Investigation of Turbulent Compressible Flows Past Airfoils Using High-Fidelity Simulations

Abstract

The phenomenon of dynamic stall often occurs on the rotor of helicopters at high forward flight speeds or during maneuver and it is responsible for large torsional airloads and vibrations on the rotor blades. Hence, it is a limiting factor for the helicopter performance. It is known that when the viscous zone extension remains of the order of the airfoil thickness, i.e., in light stall conditions, the negative damping is more likely to occur. In this regime, the airfoil geometry, reduced frequency, maximum incidence, and Reynolds and Mach numbers, influence the qualitative behavior of the flow. Furthermore, if shock-waves are involved, they change the onset mechanism for dynamic stall through boundary layer separation. Several mathematical models and methods of computational fluid dynamics have been used in the literature to predict the effects of dynamic stall. However, they failed in providing satisfactory results at Reynolds and Mach numbers appropriate to helicopter rotors. Moreover, the physical mechanisms of both dynamic stall, even in incompressible cases, and shock-turbulence interaction are still not fully understood. In this sense, this project propose to employ large eddy simulations with high-resolution schemes to study flow conditions consistent with those encountered in rotorcrafts. Then, techniques of statistical analysis will be carried out to investigate coherent turbulent structures present with the aim to understand the physical mechanisms in the compressible flows investigated. (AU)