Conditional sampling of dissipation in moderate Reynolds number grid turbulence

Abstract

Multi-point hot-wire measurements in grid turbulence have been used to conditionally average the dissipation over inertial-scale features of the turbulent field. Velocities were measured at 5 separate spatial points obtaining six simultaneous velocity components, at turbulent Rey- nolds numbers Reλ of 160 and 230. The dissipation was approximated with pseudo- or surro- gate dissipation εr′ based on one or two velocity gradients. The conditioned dissipation εr′ inside the most intense large-scale rotational regions of the flow is more than twice as large as the expected value of εr′ over the whole domain. Conditional averaging was also carried out over strong large-scale fronts showing smaller excess in dissipation.