Nonlinear effects in the unsteady, critical withdrawal of a stratified fluid

Abstract The evolution of the withdrawal through a line sink of an initially quiescent, stratified fluid in a semi-infinite, horizontal duct is investigated in the inviscid, nondiffusive limit. A weakly nonlinear, long-wave formulation of the problem of critical withdrawal is presented, which is then used to study the critical withdrawal of a two-layer fluid from a sink at the base of the duct. Solutions for the evolution of the interfacial shear front are presented and related to the steady solutions for the critical withdrawal of a two-layer fluid.