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In the present paper the decay of shock waves propagating in a kinked exhaust pipe was investigated by numerical simulations based on the TVD scheme. In order to clarify the validity of the present computational model, the numerical results on blast waves propagating in a kinked duct were compared with the experimental ones. Various initial conditions as well as mesh sizes were examined to simulate exploding wire experiments. Shock wave geometry based on computed density contours showed qualitatively good agreement with the schlieren photographs. Measured pressure changes across the shock front also showed good agreement, when they were compared quantitatively with computations on the upper and the lower walls, and on the center line along the ducts. The present simulation model putting a narrow high pressure region as initial conditions in a duct was useful to simulate blast wave propagation.

This paper describes a feasibility study of the acoustic holographic method to identify a noise source on an operating vehicle. A new acoustical holography method applicable to identification of a nonstationary noise source was assessed and developed. Based on the new method, a measurement system was made and applied to quantification of the noise source in the vehicle. The method was evaluated first for source identification capablity and confirmed by loudspeakers. The experimental approach was then applied to identify the location of vehicle tire noise under various steady state conditions. In this paper, an identification method of noise sources with relatively high power level is presented and the relationship between locations of tire noise sources under various operating conditions investigated.