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.

參考文獻

[1] 松本正一, 角田市良(著), 劉瑞祥(譯), ”液晶之基礎與應用,” 國立編譯館出版, pp. 1-54 (1996)
[2] 黃國松, “膽石醇液晶/向列型液晶複合系於增亮膜研究,” 私立元智大學化學工程研究所碩士論文, (2003).
[3] 楊博智, “含硝基偶氮苯衍生基光敏性液晶高分子之合成及特性探討,” 國立成功大學化學工程研究所碩士論文, (2003).
[4] Zharkova, G.M., “The Applications of Liquid Crystals in Experimental Aerodynamics,” Fluid Mechanics-Soviet Research, Vol. 9, No. 3, May-June, pp. 51-56, (1980).
[5] Zharkova, G.M., “Temperature Field Visualization Using Liquid Crystal Method,” Experimental Heat Transfer, Vol. 4, pp. 83-92, (1991).
[6] Hoang, Q.H., Toy, N., and Savory, E., “Liquid Crystal for Surface Shear Stress Measurements,” Guildford DU2 5XH, United Kingdom.
[7] 陳志浩, “應用液晶視流技術探討矩形截面凸狀物之分離流,” 國立成功大學航空太空工程研究所碩士論文, (2004).
[8] 林宗賢, “液晶光子晶體雷射現象與其光控制研究,” 國立成功大學物理研究所碩士論文, (2004).
[9] Huang, J.B., Ho, C.M., Jiang, F., Tai, Y.C., “Dynamic Behavior and Application of Micro Sensors with Negative Temperature Coefficient,” Proc. Of Instrumentation and Measurement Technology Conference, Pasadena, pp. 1191-1194, (1998).
[10] Folkmer, B., Steiner, P., Lang, W., “A Pressure Sensor Based on a Nitride Membrane Using Single-Crystalline Piezoresistors,” Sensors and Actuators A54, pp. 488-492, (1996).
[11] Chung, G.S., Kawahito, S., Ishida, M., Nakamura, T., “Novel Pressure Sensors with Multilayer SOI Structure,” Electronics Leters, Vol. 26, 7th June No. 12, pp. 775-777, (1990).
[12] Svelto, C.G., Suardi, G., Bava, E., ”Compact and Accurate Digital Thermometer Based on an Anderson’s Loop and Pt-100 Sensor,” Instrumentation and Measurement Technology Conference, Proceedings of the 16th IEEE, Vol. 3, pp. 1619-1623, (1999).
[13] Breuer, K., “MEMS Sensors for Aerodynamic Application the Good, the Bad,” 38th Aerospace Sciences Meeting & Exhibit, AIAA paper No. 2000-0251, January 10-13, Reno, Nevada, (2000).
[14] Kazuhiko, T., Akira, Y., Hiroshi, O., “The Experiment Study of High TCR Pt Thin Films,” IEEE Trans., Vol. 31, pp. 1002-1005, (2002).
[15] 杜榮國, “MEMS熱膜感測器設計製造及應用於探討非定常流動分離現象”, 國立成功大學航空太空工程研究所碩士論文, (2003).
[16] 陳振強, “應用MEMS熱膜感測器於渦流流量計之管流實驗”, 國立成功大學航空太空工程研究所碩士論文, (2004).
[17] Kim, K.C., Ji, H.S., Seong, S.H., “Flow Structure around a 3-D Rectangular Prism in a Turbulent Boundary Layer,” Journal of Wind Engineering and Industrial Aerodynamics, Vol. 91, pp. 653-669, (2003).
[18] Chen, Y.M., Wang, K.C., ”Simulation and Measurement of Turbulent Heat Transfer in a Channel with a Surface-Mounted Rectangular Heated Block,” Heat and Mass Transfer, Vol. 31, pp. 463-473, (1996).
[19] Wietrzak, A., Poulikakos, D., “Turbulent Forced Convective Cooling of Microelectronic Devices,” Int. J. Heat Fluid Flow 11 (2), pp. 105-112, (1990).
