From aging to memoryless turbulent stripes in channel flow

Puffs, stripes, and spots that appear during the transition in wall-bounded shear flows have finite lifetimes, and as demonstrated in many studies, their decay is typically memoryless, i.e., they do not age, and the decay probability is constant in time. As shown recently, this standard result unexpectedly does not apply to turbulent stripes in channel flow. Their decay probability increases with time in sufficiently large channels where stripes fully localize. As it will be shown, the associated lifetime distributions correspond to what is known in population ecology as a type 1 aging process. In the present study, we explore the aspect ratio (width/height) dependence of the decay process of channel stripes. Starting from the classic planar channel case and approaching the square duct limit, the nature of the decay and the corresponding lifetime distributions change from aging to non-aging (i.e., memoryless).