Introduction

Abstract

Mighty waterfalls, the sea waves breaking on beaches, the dancing cascade flows down mountain rivers and scores of other flow situations where air entrains into water causing a dazzling whiteness and presenting an intriguing spectacle have attracted the attention of research workers the world over in recent years. They are attempting to unfold the mechanics of aeration and provide for its effects such as bulking and energy dissipation characteristics. A knowledge of the laws governing the characteristics of selfaerated free surface flows is of great importance not only in understanding the phenomenon of air entrainment, but also in design problems of hydraulic structures such as overflow spillways, chutes and stilling basins. In the environmental field, the role of aeration at structures such as weirs for the oxygen balance of a river system and hence for water quality enhancement has been recognised for some time.