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Analysis of Tabs on Aerodynamic Coefficients
Lorena Moreno, C.P. van Dam
Mechanical and Aeronautical Engineering, UC Davis
 The effects of translational tabs are being studied to determine the effects on aerodynamic load control on an airfoil. In the beginning stages of this research, the complexity of the problem was greatly simplified by using fixed tabs of varying height and chord location on the upper and lower surface of the S809 airfoil. At a Reynold's number of 1,000,000, the lift and drag analysis are done in an open circuit, low speed, and low turbulence aeronautical wind tunnel at UC Davis. Lift was measured using a force balance under the test section, while drag values were found using a traverse mechanism that moves a pitot-static probe vertically and horizontally across the test section of the wind tunnel. Based on experimental testing, tabs on the upper surface lead to a decrease of the coefficient of lift, CL , up to separation of the flow where the tabs become ineffective. There is also an increase of the coefficient of drag, Cd. On the lower surface there is a general increase in CL as the flow remains attached at all angles of attack; however, the tab location survey showed a reversal of trend for the tab location of 90% chord length from the leading edge where CL decreases. The drag on the lower surface is slightly increased with the tabs, yet at about an 8º angle of attack, the drag is reduced as the tabs are positioned further away from the trailing edge. Data analysis shows that for the 95% chord location and 1% chord tab height on the lower surface there is a max increase of about 7.47% of the lift to drag ratio, CL/ Cd at 0º angle of attack. Overall, the best location for the design constraints of the translational tabs is at 95% chord length from the leading edge and tab height of 1.5% chord length. By inserting tabs at this location, there is more control of the flow on the surface which can be applied to wind turbines and airplanes.
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Particle Image Velocimetry Analysis of Rotor Vortex Wakes
Lorena Moreno, Ömer Savas, PhD
Mechanical Engineering, University of California, Berkeley
Premixers with fuel injection help burn fuel cleanly and efficiently in gas turbine combustors. However, currently there isn't a guide indicating the optimal diameter of the injection ports and the spacing between them. By systematically measuring different variations of these two, the optimal combination that minimizes the horizontal mixing distance can be discovered, improving the device's efficiency. The premixer is modeled by a wire mesh grid with heated segments downstream of a turbulence grid in a low-speed wind tunnel. The goal of the study is to determine the effect of the size of the heated segment and the separation between them on the mixing of the heated and unheated air as a function of downstream distance. The approach consists of measuring the time resolved velocity and temperature using hot wire anemometry and small diameter resistance thermometry (cold wires).
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