Accuracy at the interface is an important aspect in simulating air/porous medium problems for sound propagation in the atmosphere. Currently, high-order schemes have been used in simulation for viscous flow around steady and moving solid bodies, but still have not been applied to simulating flow field in different media. The study in this paper is intended to apply a high-order scheme to improve the accuracy at the interface between air and porous medium. In the vicinity of the interface, spatial derivatives of flux are discretized using different high order schemes: second-order upwind scheme, third-order upwind scheme, and 5th-order WENO scheme. The calculations are performed on a staggered Cartesian grid. The model equations for flow in the air used in this paper are the Navier-Stokes equations for incompressible flow. Flow inside the windscreen (porous medium) is modeled with a modified Zwikker-Kosten equation (Sound Absorbing Materials, 1949). An immersed-boundary method using direct forcing is utilized. The problem of flow over a solid cylinder is used as a validation case for different schemes that are implemented and compared. The application of the study is to investigate the sound pressure level reduction between unscreened microphone and screened microphone under different frequencies of incoming wind turbulence. The wind turbulence in the present work is introduced by placing different sizes of solid cylinders in the upstream of the microphone. The simulation shows that for low-frequency turbulence, the windscreens with low flow resistivity are more effective in noise reduction, while for high-frequency turbulence, the windscreens with high flow resistivity are more effective.
SIMULATION OF TURBULENT WIND NOISE REDUCTION BY POROUS WINDSCREENS USING HIGH-ORDER SCHEMES