Available at: http://digitalcommons.calpoly.edu/theses/1295
Date of Award
MS in Aerospace Engineering
This thesis involves the experimental wind tunnel testing of a 0.127m by 0.127m square-base bluff body to test the effectiveness of trailing edge tabulations to reduce drag in the Cal Poly 0.912m by 1.219 m low-speed wind tunnel. To accomplish this, the boundary layer was first measured on the trailing edge of the model for the three speeds at 10, 20, and 30 m/s, with Re = 8.3e4, 1.6e5 and 2.5e5 respectively, without the tabs. Three different tests were performed to determine the effectiveness of the tabs. These tests included base pressure measurements, total drag force measurements and hotwire velocity fluctuation measurements. These tests were repeated with tabs on the model’s trailing edge at the three different tab heights and without tabs at all three test speeds.
The base pressure measurements showed a decrease in average base pressure with the addition of tabs which signifies an increase in drag. The total drag measurements confirmed this by showing that the overall force increases with the addition of the tabs. The hotwire tests further confirm this by showing that the vortex is present for every configuration tested.
This thesis showed that the addition of tabs was unsuccessful in reducing the effects of the vortex shedding for a square-base bluff body. The addition of low, medium, and high tabs to the square base of the bluff body all showed an increase in vortex strength and overall drag. Further study is required to determine if drag savings are feasible for tabs all around the square base of the bluff body and at different locations.