open TELEMAC-MASCARET The mathematically superior suite of solvers

By the way, I had a model with a outfall source in deep water and I indeed don't have problem there.

Thanks for the advice. Tidal flats are treated in the same way as you. That is:

OPTION FOR THE TREATMENT OF TIDAL FLATS = 1
TREATMENT OF NEGATIVE DEPTHS = 2

I have failed to set the MINIMAL VALUE FOR DEPTH however which remains at the default value of -1000. I am assuming this means that there is no treatment for negative depths taking place.

I would also like to ask in which version the keyword THRESHOLD FOR SEDIMENT FLUX CORRECTION ON TIDAL FLATS was included? Unfortunately I am currently running this on v6p3r0 as the model was developed quite a while ago. I am seeing that I have some strange issues (perhaps related to this older version). For instance I get an execution error when including the graphic printout variable FD to check the deposit depths and erosion flux (EF) seems to produce no output with corrupted units.

Apart from setting the rigid bed level to the same as my bottom in CONDIS this is my sediment setup:

SEDIMENT = YES
COHESIVE SEDIMENT = YES

MEAN DIAMETER OF THE SEDIMENT = 0.000025
DENSITY OF THE SEDIMENT = 2650
CRITICAL SHEAR STRESS FOR EROSION = 0.15
CRITICAL SHEAR STRESS FOR DEPOSITION = 0.05
CONCENTRATION OF FRESH DEPOSITS = 100
EROSION COEFFICIENT = 0.002

INFLUENCE OF TURBULENCE ON SETTLING VELOCITY = NO
CONSTANT SEDIMENT SETTLING VELOCITY = -0.0006

GIBSON CONSOLIDATION MODEL = NO
MULTILAYER CONSOLIDATION MODEL = NO

SOLVER FOR DIFFUSION OF THE SEDIMENT = 7
OPTION OF SOLVER FOR DIFFUSION OF THE SEDIMENT = 5
PRECONDITIONING FOR DIFFUSION OF THE SEDIMENT = 2
MAXIMUM NUMBER OF ITERATIONS FOR DIFFUSION OF SEDIMENT = 350
ACCURACY FOR DIFFUSION OF SEDIMENT = 1E-6

I seem to be having a bit better luck currently as I increased the water depths and reduced the accuracy to 1E-6. The model is right on the limit of the accuracy for the diffusion however as its taking almost 350 iterations each time.

Regards,
Toby

Hi Toby,

I think you have used most of the necessary keywords for defining a SEDI-3D model. But there is one place that looks strange to me.

CONSTANT SEDIMENT SETTLING VELOCITY = -0.0006

I use a positive value here and it doesn't need a negative sign to indicate the direction. Maybe a positive value could help with the number of iterations.

I use version v7p2r1. So I can imagine there will be some differences in the source code, as well as in the keywords.

Here is my settings:

NUMBER OF TRACERS = 1
NAMES OF TRACERS = 'SEDIMENT G/L '
INITIAL VALUES OF TRACERS = 0.0
PRESCRIBED TRACERS VALUES = 0.01;0.01;0.01;0.01;0.01;0.01;0.01;0.01;0.01
TRACERS VERTICAL PROFILES = 1;1;1;1;1;1;1;1;1
COEFFICIENT FOR HORIZONTAL DIFFUSION OF TRACERS = 1.0E-04
COEFFICIENT FOR VERTICAL DIFFUSION OF TRACERS = 1.0E-04

SEDIMENT = YES
COHESIVE SEDIMENT = YES

MEAN DIAMETER OF THE SEDIMENT = 0.00005
DENSITY OF THE SEDIMENT = 2650.0
CONSTANT SEDIMENT SETTLING VELOCITY = 0.5E-3
HINDERED SETTLING = NO

BED LAYERS THICKNESS = 0.01
NUMBER OF SEDIMENT BED LAYERS = 1

INITIAL THICKNESS OF SEDIMENT LAYERS = 0.01
MUD CONCENTRATIONS PER LAYER = 500

EROSION COEFFICIENT = 1.0E-5
CRITICAL EROSION SHEAR STRESS OF THE MUD LAYERS = 0.2
CRITICAL SHEAR STRESS FOR DEPOSITION = 0.006

THRESHOLD FOR SEDIMENT FLUX CORRECTION ON TIDAL FLATS = 0.1

ADVECTION-DIFFUSION SCHEME WITH SETTLING VELOCITY = 0

But again, this is in v7p2r1...

Kind regards,
Qilong

There has definitely been some major changes between v6 and v7.

I believe in v6 the fall velocity has to be specified as as a negative value which is a bit strange. There is a mention of this on the forum somewhere.

I am still unable to get proper convergence even with the inclusion of the MINIMAL VALUE FOR DEPTH. Its strange because when the non convergence appears I begin to notice negative concentration values at random locations along the solid boundaries of my domain (which are often wet and dry). These locations are not exactly close to the source of the outfall either.

There is no option in v6 for limiting the erosion flux in shallow waters, however I set an artificially high critical shear stress for erosion to inhibit this process and it also did not help.

I converted the model to v7p2r2 and am no long having an issues with getting convergence