Forcing a low Reynolds number channel flow to generate synthetic turbulent-like structures

The effect of interacting vortices on the turbulent-like synthetic structures regeneration in a low Reynolds number flow Re = 10 is investigated through direct numerical simulations. The configuration simulates two forced synthetic jets staggered in the lateral spanwise direction. The initial vortices create wall normal vorticity layers near the wall. The stagnation flow induced by the triggering eddy compresses the wall normal vorticity associated with the mother structure that consequently disappears rapidly. That breaks up the spanwise symmetry resulting in a shear layer transforming into a compact streamwise vorticity zone. The regeneration of coherent vortical structures is subsequently triggered resulting rapidly in a local turbulent-like spot. Main characteristics of the perturbed flow field are in close qualitative similarity with a localized turbulent spot that is in principle inconceivable at such a small Reynolds number. The analysis of the passive scalar transport shows that the method leads to efficient mixing at a Prandtl number Pr = 10.

► Mimic the wall turbulence in low Reynolds laminar flows. ► Specific interaction of the longitudinal vortices. ► Show the feasibility and efficiency of the interactive mixing process. ► Synthetic vortical structures have a rich hierarchy of shapes and scales. ► Structures resulting from the interactive mechanism have a high capacity of mixing.