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研究生：	卡雷諾 BENEDIKTUS, REYNARD
論文名稱：	渦流產生器於兩不同平面彎管下游之尾流特性分析 Wake Flow Analysis of a Vortex Shedder Downstream of a Double Elbow Out-of-Plane Pipe Configuration
指導教授：	苗君易 Miau, Jiun-Jih
學位類別：	碩士 Master
系所名稱：	工學院 - 航空太空工程學系 Department of Aeronautics & Astronautics
論文出版年：	2007
畢業學年度：	95
語文別：	英文
論文頁數：	159
外文關鍵詞：	vortex shedding, wake flow, double elbow, pipe flow, MEMS
相關次數：	點閱：107 下載：1
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In this thesis work the experiments were performed in a 50 mm inner diameter pipe. The main focus of this study is analyzing the wake phenomenon downstream of the double elbow out-of-plane pipe configuration. The fully developed turbulent region was found by hotwire measurement and pipe wall pressure measurements, located at 45D downstream of the pipe inlet, where the double elbow was installed. This result was in good agreement with the result from the previous work by Miau et al. [1]. A Micro Electro Mechanical System (MEMS) sensor has been applied on top of a vortex shedder of a vortex flowmeter and applied at several locations downstream of the double elbow. The MEMS sensor is applied for analyzing the vortex shedding frequency. The lowest 95% uncertainty values which was found by the 4th sensor of the MEMS array at Re=6.25x104 was 0.319%. The location situated at 16D downstream of the double elbow was found as the location where the vortex flowmeter gave the highest signal quality value.
The aim of this thesis work is giving a physical explanation of the wake flow phenomenon downstream of the double-elbow configuration. The wake flow is a combination of the swirling flow and the vortex shedding. For analyzing the wake flow phenomenon downstream of the vortex flowmeter, an X hotwire probe was applied at 3D and 1D downstream of the vortex flowmeter.. In reference to the signal of MEMS sensor the Conditional Sampling Technique was applied to analyze the velocity obtained by the X hotwire. It was found that the vortex shedding exists at 1D downstream but greatly diffused at 3D downstream of the vortex shedder

Contents

Abstract
Acknowledgement
Contents
List of Tables…………………………………………………………………………………I
List of Figures………………………………………………………………………………..II
Nomenclatures…………………………………………………………………………….XIII

Chapter 1: Introduction……………………………………………………………………...1
1 Background……………………………………………………………………………1
2 Literature Survey………………………………………………………………………2
3 Thesis Structure and Objectives……………………………………………………….4

Chapter 2: Experimental Method…………………………………………………………..5
1 Experimental Instruments……………………………………………………………..5
2 Pressure Transducer Calibration………………………………………………………6
3 Hotwire Calibration…………………………………………………………………....6
4 Mean Velocity Profile Measurement………………………………………………….6
5 Pipe Wall Pressure Measurement………………………………………………….…..7
6 MEMS Temperature Sensor Design……………………………………………….…..7
7 Experiments at Fully Developed Turbulent Region…………………………………...8
8 Experiments Downstream of Double Elbow Out-of-Plane……………………………9

Chapter 3: Experimental Conditions and Parameters…………………………………...10
1 Pressure Transducer Calibration……………………………………………………..10
2 Hotwire Calibration…………………………………………………………………..10
3 Mean Velocity Measurement………………………………………………………...11
4 MEMS Sensor Fabrication……………………………………….…………………..12
5 Experiments at the Fully Developed Turbulent Region……………………………...13
5.1 Uncertainty Analysis…………………………………………………………...13
5.2 Signal Quality Analysis………………………………………………………...15
5.3 Hotwire Measurement………………………………………………………….16
6 Experiments Downstream of the Double Elbow Out-of-Plane………………………17
6.1 Uncertainty Analysis Downstream of the Double Elbow……………………...17
6.2 Signal Quality Analysis Downstream of the Double Elbow…………………...18
6.3 Strouhal Number Analysis Downstream of the Double Elbow………………..19
6.4 Wake Flow Phenomenon Analysis……………………………………………..20
6.5 Conditional Sampling Technique……………………………………………....22

