A Subcritical Flow Over a Stepping Bottom

A free-surface flow on a channel with step bottom is solved numerically by an integral equation method. The flow is assumed to be steady, 2 dimensional and irrotational, meanwhile the fluid is inviscid and incompressible, and the effect of gravity is not negligible. The numerical result show that solutions with a train of waves are obtained for subcritical flow, and for var- ious height of the step. The waves are characterized as long wave with ratio amplitude to wave-length of order 10^-2 or smaller.