Unsteady Numerical Simulations and Reduced-Order Modelling of Flows around Vehicles

In this thesis several simulations have been carried out aimed at improving the knowledge of vehicle aerodynamics and improving the flow around vehicles with respect to the aerodynamic drag. Five flows around different simplified vehicle models have been considered in five appended publications. One tractor-trailer model, two passenger car models, one freight wagon model and one regional train model. In the simulations of the flow around the tractor-trailer model, the focus is on the flow in the gap between the tractor and the trailer and how this flow affects the global drag of the model. Large Eddy Simulation is used to simulate the flow around four variants of the model with different geometrical configurations. The behavior of the drag coefficient of the tractor-trailer model when varying the gap width and the shape of the front edges on the tractor is explained by identifying and analysing the large vortices around and in the the gap. The focus in the study on one of the passenger vehicle models is on the so-called A-pillar vortex. This is a swirling longitudinal vortex formed along the side windows on passenger vehicles due to the separation of the flow from the side edges of the front window and th