Direct numerical simulation of turbulent round jet released in regular waves

Direct numerical simulation of the round jet released in regular waves has been reported. Evolution of the vortical structures during initial and long term evolution of the jet has been studied with the help of the swirling strength criterion. During an initial evolution of the jet, the vortex roll-up and emergence of secondary instability have been studied. The frequency of vortex roll-up in the case of wave environment was found to be lower as compared to the corresponding frequency of the free jet. The counter-rotating vortex pairs in the case of jet in regular waves was found to be asymmetric due to deflection of the jet as opposed to symmetrical structures observed in the free jet. As a long term evolution of the jet, the wave tractive mechanism has been studied. The wave tractive mechanism provided the jet, an additional opportunity to entrain fresh fluid in the jet apart from the jet momentum and the jet deflection. The analysis of the preferred mode reveals that the preferred mode in the case of the jet in regular waves is helical as opposed to the varicose mode in the free jet. The mean quantities of the jet in regular waves showed a significant spreading and entrainment in the jet as compared to the free jet. The turbulence quantities showed an elevated magnitude both axially and laterally as compared to the free jet.

Automated summary

This study investigates the evolution of a round jet released in regular waves through direct numerical simulation. It is found that the vortex roll-up frequency in the wave environment is lower compared to the free jet. The counter-rotating vortex pairs in the jet under regular waves exhibit asymmetry due to the deflection of the jet. The wave tractive mechanism provides the jet with an additional opportunity to entrain fresh fluid. The preferred mode in the case of the jet in regular waves is helical, unlike the varicose mode in the free jet. The mean quantities and turbulence levels in the jet under regular waves are significantly higher than in the free jet.