臺灣博碩士論文加值系統

本文以翼端渦漩流場為研究主題，採用Chau紊流場計算程式FV3D©，主要探討翼表流線、渦心軌跡、軸向速度分布、切向速度分布、環流分布與壓力分布，先嘗試了解翼端渦漩的流場特性，再進一步去探討影響翼端渦漩大小的因素。文中對翼端渦漩的流場特性與實驗相較，得到一可信的渦漩流場計算模式。在渦心軌跡的部份，其無因次偏移量(2y/B或2z/B)在10%以內，計算值與實驗值相當；渦漩流場在翼端面附近，由於翼端壓差使得流體由壓力面捲向吸力面，翼表流線由計算所得之現象與實驗觀測相符：在壓力面(靠近翼端)的流線向翼端面集中；在吸力面，流體則與跨過翼端面之壓力面翻轉過來的流體交互作用，造成在吸力面流體現象較複雜；計算所得的流場速度分布與實驗比較有相當一致的趨勢，但在軸向速度最大值與切向速度最大值都比實驗值低；利用計算所得切向速度估算環流分布，趨勢與實驗相合，不過估算的方法，則有待進一步改進；在渦漩中心附近，找尋壓力最低點，此處為翼端渦漩空化發生處，並預估其壓力係數最小值(Cpmin)，若與實驗所得空化初始係數比較，實驗中空化現象會比計算較早發生，不過實驗中發生空化的影響因素很多，這些因素在計算中並不能同時考慮，不過計算所得的壓力係數最小值(Cpmin)可做為空化初始的參考。

Tip Vortex flow of a finite-span hydrofoil at high Reynolds number is numerically investigated by solving the Reynolds-Averaged-Navier-Stokes equations. The tip vortex flow is computed for three angles of attack. The numerical results are compared with the experimental measurements performed in a cavitation tunnel. Core center trajectory has a good agreement with the measurement. Streamline tracing shows similar flow pattern on the pressure side, suction side and tip end as demonstrated by the experiment. It explains roll-up phenomena at the tip of hydrofoil due to the pressure difference between the pressure side and suction side. The velocity and circulation distribution are further investigated. The velocity field is divided into the axial and tangential velocity. Their distributions agree well with the measurement. But computational axial and tangential velocity has smaller maximum value than the measured ones. The tip vortex cavitation can be created by the low pressure located at the core center. The core pressure is also explored in the computation. The core pressure has a close relation to the cavitation inception number which helps to control the tip vortex cavitation.

目錄………………………………………………………………………I
圖表目錄………………………………………………………….…….III
符號說明……………….…………………………………………….…VI
中文摘要……………………..………………………………………..VII
英文摘要……………………….………………………………………IX
第一章 緒論………………………………..……………………………1
1-1 翼端渦漩流場…………………………….…………………………1
1-2 文獻回顧………………………………………….…………………2
第二章 控制方程式與數值方法……………………………..…………6
2-1 控制方程式…………………………………………………………6
2-2 邊界條件……………………………………………………….……7
2-3 數值方法……………………………………………………………8
第三章 數值網格建構….…….……………….……….………………10
3-1 數值格點分布……………..……..….…………………..…………10
第四章 結果討論………………………………………………………16
4-1 流線追跡……………………………………………………………18
4-2 渦心軌跡……………………………………………………..……18
4-3 速度分佈………………………………………………..…………19
4-4 環流分佈…………………………………………………..………21
4-5 壓力係數………….…………………………..……………………22
第五章 結論與建議……………………………………………………24
參考文獻……………………………………..…………………………25

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