CHARACTERISTIC BASED NON LINEAR SIMULATION OF PERFORATED TUBE SILENCERS

Abstract

A characteristic based model for one-dimensional compressible unsteady flow has been used to predict the non-linear attenuation effect«afperforateduihe silencers. A simulation of single pass perforated element including both long and short

resonator with low amplitude acoustic excitation and zero-mean flow bas been carried out, where the predicted results have been compared with the numerical and experimental work of Selarnet et al. [ 1993]. They showed, in general, better agreement with experimental results. Also, the effect ofporosity on the transmission loss has been investigated together with the effect of cavity length and diameter.

Thereafter, high amplitude excitation together with significant mean flow has been considered. The predicted results of the present work have been compared against the work of Chang and Cummings (1988] and show overall agreement with experimental results. Simulation of multiple-pass perforated elements have been performed and compared with the work of Dickey et al. [1998] and revealed good agreement with both two and three-pass perforated elements and highlighted the reliability of the adopted numerical model used in the simulation. VI.2 CONCLUSIONS From the present work, the following conclusions could be drawn:

The first order accuracy of the method of characteristics, which is considered one of the major recorded drawbacks resulting from the linear interpolation between grid points at the characteristic feet in the space domain, has been improved by introducing a unity courant number. Thus, to maintain the characteristic lines as diagonally as possible. In addition, introducing one correction step that uses Euler• Trapezoidal integration scheme has enhanced the integration of Riemann variables