Shear Effects in Non-Homogeneous Turbulence

Motivated by recent experimental and numerical results, a simple unifying picture of intermittency in turbulent shear flows is suggested. Integral Structure Functions (ISF), taking into account explicitly the shear intensity, are introduced on phenomenological grounds. ISF can exhibit a universal scaling behavior, independent of the shear intensity. This picture is in satisfactory agreement with both experimental and numerical data. Possible extension to convective turbulence and implication on closure conditions for Large-Eddy Simulation of non-homogeneous flows are briefly discussed.Comment: 4 pages, 5 figure

Reynolds-Averaged Navier-Stokes Calculations Of Unsteady Turbulent Flow

In this study, a combination of the unsteady incompressible Navier-Stokes equations in vorticityvelocity formulation and the Algebraic Stress Model (ASM) of Gatski and Speziale (1996) is employed for Unsteady Reynolds Averaged Navier-Stokes (URANS) calculations of turbulent boundary layer flows. The Navier-Stokes equations are solved using a fourth-order compact difference scheme in space and a fourth-order Runge-Kutta method in time. The highly accurate numerical method greatly reduces the possibility of contamination of the results by second-order artificial dissipation from the numerical schemes. A flat plate boundary layer subjected to a strong adverse pressure gradient with laminar separation and turbulent reattachment is investigated. Performing URANS calculations for this flow, we found that unsteady vortical structures remain in the flow field despite the large "effective eddy viscosity" produced by the turbulence model (ASM). This is due to the fact that a special function is ..