Abstract
Direct numerical simulations (DNSs) are performed to study single-square grid-generated turbulence at Reynolds number ReL = 20,000 based on mean inflow velocity and length of a grid bar. Different from typical multiscale/fractal generated turbulence, in current simulation only a single large square grid is set at the inlet of the computation domain. First, visual evidence (profile of instantaneous velocity) is presented to verify the existence of large scale wake interactions and the jet-like behaviors in the downstream region. Meanwhile, we show the imprints of initial condition on the far downstream region via the second invariant of velocity gradient tensor. The relationship between wake-interaction length scale and peak positions of turbulence intensity along the centerline proposed by Mazellier & Vassilicos [Physics of Fluids 2010] is confirmed here. The present DNS results (i.e., streamwise evolution of mean velocity, turbulence intensity, etc.) are compared with those obtained from fractal-square grid experiments. Turbulence flow generated by the single-square grid exhibits some characteristics which are thought to be distinguishing features for fractal-generated turbulence.
