Fluid dynamics of pitching and plunging airfoils of Reynolds number between 1×10⁴ and 6×10⁴

We consider a combined experimental (two-dimensional particle image velocimetry in a water tunnel) and computational (two-dimensional Reynolds-averaged Navier-Stokes) investigation to examine the effects of chord Reynolds number on the dynamics of rigid SD7003 airfoil undergoing pitching and plunging motion in nominally two-dimensional conditions. Appreciable qualitative distinction in a moderately dynamically-stalled case in going from Re = 1×10⁴ to Re = 6×10⁴ was observed, suggesting nontrivial impact of viscosity even in conditions of strong forcing by motion kinematics. Additionally, computed lift coefficient time history is compared with Theodorsen's unsteady linear airfoil theory. The velocity and vorticity fields were in excellent agreement between experiment and computation for those phases of motion where the flow was attached; moderate agreement was achieved when the flow was separated. The small disagreements were consistent with the expected inaccuracies due to the turbulence model used. Similarly, Theodorsen's theory was able to predict the computed lift coefficient quite well when the flow was attached, and moderately acceptable otherwise.