TELEMAC-MASCARET Forum: Calculate Bedload in Mixed Sediment Transport (1/1)

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TOPIC: Calculate Bedload in Mixed Sediment Transport

Calculate Bedload in Mixed Sediment Transport 11 years 3 months ago #10049

qilong
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Hello,

I have created a mixed sediment transport model in which I have two different sediment classes, sand and mud. I want to calculate the bedload for sand.

So I checked the SISYPHE code and I found in the subroutine LECDON_SISYPHE, it will disable the bedload calculation if it has mixed sediment in the model. I modified this subroutine in order to enable the bedload.

Then I checked the subroutine BEDLOAD_MAIN. In this subroutine, it calculates the bedload and the evolution for sand and set these two variables to 0 for mud and then add them up.

It seems possible to calculate bedload in mixed sediment model. But I got the strange message from the screen printout when I enabled the bedload in my mixed model:

 MASS-BALANCE (IN VOLUME, INCLUDING VOID):
 SUM OF THE EVOLUTIONS :    0.8124999E-08 M3
 BOUNDARY   1 BEDLOAD FLUX =        -Infinity  ( M3/S  >0 = ENTERING )
 TOTAL        BEDLOAD FLUX =        -Infinity  ( M3/S  >0 = ENTERING )
 DEPOSIT ON BOTTOM         =    0.6295298E-63  ( M3/S )
 LOST VOLUME                     :         Infinity M3  ( IF <0 EXIT )

 MASS BALANCE FOR SEDIMENT CLASS :           1
 TOTAL VOLUME:  0.000000000000000E+000
 SUM OF THE EVOLUTIONS FOR THIS CLASS:    0.6295298E-63
 VOLUME THAT ENTERED THE DOMAIN FOR THIS CLASS:     0.000000     M3
 VOLUME DEPOSITED ON BOTTOM FOR THIS CLASS:        0.6295298E-63 M3
 VOLUME PERDU                  :    0.1349401E-78 M3  ( SI <0 VOLUME SORTI )

 MASS BALANCE FOR SEDIMENT CLASS :           2
 TOTAL VOLUME:  0.000000000000000E+000
 SUM OF THE EVOLUTIONS FOR THIS CLASS:    0.8124999E-08
 VOLUME THAT ENTERED THE DOMAIN FOR THIS CLASS:        -Infinity M3
 VOLUME DEPOSITED ON BOTTOM FOR THIS CLASS:         0.000000     M3
 VOLUME PERDU                  :         Infinity M3  ( SI <0 VOLUME SORTI )

The total bedload flux and bedload flux at the boundary becomes "-Infinity". And VOLUME THAT ENTERED THE DOMAIN FOR CLASS 2 becomes "-Infinity". However, I can still continue the computation and get the results.

Can I calculate the bedload for sand without this error?

Kind regards,
Qilong

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Calculate Bedload in Mixed Sediment Transport 11 years 3 months ago #10062

cath
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Posts: 52
Thank you received: 24

Hi , what you are doing seems fine, although you should check that the value of the bed porosity for the Exner equation is correct.
However the subroutine bilan-sisyphe is assuming that there is also a bedload for the cohesive part. The bedload fluxes are not defined for the mud class (class 2) so that is why you are getting some infinite values.
One simple way to go around this problem, would be to comment all the calculations for phase 2 in bilan-sisyphe.
Let me know if this works, Cath

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Calculate Bedload in Mixed Sediment Transport 11 years 3 months ago #10064

qilong
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Posts: 340
Thank you received: 33

Thanks Cath!

Now I know where the problem is. The subroutine bilan_sisyphe checks the mass balance for each class and it uses undefined variables in the calculation.

I simply set the keyword MASS-BALANCE=NO in the steering file and the infinity number in the screen printout has gone. I suppose it does not affect the results.

Another solution I have in my mind is to pass the value 1 instead of NSICLA to the code CALL BILAN_SISYPHE(...,NSICLA,...) then it will only calculates the mass balance for class 1.

Kind regards,
Qilong

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