Aerodynamic investigation of an airfoil in deep stall using SU2

Abstract

Airfoils in deep stall have been a subject of extensive computational discussion in the past, with multiple efforts being performed by various institutions to test their solvers and turbulence/hybrid sub-grid scale (SGS) models for their use in massively separated flows. This case has an important application in turbomachinery where unsteady flow is encountered - including wind turbines and helicopter rotors - for studies in both aerodynamics as well as aeroacoustics. Stalling conditions are caused in these applications when there is blade-wake interaction, and also in the presence of strong gusts. The change in the local flow physics in both these cases is caused by a local variation in the angle of attack, which can affect the aerodynamic performance from entire blades.

Although there have been studies in the past that have involved various hybrid SGS models and turbulence models to investigate the effect of them for this flow case, the shear-layer adapted SGS (SLA-SGS) model has not found precedence for the purpose of aerodynamic investigation in this flow case. Therefore, this thesis provides an extensive aerodynamic investigation of an airfoil in deep stall, with a comparison of flow field visualization results using this approach, and comparing aerodynamic performance parameters with other hybrid SGS models. An attempt has also been made to compare the simulation results with other turbulence models and meshing strategies for similar airfoils, to present a case to estimate the similarities and differences in performance.

The results show that the there is an overprediction of the trends obtained from the 3D results compared to the 2D experimental data. The sectional 2D results also show an overpredicted output compared to experimental data. Contradictory results are obtained in comparison to the reference literature used for different SGS models.

Finally, additional studies have been performed on the aerodynamics points of view, with an overview of the acoustics code implementation in SU2 being provided. This is in order to provide an insight into not only the working of the code, but also the possibilities of implementing the code for providing acoustic outputs for the present case.