Large eddy simulation of a transition process in separated-reattached flows

摘要

Transition from laminar to turbulence in separated-reattached flow occurs frequently and plays a very important role in engineering. Hence, accurately predicting transition is crucial since the transition location has a significant impact on aerodynamics performance and a thorough understanding of the transition process can greatly help to control it, e.g. to delay the turbulent phase where laminar flow characteristics are desirable (low friction drag) or to accelerate it where high mixing of turbulent flow are of interest (in a combustor). However, it is very difficult to predict transition using conventional Reynolds-Averaged-Navier-Stokes (RANS) approach and the transition process is not fully understood. Nevertheless significant progress has been made with the simulation tools such as Large Eddy Simulation (LES) which has shown improved predictive capabilities over RANS and can predict transition process accurately. This paper presents briefly LES formalism and followed by its applications to predict/understand the transition process and unsteady behaviour of the free shear layer in separated-reattached flow.