本研究發展一項新的微製造技術用來開發可撓式熱膜感測器陣列器，可撓式元件利用聚醯亞銨(Polyimide)做結構層、內部包含鉑(Platinum)電阻感溫元件陣列以及金(Gold)金屬連結導線。設計中簡化以往複雜的製程，僅利用兩層光罩即完成可撓式熱膜感測器。自製熱膜感測器電阻溫度係數(Temperature Coefficient of Resistance , TCR)可以達到0.247% /℃，模擬液滴實驗，熱膜感測器對物理訊號之響應頻率可以達到1.1 kHz。實驗中可撓式熱模感測器陣列可以貼附在具有高彎曲度的表面，以進行風洞量測。我們嘗試將熱膜感測器貼覆於T型鈍形體，熱膜感測器可以感測到Re=5400-28800之渦流溢放頻率約為9至55Hz，將溢放頻率無因次化所得之無因次頻率St(Strouhal Number)，所得之St=0.089，與文獻相符合。此外實驗中吾人將熱膜感測器貼覆於二維圓柱體表面，成功量測到平均分離點約落在80-82˚左右。另一方面思考如何以定量的方法呈現圓柱分離的非定常特徵，本研究除利用快速傅立葉轉換(FFT)對熱膜感測器所量測之訊號分析外，亦嘗試利用小波分析法(Wavelet analysis)針對渦流溢放瞬時頻率及低頻擾動效應等特性進行探討及相關性分析，所得結果有助於進一步瞭解二維圓柱體非定常分離特性。

A flexible skin, on which an array of miniature thermal film sensors was situated, was successfully made with a MEMS fabrication process. The design was featured with using platinum as sensing material, deposited on polyimide layer as flexible substrates. In the process, only two masks were used for defining the patterns of the thermal sensors and conducting wires, respectively. The polyimide layers were deposited on top of a thin aluminum layer, which served as a sacrificial layer, hence the flexible skin could be released after metal etching and peeled off easily. The flexible skin together with thermal sensors is survived under large deformation, hence ideal for bonding to a highly curved surface. Each of the sensors shows the linear temperature-dependence characteristic, with the coefficient of resistance (TCR) of 0.247% /℃ was measured. By imposing a stepwise change of surrounding temperature to a sensor, the constant-current circuitry output showed a dynamic response up to 1.1 kHz. The thermal sensor was employed to measure the vortex shedding frequency behind a T-shaped cylinder, at Reynolds numbers 5.4×103–2.8×104. The spectral results reduced from the measured signals confirm that the measurement system was able to resolve the shedding frequency up to 55 Hz. Subsequently, experiments were made to detect the separation point on a circular cylinder normal to the incoming flow. The time-mean separation point on the circular cylinder surface reduced from the signals measured show a very good agreement with the results reported in the literature. Further, an array of thermal film sensors consisting of three sensors were employed to investigate the relation between low-frequency modulations and instantaneous vortex shedding frequency. The analysis was carried out using the wavelet analysis and a correlation technique. The results obtained successfully reveal the instantaneous characteristic behavior of unsteadiness of flow separation on the cylinder model.

參考文獻

[1] McCroskey, W. J., “Some Current Research in Unsteady Fluid Dynamics,” J.Fluids Engrg., Vol.99, 1982, pp.8-38.
[2] Huang, J. B., Ho, C. M., and Jaing, F., “Dynamic Behavior and Application of Micro Sensors with Negative Temperature Coefficient,” Proc. of Instrumentation and Measurement Technology Conference, Pasadena, 1998, pp. 1191-1194.
[3] Beebe, D. J., and Denton, D. D.,“A Polyimide Packaging Process For A Semiconductor Diaphragm Tactile Sensor,” Proc. of the Twelfth Annual International Conference of the IEEE, University of Wisconsin, USA , 1990, pp. 1058-1059.
[4] Beebe, D. J., and Denton, D. D., ”A Flexible Polyimide-Based Package for Silicon Sensors,” Sensors and Actuators A, Vol.44, 1994, pp. 57-64.
[5] Lee, G. B., Tai, Y. C., and Ho, C. M., ”A flexible micromachine-baesd shear-stress sensor array and its application to separation- point detection,” Sensors and Actuators A, Vol. 79, 2000, pp. 194-203.
[6] Jiang, F., Tai, Y. C., Walsh, K., Tsao, T., Lee, G. B., and Ho, C. M., “A flexible MEMS technology and its first application to shear stress sensor skin,” Micro Electro Mechanical Systems, 1997. Proceedings, IEEE., Tenth Annual International Workshop, Pasadena, CA, USA, 1997, pp. 465-470.
