Numerical Study of Airflow around Vehicle A-pillar Region and Windnoise Generation Prediction

Flow separation and reattachment around the vehicle A-pillar region dictates strong pressure fluctuations on the side window surfaces and can also lead to generate aerodynamic noise. The objective of this work is to investigate qualitative flow visualization of airflow behaviour around vehicle A-pillar and its potential to generate windnoise in this region. By means of Computational Fluid Dynamic (CFD) under laboratory operating conditions, a series of three-dimensional Navier-Stokes simulations for the vortical flow around two simplified basic car models with different A-pillar/windshield geometry were carried out at different cruising speed. Both models were made with 60° flat inclination angles but with deferent A-pillar/windshield curvature, a small semi-ellipsoidal shape, a slanted sharp-edged shape. Investigations were carried out at velocities 60,100 and 140 for 0 and 15 degrees yaw angles. Results of mean pressure coefficient obtaining using CFD modeling were also compared against available experimental data. Furthermore, using Boundary Layer Noise Source Model, an approximate measure of the local contribution to total acoustic power per unit surface area was carried out in a given turbulence field. The studies provided reasonable agreement against available experimental data. The studies show that the surface mean pressure coefficients magnitudes are independent of Reynolds numbers and dependent largely to A-pillar and windshield effective corner radii. In addition, surface acoustic power level analyses show that A-pillar and windshield local corner radii effects significantly to potential of noise generation around A-pillar region.