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A Discontinuous Galerkin Method for the study of airfoils with actively controlled Gurney flap

Dr Andrea Lario
Politecnico di Torino
Wednesday, January 17, 2018 - 15:00
An efficient implementation of the Discontinuous Galerkin method is proposed for the solution of the Favre averaged Navier Stokes equations, written adopting an Arbitrary Lagrangian Eulerian formulation, for turbulent compressible flows in two dimensions and for bodies whose velocity with respect to the mean flow field is not constant. The turbulence model is based either on the Spalart Allmaras equation or on the k-omega.
To partially mitigate its intrinsic high computational cost, a nodal formulation of the Discontinuous Galerkin Method was adopted.
The integration in time of the governing equations is carried out either with an explicit Runge-Kutta fourth order scheme or with an implicit time discretization based on a preconditioned Generalized Minimal RESidual algorithm for the solution of the Newton linearized system.
The numerical model is applied to the solution of unsteady flows associated to an actively controlled Gurney Flap (or micro-tab) located in proximity of the trailing edge of an airfoil, with oscillations up to 20 Hz.
Several configurations of deployment motions are considered under different free stream conditions in order to demonstrate the capability of the solver to predict accurately unsteady non-linear problems at high Reynolds numbers.
Moreover the numerical calculations are compared with experimental data in the case of the NACA 0012 airfoil, and of a modified version of the base shape employed in the experiments whose trailing edge is thickened in order to accommodate the Gurney flap and the mechanism for the active flap tests.
The flow scenarios proposed in literature in the case of a static Gurney flap, under different flow conditions and flap geometries, are confirmed. The dynamic case is investigated for different motion frequencies and flap heights, and compared with available experimental data.

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