Saline and particle-driven interfacial intrusions
Department of Applied Mathematics and Theoretical Physics,
University of Cambridge, Silver Street, Cambridge CB3 9EW, UK.
Tel. +44.1223.339737, fax: +44.1223.337918, e-mail:
†Present address: Department of Applied Mechanics and Engineering Sciences,
University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0411, USA
9 February 1998, revised 26 November 1998

This paper presents a theoretical and experimental investigation into saline and particle-driven intrusions along the interface between two layers of different densities. The conditions at the nose of an intrusion are described in an analysis similar to that applied by Benjamin (1968) to boundary gravity currents. Equations for propagation velocity and front position as functions of relative density are derived. These are used in an integral model for intrusions, which also includes the effects of sedimentation of particles and detrainment of interstitial fluid. The model describes the time-evolution of the length of the intrusion and the sediment distribution it produces. Laboratory experiments were carried out with lock-releases of a fixed volume of saline or particle-laden fluid into a two-layer stratification. Measurements were taken of the intrusion propagation, intrusion position and sediment distribution, and are found to be in good agreement with the solutions of the integral model.