2aEA3. Computational modeling of multiple-pass perforated tube silencers in the time domain.

Session: Tuesday Morning, May 14

Time: 9:25

Author: N. S. Dickey
Location: Dept. of Mech. Eng., Univ. of Michigan, Ann Arbor, MI 48109-2121
Author: A. Selamet
Location: Ohio State Univ., Columbus, OH 43210-1107


To reduce the low-frequency radiated noise from automotive engines, intake and exhaust system silencers often employ perforated tube elements. These geometries commonly consist of one or more perforated tubes aligned axially within an external duct having a length significantly larger than any cross dimension. For such a silencer, the low-frequency acoustic performance may be analyzed by considering one-dimensional flow in each of the passages, coupled by the communication between regions through the perforate interface. The behavior of these configurations depends on numerous parameters, including porosity, orifice dimensions, mean and oscillating through flow and grazing flow levels, in addition to the overall geometry. In automotive applications, nonlinear orifice behavior may be expected. The present study applies a time domain fluid dynamic model to predict transmission loss of perforated tube elements. Since the Navier-Stokes equation is retained in nonlinear form, the technique shows promise for application to the breathing systems of firing engines, where numerous nonlinearities affect the validity of frequency domain analyses. Multiple-pass silencers with zero mean flow are modeled within an extended impedance tube configuration. The effects of overall geometry, porosity, and sound-pressure level are studied and limitations of the one-dimensional assumption are addressed. [Work supported by Ford Motor Co.]

from ASA 131st Meeting, Indianapolis, May 1996