臺灣博碩士論文加值系統

摘要
題目：應用MEMS熱膜感測器與液晶視流探討矩形截面凸
狀物之回覆再接觸現象
研究生：曹榮峻
指導教授：苗君易

本研究之目的在於探討矩形截面凸狀物上表面回覆再接觸現象之三維非定常特性，所使用模型之寬高比為4。為了改善傳統之侵入式量測並對矩形截面凸狀物流場有進一步之認知，於是吾人以膽固醇型液晶為原料，搭配甲苯溶劑及寡聚合物配製成膜液晶並進行液晶視流實驗，所調製液晶配方之溫度範圍介於43℃至60℃之間，其不確定度可低於0.9%。
由液晶視流發現，當凸狀物之寬高比為4、ReH=3.17×10^4、4.22×10^4及5.12×10^4時，回覆再接觸現象約發生於距凸狀物前緣3.15H處，而伴隨於回覆再接觸現象後方之手指狀結構乃分離之剪流層回覆再接觸到凸狀物上表面後渦流拉伸之結果，由液晶視流之彩度分析發現凸狀物側向約存在4個手指狀結構，而每個手指狀結構之側向尺度約為1H，其強度雖會隨著時間改變，但整體位置幾乎是固定的，同時吾人也由彩度分析驗證了回覆再接觸現象之三維非定常現象。
為了驗證液晶視流之正確性，吾人以自製之MEMS熱膜感測器搭配X-type之熱線測速儀對回覆再接觸現象及其所伴隨之手指狀結構進行量測，並以直流放大電路搭配Thermal tuft及延遲相關性分析之觀念發現回覆再接觸現象約發生於距凸狀物前緣3.2H至3.5H處，手指狀結構之尺度則介於0.99H至1.1H之間，與液晶視流之實驗結果相符。

Abstract
Subject：Applying MEMS Thermal Film Sensors
Array and Liquid-crystal Flow
Visualization Technique on
Investigating Flow Reattachment over a
Surface-mounted Rectangular Block
Student：Jung-Chun Tsao
Advisor：J. J. Miau

The purpose of this paper is to investigate the three-dimensional, unsteady behaviors of flow reattachment over a surface-mounted rectangular block, whose ratio of width versus height of the block is equal to 4. The cholesterol- type liquid-crystal mixed with toluene and oligomer (one kind of polymer) has been used as a non-intrusive means of flow visualization. The temperature range of the liquid-crystal is between 43℃and 60℃, and the uncertainty can be less than 0.9%.
As found from the liquid-crystal flow visualization, the reattachment length is around 3.15H, for the Reynolds numbers at 3.17×104, 4.22×104, and 5.12×104, respectively. The finger-type structures inferring the three- dimensional vortices stretched in the reattachment region on the top of the model have been found in the visualization. There are approximately four finger-type structures located near the trailing edge of the model, and all of its spanwise length scales are around 1H. The intensity of the finger-type structures are varying with time, but almost fixed spatially. Also, the three-dimensional unsteady behavior of the flow reattachment over the surface-mounted rectangular block can be comfirmed by the digital image (hue level) analysis of the visualization.
In order to verify the result of the visualization, the self-made MEMS thermal film sensors and the X-type hot-wire were further employed. The DC amplifier circuit was in corporated with the thermal tuft. The cross-correlation analysis of the thermal film signals and hot-wire signals were made to gain better understandings on flow reattachment and finger-type structures. It has been found that the reattachment length is between 3.2H and 3.5H, and the dimensions of each finger-type structures are between 0.99H to 1.1H. The results obtained are consistent with those obtained by the liquid-crystal visualization.

目錄
頁次
中文摘要………………………………………………………………………I
英文摘要……………………………………………………………………II
致謝…………………………………………………………………………III
目錄…………………………………………………………………………IV
圖目錄……………………………………………………………………VII
符號說明…………………………………………………………………XV

第一章 序論…………………………………………………………………1
1-1 實驗動機與目的……………………………………………………1
1-2 液晶相關文獻回顧…………………………………………………2
1-3 MEMS感測器文獻回顧………………………………………………3
1-4 分離流相關文獻回顧………………………………………………5

第二章 理論基礎……………………………………………………………9
2-1 液晶簡介及其測溫原理………………………………………………9
2-1-1 RGB座標與HIS座標之轉換原理……………………………10
2-1-2 膽固醇型液晶之選擇性光反射………………………………...11
2-2 MEMS熱膜感測器工作原理………………………………………12
2-2-1 鉑熱電阻絲感測原理…………………………………………12
2-2-2 MEMS熱膜感測器電阻值估算………………………………13
2-3 MEMS薄膜式熱膜感測器製程……………………………………14


第三章 實驗設備與方法…………………………………………………16
3-1 實驗相關儀器及設備………………………………………………16
3-1-1 液晶相關儀器及設備…………………………………………16
3-1-2 熱膜感測器相關儀器及設備…………………………………17
3-2 成膜液晶配製………………………………………………………18
3-3 成膜液晶校驗………………………………………………………19
3-4 風洞試驗區入口流場特性…………………………………………19
3-5 影響回覆再接觸流場之物理參數…………………………………20
3-6 應用成膜液晶於矩形截面凸狀物之分離流實驗…………………21
3-7 應用熱絲感測器(Thermal tuft sensor)於回覆再接觸現象之觀察…21
3-8 延遲相關性分析(Cross correlation) ………………………………22

第四章 實驗結果與討論…………………………………………………24
4-1 成膜液晶校驗結果…………………………………………………24
4-2 成膜液晶於矩形截面凸狀物之風洞實驗…………………………25
4-2-0 銅塊模型之絕熱問題…………………………………………25
4-2-1 回覆再接觸現象 (Reattachment) ……………………………26
4-2-2 手指狀結構 (Finger-type structure) …………………………28
4-2-3 三維非定常現象………………………………………………30
4-3 熱絲感測器(Thermal tuft sensor)訊號分析…………………………31
4-3-0 熱絲感測器觀念解析…………………………………………31
4-3-1 溫度感測器訊號分析…………………………………………31
4-3-2 溫度感測器之延遲相關性分析………………………………34
4-4 利用MEMS熱膜感測器及熱線測速儀於手指狀結構之量測……36
4-4-1 感測器配置……………………………………………………36
4-4-2 延遲相關性於手指狀結構之分析……………………………37
4-4-2-1 ReH=3.17×104、Heater位於ΔZ=0H之延遲相關性分析…37
4-4-2-2 ReH=4.22×104、Heater位於ΔZ=0H之延遲相關性分析………39
4-4-2-3 ReH=5.12×104、Heater位於ΔZ=0H之延遲相關性分析………41
4-4-2-4 ReH=3.17×104、Heater位於ΔZ=0.4H之延遲相關性分析……43
4-4-2-5 ReH=4.22×104、Heater位於ΔZ=0.4H之延遲相關性分析……45
4-4-2-6 ReH=5.12×104、Heater位於ΔZ=0.4H之延遲相關性分析……47

第五章 結論與建議………………………………………………………49
5-1 結論…………………………………………………………………49
5-1-1 液晶視流實驗…………………………………………………49
5-1-2 MEMS熱膜感測器訊號量測…………………………………50
5-2 未來工作與建議……………………………………………………51
5-2-1 液晶方面………………………………………………………51
5-2-2 MEMS熱膜感測器方面………………………………………52

參考文獻……………………………………………………………………53

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