臺灣博碩士論文加值系統

摘 要
本文研究旨在探討具有移動蓋板圓弧凹槽內的浮力效應對週期暫態流場及熱傳對流特性綜合影響進行研究數值分析。 在數值方法方面，研究採用流線函數-渦漩量法(stream function-vorticity)、貼壁座標轉換(body-fitted coordination transfer) 及有限體積法(finite-volume method)來求解統制方程式，而得流場及溫度場數據。在實驗方面，以熱電偶(thermocouples)測量穩態溫度值且用煙線法來方便觀察流場流動之情行。
本研究探討內容包括：
(1) 水平及傾斜凹槽之自然對流熱傳特性及流動型態
(2) 具移動蓋板凹槽之穩態對流熱傳特性及流動型態
(3) 具等速移動或振動蓋板之圓弧或不同形狀凹槽之暫態(週期性)混合對流及流動型態
主要針對慣性力及浮力流場的綜合影響進行研究。結果顯示當慣性力及浮力的強度相近時，流場會出現暫態式的週期振盪現象。當慣性力及浮力其中之一獨大時，該週期振盪現象則無所見。在寬廣關係參數中，針對流場形態、摩擦因子及紐塞數(Nusselt number)進行研究，分別比較實驗解與數值解之流場形態之一致性及數值解的可靠性。研究發現圓弧凹槽內可能發生兩種週期流場型態現象，分別為橫貫型(traversing-periodic pattern)及半區間型(half-periodic pattern)週期流場型態，本研究同時探討此二不同型態的週期流場特性、局部及平均紐塞數分佈。深入研究圓弧凹槽的置放角度(inclination angle)及移動蓋板振動對凹槽內週期流場的影響。此外，亦針對九種不同的截面形狀凹槽進行分析，研究具不同截面形狀凹槽的週期流場特性。

ABSTRACT
Experimental and numerical study has been performed to investigate the combined effects of lid movement and buoyancy on flow pattern and heat transfer characteristics for the mixed convective flow inside an arc-shape cavity. The governing equations in terms of the stream function-vorticity formulation are solved by the finite-volume method coupled with a body-fitted coordinate transformation scheme. In experiments, steady-state temperature data are measured by K-type thermocouples, and the flow field is visualized by using kerosene smoke.
The task of the present study includes the numerical and experimental investigation of
(1) Natural convection heat transfer and flow pattern in the horizontal and the inclined cavities.
(2) Steady mixed convection heat transfer and flow pattern in the horizontal cavities with a moving lid.
(3) Unsteady (periodic) mixed convection heat transfer and flow pattern in the horizontal and the inclined cavities, particularly under the effects of irregular shape and lid oscillation.
Results show that only when the inertial and buoyant forces are of approximately equal strength the periodic flow pattern can be observed. For an inertia-dominant or buoyancy-dominant situation, the periodic flow pattern is not visible. Flow pattern, friction factor, and Nusselt numbers are investigated in wide ranges of parameters. Close agreement in the comparison between the predicted and the visualized flow patterns has been found. In these above ranges of the parameters, two kinds of oscillatory flow pattern have been observed, namely, the traversing-periodic and the half-periodic patterns. Attention has been focused on the effects of the inclination effects on the occurrence of these two different oscillatory flow patterns. Meanwhile, periodic variation in the mixed convection heat transfer accompanying the oscillatory moving lid has also been studied, and the results for the local and the overall Nusselt numbers are presented. This report is also concerned with transient behavior of a buoyancy-induced periodic flow in different lid-driven cavities with different cross-sectional shapes. Periodic flow patterns and heat transfer characteristics for various geometries are predicted.

TABLES OF CONTENTS

CHINESE ABSTRACT……….……………….……………………….…………….i
ENGLISH ABSTRACT…….……………................…………..………….iii
ACKNOWLEDGEMENTS…..…………………......…………………………………v
TABLE OF CONTENTS….………………………....…….…………..………….vi
LIST OF TABLES…………………........….....……………..……..…… viii
LIST OF FIGURES………….…………………....……………….………….…ix
NOMENCLATURE….…………………….……....………………….…………….xv
CHAPTER
I Introduction…..................................……….…….1
1.1 Literature Review...…………….....…………….……1
1.2 Scope of the Present Study....………..…....….….5
II Natural Convection….................…….……..……….…….8
2.1 Theoretical Analysis…………………………….….…...8
2.2 Numerical Methods…………....………….………….…..11
2.3 Effects of Grashof Number.………..…………….….….12
2.4 Experimental System…….….………….………….….….13
2.5 Effects of the inclination angle.……… …….……..16
III Steady Mixed convection…………………....................….31
3.1 Theoretical Analysis……………………………….…..…31
3.2 Numerical Methods..…………...……………….….….…35
3.3 Experimental System...………….……..……………..…35
3.4 Effects of Grashof Number and Reynolds Number...….37
IV Unsteady Mixed Convection….……………………..….….…..……53
4.1 Theoretical Analysis……………….……….….…..…..54
4.2 Numerical Methods…………………..……….….…..…..56
4.3 Experimental System…….….…………..…………….….57
4.4 Effects of Grashof Number and Reynolds Number..……59
4.5 Effects of Inclination ……………………………..……64
4.6 Effects of Irregular Cavities……..………….....….70
4.7 Effects of Oscillatory Wall………………..….……….72
V Concluding Remarks……………….…………………..….……...….123
REFERENCES…………………………….…………………………..…...….….129
APPENDIX: Comparison between the present code and commercial software CFD-RC................................................................134

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