This paper presents results of a series of experiments carried out on models of a car and a truck in a wind tunnel to observe the pressure coefficient variation when the truck was overtaken by the car. However, conventional wind tunnels are not equipped to measure the yaw moment and side force created due to pressure difference created as a result of the interaction of two vehicles and the cross wind. An additional attachment for the wind tunnel was de-signed and built to measure the yawing moment and the side force experienced by the car when the cross wind is ap-plied. The attachment consists of a “top plate” which is independent from the wind tunnel frame and free to rotate. The car model is fixed to the “top plate” the top plate is connected to the base plate via a load measuring shaft which is connected to load cells that enable to measure the yaw moment. The pressure coefficient variation was measured by a series of pressure tapings provided by the circumference of the car. The two models were tested independently in the wind tunnel for their pressure coefficient variation. It was found that the pressure coefficient around the car varies substantially when it is overtaking the truck. It was also observed that when the cross wind is applied the yawing moment and the side force on the car increases with the air speed. The attachment was calibrated prior to the investigation and have been able to obtain consistent results. To relate the observations to real world conditions, fur-ther investigations are necessary.
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