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Turning off non-linear terms in the flow equations
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TOPIC: Turning off non-linear terms in the flow equations

Turning off non-linear terms in the flow equations 9 years 9 months ago #15646

  • Watermotion.eu
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Hi all!

Before diving into the (hard-to-get) manual, I would ask whether one can linearise the following features by setting specific flags in the steering file (which ones?) or the task requires hacking into the source code.

Specifically, it goes about the following features:
  1. continuity equation: linearising advection terms (from water-column depth to bed depth only)
  2. momentum equations: making bottom friction linear
  3. momentum equations: turning off advection terms
  4. momentum equations: turning off horizontal diffusion terms

Prior experiences, tips and caveats will help me greatly. Thanks in advance for sharing these.

Giordano Lipari
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Turning off non-linear terms in the flow equations 9 years 9 months ago #15654

  • c.coulet
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Hi

You could have a look into the dictionnary file which will gives you some informations about the possibilities.
For example, for the features 3, you could use ADVECTION = NO
...

regards
Christophe
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Turning off non-linear terms in the flow equations 9 years 9 months ago #15690

  • jmhervouet
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Hello,

I'll not be at work to check for some time but other points are also possible :

LINEARISED PROPAGATION : YES (but look at documentation to check this keyword, and there is a subroutine to specify the depth that should be taken for linearising).

Bottom friction linear is law number 1.

turning off horizontal diffusion can be done by setting the horizontal diffusion to 0.

Regards,

Jean-Michel Hervouet
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Turning off non-linear terms in the flow equations 9 years 9 months ago #15710

  • riadh
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Hello

The key-words to use for the linearization of propagation step are the followings:
LINEARIZED PROPAGATION =YES
MEAN DEPTH FOR LINEARIZATION (default =0.)

to turn off the horizontal diffusion, you can use the following key-word
DIFFUSION OF VELOCITY = NO
you can also use solution suggested by Jean Michel.

with my best regards

Riadh ATA
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Turning off non-linear terms in the flow equations 8 years 11 months ago #19120

  • abernard
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Hi,

I would like to know if it is possible to desactivate non linear terms in the propagation.

I've seen it is possible to do it considering a mean depth for linearized propagation but I would like to test a linearized case on a regular slope.
Using mean depth for linearization make no sense.
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Turning off non-linear terms in the flow equations 8 years 11 months ago #19125

  • Watermotion.eu
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Hi! It sounds like the keyword LINEAR PROPAGATION does what you asked for.
From the dico file of Telemac2d (folder v7p0r1/sources/telemac2d)
NOM = 'PROPAGATION LINEARISEE'
NOM1 = 'LINEARIZED PROPAGATION'
TYPE = LOGIQUE
INDEX = 20
MNEMO = 'PROLIN'
TAILLE = 0
DEFAUT = NON
DEFAUT1 = NO
RUBRIQUE = 'EQUATIONS';'PROPAGATION'
RUBRIQUE1 = 'EQUATIONS';'PROPAGATION'
NIVEAU = 3
AIDE = 'Permet de lineariser l''etape de propagation;
par exemple lors de la realisation de cas tests pour lesquels on dispose
d''une solution analytique dans le cas linearise.'
AIDE1 = 'Provided for linearizing the propagation step, e.g. when
performing test-cases for which an analytical solution in the linearized
case is available.'

Is that what you were looking for? Hope this helps
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Turning off non-linear terms in the flow equations 8 years 11 months ago #19129

  • abernard
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Hi,

Thanks for your answer. In my mind, the activation of LINEARIZED PROPAGATION automaticly consider a MEAN DEPTH FOR PROPAGATION.

Running a case with no friction (on the bottom or on solid boundaries), desactivated advection and no diffusion of velocities should be close to a linear case (with analytical solution).
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Turning off non-linear terms in the flow equations 8 years 11 months ago #19130

  • jmhervouet
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Hello,

Yes, in that case the depth is constant. What you could do is changing subroutine hpropa.f so that the depth for the linearization is taken equal to the initial depth. This could be done by copying HN at the first call, and then doing nothing afterwards.

With best regards,

Jean-Michel Hervouet
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Turning off non-linear terms in the flow equations 8 years 11 months ago #19131

  • abernard
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OK,

So you suggest to activate the linearized propagation
LINEARIZED PROPAGATION =true
>>> PROLIN = t

What do you mean by copying HN at the first call.
What is the difference with H0 ?
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Turning off non-linear terms in the flow equations 8 years 11 months ago #19132

  • jmhervouet
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Hello,

Yes and no, the only thing to do is changing the computation of HPROP in subroutine hpropa.f. If you choose HPROP=HN from the initial conditions, this will linearise with a space varying depth. It is exactly like H0 but H0 is filled only for Boussinesq equations, so this would require more programming.

Just do in hpropa.f

LOGICAL DEJA
DATA DEJA/.FALSE./

IF(.NOT.DEJA) THEN
CALL OS('X=Y ',X=HPROP,Y=HN)
DEJA=.TRUE.
ENDIF

so that HPROP is done once at the first call.

With best regards,

Jean-Michel Hervouet
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