[20] Eaton, J.K., Johnston, J.P., “A Review of Research on Subsonic Turbulent Flow Reattachment,” AIAA Journal, Vol. 19, No.9, September, pp. 1093-1100, (1981).
[21] Bradshaw, P., Wong, F.Y.F., “The Reattachment and Relaxation of a Turbulent Shear Layer,” Journal of Fluid Mechanics, Vol. 52, Pt. 1, pp. 113-135, (1972).
[22] Patel, R.P., “Effects of Stream Turbulence on Free Shear Flows,” Aeronautical Quarterly, Vol. 29, Pt. 1, pp. 1-17, (1978).
[23] Kiya, M., Sasaki, K., “Structure of a Turbulent Separation Bubble,” J. Fluid Mech., Vol. 137, pp. 83-113, (1983).
[24] Kuehn, D.M., “Effects of Adverse Pressure Gradient on the Incompressible Reattaching Flow over a Rearward-Facing Step,” AIAA Journal, Vol. 18, March, pp. 343-344, (1980).
[25] Iwai, H., Nakabe, K., Suzuki, K., “Flow and Heat Transfer Characteristics of Backward-Facing-Step Laminar Flow in a Rectangular Duct,” Heat and Mass Transfer, Vol. 43, pp. 453-471, (2000).
[26] Adams, E.W., Johnston, J.P., “Effects of the Separating Shear Layer on the Reattachment Flow Structure - Part2: Reattachment Length and Wall Shear Stress,” Experiments in Fluids, Vol. 6, pp. 493-499, (1988).
[27] Acrivos, A., Snowden, D.D., Grvoe, A.S., Petersen, E.E., “The Steady Separated Flow Past a Circular Cylinder at Large Reynolds numbers,” J. Fluid Mech., Vol. 21, pp. 737-760, (1965).
[28] Back, L.H., Roshke, E.J., “Shear-layer Flow Regimes and Wave Instabilities and Reattachment Lengths Downstream of an Abrupt Circular Channel Expansion,” J. Appl. Mech., Vol. 94, pp. 677-781, (1972).
[29] Abu-Mulaweh, H.I., Armaly, B.F., Chen, T.S., “Measurements of Laminar Mixed Convection Flow over a Horizontal Forward-Facing Step,” Journal of Thermophysics and Heat Transfer, Vol. 7, No. 4, pp. 569-573, (1993).
[30] Abu-Mulaweh, H.I., “A Review of Research on Laminar Mixed Convection Flow over Backward- and Forward-Facing Steps,” International Journal of Thermal Sciences, Vol. 42, pp. 897-909, (2003).
[31] Abu-Mulaweh, H.I., “Turbulent Mixed Convection Flow over a Forward-Facing Step – the Effect of Step Heights,” International Journal of Thermal Sciences, Vol. 44, pp. 155-162, (2005).
[32] Zharkova, G.M., “Optical Phenomena in Liquid Crystals and Their Application on Aerophysical Studies,” Optics and Laser Technology, Vol. 32, pp. 611-619, (2000).
[33] Zharkova, G.M., Samsonova, I.V., Strel’tsov, S.A., Khachaturyan, V.M., “Structure and Optical Properties of Liquid-crystal Composites with Induced Helices,” IEEE 5th International Conference, (2000).
[34] Lee, G.B., Wu, J.H., Miau, J.J., “A New Fabrication Process for a Flexible Skin with Temperature Sensor Array,” Journal of the Chinese Institute of Engineers, Vol. 25, No. 6, pp. 619-625, (2002).
[35] Tutu, N.K., Chevray, R., “Cross-wire Anemometry in High Intensity Turbulence,” J. Fluid Mech., Vol. 71, pp. 785-800, (1975).
