ABSTRACT
Rivers, streams, aqueducts, drainage and irrigation ditches, and sewer pipes are usually only partially full. Open Channel Flow exists in conduits where the water has a free surface exposed to atmospheric pressure. A distinction in flow characteristics occurs between open channel flow and closed pipe flow. The basic hydraulic principles apply, however. Open channels have a degree of roughness, as water pipes under pressure do, and friction occurs as the moving water rubs against the sides of the channel. In open channels, maintenance of proper velocity is of prime importance. Calculation for head loss at a given flow is necessary, and the Hazen-Williams formula is useful. The circular conduit is certainly the most frequently used open channel. Solving for cross sectional area and wetted perimeter involves more complex mathematics which can be avoided by using a Hydraulic Elements Curve.
