Modelling of a passenger vehicle's aerodynamics efficiency

For modeling the aerodynamic efficiency of passenger vehicles has been benefited from wind tunnel tests and numerical studies. In order to increase aerodynamics efficiency of passenger vehicles by numerical and experimental studies, improvements in their exterior body design has been made. In this way, harmful exhaust emissions of vehicles is reduced, provided significant increases in their fuel economies, road holding and maneuverability. When compared with the numerical studies, wind tunnel tests are very time consuming and cost. Accordingly, interest in the numerical studies in parallel with the rapid advances in computer technology in recent years has been increased steadily. In this study, comprehensive literature research regarding vehicle aerodynamics was made, aerodynamics forces occurring over a vehicle because of airflow around it and basic parameters creating this aerodynamics forces were examined. Later, experimental and numerical studies were carried out in order to determine basic parameters regarding aerodynamics efficiency of a vehicle model used at the present time. Based on the data obtained from both studies, an improvement work for its exterior design to increase aerodynamics efficiency of related vehicle model was made. In this way, by a diffuser channel opened to lower side of vehicle's boot compartment, decreasing its drag coefficient % 2 and increasing its road holding significantly was determined. Consequently, it was determined that results obtained from experimental and numerical studies made for 1:24 scaled Audi A4 vehicle model are in agreement with each other. Reynolds number independence of drag coefficient was provided by having enlarged sizes of vehicle model up to 1:1 scale for numerical study. However, Reynolds number independence of drag coefficient couldn't be provided since vehicle model used for experimental studies was too small and maximum inlet velocity for the wind tunnel set couldn't be reached Key Words; Vehicle Aerodynamics, Fuel Consumption, K-ε Turbulence Model