A Study of the Beginning Boundary Layer Influence on the Flow Field about a Two-Dimensional Automotive Model

An experimental investigation was performed to analyze the beginning boundary layer produced on the floor of a subsonic wind tunnel and its influence on the flow field about a two-dimensional automotive model. Hot film anemometer measurements were taken in the test section of the wind tunnel operating under various inlet configurations. The use of a splitter plate and modifications to the contour of the inlet to the wind tunnel were then studied to find their affects on the height of the boundary layer in the wind tunnel test section. Finally, a 2-D automotive model was constructed with pressure taps along the centerline of the model. This model was tested in the wind tunnel on the floor of the test section and on top of the splitter plate to resolve any differences created in the data from the different boundary layers created in the test section.

The hot film anemometer measurements provided a baseline boundary layer thickness produced in the test section of the wind tunnel. The modifications to the inlet contour of the wind tunnel resulted in a reduction in boundary layer height experienced in the wind tunnel test section. This decrease in boundary layer thickness can attributed to the elimination of the flow disturbance created by the step where the flow straightener and screens mount to the inlet of the wind tunnel. The model data from the test section and splitter plate showed an increase in velocity across the top of the model when placed on the splitter plate that can be partially attributed to the reduced height of the boundary layer created by the splitter plate.