Dynamic stall in vertical axis wind turbines: Comparing experiments and computations

• Dynamic stall of a vertical axis wind turbine is modelled using unsteady RANS.
• The Menter-SST turbulence model is assessed for this unsteady separating flow.
• The turbulence model is found to be too dissipative.
• Nevertheless, stall angle, topology, and strength are simulated accurately.

Dynamic stall is often found in unsteady aerodynamic flows where the angle of attack can vary over a large range. It is of particular interest in the context of vertical axis wind turbines, where dynamic stall is the principal impediment to achieving improved aerodynamic efficiency. Here, we report computations using the unsteady Reynolds-averaged Navier–Stokes (URANS) equations with the Menter-SST turbulence model on a two-dimensional domain, over a range of tip speed ratios typical of the operation of vertical axis wind turbines. Comparisons are made against high resolution experimental data from particle image velocimetry (PIV), with special attention to the ability of the turbulence model to emulate the turbulence properties of the flow. It is shown that the computations approximate the experimental results well in most respects.