Development of a Test Environment for Air Intake Aerodynamics of Road Vehicles

Licentiate thesis, 2007

In the past years work on aerodynamics of road vehicles, the focus has mainly been on shaping the exterior. Recently, however, the focus has shifted towards an optimization of details. One such detail is the air intake for the cooling system. On most vehicles there are several of these and they are required to provide an air flow to cool a range of components. The combined drag of the cooling air intakes can constitute up to 15% of the total drag of the vehicle. The foremost important of these systems, is that for the engine cooling system. To reduce cost and lead time in the aerodynamic development of road vehicles, it is crucial to be able to conduct detailed model tests. To do so however, requires a profound knowledge of the scaling or so called Reynolds effects associated with model scale testing. The overall aim of this project is to establish such knowledge base. To reach that point however, certain prerequisites are required. This thesis describes how an environment that enables detailed studies of cooling airflow on road vehicle models, was established. The work focused on two main parts. The first was to realize what aspects of the existing aerodynamics laboratory inventory that needed updating or improved to facilitate the aforementioned studies. The second task was to design a wind tunnel model of a modern road car that would enable studies of cooling air inlet flows. It was decided that a 30\% model of a Volvo S60 would be suitable. The model was designed with detailed underhood and underbody geometry and running in "wheels off" configuration. Furthermore the model was equipped with a representative radiator model and a system that enables 2 dimensional measurements of the cooling air inlet flow.