Experimental and Numerical Investigations of the Base Wake on an SUV

Artikel i vetenskaplig tidskrift, 2013

With the increase in fuel prices and the increasingly strict environmental legislations regarding CO2 - emissions, reduction of the total energy consumption of our society becomes more important. Passenger vehicles are partly responsible for this consumption due to their strong presence in the daily life of most people. Therefore reducing the impact of cars on the environment can assist in decreasing the overall energy consumption. Even though several fields have an impact on a passenger car's performance, this paper will focus on the aerodynamic part and more specifically, the wake behind a vehicle. By definition a car is a bluff body on which the air resistance is for the most part driven by pressure drag. This is caused by the wake these bodies create. Therefore analyzing the wake characteristics behind a vehicle is crucial if one would like to reduce drag. With the recent upgrade of wind tunnels with a moving belt system, the opportunity has emerged to investigate the flow field in the wake behind vehicles, matching closer the real on-road driving conditions. This study investigates experimentally and numerically the wake behind a passenger car of an SUV-type. Three configurations with a significant change in CD have been chosen for the analysis. Their wake shape together with their respective closure points have been analyzed using three planes, namely one x-plane, one y-plane and one z-plane. Results have shown that the numerical simulations correlate well with the experiments in wake shape and wake behavior. However in the chosen configurations they underestimate the wake length. A distinct interference of the traversing unit presence can be noted in the experimental results.