The ground simulation upgrade of the large wind tunnel at the Technische Universität München

The large wind tunnel at the Technische Universität München was upgraded by integrating a modular single-belt system, which enables the simulation of moving ground conditions for ground vehicle testing. Central part of this system is its large belt that moves at a maximum speed of 50 m/s. This belt not only simulates the relative motion between the model vehicle under investigation and the floor, but also drives the model's wheels. Due to its size, the wind tunnel facility is suited for testing 40 % scaled models of typical passenger cars, which are held in place by a newly designed model support system consisting of five struts: One strut to support the body of the model and four struts to hold the model's wheels on top of the moving belt. Another crucial step in upgrading the wind tunnel was to install a boundary layer scoop system to reduce the thickness of the boundary layer approaching the moving belt. All new systems were designed such that they can be moved into and out of the test section of the wind tunnel to be able to restore the old setting of the test section floor. This report addresses the key challenges we had to face during the process of upgrading the wind tunnel facility and introduces its special features and its most important sub-systems. The current report also contains results of tests we conducted to measure the distribution of the static pressure along the test section and the size of the boundary layer at different locations on top of the moving belt. Even though we did not obtain perfect conditions regarding the size of the boundary layer thickness on top of the moving belt, we still were successful in improving the scope of the wind tunnel facility in terms of ground vehicle testing.