Effects of aspect ratio and inclination angle on aerodynamic loads of a flat plate

Abstract

AbstractLarge Eddy Simulations are carried out to analyze flow past flat plate in different configurations and inclinations. A thin flat plate is considered at three inclination angles (α = 30°, 60° and 90°) and three aspect ratios (AR = 0.5, 2 and 5). The Reynolds number based on the free stream velocity and chord length of the plate at different inclination angles varies between 75,000 to 150,000. An increase in the inclination angle while the aspect ratio (span to chord) is constant results in higher drag and lower lift on the plate. Increasing the aspect ratio at a constant inclination angle increases the mean aerodynamic loading except for the α = 30° and AR = 0.5 case where the mean forces are larger than the other aspect ratios for this specific inclination angle. The small aspect ratio suppresses and blocks the separation of the flow from the top and bottom edges causing larger aerodynamic forces relative to AR = 2, 5. Visualization of the flow structures shows the tip vortices have a significant role in controlling the shedding vortices from the top and bottom edges. At α = 30° and AR = 0.5, the two tip vortcies control and suppress the flow separation from the top and bottom edges. A stable wake was found for this case with no fluctuation. As the aspect ratio increases, the influence of the tip vortices on flow separation from the top and bottom edges reduces. As a result, larger fluctuations were found for cases with higher aspect ratios.