Investigation of Transition Delay on a Wing Section by Dynamic Surface Deformation

Abstract

Numerical calculations were carried out in order to investigate the delay of transition to turbulence on a wing section by means of local dynamic surface deformation. Physically, the deformation may be produced by piezoelectrically driven actuators located below a compliant aerodynamic surface, which have been explored experimentally. One actuator was located in the upstream region of the wing, and it was oscillated at the most unstable frequency in order to develop small disturbances corresponding to Tollmien–Schlichting instabilities. A second controlling actuator was placed further downstream, and then it was oscillated at the same frequency but with an appropriate phase shift and modified amplitude in order to decrease the disturbance growth and delay the transition process. The configuration consists of a NLF(1) 0414F natural laminar flow wing section in subsonic flow at a chord-based Reynolds number of $1\times {10}^6$ . Angles of attack of both 3.0 and 4.0 deg were considered. Large-eddy simulations were carried out via solution of the unsteady three-dimensional compressible Navier–Stokes equations using a high-fidelity computational scheme and an implicit time-marching approach. Two-dimensional simulations were used to develop an empirical process that was applied to determine the optimal phase shift and amplitude of the controlling actuator. Results of the simulations are described, features of the flowfields are elucidated, and comparisons are made between solutions for the uncontrolled and controlled cases in order quantify effectiveness of the control. It is shown that dynamic surface control can return approximately 20% of the upper wing surface to laminar flow that is lost to premature transition when disturbances are present.