DF CARD: Effective Diffusion Coefficient
Required
Card Description: Diffusion of suspended sediment occurs because of turbulence
in the flow field. When the transport equation is simplified by averaging over depth,
as in SED2D WES, dispersion is introduced because of vertical variations in the flow
field and settling of the sediment through the water column. In practice, this effect is
lumped together with turbulent diffusion and the effect of averaging in time and the
combined effect is called dispersion or effective diffusion. In this program, these
various effects are combined in a pair of effective diffusion coefficients given on the
ED card.
Field
Variable
Value Description
0, C 1-2
IC1
DF
Card group identifier.
0,C3
IC3
b/
Option 1: Global: Starting with node = J
T
Option 2: Explicit by material type = J
E
Option 3: Explicit assignment for Element = J
N
Option 4: Explicit assignment for Node = J
1
J
+
Starting or explicit value
≥0
Turbulent exchange coefficient in X direction (X
2
DIF (J,1)
plane). (units = m2/sec)
<0
Default = 0.0
≥0
Turbulent exchange coefficient in Y direction (Y
3
DIF (J,2)
plane). (units = m2/sec)
<0
Default = 0.0
NOTE: As of 12-2-2004, the DF Card replaced the ED card.
Run Control DF Card 89
Users Guide To SED2D-WES
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