Hello,
I am making a compositional oil-gas simulator in DuMux. An important
part of it, and arguably the most CPU-demanding, is the determination if
the given composition is going to stay in one phase (stability test)
and, in case the stability test returned false, the two-phase flash.
VolumeVariables::update seems to be the most appropriate place to do
this kind of calculations. Please correct me if I am wrong.
I defined my own MyVolumeVariables and I call completeFluidState() in
its update() method every time. Now, the less
MyVolumeVariables::update() calls, the better. I found out that my
program performs far more calls than I anticipated.
1. Some of the extra calls were coming from the (unmerged) fix
<https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/-/merge_requests/2146>
that allowed relative permeabilities of an scv to depend of neighbor
dofs. The fix was needed for another problem (surfactant simulation), so
I reverted it for now. OK.
2. Some of the extra calls were coming from the PrimaryVariableSwitch
machinery which is not required at all in the task. I set my own
PrimaryVariableSwitch implementation via VolumeVariables with an empty
update(). OK.
3. I am using the box method. Each node has its primary variables that
go into MyVolumeVariables::update() and then into completeFluidState().
This is good. What is bad is that this is done independently for every
scv that is connected to this node. So with a rectangular 2D grid I get
four completeFluidState() calls with the same primary variables. So I am
repeating the same calculations four times. Can this be avoided at
present? Can this be avoided in principle?
4. As soon as one step of the Newton method is completed,
computeResidualReduction_ is called, then in calls assembleResidual, and
after that, MyPrimaryVariables::update() for every scv, without any
change in primary variables, is being called twise: first via
bindLocalViews -> curElemVolVars.bind -> bindElement
and then via
bindLocalViews -> prevElemVolVars.bindElement
I honestly do not understand what is going on here.
5. Then the next step is started, during which the system is assembled.
There, MyPrimaryVariables::update() is called 7 times for each scv. I
have 5 components, so 5 dofs (pressure + 4 mole fractions). Why 7 calls
and not 5? I figure that 5 calls should be made to calculate the
numerical derivatives w. r. t. the current state that has been already
assembled in the end of the previous step. Even if we reassemble it, it
is expected that we have only 6 calls.
Please bear with me as I may have misconceptions about the box method
and the DuMux ways of work. The above is not critique but a call for advice.
Best regards,
Dmitry
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