Vortex dynamics in the wake of a finite span wing in stable stratification.*

A numerical investigation is carried out to study the evolution of wing-tip vortices in a stably stratified environment. Earlier studies have mostly

modeled the wake behind a wing using a pair of counter rotating vortices(Spalart 1996, Ortiz et al. 2015). In the present work we simulate the full

wake behind a finite span wing upto a downstream distance of 60 chord lengths for various levels of stratification. In the unstratified case, nearwake

consists of the vortex rollup and far wake consists of fully developed wing-tip vortices (Navrose et al. 2019). The calculations are carried out at Re

(Reynolds number)=1000 and 1< Fr(Froude number) <10. The results show that as strength of stratification increases, the rollup process of wing-

tip vortex formation is inhibited. The stratification suppresses the vertical motion and baroclinic vorticity of opposite sense as that of wing-tip vortices

is generated that persists along with vortex sheet. At relatively large stratification elongated flat 'V'-shaped structures are observed in the near

wake. The far wake in this case comprises of a mixture of pancake like strutures (Pal et al. 2017) and streamwise elongated vortical structures. The

vortical structures appears to have a well defined wavelength in the streamwise direction.