PIV Measurements of Turbulent Flow Associated with Propeller-Tip-Vortex/Cavitation/ Cavitation-Bursting

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Project title

Code/計畫編號

NSC96-2628-E019-030-MY2

Translated Name/計畫中文名

運用質點影像測速法量測螺槳葉尖渦/空泡/空泡爆裂之紊流流場

Project Coordinator/計畫主持人

Yi-Chih Chow

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=1618081

Year

2008

Start date/計畫起

01-08-2008

Expected Completion/計畫迄

01-07-2009

Bugetid/研究經費

435千元

ResearchField/研究領域

機械工程

"螺槳葉尖渦的流場結構和物理是相當複雜的。在葉尖渦渦旋的中心經常產生空化現象，水氣空泡因此而產生，故形成一個多相流的現象。再者，當螺槳負載增加到某種程度，空化過程變成不穩定而空泡會開始爆裂成雲霧狀的氣泡群，並隨之產生一呈寬頻分佈的噪音。因為空泡的爆裂，葉尖渦紊流的特性應該更偏離理想的紊流狀態，像是均勻性和等向性。換句話說，建構於這些理想狀態的紊流模式可能無法準確預測螺槳葉尖渦的流場。因此，需要涵蓋螺槳葉尖渦/空泡/空泡爆裂這些現象的實驗數據來說明這些紊流模式的問題和引導更好的紊流模式之發展。我們計畫使用質點影像測速法來量測一具有五葉、NACA 翼形的螺槳之葉尖渦的詳細流場結構和紊流。利用影像處理技術，例如中值過濾法、邊緣偵測、交互相關性等，不同相之影像可以有效的被分離而噪音被移除。在液相中的質點影像會被分析以得到流場速度的分佈。數個之前被作者使用或發展的分析方法，像是紊流頻譜分析、紊流黏滯性之先驗測試和雙重平均分解法，將會被運用來分析數據。最後的結果可被期望用來增進我們對螺槳葉尖渦的物理和紊流模式的知識。" "The flow structure and physics of a propeller tip vortex is complex. Inception of cavitation usually occurs in the vortex core, and vapor cavity is thus generated, resulting in a multi-phase flow phenomenon. Furthermore, with propeller loading increasing to certain point, the cavitation process becomes unstable and the cavity starts to burst into a cloud-like bubble cluster, along with a broad-band noise generation. Due to the cavitation bursting, characteristics of turbulence in and around the tip vortex, as being already affected by the cavitation, should deviate more from the ideal conditions of turbulence such as homogeneity and isotropy. In other words, turbulence models based on these ideal conditions may fail to predict accurately the tip vortex flow of a propeller. Therefore, experimental data covering the propeller-tip-vortex/cavitation/cavitation-bursting phenomena are needed in order to address these modeling issues and guide the development of a better model. We plan to use PIV to measure detailed flow structures and turbulence in and around the tip vortex of a 5-blade, NACA-section propeller. Utilizing image processing techniques, e.g., median filtering, edge detecting, cross-correlation, etc., the images of different phases can be effectively separated and noise removed. Particle images in the liquid phase will be analyzed to yield flow velocity distributions. Several analysis methodologies previously used or developed by the author, such as turbulence spectral analysis, eddy-viscosity a-priori test, and dual-averaging decomposition, will be applied to the data. The final results can be expected to advance our knowledge of physics and turbulence modeling of the propeller tip vortex flow."

Keyword(s)

螺槳葉尖渦
空化
空泡爆裂
質點影像測速法
紊流
紊流模式
propeller tip vortex
cavitation
cavitation bursting
PIV
turbulence

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PIV Measurements of Turbulent Flow Associated with Propeller-Tip-Vortex/Cavitation/ Cavitation-Bursting

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