Glossary Related to Sediment Transport - Sediment Transport in Irrigation Canals: A New Approach - page 283

Specific energy Quantity proportional to the energy per unit mass, measured with the

channel bottom as datum and expressed in meter of water.

Specific volume The volume of a unit mass of dry soil in an undisturbed condition, equalling

the reciprocal of the dry bulk density of the soil.

Steady flow Flow that occurs when conditions at any point of the fluid do not change

with the time.

Steady state Fluid motion in which the velocity at every point of the field is independent

of time in either magnitude or direction; flow condition in which the input
energy equals the output energy.

Stochastic Having random variation in statistics.

Stream function Vector function of space and time which is related to the velocity field.

The stream function exists for steady and unsteady flow of incompressible
fluid as it satisfies the continuity equation. Lagrange introduced the stream
function.

Streamline A line drawn so that the velocity vector is always tangential to it (no flow

across a streamline); in steady flow the line coincides with the trajectory
of the fluid particles.

Subcritical flow The flow in an open channel is subcritical if the flow depth is larger than

the critical depth. A flow for which the Froude number is less than unity;
surface disturbances can travel upstream.

Super-critical flow The flow in an open channel is super-critical if the flow depth is smaller

than the critical depth. A flow for which the Froude number is larger than
one; surface disturbances will not travel upstream.

Surge A surge in an open channel is a sudden change of flow depth (i.e. Abrupt

increase or decrease in depth). An abrupt increase in flow depth is called a
positive surge while a sudden decrease in depth is termed a negative surge.
A positive surge is also called (improperly) a 'moving hydraulic jump' or
a 'hydraulic bore'.

Suspended concentration The in time-average ratio of the mass (or volume) of the dry sediment

in a water/sediment mixture to the total mass (or volume) of the mixture;
also average of the mean (time average) suspended concentration over
the entire area.

Suspended load Transported sediment material maintained into suspension by turbulence

of the flow for considerable periods and without contact with the bed;
the velocity of the load is almost the same as that of the flow; it is part
of the total sediment transport.

Suspension A two-phase system, which may consists of solid particles suspended in

water.

Tertiary off-take A discharge regulator on the secondary or primary canal to supply a

tertiary unit.

Textural class The name of a soil group with a particular range of sand, silt and clay

percentages of which the sum is 100% (e.g. sandy clay: 45-65% sand,
0-20% silt, 35-55% clay).