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This thesis presents an experimental investigation of drag reduction devices on a bluff body in ground effect. It has previously been shown that the addition of end-plate tabs to a rectangular based bluff body with an aspect ratio of 4 is effective in eliminating vortex shedding and reducing drag for low Reynolds number flows. In the present study a square based bluff body, both with and without tabs, will be tested under the same conditions, except this time operating within proximity to a ground plane in order to mimic the properties of bounded aerodynamics that would be present for a body in ground effect. The testing was done in the Cal Poly 3ft by 4ft wind tunnel, and was conducted in two phases. The first phase was base pressure measurements on the body with no tabs. Pressure readings were achieved via thirty pressure ports that were tapped into the base of the model, allowing for fifteen pressure readings in each of the spanwise and normal directions. Baseline data was taken with no ground plane installed in the wind tunnel, mimicking an unbounded flow case and creating a baseline against which further data could be compared once the ground plane was introduced. Three tests were then performed with the ground plane 12.7, 6.35, 3.175 cm (5, 2.5, and 1.25 inches) away, corresponding to values of 1h, 0.5h and 0.25h, with h being the models height, respectively. In addition to the pressure readings an overall force measurement was taken during each test setup and overall drag coefficients were able to be calculated. Tests were performed at Reynolds numbers of 1. The second phase of testing was similar to the first, but utilized an end plate that attached to the trailing edge of the model. This test used a end plate with tabs on two normal sides of the model. There were three tabs on each side, with a height of 0.03h. This thesis verifies that the addition of tabs to the trailing edge of a bluff body is unsuccessful in reducing the overall pressure drag due to vortex shedding along the trailing edge, as presented in previous work. However, it can also be seen that the introduction of a stationary ground plane has an obvious effect on the base pressures of a bluff body and that the bounded flow characteristics of a bluff body in ground proximity lead to an overall lower …

Experimental Investigation of Drag Reduction by Trailing Edge Tabs on a Square Based Bluff Body in Ground Effect