On the rate of spatial predictability in near-wall turbulence

Spatial evolution of small perturbations introduced into in inlet cross-section of fully developed turbulent flow in a long straight Circular pipe is investigated via direct numerical simulation (DNS). The turbulent inflow field is extracted From an auxiliary streamwise-periodic simulation running in parallel with the main spatial simulation. It is shown that mean perturbation amplitude T increases exponentially with distance downstream. The growth rate is found to be constant when normalized by viscous length, (epsilon) over bar similar to exp(0.0021x(+)) over the considered Reynolds-number range 140 <= Re-tau <= 320. The Universal character of perturbation growth is confirmed by channel-flow simulations.