Unsteady Computational Investigations of Deploying Load Control Microtabs

Flow about a wind turbine airfoil with a deploying microtab device has been numerically simulated by solving unsteady turbulent compressible two-dimensional, Navier-Stokes equations with the OVERFLOW 2 solver. Using a Chimera/overset grid topology, microtabs were placed at 95 % of chord of a S809 airfoil. Microtab heights on the order of 1 % of chord, deployed on the order of one (1) characteristic time unit were utilized. The effects of freestream angle of attack on the aerodynamic response was also investigated. Validation studies with experimental results for static deployed microtabs and a dynamically deployed spoiler were also performed to ensure accurate temporal and spatial resolution of the numerical simulations. Nomenclature c = main airfoil chord CD = aerodynamic drag coefficient CL = aerodynamic lift coefficient CL,adverse = peak lift coefficient opposite in sense to the desired effect from device deployment CM = aerodynamic pitching moment coefficient (about c/4, nose-up positive) CP = coefficient of pressure DT = non-dimensional time step h(T) = tab position at time, T htab = fully deployed tab height t = physical time (seconds) T = non-dimensional time (Ut/c) T50 % = non-dimensional time to 50 % of mean steady state lift Tdelay = non-dimensional time to peak adverse lift Tdeploy = non-dimensional deployment time u ∞ or U = freestream velocity x = Cartesian coordinate v(T) = tab velocity at time, T α = angle of attack (deg) δ = normalized device position (0.00 when retracted, 1.00 when fully deployed) θ = spoiler deployment angle