Opposing Wave Effect on Momentum Jets Spreading Rate

Abstract

A theoretical expression for the change of the spreading rate of momentum surface jets due to opposing surface gravity waves is obtained. A scale analysis performed on the depth averaged Eulerian momentum equation of the jet wave flow has revealed that wave momentum flux, induced by wave refraction, is the dominant force to cause the increase of the jet spreading rate. An estimate of this increase is derived from the transverse momentum equation. The theory predicts a linear increase in the rate of spreading of the jet, within the jet zone of established flow. The increase in the rate is expressed by the ratio of the wave momentum action, on the jet, to the jet initial momentum density. Deductions made from the experimental results, using flow visualization techniques, agree quite well with theoretical predictions. The agreement is excellent within a longitudinal distance equal to 64 times the jet nozzle half‐width.