Study on the Interaction between the Vortex Shedding Due to Flow Past a Circular Cylinder and a Jet

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Project title

Code/計畫編號

MOST105-2221-E019-017

Translated Name/計畫中文名

圓柱渦流與噴流的交互作用研究

Project Coordinator/計畫主持人

Jiahn-Horng Chen

Funding Organization/主管機關

National Science and Technology Council

Department/Unit

Department of Systems Engineering and Naval Architecture

Website

https://www.grb.gov.tw/search/planDetail?id=11893379

Year

2016

Start date/計畫起

01-08-2016

Expected Completion/計畫迄

01-07-2017

Bugetid/研究經費

917千元

ResearchField/研究領域

機械工程

"圓柱流場所造成的複雜流體運動現象是流體動力學的經典課題，其中的渦流流洩（vortex shedding）現象則兼具工程應用、基礎物理機制研究、以及理論分析價值。本計畫旨在探討側向噴流與圓柱後方渦流流洩的交互作用，以兩年的時間，試圖了解  噴流對渦流結構發展的影響；  噴流是否可以抑制渦流流洩的產生；  噴流與渦流流洩如何彼此融合或彼此解構；  是否有流動不穩定性（flow instability）。第一年將在層流範疇內，討論以上四個問題；第二年將在紊流範疇內，討論以上前三個問題。經過兩年的探討，我們將可對此等交互作用在不同雷諾數下有全面性的了解。為研究相關的交互作用現象，我們設定的流場幾何與模式為：全展管道流（fully‐developed channel flow）通過一圓柱，並從圓柱後側、下方壁面上固定寬度的開口射出噴流，進入渦流流洩區。此設定除對下游邊界條件較易設定之外，對於紊流模型的選取也比較沒有爭議。在本研究中，除了雷諾數以及圓柱-管道徑寬比（diameter‐width ratio）外，我們還有以下幾個參數必須做適當的設定：  無因次噴流速度係數（噴流速度Ujet 與入流平均速度U 之比值，Ujet/U）；  無因次噴流位置（噴流中心點到圓柱中心點之距離L 與圓柱直徑d 之比值，L/d）。" "The complicated flow phenomena arising from flows past a circular cylinder are classical issues in fluid mechanics. Among them, the vortex shedding appearing behind the cylinder is especially important in engineering applications, fundamental physics of fluid flows, and theoretical analysisin mathematics. In the present 2‐year proposal, we attempt to study the interaction lateral jet which is perpendicular to the incoming stream and the vortex shedding behind a cylinder for the following issues:  the effects of the jet on the development of vortex shedding structure,  the possibility of vortex shedding suppression by the jet,  how the two flow phenomena merge to or destruct each other, and  any flow instability due to the interaction. In the first year, the study will focus on the above four issues in the regime of laminar flow. In the second year, the study will be switched to the turbulent flow regime. Then we can have the whole picture of the interaction at different orders of the Reynolds number. To specifically investigate the interaction, we will conduct the study for fully‐development channel flow past a circular cylinder. The jet is introduced into the vortex‐shedding flow behind the cylinder from one of the side walls at a position. This flow geometry makes easier not only the specification of the downstream boundary condition but also the selection of turbulent flow model. The parameters included in this flow include, in addition to the well‐known Reynolds number and diameter‐width ratio,  jet velocity factor  (defined as the ratio of jet speed, Ujet, to average speed of the incoming flow, U: Ujet/U), and  jet position  (defined as the ratio of the distance between the centers of the cylinder, L, and the jet to the cylinder diameter, d: L/d). Their influences will be studied in the present investigation."

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Study on the Interaction between the Vortex Shedding Due to Flow Past a Circular Cylinder and a Jet

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