Turbulent structures of buoyant jet in cross-flow studied through large-eddy simulation

Carlo Cintolesi (1) , Andrea Petronio , Vincenzo Armenio

1 Università degli studi di Trieste = University of Trieste

In the present paper we study buoyant (plume) and non-buoyant (jet) fluid injection in a neutrally stratified uniform cross-flow. Both cases are of practical importance in environmental fluid mechanics. The study is carried out numerically , using highly resolved large-eddy simulation in conjunction with the La-grangian dynamic sub-grid scale model for both momentum and scalar transport equations. The velocity ratio is κ = 8. In the plume case, the Froude number is F = 10, such to allow the use of the Boussinesq approximation. The simulations are successfully validated against experimental data and well established semi-empirical relations. The study shows the existence of three different regions as regards the plume evolution, each of them characterised by different peculiarities: in momentum-buoyancy region the plume exhibits an almost steady cylindrical shape with relative small turbulence structures; in deflection region the plume is deviated horizontally and a high shear rate is detected; in entrainment region the vortex pair develops, along with the sausage-like turbulent structure. The comparison between the plume and the jet case shows that the latter has a higher eccentricity while its trajectory height is sensibly lower. Also, the sausage-like structures are not present. Finally, an empirical formula for the jet trajectory is given, although its full validation will require additional studies.

Domaines: Modélisation et simulation; Mécanique des fluides [physics.class-ph]

Carlo Cintolesi, Andrea Petronio, Vincenzo Armenio. Turbulent structures of buoyant jet in cross-flow studied through large-eddy simulation. Environmental Fluid Mechanics, 2018, ⟨10.1007/s10652-018-9629-1⟩. ⟨hal-02070287⟩