FURI | Summer 2020

Study of the Interaction of Vortex Tubes with Suspended Dust Particles

Vortex stability is a key area of interest. Vortical flows over aircraft wings at high angle of attack can enable the aircraft to perform maneuvers that are impossible otherwise. On the downside, vortices shed by aircrafts, the so-called wingtip vortices, are one of the main factors in limiting airport efficiency and induce contrail cirrus that persist for long durations in our atmosphere. Although the stability and resilience of unladen vortex tubes has been thoroughly documented, currently there is no effective way of destabilizing them. The research team proposed to investigate dispersing dust particles as a mechanism to increase the decay rate. The research goal was to investigate the role of Stokes number (a measure of particle inertia) on the decay rate of the vorticity while keeping the Reynolds number (a measure of non-linear convective effects)  constant. This study found that particles with Stokes number (St) of .6 dissipate 40% of the vorticity after 3 seconds while St=8 only dissipates 20 % vorticity within the same time. Smaller particles have a more lasting effect than larger particles and dissipate the vorticity rapidly. Conversely, based on the volume fraction and the particle number density, large particles are shown to be quickly thrown outwardly in comparison to smaller particles.