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 0.01% and 30m/s, respectively. The speed has been continuously increased by an invertercausing 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. پرونده مقاله

In this study, the time-average velocity in the near wake of a two-dimensional Notch-Back car model that located in the wake of a trailer has been investigated. The present experiments were carried out in an open circuit low-speed wind tunnel made by Fara Sanjesh Saba Ltd, in Iran and was used to simulate uniform air flow. Results show: at the close spacing, time- average velocity profile at the behind of car only has a maximum peak due to the interaction of the jet fluid with the wake of car, so that with increasing vehicles spacing, the jet fluid effect at the create velocity maximum pick gradually pale. In additional with increasing the vehicle spacing we see that the velocity in the wake of car started to grow from the lower height. To measure the drag coefficient it was preferred to use wake–survey method and also the equation recently derived by Van Dam. The dimensionless distance between vehicles derived based on the length of the front one ranges from 0.1 to 3. It was observed that the value of car drag coefficient experiences a rising trend in the beginning and then a descending one along dimensionless distance of 0.1 to 1.3 compared to individual condition. In further distances it will be less than the individual condition. پرونده مقاله