[7] Gardner, J. W., Microsensors Principle and Application, Fourth Edition, John Wiley & Sons, Inc., 1944.
[8] Tritton, D. J., “Experiments on the Flow Past a Circular Cylinder at Low Reynolds Number,” J. Fluid Mech., Vol. 16, 1959, pp. 547-567.
[9] Gerrard, J. H., “The Three-Dimensional Structure of the Wake of a Circular Cylinder,” J. Fluid Mech., Vol.25, part 1, 1966, pp. 143-164.
[10] Bloor, M. S., “The Transition to Turbulence in the Wake of a Circular Cylinder,” J. Fluid Mech., Vol.19, 1964, pp. 290-304.
[11] Gerrard, J. H., “The Three-Dimensional Structure of the Wake of a Circular Cylinder,” J. Fluid Mech., Vol.25, part 1, 1966, pp. 143-164.
[12] Williamosn, C. H. K., “Vortex Dynamics in the Cylinder Wake,” Ann. Rev. Fluid. Mech., Vol. 28, 1996, pp. 477-539.
[13] Szepessy, S., and Bearman, P. W., “Aspect Ratio and End Plate Effects on Vortex Shedding from a Circular Cylinder,” J. Fluid Mech., Vol. 234, 1992, pp. 191-217.
[14] Yang, P. M., Hussein, M., and Williams, D. R., “Oblique and Parallel Wave Interaction in the Near Wake of a Circular Cylinder,” Phys. Fluids A., Vol. 5, No.7, 1993, pp. 1657-1661.
[15] Blackburn, H. M., and Melbourn, W. H., “The Effect of Free-Stream Turbulence on Sectional Lift Forces on a Circular Cylinder,” J. Fluid Mech., Vol. 306, 1996, pp. 267-292.
[16] Miau, J. J., Wang, J. T., Chou, J. H., and Wei, C. Y., “Characteristics of Low-Frequency Variations Embedded in Vortex Shedding Process,” J. Fluids Struct., Vol. 13, 1999, pp. 339-359.
[17] Norberg, C., “An Experimental Investigation of the Flow Around a Circular Cylinder: Influence of Aspect Ratio,” J. Fluid Mech., Vol. 258, 1994, pp. 287-316.
[18] Roshko, A. “On the development of turbulent wakes from vortex streets”, NACA TN.2913, 1954.
[19] Roshko, A. “On the drag and shedding frequency of two-dimensional bluff body”, NACA TN.3169, 1954.
[20] Roshko. A. “On the wake and drag of bluff bodies”, J. Aero. Sci, vol.22, 1955, pp.124-132.
[21] Roshko, A., and Fiszdon, W., “On the persistence of transition in the near wake”, problems in Hydrodynamics and Continunm mechanics, Philadelphia, SIAM, 1954, pp.606-616.
[22] Wieselsberger, C., “New data on the law of hydro and aerodynamic resistance”, Physikalsche Zeitschrift, 22, 1922, pp.321-328.
[23] Koromilas, C. A., and Telionis, D. P., “Unsteady Laminar Separation：an experimental study”, J. Fluid Mech., Vol. 97, 1980, pp. 347-384.
[24] Moore, F. K., In boundary layer Research, 1958, pp.296.
[25] Telion, D. P., “Review-Unsteady Boundary Layers, Separated and Attached”，J. of Fluids Engineering, vol.101, 1979, pp29-43.
[26] Lee, G. B., Hu, J. H., and Miau, J. J., “A Flexible Skin with Temperature Sensor Array,” Journal of the Chinese Institute of Engineers, 2002 .
[27] Anthony, R. J., and Jones, T. V., ”Visualization of Transitional Boundary Layer Heat Flux Using High Density Thin Film Arrays,” AIAA Paper No.2001-0553, 2001 .
[28] Ghosh, M. K., and Mittal, K. L., “Polyimides: Fundamentals and Applications,” Marcel Dekker, New York, 1996.
[29] Wilson, D., Stenzenberger, K. L., and Hergenrother, P. M., “Polyimides,” Blackie, Glasgow and London, 1990.
[30] Bessonov, M. L., Kotondryavtsev, M. M., and Laius, L. A., “Polyimides: Thermally Stable Polymers,” Consultants Bureau, New York and London, 1987.
[31] Bessonov, M. L., Kotondryavtsev, M. M., and Laius, L. A., “Polyimides: Thermally Stable Polymers,” Consultants Bureau, New York and London, 1987.
[32] Knudsen, J. D., and Katz, D. L., Fluid Dynamics and Heat Transfer, McGraw-Hill Book Company, New York, 1958.
