因為汽車排氣管所排放的廢氣是一種脈衝式的流體，它是非穩態及非線性的，以及不易以傳統的線性聲學理論來預測的。在本次研究中我們建立了非線性可壓縮流体模擬程式，來探討壓力波在排氣管內的擾動，這與排氣管所產生的噪音有很直接的關係。
　　本次研究的車輛是由裕隆汽車所提供的SENTRA系列車型，在數值模擬方面我們使用一維非線性可壓縮流模擬程式，分別以有黏滯效應與沒有黏滯效應加以討論，在對流項使用5th-order WENO SCHEME，時間積分上使用4th-order Runge-Kutta，為了確認排氣管內數值模擬的準確性，在不同引擎轉速下以實驗量測排氣管內的壓力與時間平均流速，發現我們的一維非線性黏滯流模擬程式，可以準確的預測排氣管內在不同引擎轉速下的壓力峰值與時間平均流速。

　　Because an exhaust flow is a kind of pulsating flow, it is unsteady, highly non-linear and is not easiy to accurately predict pressure oscillations by a traditional linear acoustic theory. In this study, we establish a non-linear compressible flow model for investigating pressure oscillations inside the exhaust pipe, which are closely related to the noise generated by the exhaust pipe.
　　In order to study the pressure oscillations inside the exhaust pipe associated with a HS-2L car provided by YULOM MOTOR Co. We use a one-dimensional non-linear compressible flow model with and without viscous effects. A 5th-order WENO scheme is used for discretizing convective terms, and a 4th-order Runge-Kutta scheme for time integration. In addition, experimental facilities of pressure, temperature, velocity of the pipe flow have been set up. To validate the computed temperature and pressure results inside the exhaust pipe, we conduct experiments to measure the pressure and flow velocity at some specific points for different engine speeds. It is found that the present one-dimensional, non-linear, viscous flow model is reasonably accurate to predict the pressure peak and the flow speed inside the exhaust pipe at different engine speeds.

[1] 孫哲南，“引擎缸內流場三維視流測試模擬”，碩士論文，機械工程學系，國立成功大學，1982。
[2] 江木勝，“二行程引擎排氣管壓力波數值模擬研究”，碩士論文，機械工程學系，國立成功大學，1988。
[3] 林嘉文，“四行程機車引擎近排氣管數值模擬及實驗分析”，碩士論文，機械工程學系，國立成功大學，1996。
[4] 王又宏，“單缸機車引擎進氣道與排氣系統瞬時流場數值模擬與量測”，碩士論文，機械工程學系，國立中興大學，2000。
[5] 蘇怡昌，“排氣管對於引擎性能及噪音之影響”， 碩士論文，機械工程學研究所，國立臺灣大學 ，2001。
[6] G .P. Blair and J.A. Spechko, “Sound Pressure Levels Generated by Internal Combustion Engine Exhaust System,” SAE Paper 720155, 1972.
[7] G .P. Blair and S .W. Coates, “Noise Produced by Unsteady Exhaust Efflux from an Internal Combustion Engine,” SAE Paper 730160, 1973.
[8] A. D. Jones, “Modeling the Exhaust Noise Radiated from Reciprocating Internal Combustion Engines - A Literature Review,” Noise Control Engineering Journal, Vol. 23, No. 1, pp. 12-31, 1984.
[9] P. Li and G. Dai, “Experiment and Formulation of Pulsed Jet Noise,” Noise control engineering journal, Vol. 36, No. 1, pp. 33-38, 1990.
[10] Y. Sathyanarayana and M. L. Munjal, “A Hybrid Approach for Aeroacoustic Analysis of the Engine Exhaust System,” Applied Acoustics, Vol. 60, pp. 425-450, 2000.
[11] P. Li, G. Dai and Z. Zhu, “Noise Radiation of a Strongly Pulsating Tailpipe Exhaust,” Journal of Sound and Vibration, Vol. 167, No. 3, pp. 385-400, 1993.
[12] M. Endo, Y. Futagami, and J. Iwamoto, “Relation between the Flow Pattern Downstream of Duct and the Noise,” JSAE Review, Vol. 21, pp. 125-132, 2000.
[13] A. Cummings, “Sound Transmission through Duct Walls,” Journal of Sound and Vibration, Vol. 239, No. 4, pp. 731-765, 2001.
[14] M. Endo and J. Iwamoto, “Numerical Analysis of Pulsatile jet from Exhaust Pipe,” JSAE Review, Vol. 20, pp. 243-249, 1999.
[15] K. A. Hoffmann, Computational Fluid Dynamics for Engineers, Engineering Education System, 1989.
[16] J. E. A. JOHN, Gas Dynamics, Allyn and Ba con, Inc., USA, 1984.
[17] G.-S, Jiang. and C.-W, Shu, “Efficient Implementation of Weighted ENO Schemes,” J. Comput. Phys., Vol. 126, No. 1, pp. 202-228, 1996.
[18] C.-W, Shu. and S. Osher, “Efficiently Implementation of the Essentially Non- Oscillatory Shock-Capturing Schemes,” J. Comput. Phys., Vol. 77, pp. 439-471, 1988.
[19] Gasdynamics Tables, http://shock.iaa.ncku.edu.tw/1/root.html