Numerical solution of unsteady flow on airfoils with vibrating local flexible membrane

  Unsteady flow separation on the airfoils with local flexible membrane (LFM) has been investigated in transient and laminar flows by the finite volume element method. A unique feature of the present method compared with the common computational fluid dynamic softwares, especially ANSYS CFX, is the modification using the physical influence scheme in convection fluxes at cell surfaces. In contrary to the common softwares which use mathematical methods for discretization, this method considers the physical effects on approximation and discretization and thus increases the accuracy of solution and decreases the diffusion errors significantly. We have focused on the effects of deformation of the membrane on aerodynamic characteristics. For this purpose, first, we have solved the flow on NACA0012 airfoil in Reynolds number of 5000 and investigated the effects of local flexible membrane on aerodynamic coefficients in laminar flow. Then, we have solved the flow over LH37 airfoil in Reynolds number of 1.1×106 and studied the effects of flexible membrane on aerodynamic characteristics in transient flow. To calculate the Reynolds stress in turbulence equations, transient γ-Reθ model has been used. According to the results, airfoil with local flexible membrane prevents flow separation, eliminates laminar separation bubble (LSB) and delays the stall.