In this study, viscous, turbulent, and steady flow around an airfoil near the water surface has been simulated through a numerical method. In this simulation, Navier-Stokes equations have been solved using the finite volume method with a discretized second-order accuracy and PIMPLE algorithm. The Volume of Fraction (VOF) method has been employed to predict the free surface flow. A part of the simulation results has been validated through numerical and experimental data. Besides considering the style of flow separation in the angles of numerous attacks and airfoil static stall near the surface of the water. For this purpose, the airfoil simulation has been processed airfoil in the 68,000 Reynolds number, angle of attack of 2.5 to 11 degree and different distances from the water surface ( h/c = 0.5, 1, ). In a larger angle of attacks, flow is initially separated from the leading edge of the surface, and then it attaches to the surface at a lower point. This reattachment leads to an increase in adverse pressure gradient and the formation of a larger separation in the downstream of the airfoil. The pressure gradient dramatically increases, and the flow gets separated from the upstream of the airfoil. Upon lowering distance from the surface, static stall takes place at a higher point and a lower angle of attack, respectively.
In this research, viscous, unsteady and turbulent fluid flow is simulated numerically around a pitching NACA0012 airfoil in the dynamic stall area. The Navier-Stokes equations are discretized based on the finite volume method and are solved by the PIMPLE algorithm in the open source software, namely OpenFOAM. The SST k - ω model is used as the turbulence model for Low Reynolds Number flows in the order of 105. A homogenous dynamic mesh is used to reduce cell skewness of mesh to prevent non-physical oscillations in aerodynamic forces unlike previous studies. In this paper, the effects of Reynolds number, reduced frequency, oscillation amplitude and airfoil thickness on aerodynamic force coefficients and dynamic stall delay are investigated. These parameters have a significant impact on the maximum lift, drag, the ratio of aerodynamic forces and the location of dynamic stall. The most important parameters that affect the maximum lift to drag coefficient ratio and cause dynamic stall delaying are airfoil thickness and reduced frequency, respectively.
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