THE ROLE OF INFLOW TURBULENCE FOR LARGE EDDY SIMULATION ON MODELLING OF BLUFF BODY FLOWS

摘要

A random flow generation (RFG) technique for large eddy simulation (LES) is successfully adopted into a finite element based conventional fluid flow solver to generate the required inflow/initial turbulence boundary conditions for the LES computations of viscous incompressible turbulent flow over a two-dimensional circular cylinder at Reynolds number of 140,000. The effect of generated turbulent inflow boundary conditions on the transitional nature of the flow regime is studied during the early development of the very near wake of the cylinder. The numerical results obtained from the Smagorinsky sub-grid scale (SGS) model based simulations are compared with each other and with the experimental data for varying degree of inflow turbulence to discuss the issues such as the inflow turbulence effects on the time evolution of the local flow structures in the very near wake and on the integral flow parameter predictions such as separation points, transient fluid forces that the cylinder experience, and the local flow resolutions in the vicinity of the cylinder wall and the free shear layer. The influence of mesh resolution on the quality of the predicted results is also investigated. The comparison of present LES results with those of case without inflow turbulence and the experimental data indicates that the present LES approach coupled with the suggested RFG technique enhance the resolution of the turbulent flow and can be used with a confidence for a bluff body problem where the inflow turbulence is significant.