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UNSTEADY WALL PRESSURE FIELD OF A MODEL A-PILLAR CONICAL VORTEX

Cedric Hoarau
Laboratoire d'Etudes Aérodynamiques (LEA UMR 6609), Téléport 2 , 1 Av. Clément Ader, BP 40109, 86961 Futuroscope Chasseneuil , FRANCE

Jacques Boree
Institut Pprime, UPR CNRS 3346, ENSMA, Universite de Poitiers, BP 40109, 86961 Futuroscope Chasseneuil Cedex, France

Janick Laumonier
Laboratoire d'Etudes Aérodynamiques (LEA UMR 6609), Téléport 2 , 1 Av. Clément Ader, BP 40109, 86961 Futuroscope Chasseneuil , FRANCE

Yves Gervais
Département Fluides, Thermique et Combustion Institut Pprime CEAT, Poitiers, FRANCE

Abstract

The spatio-temporal properties of the unsteady wall pressure field of a model A-pillar conical vortex are studied in this paper by combining 2 components LDV measurements and multi-points pressure measurements using off-set microphones. Detailed LDV measurements are displayed and discussed in the vortex region. A spectral analysis of the fluctuating pressure under the vortex core is used to analyse the link between the temporal and spatial scales of the unsteady aerodynamic and the wall pressure field. We show that the conical vortex is a guide for the velocity perturbations and that their hydrodynamic pressure footprint is transported at the measured mean axial velocity in a local reference frame aligned with the vortex core. The energy containing higher frequency parts of the PSD are only weakly correlated when distant sensors are considered. However, two distinct peaks of coherence at lower frequencies are observed and discussed physically. The distinct contributions extracted here have a significant impact as Cp' is concerned and should be transmitted in very different ways by the car structure because the frequency and length scale range is very distinct.