Heavy traffic volume makes tailgating a common picture on the road today. Wake interference, particularly in the scenario when a relatively small sedan drives into the wake of a large truck, may raise some serious highway safety concerns. In this study, the characteristics of separation bubble in the wake of model trucks with various degrees of model details are studied. The objective is to uncover the impact of truck model details on the characteristics of the wake bubble. Furthermore, how the spacing between the leading sedan and truck affects the bubble is also investigated. The hotwire measurements as well as flow visualization using a tuft grid have been conducted in a closed-loop wind tunnel at Re=2–7×105. The wind tunnel results revealed that both the degree of model details and the spacing between sedan and truck have significant impact on the three dimensional structure of the wake bubble
