Axisymmetric Submerged Intrusion in Stratified Fluid

Abstract

This paper presents the results of laboratory experiments conducted to study the spreading rates of axisymmetric intrusive gravity currents produced by a constant inflow into a stratified body of water. The experiments were conducted over a wide range of initial parameters. A balance of the forces that drive and retard the flow indicate that the intrusion is characterized by four spreading regimes: (1) the radial jet; (2) the radial momentum flux balanced by the inertia force; (3) the pressure (buoyancy) force balanced by the inertia force; and (4) the pressure force balanced by the interfacial drag (“viscous force”). The experimental results seem to confirm the derived spreading relations. The paper makes three significant contributions. It resolves theoretically and experimentally the existing conflict regarding the proper radial growth of the intrusion in the inertia-buoyancy regime. In addition, it relates the observed transition from the inertia-buoyancy regime to viscous buoyancy regime. It does so using scaling arguments to find the length and time scales for this transition. The paper also gives extensive experimental evidence for the spreading relationships in the inertia-buoyancy and viscous-buoyancy regimes, and it facilitates the determination of the corresponding experimental coefficients.