Predicting transition with algebraic intermittency function

Abstract

An algebraic intermittency function is developed for “laminar-to-turbulent” transition flow within the framework of Bradshaw stress–intensity factor (ratio of principal shear-stress over turbulent kinetic energy in the boundary layer), which is parameterized with a “flow-structure-adaptive” variable (eddy-to-laminar viscosity ratio). Naturally, the intermittency inherits the “flow-structure-adaptive” character and captures various transition phenomena like bypass, separation-induced, and natural transitions when incorporated in an undamped eddy-viscosity transport equation. An additional viscous-production term is added with the eddy-viscosity transport equation to ensure proper generation of eddy-viscosity at the viscous sublayer when computing separation-induced transition over a low-Reynolds number airfoil. Splitting the intermittency into low and elevated free-stream turbulence intensities has the potential to avoid the “trial-and-error” inconsistency involved in most of the correlation-based transition models for precise computations. The results demonstrate that the proposed algebraic intermittency model is rational and feasible.