Date of Award
Flow separation is a phenomenon that occurs when pressure increases in the streamwise direction of a flow, making a distinctive boundary layer or separation bubble. It causes aircraft to experience an increase in drag and noise and a decrease in a lift, hence degrading their aviation performance. This study uses numerical simulations to understand better the effects of high-frequency translational surface actuation (HFTSA) on flow separation control. The numerical simulations mimic the experimental parameters of an experiment performed by Okoye et al. on using the HFTSA system to control flow separation. A symmetrical airfoil structure of chord length of 0.3 m is drawn inside a computational domain with two velocity inlets and two pressure outlets. The velocity of streamwise flow is 4.3 m/s with the angle of attack -14 degrees. Structural grids of 946k nodes and 872k elements were generated for the computational domain. An actuation surface located on the suction surface of the airfoil uses User Defined Function to realize 122-micron mean-to-peak displacement with 565 Hz frequency. Large-eddy simulation turbulence model is adopted to capture vorticial structures within the airfoil wake. Velocity contours, pressure contours, velocity profiles, pressure profiles, and aerodynamic forces were examined before and after actuation. It is revealed that after actuation, the flow re-attaches, and separation bubbles were shrunk. After actuation, the lift coefficient increased by 180%, and the drag coefficient decreased by 28%. Hence, the HFTSA could suppress flow separation and improves aviation efficiency.
Gupta, Bibek, "Computational Study on Suppression of Airfoil Flow Separation using High-Frequency Translational Surface Actuation" (2021). Honors Theses. 1916.
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