ZETA II Code for Determining the Flow Around Multielement and Deformable Airfoils.

The present NASA-University consortium involves research on the development of an efficient and accurate numerical procedure to treat general unsteady viscous flows. Of particular interest in the present work are flows relevant to helicopter rotors. Special efforts are centered on new concepts applied to the rotorblade configuration on the helicopter to improve the rotor aerodynamic characteristics. Among them airfoil dynamic stall and the aerodynamic noise of vortex-airfoil interactions were extensively studied by using the numerical procedure. The procedure, based on the formulation of an integral representation of the velocity vector and the vorticity transport equation, is used to solve incompressible Navier-Stokes flows. ZETA, a computer code developed at Georgia Tech, is used as the basis for the development of an extended computer code, ZETA II. The ZETA code is very efficient in the treatment of single solid airfoils undergoing arbitrary motions. The extended ZETA II can treat the two-element airfoil, the deformable airfoil, and vortex-airfoil interaction. New concepts aimed at improving the helicopter maneuverability and susceptibility are studied, including the slatted airfoil and the deformable airfoil. Numerical results obtained by using the ZETA II code show that both slatted and deformable airfoils reduce the dynamic stall and that the deformable airfoil reduces the blade-vortex interaction BVI noise.