A Galilean-Invariant-Variable-Based RANS Closure Model for Bypass and Laminar-Separation-Bubble Induced Transition

A one-equation Reynolds-averaged Navier-Stokes closure model has been established for the bypass and laminar separation bubble (LSB)-induced transition. A new local indicator is proposed to describe the influence of turbulence intensities and pressure gradients which makes the model Galilean invariant. Based on this new indicator, a novel and efficient transition criterion is formulated. For LSB-induced transition, an empirical correlation is developed to modify the intermittency factor and control the size of separation bubbles. Several flow cases, including the flat plates with or without LSBs, the semicircular leading-edge flat plates and the SD 7003 airfoil, are employed for the model verification. The predictions show good agreement with the experimental data and large eddy simulation data for different inlet conditions, which indicates that the increment of freestream turbulence intensity reduces the size of the LSBs.