Investigation of Turbulence Properties in Wall-Bounded Flows with Pressure Gradients and Separation

摘要

Turbulence properties of wall-bounded flows with pressure gradients and separation are investigated using numerical simulation. Incompressible, highly-resolved, large eddy simulations (LES) are performed to investigate both straight and convergent-divergent channels. The channel has a bump profile that induces pressure gradients in the flow and a separation bubble. LES results are obtained using a semi-spectral formulation for low to moderate Reynolds numbers, Re_τ = 170 and 615, based on the friction velocity at the channel inlet. The aim of this work is to analyse the turbulent kinetic energy (TKE) balance in physical and wave spaces for problems involving favorable and adverse pressure gradients. Proper orthogonal decomposition (POD) is also used to reconstruct the TKE balances with the most energetic scales and assess the role of viscous effects and turbulence production in the TKE budgets. The results show that important viscous effects occur at the same range of wavelengths for which production is found.