二維翼片狀空化流場之數值研究

Numerical Study on Sheet Cavitation Flow of Two Dimension Hydrofoil

簡鴻斌(Hung-Pin Chien)

指導教授 ： 郭真祥

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.01181

摘要

空化(Cavitation)現象在流體中是普遍存在的現象，在造船產業的應用上尤其有很多明顯的例子，如螺槳和噴射推進器等。空化現象除了會造成流體機械效率的衰減，同時並產生震動、噪音和侵蝕問題。對於高速船舶，空化現象一直是重要的研究主題。然而高速推進器如噴射推進器、超空化螺槳、穿水式螺槳等也皆面臨來自空化現象的挑戰，因此有必要對空化現象進行完整的研究。由於分析空化現象的複雜度與困難度高，大部分的研究多以實驗方式進行。目前因為計算流體力學技術的快速發展，對於空化現象的紊流模式計算似乎變得較為可行。為了模擬片狀空化流場，本篇研究擬以自行建立完成之二維黏性流計算方法出發，導入以流體體積法為觀念之二相流的數值模型，利用等效流體模型，考慮流場中每一個控制體積內的兩種流體的分佈，使計算方法得以考慮流場中兩種不同的流體，再利用壓力、速度和密度之間的偶合關係使流場之計算可趨於穩定，其中經由疊代方式進行計算，直到片狀空化流場的形狀穩定為止。本文是應用二相流法來模擬二維水翼之片狀空化流場，進而預測空化區大小、形狀以及空化水翼的升力和阻力係數衰減。

關鍵字

空化現象 ； 二相流法 ； 片狀空化流場

並列摘要

Marine applications involving attached bubbles on propellers and underwater vehicles are obvious examples of cavitation phenomena. For naval architecture issues, cavitation is always a very important topic related to high-speed ships. However, high-speed propulsors, including water jet system, super-cavitating propeller and surface-piercing propeller, are facing critical challenge from cavitation problems. For this reason, it is necessary to make a thorough study of cavitation phenomena. Due to the complexities and difficulties of theoretical analysis of cavitation, most of the researches are based on experimental approaches. With the fast development of computational fluid dynamics techniques, computations of turbulent flow for cavitation problems seem to become popular. In order to simulate sheet cavitation flows, the present method started from a two-dimensional flow code capable of computing turbulent hydrofoil flows. In order to take cavitation region into account, a two-phase flow scheme was further implemented. The proposed approach treats gas and liquid phases as an effective fluid with density varied in space. The flow field was computed in both phases with vapor pressure recovered inside the cavitation cavity via a pressure-velocity-density coupling scheme. The computation is iteratively conducted, until the shape of the sheet cavitation become stable. This thesis is to simulate steady sheet cavitation flows of a two-dimensional hydrofoil using a two-phase approach. The size and shape of sheet cavitation, and the lift and drag coefficient of a cavitating hydrofoil are predicted.

並列關鍵字

Cavitation ； Sheet cavitation flow ； Two phase flow scheme

參考文獻

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