DNS of turbulent channel flow at high Reynolds number under a uniform magnetic field

A direct numerical simulation (DNS) of turbulent channel flow with high Reynolds number has been carried out to show the effects of magnetic field. In this study, the Reynolds number for channel flow based on bulk velocity ub, kinematic viscosity ν, and channel width 2δ was set to be constant; Reb=2δub/ν=45818. A uniform magnetic field was applied in the direction of the wall normal. The Hartmann number was Ha=2δB0√σ/ρν=32.5 and 65. Turbulent quantities such as the mean flow, turbulent stress, and the turbulent statistics were obtained by DNS. Although the influence of the magnetohydrodynamic dissipation terms in the turbulent kinetic energy budget was small, large-scale turbulent structures, such as vertical structures, low-speed streaks, ejection, and sweep, disappear at the central region of the channel. Consequently, the difference between production and dissipation in the turbulent kinetic energy decreases with increasing Hartmann number at the central region and large-scale structures at this region disappear. (author)