Principal stage of wake collapse in a stratified fluid: Two-dimensional theory

A complete theory of the collapse of a wake in the form of a two-dimensional circular mixed region of uniform density in a linearly stratified fluid is given. The initial stage is based on existing theories and the principal stage is based on the concept of a quasi-steady density current in a stratified environment. The two stages are properly matched. The dimensionless time at the initiation of the principal stage is determined theoretically. The theoretical result is in excellent agreement with previous numerical and experimental results.