Search Results

The influence on aerodynamic drag of a non-uniform, streamwise pressure distribution over the wake of an automobile model in both open-jet and closed-jet wind tunnels is considered in this paper. It has long been an unsolved issue in the theory of open-jet interference and is usually not important in closed-wall wind tunnels unless the model is very long. A new, semi-empirical approach is presented that is based on the observation that the drag changes due to a pressure gradient over a wake correlate with the empty-test-section pressure-coefficient difference between the base of the vehicle and the position of wake closure. A method is demonstrated that is able to remove the effect of the pressure gradient and that is not buoyancy related. This method is applied to a range of simplified and detailed automobile shapes at model scale and at full scale in various wind tunnels, as well as to normal flat plates.

Overtaking vehicles are among the most difficult driving maneuvers. In particular, young or inexperienced drivers often misjudge the current traffic situation when planning to pass a vehicle ahead. In most cases however, false situation estimations lead to dangerous traffic scenarios. For instance, in Germany about 18000 accidents occur due to misjudged overtaking maneuvers per year. The planning process for overtaking a vehicle requires to gather, weight and estimate different information pieces, like vehicle speed of oncoming traffic, road track ahead, velocity of the vehicle to be passed, etc. Besides sensing information, such a planning process demands a considerable amount of experience, particularly when estimating certain information that cannot be measured or sensed by the driver.