Tracer particle dispersion around elementary flow patterns

The motion of tracer particles is kinematically simulated around three elementary flow patterns; a Burgers vortex, a shear-layer structure with coincident vortices and a node-saddle topology. These patterns are representative for their broader class of coherent structures in turbulence. Therefore, examining the dispersion in these elementary...

Coherent structures in turbulence: Their generation, identification, and contribution to tracer particle dispersion

Turbulence is implicitly present or explicitly desired in many natural and industrial processes, such as, flow over solid surfaces, cloud formation, pollination, combustion, and chemical mixing. Hence, a better understanding of turbulence can aid in fuel saving by reducing drag in the case of flow over solid surfaces, namely, cars, airplanes,...

The scaling of straining motions in homogeneous isotropic turbulence

The scaling of turbulent motions is investigated by considering the flow in the eigenframe of the local strain-rate tensor. The flow patterns in this frame of reference are evaluated using existing direct numerical simulations of homogeneous isotropic turbulence over a Reynolds number range from up to 1131, and also with reference to data for...

Auto-generation by interaction of weak eddies

For channel flow, we explore how the interaction of weak eddies produces additional eddies by means of auto-generation. This is done by DNS of two eddies with different initial strengths, initial sizes and initial stream-wise spacing between them. The numerical procedure followed is similar to Zhou et al[1]. The two eddies merge into a single...

Auto-generation in wall turbulence by the interaction of weak eddies

For channel flow, we explore how commonly found weak eddies can still auto-generate and produce new eddies. Before, only strong eddies (above a threshold strength) were considered to auto-generate. Such strong eddies are rarely observed in actual turbulent flows however. Here, the evolution of two weak conditional eddies with different initial...

Possible modification of the large-scale flow structures by vortical structural interactions

We explore the mechanisms behind vortical structural interactions modifying largescale structures in wall turbulence. The evidence for this in terms of vortex interactions, such as merging and intense vortex strengthening, is found in [4] in ideal flow conditions. Here, these interactions are studied experimentally and numerically in turbulent...

Merging and auto-generation of vortices in wall bounded flows

For channel flow, we explore how a hairpin eddy may reach a threshold strength required to produce additional hairpins by means of auto-generation. This is done by studying the interaction of two eddies with different initial strengths (but both below the threshold strength), initial sizes and initial streamwise spacing between them. The...