Predicting transition with wall-distance-free SST k-[formula omitted] model

Abstract

Unlike the correlation-based γ–Reθ transition model, an exceptionally simplified approach is applied to extend the wall-distance-free (WDF) model toward transition predictions. An anisotropic stress-intensity parameter as a function of eddy-to-laminar viscosity ratio is introduced, preserving the “flow-structure-adaptive” characteristic. The prospective parameter is included with the constitutive relation for the eddy-viscosity. The proposed formulation is intrinsically plausible, having a dramatic influence on the prediction of bypass, separation-induced and natural transitions. The newly devised transitional WDF (TWDF) model is further modified to compute separation-induced transition over a low-Reynolds number (LRN) airfoil. The curiosity toward airfoil performance at an LRN has been executed with growing attention to marine autonomous systems. An extra viscous-production term Pklim is added to the turbulent kinetic energy (k) equation to ascertain proper development of k at the viscous sublayer region. Reliance on this Pklim is likely to be suitable for forecasting separation-induced transition over an LRN airfoil. Results illustrate that the TWDF model sustains decent agreement with the four-equation γ–Reθ transition model.