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研究生: 王永勳
Wang, Ung-Shin
論文名稱: 具側面流的傾斜噴流之 三維數值模擬
Three-Dimensional Numerical Simulation of an Inclined Jet with Crossflow
指導教授: 楊玉姿
Yang, Uie-Su
學位類別: 碩士
Master
系所名稱: 工學院 - 機械工程學系
Department of Mechanical Engineering
論文出版年: 2002
畢業學年度: 90
語文別: 中文
論文頁數: 106
中文關鍵詞: 紊流數值模擬噴流衝擊
外文關鍵詞: Numerical simulation, Jet impinging, Turbulence
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  • 本文主要以數值方法模擬具側面流的傾斜紊流噴流衝擊于等熱通量加熱片(上壁面)之流場結構及熱傳現象。紊流統御方程式是以控制體積法(Control Volume Approach)為基礎,配合有限差分法(Finite Difference Method)及冪次法則(Power Law Scheme)來離散成差分方程式。對於紊流的行為與結構則是以 紊流模式( turbulence model)配合牆函數(Wall function)來描述。動量方程式的速度及壓力則以SIMPLE法來解出。本文採用交錯式不等間距之格點設計,使用實體吻合曲線座標系統將不規領域轉換到適當規則之平面。
    本文研究的參數為傾斜紊流噴流與側面流的速度比VR = 7、5、3,側面流與噴流之工作流體溫度相同,設為Tin = 30、40℃,上壁面加熱片熱通量qw=340、640、1000 ;而噴孔直徑d 固定為6 mm,傾斜噴流與底面夾角 =45°,側面流入口高度HD 固定為30mm,側面流入口處之Re數固定為5000,工作流體為水。數值計算結果顯示,改變傾斜噴流入口速度(VR值)對整個流場的趨勢與結構影響最大,當VR 值由7降為3時,右側的順時針渦漩強度快速減弱,相對的左側的逆時針渦漩強度遠大於右側的渦漩強度。左側的渦漩中心偏移至(z/d=1),而Nakabe (1998)的實驗值則固定在(z/d=0)。
    在熱傳效應方面,當傾斜噴流入口速度越快時,其整體Nu平均值越高,VR=7時,(Nu)max=750,約在(x/d,z/d)=(6.0,4.0)處,這是縱向渦漩效應造成的。當加熱片熱通量qw由1000 降為340 時,無因次熱傳係數Nu減少約5﹪~10﹪。

    Three-dimensional numerical simulation of fluid flow and heat transfer characteristics for an inclined jet with crossflow impinging on a heating plate is presented. The turbulent governing equations are solved by a Control-Volume-based finite-difference method with power-law scheme and the well know turbulence model and its associate wall function to describe the turbulent structure. The velocity and pressure terms of momentum equations are solved by SIMPLE (Semi-Implicit Method for Pressure-Linked Equation) method. In addition, body fitted curvilinear coordinates system is employed to transform the irregular region into the regular one.
    The parameters studied include the inclined impinging jet to crossflow velocity ratio VR=7、5、3; the working medium temperature of crossflow and inclined jet flow are the same (Tin=30,40℃), the heat flux of the heated area qw= 340、640、1000 .The jet diameter d is fixed at 6mm, the angle between the inclined jet and the bottom is fixed at = , the height of the crossflow entrance is fixed at HD=30mm, the Re number of the crossflow entrance is fixed at 5000 with the working medium is water. The flow field numerical calculations indicate that the value of VR has a significant effect on the structure of the flow field. When the value of VR decrease from 7 to 3, the intensity of the right clockwise-rotating vortex decreases quickly. The intensity of the left anti-clockwise-rotating vortex is bigger than the intensity of the right vortex. The center of the left vortex is shifted a little in the spanwise direction towards a position z /d =1 with respect to the experimental data of Nakabe (1998), z/d=0.
    As to the heat transfer effect, the average value of Nu increases due to the increasing of VR. When VR=7, (Nu)max= 750 located at ( x /d , z /d ) =(6.0 ,4.0), this is caused by longitudinal vortices. When the heat flux decreases from 1000 to 340 , the average value of Nu decreases about 5~10﹪.

    目錄 中文摘要 ………………………………………………I 英文摘要 ………………………………………………II 誌謝 ……………………………………………………IV 目錄 ……………………………………………………V 表目錄 …………………………………………………VII 圖目錄 ………………………………………………. VIII 符號說明 …………………………………………….XVI 第一章 緒論 .…………………………………… 1 1-1研究動機及背景…………………………… 1 1-2文獻回顧 .………………………………… 2 1-3本文探討之主題及方法 .………………… 4 第二章 理論分析 ……………………………… 7 2-1 三維流場解析 ……………………………7 2-2 紊流模式 .………………………………11 2-3 系統之統御方程式 ……………………19 2-4 邊界條件 .……………………………..21 2-4 平均Nusselt number的計算………..24 第三章 數值方法 …………………………………28 3-1 概述 ……………………………….28 3-2 格點的配置 …...……………………28 3-3 之差分方程式 …..……………….30 3-4 u、v、w動量方程式之差分方程式 ………..38 3-4-1 壓力修正方程式……………………….38 3-5 收斂條件 ……..……………………….42 3-6 差分方程式的解法 ……..…………….44 3-6-1 數值序 …………….…………………...44 3-6-2 電腦運算時間 …..…………………...45 第四章 結果討論 .…………………………….48 4-1 格點獨立測試 …………………….…49 4-2 流場結構分析 ….…………………….50 4-3 無因次熱傳析 …….…………..……..52 第五章 結論與建議 ….…………………...101 5-1 結論 …………………………….101 5-2 未來研究方向之建議 …….…..………..102 參考文獻 ..…………………………………104

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