Further Analysis of the Blockage Phenomenon During the Testing of Bluff Automotive Bodies in Closed Wall Wind Tunnels
2022-01-1085
03/29/2022
- Event
- Content
- The difficulties of testing a bluff automotive body of sufficient scale to match the on-road vehicle Reynolds number in a closed wall wind tunnel has led to many approaches being taken to adjust the resulting data for the inherent interference effects. But it has been impractical if not impossible to experimentally analyze the effects that are actually occurring on and around the vehicle when these blockage interferences are taking place. The present study is an extension of earlier work by the author and similarly to that study uses the CFD analysis of several bodies of differing configurations to examine the interference phenomena in solid wall wind tunnels and the effects that they have on the pressures, forces and force increments experienced by the vehicle model. This is accomplished by executing a series of CFD configurations with varying sized of the cross section from 0.2% to 13% blockage enabling an approximation of free air conditions as a reference. The earlier work is extended by using additional body configurations which include reference bodies from the Technical University of Munich and Ford Motor company to complement the simple shapes used in that study along with the use of a SAE Notchback model simple shape. Examination is made of the actual physical phenomena occurring around the vehicle as the proximity to the walls and ceiling is changed holding the test section aspect ratio and length constant. Static Pressure distortions, skin friction changes, velocity distortions and changes to the distribution of forces on the vehicle body are examined. The process is also used to attempt to suggest a limit on the blockage that should be used to ensure that the incremental changes made during a development project can be trusted to faithfully predict the free-air increments to be achieved on the production vehicle.
- Citation
- Gleason, M., and Riegel , E., "Further Analysis of the Blockage Phenomenon During the Testing of Bluff Automotive Bodies in Closed Wall Wind Tunnels," SAE Technical Paper 2022-01-1085, 2022, .