NUMERICAL INVESTIGATION OF STEADY BLOWING ON ACTIVE DRAG REDUCTION OF A TRUCK MODEL

Large trucks are an important way of transporting goods worldwide. Aerodynamic drag is responsible for a large portion of the energy consumption in trucks, hence there are increasing interests in reducing the aerodynamic drag to achieve better fuel efficiency. Many active and passive flow control strategies have been proposed to reduce the aerodynamic drag of trucks. The effects of steady blowing on drag reduction of the Ground Transportation System (GTS) truck model are studied using an Improved Delayed Detached Eddy Simulation (IDDES) model, with a Shear Stress Transport (SST) k - omega model in the boundary layer. A bounded central difference scheme is used for the momentum equation, and a second-order upwind scheme is used for the k and omega equations. A bounded second order implicit scheme is used for time marching. For the baseline case, the predicted pressure coefficient and drag coefficient are in good agreement with the experimental data. The locations of the vortices in the wake along a vertical streamwise cut and a horizontal stream-wise cut are also in reasonable agreement with the experimental data. In addition to the baseline case, cases with steady blowing introduced from four slots at the edges of the truck base are also considered. The blowing velocities have a component in the streamwise direction, and another component perpendicular to the streamwise direction and pointing to the center of the truck base, forming a 45 degrees angle with the streamwise direction. Cases with three different blowing velocity magnitudes (10 m/s, 50 m/s, and 100 m/s) are reported. It has been found that the length of the recirculation zone, as well as the locations and sizes of the vortices in the wake have changed due to steady blowing for the 50 m/s and 100 m/s cases. Compared to the baseline case, cases with steady blowing velocity magnitudes of 10 m/s, 50 m/s, and 100 m/s have a drag reduction of 2.41%, 8.84%, and 9.24%, respectively. However, taking into account the power consumed to produce the steady blowing, the blowing efficiency for the three cases are 2.40%, 7.34%, and -2.76%, respectively. Among the three cases considered here, the 50 m/s case is the most efficient in reducing the aerodynamic drag. On the other hand, the 100 m/s case actually increases power consumption by 2.76%.