[33] Kirk D. Hagen, Heat Transfer with Applications, Prentice-Hall Inc., New Jersey, 1999.
[33] Schlichting, H., Boundary Layer Theory, 4th ed., McGraw-Hill, New York, 1960, pp. 407-412.
[34] Zinoviev, V., Lebigia, V., Chung, K. M., and Miau, J. J., Using Hilbert Spectral Analysis in Hot-Wire Measurements in Compressible Subsonic Flows, AIAA paper No.2001-0308, 2001.
[35] Roshko, A., “Experiments on The Flow Past a Circular Cylinder at Very High Reynolds Number,” J. Fluid Mech., Vol. 10 , 1961, pp. 345-356.
[36] Kirk, D., Heat Transfer with Applications, Upper Saddle River, N.J., 1999, pp. 260-265.
[37] Zhou, Y., and Wong, W., “Fluctating Temperature Measurements on a Cylinder in Cross-Flow Using Fiber-Optic Bragg Grating Sensor, Lisbon,“ 10th International Symposium on Applications of Laser Techniques to Fluid Mechanics, 2001.
[38] Prophet. G.., “Vortex flowmeters” Control and Instrum, vol.9, No.8, 1977, pp. 54-57.
[39] Ogawa. Y., and Matsubara. N., “New type of vortex shedding flowmeter”, Proc. International Symposium ‘FLUCOME 85’ Tokyo, 1985, pp.1009-1014.
[40] EI Wahed, A.K., and Sproston, J.L., “The influence of shedder shape on the performance of the electrostatic vortex flowmeter”, Flow Meas. Instrun, vol.2, July 1991, pp169-174.
[41] 楊啟昌，“延長平板對鈍形體所產生渦流溢放之影響”，成大航太所碩士論文，1992。
[42] Hu, C. C., Miau J. J., and Chau, J. H., “Instantaneous vortex-shedding behavior in periodically varying flow”, Proc. R. Soc. Lond. A (2002) 458, 2002, pp.911-932.
[43] Coureglongue, J., On the existence of two families of eddies behind immersed solids, Comptes Rendus Academie Sciences, vol.189, 1929, pp.972-974.
[44] Linke, W., New measurements on aerodynamics of cylinders particularly their friction resistance, Physikalische Zeitschrift, vol.32, 1931, pp.900-914.
[45] Mattingly, G. E., An experimental study of the three dimensionality of the flow around a circular cylinder, University of Maryland, Tech. Note BN-295, 1962.
[46] Toebes, G. H., Fluidelastic Features of flow around cylinder, Proceeding International Seminar on Wind Effects, ed. A. Davenport, Canada, 1967, pp.323-341.
[47] Toebes, G. H., The unsteady flow and wake near an oscillating Cylinder, ASME, Journal Basic Engineering, vol.91, 1969, pp.493-505.
[48] Dwyer, H. A. and Mccroskey, W. J., Oscillating flow over a cylinder at large Reynolds number, Journal of Fluid Mechanics, vol. 61(4), 1973, pp.753-767.
[49] Higuchi, H., Kim, H. J. and Farell, C., On flow separation and reattachment around a circular cylinder atcritical Reynolds numbers. Journal of Fluid Mechanics, vol 200, 1989, pp.149-171.
[50] Achenbach, E., Distribution of local pressure and skin friction around a circular cylinder in cross-flow up to Re = 5 x 106, Journal of Fluid Mechanics, vol. 34(4), 1968, pp.625-639.
[51] Chen, S. S., Flow-induced vibration of circular cylindrical structures. Hemisphere Publishing Corporation, Washington, 1987.
[52] Amadi, E., and Hengjun Z., Signal Analysis Applied to Vortex Flowmeters, IEEE Transactions on Instrument and Measurement, vol.41, December 1992, pp.1001-1004.
[53] Daubechies, I., Ten Lectures on Wavelet, Philadelphia, Pa. :/Society for Industrial and Applied Mathematics, 1992.
[54] Daubechies, I., and Lagarias, J., Two-scale difference equations. Part I: Existence and global regularity of solutions, SIAM J. Math. Anal. vol.22, 1991, pp.1388-1410.
[55] Daubechies, I., and Lagarias, J., Two-scale difference equations. Part II: Local regularity, infinite products of matrices and fractals, SIAM J. Math. Anal. vol.24, 1992.
[56] Grossmann, A., and Morlet, J., “Decomposition of Hardy function intosquare integrable wavelets of constant shape,” SIAM J. Math. Anal. vol.15(4), 1984, pp. 736-783.