Microscopic fluid dynamics of a wire screen bound to a slit resonator excited by acoustic waves

Abstract

The microscopic fluid dynamics of a wire screen bound to a slit resonator excited by incident sound waves of different intensity are investigated numerically. The microscopic flow features help in understanding the acoustic behavior. A normal impedance-tube model is used in this investigation, and the wire mesh is modeled as an array of eight identical tiny circular cylinders arranged in parallel. Tonal waves of different sound pressure levels and frequencies are introduced from the termination of the tube through a non-reflecting boundary condition. Direct numerical simulations are carried out to solve for the flow and acoustic fields simultaneously, and the velocity and vorticity fields around the resonator are resolved. Upon closer inspection, the tiny cylinders suppress the vortex shedding from the slit excited by high-intensity incident sound waves, thereby retarding the nonlinear acoustic behavior of the slit. Furthermore, the wire mesh contributes greatly to the absorption of acoustic energy through scrubbing loss and flow separation. The acoustic impedance and absorption coefficient are derived using a two-microphone method. The numerical results show that the wire mesh increases the resistance of the resonator significantly while hardly affecting its reactance.