Control of suction distributions on Boundary layer suction systems for automotive wind tunnels

Abstract

Wind tunnels are used to study airflows around objects like cars, airplanes and ice-skaters. This is done, simulating the real world, by blowing an airflow over a fixed body. In the real situation an object moves through the air, while in a wind tunnel it is the air that is moving. So a wind tunnel needs to generate an airflow. In this airflow, at the walls of the wind tunnel, an undesired effect occurs called boundary layer development. A thin layer of air is retarded due to friction of the airflow with the walls of the tunnel. In an automotive wind tunnel, which simulates airflows around cars, this boundary layer will also develop over the ground plane under the car. Because this boundary layer is not present on the road, this ground plane boundary layer should be minimized for accurate simulations. To minimize the ground plane boundary layer many techniques are implemented in wind tunnels and one of them is boundary layer suction. With boundary layer suction, a suction section in the wind tunnel floor removes, or partly removes, the boundary layer by sucking air away from the main airflow. This suction section is the main subject of this master thesis. Research will be done on a new suction system with an adaptive suction duct geometry. It will explore the possibilities to control the suction speed distribution on this suction system by adapting the geometry of the duct by actuators. A model of a system with an adaptive geometry is made based on the physical properties of the airflow in the duct. This model is verified by measurements on a test setup. It is found that different control techniques can be used to control the suction speed distribution of the airflow through a porous material. The capabilities of the controlled system are quantified for wind tunnel integration.