D-R-A-F-T
above them increases. Data for the CI cards should come from laboratory tests on
the sediments to be modeled.
Cohesive bed behavior as a function of shear stress
Dry density as specified on the CI cards can be calculated by the following
formula:
Equation 61
( ρB - ρw )
ρdry = ρS
( ρS - ρw )
where
=
density of individual sediment particles
S
=
bulk (wet) density of sediment
B
=
density of water entrained in the sediment
w
Note that a lower density for layer types 1 - 4 will result in fluffier deposits,
increased thickness of deposited layers, and greater bed change.
In the field, the density and shear strength of cohesive layers generally increase as
they consolidate. The shifting to higher layer types in the program accounts for this,
but the user must accurately specify the parameters for each layer type in order to
obtain a realistic solution. The greatest accuracy will be achieved by specifying a
larger number of layers, each having a small thickness. When a thin layer is filled up
it will move down into the bed and be given a higher layer type, and the effect of the
overburden will be calculated more accurately than if a small number of thicker
layers are used.
58 Run Control
Users Guide To SED2D-WES
Previous Page
