Assessment of gamma−theta transitional model for laminar-turbulent transition prediction in supercritical airfoils

Abstract

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.A numerical study on the capability of the γ−θ turbulence model for predicting the laminar/turbulent transition in the boundary layer developing around a supercritical airfoil (NLR 7301) is described. The range in the Mach number explored is [0.3, 0.825], thus covering a fully transonic flow regime. For this purpose, a CFD solver (ANSYS CFX©) is used on a hybrid structured-triangular grid, where an accurate mesh setup of the wall boundary layer was performed in order to ensure (i) a value of y+ less than 6 everywhere and (ii) a number of boundary layer rows within the physical boundary layer no less than 4. Results obtained are compared to the experimental data described in the open literature and discussed in detail. Despite the various sources of uncertainty affecting the experimental data, the results regarding the transition location revealed a very good model predictive capacity for low-to-medium Mach numbers (Mach<0.6), while exhibiting a less satisfactory ability in the transonic regime (Mach>0.6). In this case, prediction of transition location on both sides of the airfoil is still accurate even if the correlation on the pressure distributions gets poorer.