Low reynolds number turbulent flows around a dynamically shaped airfoil

A computational investigation for flows surrounding a dynamically shaped airfoil, at a chord Reynolds number of 78,800, is conducted along with a parallel experimental effort. A piezo-actuated flap on the upper surface of a fixed airfoil is adopted for active control. The actuation frequency focused on is 500 Hz. The computational framework consists of a multiblock, moving grid technique to handle the geometric variations in time, using the eⁿ-based laminar-turbulent transition model and two-equation turbulence closures, and a pressure-based flow solver. The dynamic grid redistribution employs the transfinite interpolation scheme with a spring network approach. Comparing the experimental and computational results for pressure and velocity fields, effects of the detailed geometric configuration of the flap, the flapping amplitude, turbulence modeling, and grid distributions on the flow structure are assessed. Even though the gap between the flaps is narrow (0.016), it causes noticeable impact on flow structures in the spanwise direction. Interaction between the movement of the flap and the separation location and vortex dynamics is investigated. In the context of the k-z turbulence model, the low-Reynolds number formulation performs better than the wall function treatment.