Experimental investigation of the local pressure and velocity fluctuations due to a flow separation behind the A-pillar is presented. The separation is responsible for the generated in the car interior. Due to the non-isotropic 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) thepressure and velocity fluctuations on the model car (at several distances from the wall) measured as RMS values and using the coherencefunction; (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. (A).
Abstract