P. Orlandi

Direct numerical simulations of turbulent channel flow with transverse square bars on one wall

Direct numerical simulations have been carried out for a fully developed turbulent channel flow with a smooth upper wall and a lower wall consisting of square bars separated by a rectangular cavity. A wide range of

Vortex dipole rebound from a wall

w/k

Large Eddy Simulation in Complex Geometric Configurations Using Boundary Body Forces

, the cavity width to roughness height ratio, was considered. For

Direct simulations of turbulent flow in a pipe rotating about its axis

w/k\,{\ge}\,7

Vortex rings impinging on walls : axisymmetric and three-dimensional simulations

, recirculation zones occur immediately upstream and downstream of each element while mean streamlines and spatial distributions of the skin frictional drag indicate that each element is virtually isolated. The maximum form drag occurs at

On the generation of turbulent wall friction

w/k\,{=}\,7

DNS of turbulent channel flows with two- and three-dimensional roughness

and coincides with the minimum skin frictional drag. The dependence on

Numerical simulation of tripolar vortices in 2D flow

w/k

A tentative approach to the direct simulation of drag reduction by polymers

of the Clauser roughness function reflects that of the form drag.

Properties of d-and k-type roughness in a turbulent channel flow

Accurate numerical simulations of vortex dipoles impinging on flat boundaries have revealed interesting new features. In the case of free‐slip boundaries the dipole does not rebound from the wall. In the case of nonslip walls rebounding occurs and complex interactions of secondary and tertiary vortices appear. The numerical simulation of the first dipole rebound from the wall agrees with experimental visualizations. Numerical experiments extending in time beyond the real experiments show multiple rebounding. Each rebound is associated with the detachment of a secondary vorticity layer from the wall, these layers merge, and at a value of Reynolds number Re=1600, form a new dipole. This dipole has sufficient circulation to induce on itself a motion in the opposite direction to the motion of the initial dipole.