Chapter 4: Result and Discussion………………………………………………………….25
1 Pressure Transducer and Hotwire Calibration………………………………………..25
1.1 Pressure Transducer Calibration……………………………………………….25
1.2 Hotwire Calibration…………………………………………………………….25
2 Hotwire Measurement in Developing Region and Fully Developed 
	Turbulent Region..........................................................................................................26
2.1 Mean Velocity Profile at the Developing Region...............................................26
2.2 Mean Velocity Profile at Fully Developed Turbulent Region………………....27
3 Pipe Wall Pressure Measurement………………………………………………….....27
4 Turbulence Intensity of the Straight Pipe………………………………………….....28
5 MEMS Temperature Sensor as the Vortex Flowmeter………………………………28
6 Experiments at Fully Developed Turbulent Region………………………………….29
6.1 Uncertainty Analysis…………………………………………………………...29
6.2 Strouhal Number Analysis…………………………………………………..…31
6.3 Signal Quality Analysis………………………………………………………...32
6.4 Hotwire Measurement Downstream of the Vortex Flowmeter at Fully 
Developed Turbulent Region…………………………………………………..33
6.4.1 Mean Velocity Profile……………………………………………….....33
6.4.2 Reynolds Stress………………………………………………………...34
6.4.3 Turbulence Intensity…………………………………………………....35
6.4.4 Fast Fourier Transform Result of the Hotwire Signal……………….…35
7 Experiments Downstream of the Double Elbow Out-of-Plane………………………36
7.1 Strouhal Number………………………………………………………..……...36
7.2 Uncertainty Analysis……………………………………………………..…….38
7.3 Signal Quality Analysis…………………………………………………..…….40
7.4 Wake Flow Phenomenon Analysis at 3D Downstream of The Vortex Shedder 42
7.4.1 Hotwire Reference Signal………………………….…………………..42
7.4.1.1 Mean Velocity………………………………………………..42
7.4.1.2 Fluctuating Velocity………………………………………….43
7.4.1.3 Reynolds Stress………………………………………….…...44
7.4.2 Peak Values of MEMS Signal………………………….………………45
7.4.2.1 Mean Velocity………………………………………….…….45
7.4.2.2 Fluctuating Velocity………………………………………….46
7.4.2.3 Reynolds Stress……………………………………………....46
7.4.3 Valley Values of MEMS Signal………………………………………..47
7.4.3.1 Mean Velocity………………………………………………..47
7.4.3.2 Fluctuating Velocity……………………………………….…48
7.4.3.3 Reynolds Stress………………………………………….…...49
7.5 Wake Flow Phenomenon Analysis at 1D Downstream of The Vortex Shedder 50
7.5.1 Hotwire Reference Signal………………………….…………………..50
7.5.1.1 Mean Velocity………………………………………………..50
7.5.1.2 Fluctuating Velocity………………………………………….50
7.5.1.3 Reynolds Stress………………………………………….…...51
7.5.2 Peak Values of MEMS Signal………………………….………………51
7.5.2.1 Mean Velocity………………………………………….…….51
7.5.2.2 Fluctuating Velocity………………………………………….52
7.5.2.3 Reynolds Stress……………………………………………....53
7.5.3 Valley Values of MEMS Signal………………………………………..53
7.5.3.1 Mean Velocity………………………………………………..53
7.5.3.2 Fluctuating Velocity……………………………………….…54
7.5.3.3 Reynolds Stress………………………………………….…...54
7.6 Available Peaks and Valleys Represent the Vortex Shedding………………....55
7.7 Swirling Number……………………………………………………………….56

Chapter 5: Conclusion……………………………………………………….……………..57
1 Developing Region and Fully Developed Turbulent Region………………………...57
2 Experiment at Fully Develop Turbulent Region……………………………………..57
3 Vortex Flowmeter Downstream of the Double Elbow……………………………….57
4 Hotwire Measurement Downstream of the Vortex Flowmeter………………………58
4 Available Peaks and Valleys Represent the Vortex Shedding……………….............58
6 Future Work………………………………………………………………………….58

References…………………………………………………………………………….……..59
                                    

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校內：2008-07-31公開
校外：2008-07-31公開

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