Vortical turbulence structure and transport mechanism in a homogeneous shear flow

Direct numerical simulations (DNS) are carried out to investigate the kinematics of vortical structures in a homogeneous shear flow, and their association with the momentum transfer is studied in detail. Longitudinal streamwise vortices are generated and conditionally averaged over all the computational region. The effects of the nonlinear term on their kinematics are investigated by comparing the DNS and Rapid Distortion Theory (i.e., RDT). As a result, some important similarities are found in the vortical structure between the homogeneous shear flow and near-wall turbulence. It is also found that the strain rate in the vortical structure, which is markedly affected by the nonlinear term, determines the transfer functions associated with the energy cascade of the turbulence. (C) 2000 American Institute of Physics. [S1070-6631(00)51111-8].