Experimental study of the characteristics of the wake and drag coefficient changes of a car model in unsteady flow

In this study, changes in velocity, turbulence intensity and drag coefficient in the wake of a notch-back car modelling steady and unsteady flow is measured and evaluated. The blow open circuit wind tunnel is used to simulate fluid flow. Turbulence intensity and nominal maximum speed of the device is measured to be ۰.۰۱% and ۳۰m/s, respectively. The speed has been continuously increased by an inverter causing changes in rotational speed of the electromotor. In the near location to the model, the results showed three different regimes in the velocity profile of the model’s wake. With increasing distance from the model and with increasing the speed, three regimes in the wake are close to each other. Drag coefficient for several velocities is measured, where the result shows that decreasing in drag coefficient is proportional with increasing velocity. In addition, the changing trends of higher order velocity of parameters like flatness and skewedness are depicted. 

Keywords:

Unsteady Flow , Car model , Drag coefficient , Hot wire anemometry