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hello

it's a stupid question but i'm a little bit confused and prefer be sure.

i want imposed the sediment concentration for one of my boundaries.
but i have a problem with the unit of the sediment concentration used in SISYPHE.

is it correct that you impose the concentration in g/l ?

thank you

Julien.

Hi Julien,

With default options, suspended concentrations are input as non-dimensional volumes (e.g. 0.001 for 1g/L, assuming water density = 1kg/L).

If you use MASS CONCENTRATION = YES, input and output concentrations are in g/L.

cheers,
Dougal

Hi!

I am afraid the documentation may be rather confusing (mass or volume concentrations) and will be clarified in the new documentation! Sisyphe calculates concentrations in adimensional form. So every varaibles are converted in adimensional form, before computation starts.

If you assume 'mass concentration'= Yes, this is only going to affect the unit of the output file and input file (seraphin results).

For boundary conditions, it all depends on how you specify your concentations at the boundary.

First option: Concentrations are imposed in the steering file through key word 'CONCENTRATION PER CLASS AT BOUNDARIES' : Concentrations are volume concentrations.

New option (6.2): you want to impose a time-varying concentration field from the 'liquid boundary file': concentrations are specified in g/l.

I hope this helps,
Best luck, Cath

Dear all,

Sorry I have a question related to imposing boundary condition. I want to prescribe stationary suspended sediment concentrations at the same boundary nodes at which were prescribed water level values for the hydrodynamic simulation. Is it enough if I just impose the SSC value by means of the keyword CONCENTRATION PER CLASS AT BOUNDARIES in the SISYPHE steering file or should I also define a boundary section in Blue Kenue with prescribed tracer value?

Thank you

Jean-Philippe

Hello!

In addition to the key word 'CONC....AT BOUNDARIES', You also need to specify the boundary as a 'prescribed tracer'. It is fairly easy to change the flag corresponding to the imposed tracer to N0 5 in the condim file.

Good luck, Catherine

Hi Cath,

Are you able to expand a bit further on what needs to be specified, given I can't see it in any documentation?

Do you mean changing a value in the BOUNDARY CONDITIONS FILE called by the sisyphe steering file? If so, which column?

(I thought I was correctly specifying input suspended sediment concentrations, but had never heard of setting boundary as 'prescribed tracer')

Thanks,

Hi Cath,

Thank you for your reply, however I am still a bit confused. You said in a previous post that two boundary condition files were needed, one for telemac2d and one for sisyphe. However, when I look at some validation cases (e.g., conservation vas, bosse vase) both steering files t2d.cas and sis.cas shared a same boundary condition file.

Regarding specifying boundary conditions as a "prescribed tracer", are you sure I need to change the corresponding flag for prescribed tracer (i.e., LIEBOR) to the value of 5 ? In a documentation (called solid_discharge_sisyphe_2012-10-05) which was forwarded in a previous post entitled "Problem with sisyphe v6p2", it was written that if you want to prescribe solid boundary discharge you need to put LIQBOR=5 and LIEBOR = 4.

Thank you for clarification,

JP

Hi,

I too am confused - it seems I can successfully prescribe bedload at the boundaries (PRESCRIBED SOLID DISCHARGES) by setting LIEBOR = 4 and LIQBOR = 5 in the sisyphe BOUNDARY CONDITIONS FILE *or* successfully prescribe suspended concentrations at the boundaries (CONCENTRATION PER CLASS AT BOUNDARIES) by setting LIEBOR = 5 in the same file.

There doesn't seem to be a way to prescribe both bedload and suspended concentration at the boundary.

Can you please advise how this is possible?

Thanks,
Dougal

(It turns out I wasn't correctly specifying input suspended concentrations in my prev post.)

Hello,

In the general case, you need two different boundary condition files. This allows you to apply different boundary conditions for a tracer in TELEMAC-2D and for the bed evolution or concentration in SISYPHE. However in most (simple) applications, you can use the same boundary condition file.

If you are working with suspension only : LICBOR = LITBOR, CBOR being generally specified by key word. The same boundary condition file can be used in both Telemac-2D and Sisyphe.

For example, for bedload, we generally need to impose at the entrance 'zero bed evolution'. For this 'classical' type of entrance boundary condition, the same condim file can be used for Telemac-2D and Sisyphe.

For hydrodynamics:
For imposed flow rate (LIUBOR= 5 and LIVBOR= 5)and imposed tracer (TBOR=5):
LIHBOR lIUBOR LIVBOR ... LITbor TBOR
4 5 5 .... 5 0.

For imposed zero bed evolution (LIEBOR=5):
(not used) LIQBOR (not used ... LIEbor EBOR
(4) (5 ) .... 5 0.
but It also works if LIQBOR= 5
4 5 5 ..... 5 0.
So you can use also the same boundary condition file.

For imposed transport rates :
(not used) LIQBOR (not used) QBOR ... LIEbor EBOR
( 4 ) 5 (5) 1.E-5 .... 4 0.
You definitely need two different boundary files.

To answer the question about imposing a bedload transport rate and the concentration, you will have to program the conlit subroutine line 186
change LICBOR to LIQBOR instead of LIEBOR

We will try to make this all simpler in the next release, and explain this all very clearly in the new documentation (6.2) coming out soon.

Good luck, Cath

Hi,

I have another similar question.
I run a computation with both bed-load and suspended load.
I chose MASS CONCENTRATION = YES. My initial concentration is 0.

Why does the listing shows the concentration in % and not in g/L? :

ITERATION 600 TIME: 10 MN 0.0000 S ( 600.0000 S)

BEDLOAD EQUATION SOLVED IN 10 ITERATIONS
EQUNOR (BIEF) : 3 ITERATIONS, ABSOLUTE PRECISION: 0.3799725E-09
MAXIMAL CONCENTRATION : 0.7537134E-02 %, NODE = 3533
MINIMAL CONCENTRATION : -0.1549901E-15 %, NODE = 3604
MAXIMAL EVOLUTION : 0.5707677E-03 , NODE = 3714
MINIMAL EVOLUTION : -0.6049789E-03 , NODE = 3622
MAX. CFL FOR SUSPENSION : 1.952156 , NODE = 3577

QUANTITY OF CLASS 1 IN SUSPENSION AT TIME T : 26.79046 M3
QUANTITY OF CLASS 1 IN SUSPENSION AT TIME T+DT : 26.62991 M3
BOUNDARY 1 FLUX TRACER 1 = -0.2721822E-07 ( >0 : ENTERING <0 : EXITING )
VOLUME OF DEPOSIT : 0.9355380E-01 M3
ERROR ON VOLUME : 0.6699186E-01

Thank you for your help!
PL