[36] Ishihara, T., Hibi, K., Oikawa, S., “A Wind Tunnel Study of Turbulent Flow over a Three-dimensional Steep Hill,” Journal of Wind Engineering and Industrial Aerodynamics, Vol. 83, pp. 95-107, (1999).
[37] Takahashi, T., Ohtsu, T., Yassin, M.F., Kato, S., Murakami, S., “Turbulence Characteristics of Wind over a Hill with a Rough Surface,” Journal of Wind Engineering and Industrial Aerodynamics, Vol. 90, pp. 1697-1706, (2002).
[38] Yamaguchi, A., Ishihara, T., Fujino, Y., “Experimental Study of the Wind Flow in a Coastal Region of Japan,” Journal of Wind Engineering and Industrial Aerodynamics, Vol. 91, pp. 247-264, (2003).
[39] Cao, S., Tamura, T., “Experimental Study on Roughness Effects on Turbulent Boundary Layer Flow over a Two-dimensional Steep Hill,” Journal of Wind Engineering and Industrial Aerodynamics, Vol. 94, pp. 1-19, (2006).
[40] Baughn, J.W., Mayhew, J.E., Butler, R.J., Byerley, A.R., Rivir, R.B., “Turbine Blade Flow Separation and Reattachment at Low Reynolds Numbers,” J. Heat Transfer, Vol. 121, August Insert, (1999).
[41] Butler, R.J., Byerley, A.R., Van Treuren, K.W., Baughnm, J.W., “The Effect of Turbulence Intensity and Length Scale on Low-pressure Turbine Blade Aerodynamics,” Int. J. Heat Fluid Fllow, Vol. 22, pp. 123-133, (2001).
[42] Byerley, A.R., Stormer, O., Baughn, J.W., Simon, T.W., Van Treuren, K.W., List, J., “Using Gurney Flaps to Control Laminar Separation on Linear Cascade Blades,” J. Turbomachinery, Vol. 125(1), pp. 114-120, (2003).
[43] Smith, J.S., Baughn, J.W., Byerley, A.R., “Surface Flow Visualization Using Thermal Tufts Produced by an Encapsulated Phase Change Material,” International Journal of Heat and Fluid Flow, Vol. 26, pp. 411-415, (2005).
[44] Byerley, A.R., Stormer, O., Baughn, J.W., Simon, T.W., Van Treuren, K.W., “A Cool Thermal Tuft for Detecting Surface Flow Direction,” J. Heat Transfer, Vol. 124, pp. 594, (2001).
[45] Smith, J.S., Baughn, J.W., Byerley, A.R., “Surface Flow Visualization Using Thermal Tufts Produced by Evaporatively Cooled Spots,” Journal of Fluids Engineering, Vol. 127, pp. 186-188, (2005).
[46] 李國忠, “振動平板對分離流場之影響,” 國立成功大學航空太空工程研究所碩士論文, (1989).
[47] 伍湘杰, “渦流溢放過程低頻調變與三維性之瞬間特性,” 國立成功大學航空太空工程研究所博士論文, (2003).
[48] Zharkova, G.M., Zanin, B.Y., Kovrizhina, V.N., Sboev, D.S., Brylyakov, A.P., “Formation of a System of Longitudinal Vortices on the Windward Side of a Wing at increased External Turbulence,” Thermophysics and Aeromechanics, Vol. 9, No. 2, pp. 201-203, (2002).
[49] Zharkova, G.M., Zanin, B.Y., Kovrizhina, V.N., Brylyakov, A.P., “Free Stream Turbulence Effect on the Flow Structure over the Finite Span Straight Wing,” Journal of Visualization, Vol. 5, No. 2, pp. 169-176, (2002).
[50] Brylyakov, A.P., Zanin, B.Y., Zharkova, G.M., Sboev, D.S., “Effect of Turbulizing Grid near Wake on a Boundary Layer on a Wedge,” Institute of Theoretical and Applied Mechanics SB RAS, 630090 Novosibirsk, Russia, (2002).