Glossary Related to Sediment Transport - Sediment Transport in Irrigation Canals: A New Approach - page 280

Open canal Natural or man-made structure that contains, restricts and directs the flow

of water. The surface of the water is open to the atmosphere, and therefore,
the flow is referred to as free flow. The design of canals includes the solution
of relationships between bed and bank roughness, channel geometry, and
flow velocity. Free surface flows are driven by gravity and they can vary
in both time and space.

Open channel Channel in which the water surface is in free contact with the air (free

surface).

Overflow structure Structure with water flowing over its crest.

Particle size distribution The fractions of clay, silt and sand particles in a soil.

Pascal Blaise Pascal (1623-1662) - French mathematician, physicist and

philosopher, who developed the modern theory of probability. Between
1646 and 1648, he formulated the concept of pressure and showed that the
pressure in a fluid is transmitted through the fluid in all directions.
The unit of pressure is named after Pascal: one Pascal equals a Newton per
square-metre.

Physical modelling Investigations of hydraulic processes using a (physical) scale model.

Porosity Percentage of the total volume of a soil occupied by air and/or water.

Positive surge Positive surge results from a sudden change in flow that increases the depth.

It is an abrupt wave front. The unsteady flow conditions may be solved as
a quasi-steady flow situation.

ppm Abbreviation for parts per million.

Prandtl Ludwig Prandtl (1875-1953) - German physicist who introduced the

concept of the boundary layer and developed the turbulent, mixing

length' theory.

Precision The degree of mutual agreement among a series of individual measure-

ments. Precision is often, but not necessarily, expressed by the standard
deviation of the measurements.

Primary canal Canal that conveys water from the head works to the secondary canals and

tertiary units.

Probability The chance that a prescribed event will occur, represented as a pure num-

ber ( p ) in the range 0 < p < 1. It can be estimated empirically from the
relative frequency (i.e. The number of times the particular event occurs,
divided by the total count of all events in the class considered).

Prototype Actual structure or condition being simulated in a numerical or physical

model.

Rapidly varied flow A flow characterized by large changes over a short distance (e.g. weirs,

gates, hydraulic jump).

Rating curve Graphic or tabular presentation of the discharge or flow through a structure

or channel section as a function of water stage (depth of flow).

Rayleigh John William Strutt, Baron Rayleigh (1842-1919) - English scientist in

acoustics and optics. His works are the basis of wave propagation theory
in fluids.