Aerodynamic Drag Reduction of a Generic Lorry Model using Continuously Blowing Jets

Aerodynamic drag reduction is one of available techniques to reduce energy consumption and greenhouse gas emissions from the road transport sector. In the present study, the squared-back Ahmed body, representing the generic model of a lorry, is investigated. Continuously blowing jets, were installed at the top of the rear part of the squared-back Ahmed body to alter wake structures behind it. The drag reducing mechanisms by means of continuously blowing jets were identified. Numerical simulations of airflow over the Ahmed body at ReH = 33,000 were carried out using OpenFOAM. The results show that the drag coefficient of the squared-back Ahmed body for uncontrolled flow agrees well with the literature value. For controlled flow, six different cases were investigated based on the magnitude of the jet velocity at 20%, 40%, 50%, 60%, 80%, and 100% of the free-stream velocity, Uꝏ, respectively. It shows that the optimum drag coefficient Cd can be achieved when the continuously blowing jet velocity is approximately equal to 0.6Uꝏ. The corresponding drag reduction of 3.81% is reached; the mean base pressure recovery of 8.76% is obtained. In addition, the correlation between an increasing recirculation length and a base pressure recovery is established.