Uniform Flow

Fluid flow in open channels is characterised primarily by the exposure of a free surface to atmospheric pressure. For this reason the fluid concerned is always a liquid and nearly always water. Indeed rivers and canals, which together make up most instances of this type of flow, form a frequent and clearly visible part of the landscape. Problems connected with river and canal flow represent a high proportion of the work of the hydraulic engineer and the ease of access resulting from a free surface does not compensate for the increased complexity of such flows by comparison with flow in closed conduits. Water flowing in open channels is acted upon by all the forces that affect pipe flow with the addition of gravitational and surface tension forces that are the direct consequence of the free surface.