engleski

Boundary layer method for unsteady aerodynamic loads determination

In this work a simple and accurate method for two-dimensional unsteady aerodynamic load determination on airfoil is developed. The method employs viscous-inviscid coupling. The inviscid flow is governed by the unsteady Euler equations solved by finite volume method on moving C-type rigid grid, while viscous flow is governed by steady boundary layer integral equations. The Euler equations are solved in conservative form, in transformed body-fitted coordinates. The viscous-inviscid coupling is performed by transpiration velocity incorporated in the boundary condition on airfoil. Therefore, the method requires no grid deformation for the boundary layer influence inclusion. The transition is predicted by the e^n method. The viscous-inviscid method is focused on subsonic and transonic flows, at high Reynolds number, with shock-wave appearance. The steady and unsteady test cases for three characteristic airfoils are performed, namely NACA 0012, NACA64A010, NLR 7301. The results are compared with experimental data and with unsteady RANS calculations. The method gives results which are in good agreement with experimental data and with calculated unsteady RANS results. The method has convergence problems in the test cases with separation. The method is applicable in the design processes where unsteady loads are required within reasonable time and with accuracy comparable with RANS methods.

viscous-inviscid coupling; viscous flow; Euler equations; transpiration velocity; computational fluid dynamics; mach number; airfoil; shock-wave; airfoil pressure coefficient distribution

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