MAXIMUM VERTICAL PENETRATION OF PLANE TURBULENT NEGATIVELY BUOYANT JETS

Series of plane turbulent negatively buoyant jet (or fountain) experim ents were carried out by discharging saline water vertically upward fr om a rectangular slot into a stagnant fresh water environment. The pla ne jets were characterized by the formation of fronts that became unst able as the densimetric Froude number increased. When the Froude numbe r was large (F > 10) the maximum penetration Z(m) was mainly controlle d by the momentum flux M-o and the buoyancy flux B-o, and the measurem ents confirmed that the asymptotic solution for large Froude numbers i s Z(m) = C(m)b(o)F(4/3), where b(o) is the slot half-width, and the co nstant C-m = 2.0. At small Froude numbers, the maximum penetration was less than predicted by this asymptotic solution, and the deviations f rom this asymptotic solution were correlated using the mass flux Q(o) and the buoyancy flux B-o. This correlation suggested that the virtual origin defined by the deviation from the large Froude number solution was located at a distance Z(q) = C(q)b(o)F(2/3), with the constant C- q = 1.12. An attempt was made to explain large discrepancies in previo us investigations.