Quantitative Analysis of Vehicle Aerodynamics during Crosswind Gusts

This thesis deals with unsteady vehicle aerodynamics during gusty crosswind. One of its achievements is to provide detailed information from on-road measurements on the oncoming flow which faces a vehicle during crosswind gusts. This information is used to set up a wind tunnel experiment that replicates realistic flow conditions during gusty crosswind. To this end, a 1:2 scale generic notchback model is oscillated around its vertical axis while being exposed to constant flow. It is shown that a delayed reaction of the wake flow results in a lateral force at the rear which increases the total unsteady yaw moment amplitude. This may deteriorate driving stability. The experimental data are used to validate a CFD simulation tool. Though the general characteristics of the unsteady mechanism are correctly reproduced, numerical errors appear which prohibit its application for a reliable prediction of unsteady aerodynamic loads in industry.