Experimental Investigation of the Effect of Flow Acceleration Magnitude on Wake Parameters and Drag Coefficient of a Model Vehicle in Accelerated Flow

In the present research, effects of flow acceleration magnitude on velocity profiles, near-wake and far-wake turbulences, and drag coefficients of a model vehicle are studied. Moreover, rate of changes in the mentioned parameters in an accelerated flow at various accelerations was considered. An open-circuit blowing wind tunnel was used for fluid simulation, whose maximum nominal turbulence and velocity were 0.1% and 30 m/s, respectively. Velocity was increased continuously at different accelerations using an inverter device. The results indicate that, geometry of the developed wake is consistent and independent of inlet flow acceleration. Furthermore, with the passage of time and increasing velocity, near-wake and far-wake velocity defects decreased largely and slightly, respectively. With increasing the inlet flow acceleration, momentum and turbulence components of drag coefficient increased. By enhancing the flow acceleration, drag coefficient increased. The lowest value of the drag coefficient often occurs in the current with minimal acceleration, which is approximately equal to the corresponding values in the flow at constant speed.