Experimental and numerical aerodynamic analysis of a passenger car: Influence of the blockage ratio on drag coefficient

Abstract

Experimental and numerical investigations were performed to determine the pressure distributions and the drag forces on a passenger car model. Experiments were carried out with 1/5th scale model FIAT Linea for 20% and similar to 1% blockage ratios in the Uludag University Wind Tunnel (UURT) and in the Ankara Wind Tunnel (ART), respectively. Computational fluid dynamics (CFD) analysis for 1/5th scale model with 0%, 5%, and 20% blockage ratios was performed to validate various blockage correction methods supplementary to the experimental results. Three-dimensional, incompressible, and steady governing equations were solved by STAR-CCM+ code with realizable k-epsilon two-layer turbulence model. The calculated drag coefficients were in good agreement with the experimental results within 6%. Pressure coefficients on the model surfaces have shown similar trends in the experimental and numerical studies. Some of the existing blockage correction methods were successfully compared in this study and predicted drag coefficients were within +/- 5%. The authors propose the continuity and the Sykes blockage correction methods for passenger car models because they are very simple and practical and they can be used economically for engineering applications.