160)、不同的控制位置、不同的大圓柱對控制圓柱直徑比(3~6.67)、不同的大圓柱尺寸及不同的控制國柱數目下，以系統性之方法進行流場現象觀察與其控制特性之探討。實驗的結果發現：在未加入控制前，在臨界雷諾數48以上所產生的馮卡門渦街，在適當位置加入控制圓柱後，則原有渦街會完全消失；此臨界雷諾數可增大約一倍。而若在原控制圓柱的鏡射位置加入第二支控制圓柱峙，則其抑制渦漩剝離之效果可再增強。此控制法之有效控制區域會隨雷諾數之增加或大圓柱對控制圓柱直徑比之增加而減小。
The phenomena of vortex shedding is commonly considered as the main source which causes the flow-induced vibrations, noises, and even collapse of a body in an exteral flow. Main purpose of this paper is to systematically study a new control method by a proper placement of small cylinder around a bluff body (here a circular cylinder). Controlling parameters included Reynolds number, positions and arrangements of controlling cylinder, dimensional size of cylinder and number of controlling cylinder in this study. It has been found that the vor Kármán vortex street can be completely suppressed at low Reynolds number. The critical Reynolds number has been about doubled. The effect for the supression of vortex could be enhanced by placed a second controlling cylinder. The effective controlling region for this control method is shrunk by increasing Reynolds number or increasing diameter-ratio of main-to-controlling cylinder.
Subjects
抑制渦漩剝離
控制圓柱
流場顯影
Vortex shedding surpression
Controlling cylinder
Flow-visualization
Type
journal article