Analyzing the Near-Wall Behavior of the Langtry–Menter Transition Model

The local-correlation laminar-turbulent transition model of Langtry and Menter has seen use over a wide range of fluid dynamic flows. The model is often coupled to two-equation turbulence models via modification to the turbulent kinetic energy equation. A near-wall analysis of turbulent kinetic energy and specific dissipation shows that the coupling of the transition model introduces singular behavior in the turbulent kinetic energy destruction and diffusion terms. This causes the fully turbulent behavior post-transition to deviate from that intended by the shear stress transport model, raising uncertainty in its ability to model relevant turbulent flow physics. An extensively verified Reynolds-averaged Navier–Stokes solver was used to numerically examine the near-wall behavior for a suite of practical test cases, confirming the singular behavior of the destruction term. From the new understanding of the near-wall behavior, a new turbulence index function is derived to detect laminar-turbulent transition for practical aerodynamic configurations. The index is designed such that a value of 0 indicates laminar flow and a value of 1 indicates turbulent flow. Several two-dimensional and three-dimensional test cases were used to test the new turbulence index. The new turbulence index was found to be more reliable and less ambiguous for transition detection in comparison to that designed for use with a shear stress transport model.