The Energy losses property page is used to define energy losses associated with local flow obstructions such as sudden flow contractions or expansions and gradual or abrupt changes in the river alignment. Moreover, a user defined energy loss coefficient can be defined.
Location
ID. String identification of the energy loss point. ID will be used in structure results and hence makes it easier to identify a specific structure if setup contains many structures, or if multiple structures are defined at the same location.
Branch name. The Branch name is automatically registered where the energy loss point is located.
Chainage. Chainage at which the energy loss point is located.
Energy losses
At each specified energy loss point a discharge grid point is inserted at run-time. At each time step of the computation the discharge at energy loss points is computed by use of the energy equation:
in which
is the energy loss, g is the acceleration of gravity, Q is the discharge, A is the cross-sectional wetted area and
denotes the energy loss coefficient.
Five different types of energy losses may be included in the simulation:
· User defined loss
· Contraction loss
· Expansion loss
· Abrupt change in alignment
· Gradual change in alignment
For user defined loss, contraction loss and expansion loss an energy loss coefficient must be defined for both positive and negative flow.
For alignment change, the angular change in river alignment at the energy loss point must be specified. Additionally, for gradual change the roughness coefficient must be defined. The roughness coefficient is of the order of 0.2 for rough pipes and of the order of 0.1 for smooth pipes.
