Physics and modeling of unsteady shock wave/boundary layer interactions over transonic airfoils by numerical simulation

摘要

Shock wave/boundary layer interactions arising in the transonic flow over airfoils are studied numerically using different levels of turbulence modeling. The simulations employ standard URANS models suitable for aerodynamics and hybrid RANS-LES methods. The use of a compressibility correction for one-equation closures is also considered. First, the intermittent shock-induced separation occurring over a supercritical airfoil at an angle of attack close to the buffet onset boundary is investigated. After a set of URANS computations, a scale-resolving simulation is performed using the best statistical approach in the context of a Delayed Detached-Eddy Simulation (DDES). The analysis of the flow topology and of the statistical wall-pressure distributions and velocity fields show that the main features of the self-sustained shock-wave oscillation are predicted by the simulations. The DDES also captures secondary flow fluctuations which are not predicted by URANS. An examination of the unsteady RANS-LES interface shows that the DDES successfully prevents modeled-stress depletion whether the flow is attached or separated. The gray area issue and its impact on the results are also addressed. The conclusions from the supercritical airfoil simulations are then applied to the numerical study of a laminar transonic profile. Following a preliminary characterization of the airfoil aerodynamics, the effect of the boundary layer transition location on the properties of two selected shock wave/boundary layer interaction regimes is assessed. In transonic buffet conditions, the simulations indicate a strong dependence of the shock-wave motion amplitude and of the global flow unsteadiness on the tripping location.