Title
Reduction of the performance of a noise screen due to screen-induced wind-speed gradients: Numerical computations and wind-tunnel experiments
Author
Salomons, E.M.
Technisch Physische Dienst TNO - TH
Publication year
1999
Abstract
Downwind sound propagation over a noise screen is investigated by numerical computations and scale model experiments in a wind tunnel. For the computations, the parabolic equation method is used, with a range-dependent sound-speed profile based on wind-speed profiles measured in the wind tunnel and wind-speed profiles computed with computational fluid dynamics (CFD). It is found that large screen-induced wind-speed gradients in the region behind the screen are responsible for a considerable reduction of the performance of the screen, for receivers near the boundary of the shadow region behind the screen. The screen-induced wind-speed gradients cause a considerable reduction of the size of the shadow region. If the screen-induced wind-speed gradients are taken into account, computed sound-pressure levels near the shadow boundary are in reasonable agreement with levels measured in the wind tunnel. In contrast, computed levels are considerably lower, up to 10 dB, if the screen-induced wind-speed gradients are ignored. This implies that the performance of a screen can be considerably improved if the screen-induced wind-speed gradients can be suppressed, e.g., by the use of 'vented' screens. The reduction of screen attenuation by RESWING (refraction by screen-induced wind speed gradients) for receivers is studied. The sound propagation over a screen in a refracting atmosphere is computed by parabolic equation method. The wind-speed profiles measured in the wind tunnel and wind-speed profiles are computed by computational fluid dynamics. The computer sound-pressure levels in the shadow of the screen are in good agreement with the measured levels.
Subject
Acoustic fields
Acoustic receivers
Acoustic wave refraction
Acoustic wave transmission
Attenuation
Computational fluid dynamics
Computer simulation
Mathematical models
Wind tunnels
Parabolic equation
Screen-induced wind speed gradients
Noise pollution control equipment
Noise measurement
Noise reduction
Sound detection
Sound pressure
Sound transmission
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TNO identifier
235006
Publisher
American Institute of Physics, Woodbury, NY, US
ISSN
0001-4966
Source
Journal of the Acoustical Society of America, 105 (4), 2287-2293
Document type
article