Title: Separated flow on the car body: spectral and spatial characteristics analysed from the aeroacoustic viewpoint
Authors: E. Nienaltowska
Addresses: Renault Research Dept., 9-11 Ave. du 18 Juin 1940, F92 500 Rueil, Malmaison, France
Abstract: Experimental investigation of the local pressure and velocity fluctuations due to a flow reparation behind the A-pillar is presented. The separation is responsible for the noise generated in the car interior. Due to the non-isotopic character of flow fluctuations, the scaling laws known for turbulent boundary layer may not be applied. The local features of flow are discussed for several points chosen from the flow visualization using two sets of experiments: (i) the pressure and velocity fluctuations an the model car (at several distances from the wall) measured as RMS values and using the coherence function; (ii) the coherence between the fluctuations in flow (velocity) and on the surface pressure) measured on the full-scale car. The data obtained for separation area are discussed by comparison with different flow configurations where no separation has been observed or where it has been reduced. The coherence measurements appear to be a very interesting tool for comprehension of spectral content of flow fluctuations.
Keywords: aeroacoustics; aerodynamics; local flow coherence; pressure fluctuations; separated flow; wind noise; vehicle noise; flow visualisation; velocity fluctuations; vehicle interiors; vehicle design.
International Journal of Vehicle Design, 1993 Vol.14 No.5/6, pp.511 - 529
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