On 17.06.19 15:42, Flemisch, Bernd wrote:
Hi Felix,
the derivatives are currently only used inside the laws themselves,
particularly for the regularization. See for example the pc function
in regularizedvangenuchten.hh. There, the function
VanGenuchten::dpc_dswe is called to determine the correct slope of the
regularized curve.
If you implement your own law, you don't need the derivative functions
since they are never called from outside.
One could use the derivative functions to calculate analytical
derivatives for the Jacobian matrix, but this hasn't been done so far.
Maybe a clean approach for the future would be to remove these
functions from the interface.
Hi Felix, hi Bernd,
just as a side-note to that, the derivatives are actually used to
calculate an analytical Jacobian matrix for the 2p model (
incompressible, constant viscosities)
(https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/blob/master/dumux/porousmediumflow/2p/incompressiblelocalresidual.hh).
But per default numeric differentiation is used to compute the Jacobian.
This can be changed by switching the DiffMethod (template parameter) of
the Assembler class. Analytic Jacobians are currently only implemented
for the incompressible 1p and 2p model. To use it, the corresponding
local residual class that implements the derivative has to be set for
the LocalResidual property.
Best wishes
Timo
Kind regards
Bernd
--
_______________________________________________________________
Bernd Flemisch phone: +49 711 685 69162
IWS, Universität Stuttgart fax: +49 711 685 60430
Pfaffenwaldring 61 email: be...@iws.uni-stuttgart.de
D-70569 Stuttgart url: www.hydrosys.uni-stuttgart.de
_______________________________________________________________
------------------------------------------------------------------------
*Von:* Dumux <dumux-boun...@listserv.uni-stuttgart.de> im Auftrag von
Felix Feldmann <felix.feldm...@ku.ac.ae>
*Gesendet:* Montag, 17. Juni 2019 15:18:16
*An:* DuMuX User Forum
*Betreff:* [DuMuX] Fluidmatrix interactionlaws - partial derivatives
Dear DuMux developer,
Looking at the fluidmatrixinteractionlaws, I do find the
implementation of several partial derivatives.
For example, in case of the BrooksCorey model:
• The derivative of the relative permeability for the
non-wetting phase in regard to the wetting saturation dkrn_dswe()
• The derivative of the relative permeability for the
wetting phase with regard to the wetting saturation dkrw_dswe()
• The partial derivative of the capillary pressure w.r.t.
the effective saturation dpc_dswe()
• The partial derivative of the effective saturation w.r.t.
the capillary pressure dswe_dpc()
I don’t really understand the purpose of the derivatives. In case I
remove them, my code is still running fine and is given me the
identical result. However, since I am currently implementing a
modified fluidmatrixinteractionlaw, I would like to understand the
purpose of the derivatives. Unfortunately, in this case, the DuMux
Handbook as well as the online documentation provides quite limited
information.
Best regards,
Felix
*--------------------------------*
*Felix Feldmann*
Research Assistant
cid:image001.png@01D3DFD3.27E5A010
SAN Campus
P O Box 2533, Petroleum Institute
Abu Dhabi, UAE
M +971 565624402
felix.feldm...@ku.ac.ae <mailto:felix.feldm...@ku.ac.ae>
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_______________________________________________________________
Timo Koch phone: +49 711 685 64676
IWS, Universität Stuttgart fax: +49 711 685 60430
Pfaffenwaldring 61 email: timo.k...@iws.uni-stuttgart.de
D-70569 Stuttgart url: www.hydrosys.uni-stuttgart.de
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