Selective Withdrawal Criteria of Stratified Fluids

A general criterion for the presence or absence of selective withdrawal in a fluid or arbitrary stratification due to a line sink in a channel is presented. Several examples are given. The criterion is based on whether the speed of upstream propagating columnar disturbances is greater or less than the initial uniform velocity induced by the line sink. The result is then extended to topographical influence in the form of a lateral contraction of the channel walls. Experiments were conducted and they verified the conclusions for the lateral contraction. The use of lateral contractions to insure uniform flow in a stratified channel or reservoir is indicated.