ABSTRACT
Study of civil engineering hydraulics tends to concentrate on two main types of flow. The first is pipe flow in which a liquid flows in a pipe under pressure. The second is open-channel flow, in which a liquid flows in a channel by gravity, with a free surface at atmospheric pressure. This chapter presents the main principles of hydraulics relevant to urban drainage. Pressure is a force per unit area. Absolute pressure is pressure relative to a vacuum and gauge pressure is pressure relative to atmospheric pressure. A flowing liquid has three main types of energy: pressure, velocity, and potential. The head or energy losses in flow in a pipe are made up of friction losses and local losses. The common flow condition in urban drainage pipes is part-full pipe flow. The presence of the free surface must be taken into account in hydraulic computations. An alternative, more direct method for part-full pipe problems is provided by the Butler-Pinkerton charts.
