The momentum flux in turbulent submerged jets

Abstract

Although the jet momentum flux has been traditionally accepted as constant, this is not in general true because a weak pressure field is induced in the ambient fluid with positive gradient and because the induced flow field carries momentum flux to the jet. The angle ϕ, at which the induced flow streamlines enter the jet, is the basic parameter which determines whether the jet momentum flux increases, remains constant or decreases. A theoretical solution is presented for the variation of the jet momentum flux in turbulent submerged jets in stationary ambient fluid. The solution presented in this paper generalizes previous theoretical solutions and is in good agreement with existing experimental results. The contribution of the induced pressure field relative to the induced velocity field in varying the jet momentum flux is investigated. The induced flow streamlines are calculated using non-constant jet momentum flux and are compared with Taylor's solution (where constant jet momentum flux was assumed).