Study of Fluid-Structure Interaction and Cavitation for Internal Flow Past a Valve

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Project title

Code/計畫編號

NSC100-2221-E019-009-MY2

Translated Name/計畫中文名

內流場通過閥門的耦合效應與空化現象研究

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=2335732

Year

2011

Start date/計畫起

01-08-2011

Expected Completion/計畫迄

01-07-2012

Bugetid/研究經費

537千元

ResearchField/研究領域

機械工程

"本計畫擬採用數值解析的程序，配合先進的空化模擬模型，來研究管流內的閥門作動所造成的空化流場與流固耦合問題。管流閥門是工業應用（包括船舶產業）非常常見的裝置，新近隨著科技的發展，相關的應用更是日新月異，包括微流管中的閥門、人工心臟輔助器的閥門等，不一而足。本研究將區分為兩年，以計算的方式來進行，第一年進行閥門作動下的空化流場解析，這種狀況最常發生在閥門行將關閉的剎那，由於此時流場中部份流體的速度變快，導致瞬間空化現象的出現。我們將特別著重於不同關閉速度所造成的不同流場現象。在解析上，我們將採用黏性流、配合較先進的空化模型來進行計算，由於閥門在運動，所以計算上必須採用動網格；至於空化現象的模擬，則將採用「完全空化模型」（full cavitation model），同時考慮以下幾個效應： (a) 蒸氣泡的形成與傳輸； (b) 壓力場與速度場的紊流擾動； (c) 不可凝縮（noncondensible）氣體的尺度等三種第一階效應。另外，我們假設 (a) 液相是不可壓縮的，只有氣相是壓縮的； (b) 考慮溫度變化效應。第二年所要進行的是流固耦合的計算，就是由流體運動推動閥門的開合。相關的計算除了第一年的成果繼續往下延伸之外，必須考慮耦合的方式。整個計算包括流體力學程序與結構力學程序。其中結構力學的程序部份，我們將採用Lagrange 共轉座標（corotation coordinate system）來進行結構行為的模擬；而兩個程序的耦合介面則透過兩階段的程序，相互傳輸，第一階段為顯式耦合，第二階段為隱式耦合，以期能得到較準確的迭代解析。" "In this project, we propose a numerical procedure with an advanced cavitating model to study an internal flow past a moving valve and the fluid-structure interaction. Valves in an internal flow are very common in industrial applications, including naval architecture. Recently, modern and important applications have been developed with the advancement of new technologies. Some examples include the flow in a microchannel past a valve and the flow in an artificial heart past a valve. The proposed project will be carried out in two years. In the first year, the cavitating flow phenomena will be computationally studied with the assumption that the valve motion is known. It is also known that cavitation often occurs at the moments when the valve is closing. This is due to the fact that at these moments, the local flow often accelerates and a local high velocity distribution results. We will focus on the effects of closing velocity of the valve on the flow development. In computations, a viscous flow model will be incorporated with an advanced cavitating model. A moving grid technology will be developed to cope with the movement of the valve. Furthermore, the simulation of cavitation will be modeled by the “full cavitation model,” which takes considerations of the first-order effect of (a) the formation and transport of vapor bubbles, (b) the turbulent fluctuations of pressure and velocity, and (c) the magnitude of noncondensible gases. In addition, we also assume that (a) the liquid phase is incompressible, and the gas phase is compressible, and (b) all parameters and physical variables are independent of temperature. In the second year, the fluid-structure coupling will be investigated. In this investigation, the motion of the valve is controlled by the fluid motion and, therefore, is not known. The computation is divided into the fluid procedure and the structure procedure. In the structure procedure, the structure model will be formulated in a Lagrangian corotational framework. It allows for arbitrarily large displacements and rotations under the assumption that the strain must be small. The coupling interface is provided at two levels, one being an explicit coupling and the other an implicit coupling, to ensure a more accurate solution in time marching."

Keyword(s)

空化
空化
閥門不穩定流場 Cavitation Valve Unsteady flow

DSpace CRIS

Study of Fluid-Structure Interaction and Cavitation for Internal Flow Past a Valve

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