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Numerical study of boundary layer receptivity of airfoil cascade using vorticity criteria

Abstract:

Receptivity is the beginning of the transition phenomenon between laminar and turbulent flow. Direct Numerical Simulation (DNS) approach is used to solve the momentum and continuity equations in the domain. The purpose of the study is to characterize the decrement of the transport of vorticity in the flow direction, the dependence relationship of vorticity and the pressure gradient, the creation and destruction of vorticity and the relation between those phenomena and the receptivity inside the boundary layer. The study covers considerations related to different conditions as normal flow and perturbed flow with time dependent signals superimposed to the normal flow. The characterization of the vorticity field in the domain is product of the mathematical analysis of the pressure and velocity field in every location of the domain. For both cases, the normal flow and the perturbed flow conditions corresponding to the super-critic flow condition, the results show the receptivity phenonmenon is clearly represented by the vorticity parameter, especially in the change of the wavelength that vorticity suffers inside the boundary layer, as well as, the detached of some structure of vorticity from the airfoil surface in the inter channel section. However, in sub-critic flow condition neither normal nor perturbed flows do not show any relevant change in the behaviour of the vorticity parameter.