Efficacy of turbulence modeling techniques in capturing dynamic stall at low Reynolds numbers

Dynamic stall is a subject of continued interest in the aerodynamics and aeroelasticity communities due to its broad range of engineering and biological applications, such as helicopter rotor blades, rapidly maneuvering flight, wind turbines, jet engine compressor blades, or flapping of insect wings. This study focuses on investigating the unsteady flow physics of the dynamic stall phenomenon associated with a harmonically pitching NACA 0012 airfoil for different reduced frequencies (k) at Re = O(104) and comparing the evolution of the unsteady flow structures. To that end, the effect of turbulence modeling on the prediction of Dynamic Stall is investigated using Unsteady Reynolds Averaged Navier Stokes (URANS) and Improved Delayed Detached Eddy Simulation (IDDES) techniques. The k- ω Shear Stress Transport (SST) model is adopted for URANS closure and the Spalart–Allmaras-based IDDES strategy is used in this study. The simulation results are compared to those obtained from low-speed wind tunnel experiments. It is observed that 3D IDDES outperforms 2D URANS in capturing the reattachment phase and the dynamic stall onset due to its ability to resolve finer turbulence scales that play an important role in highly separated flows. The present findings hint that there is a need for 3D scale resolving techniques to capture the 3D nature of dynamic stall. This study will further be extended for three different airfoil sections, i.e., a flat plate, a NACA0012, and a NACA0018 in order to investigate the effect of thickness on the nature of dynamic stall, such as light and deep dynamic stall.