[Kratos] proposal of change in the solving_strategy

Riccardo Rossi rrossi en cimne.upc.edu
Mie Oct 7 11:57:48 CEST 2015


Dear Nelson,

 the point is the following:

imagine that you do a FSI simulation and your structure is elastoplastic:
you first have a  wrong guess (too high)  of the forces acting on the
structure and you call "solve". The structure becomes plastic and after
reaching convergence it calls FinalizeSolutionStep where the constitutive
law stores the internal variables for the next step.

then you correct the forces (now much smaller) and you call solve again.
The structure should not become plastic anymore HOWEVER it already stored
the internal variables at the end of the previous step, so the results
would wrongly believe that the structural behaviour is plastic, while
really should have stayed elastic

still... note that if you call "Solve" it will behave only as before. The
difference is that you can choose when your Internal variables have to be
stored (at the end of the complete fsi loop, not at the end of each solve!!)

cheers
Riccardo



On Wed, Oct 7, 2015 at 9:40 AM, <maireni en cimne.upc.edu> wrote:

> Hi Riccardo,
>
> I do not understrand yet why it is not necessary to call the initialize,
> predict and finalize functions.
> This methods are escencially important in structural and solid
> application where some internal variables
> or other need to be updated or reseted (mainly  in constitutive law).
> If bassically  does not want to call this method i prefere in my opinion
> to include a new member in base
> class of strategy where those calls can be avoided.
>
> It really cost calls this function in each time step?
>
> Regards
>
> Nelson
>
>
>
> El 2015-10-07 15:05, Riccardo Rossi escribió:
> > Dear All,
> >
> >   i believe there is a weakness in the current design of the solving
> > strategies, and i would like to propose a small improvement to the
> > current interface:
> >
> > the point is that as of today the strategy has essentially the
> > following methods:
> >
> > Initialize (to be called once)
> > InitializeSolutionStep
> > Predict
> > FinalizeSolutionStep
> >
> > and
> >
> > Solve --> which combines everything in one single call.
> >
> > the problem is that is someone calls solve the InitializeSolutionStep
> > and FinalizeSolutionStep are inevitably called, which is a problem if
> > for example one
> > would like to do repeated solves within a single time step.
> >
> > the typical scenario is that of a FSI simulation, but the same problem
> > is also found for example in the RVE solver.
> >
> > My proposal would be to add a new function
> >
> > "SolveSolutionStep"
> >
> > which ONLY does the solution but WITHOUT CALLING
> > InitializeSolutionStep, Predict, FinalizeSolutionStep
> >
> > The point of doing this is that the "solve" call would be:
> >
> > Solve()
> >     InitializeSolutionStep
> >     Predict
> >     SolveSolutionStep
> >     FinalizeSolutionStep
> >
> > but one would be able to call the very same thing from the python (or
> > from a higher level strategy)
> >
> > so that for example a FSI loop would become
> >
> >     structural_solver.InitializeSolutionStep()
> >     fluid_solver.InitializeSolutionStep()
> >
> >     structural_solver.Predict()
> >
> >     while(not converged)
> >         structural_solver.SolveSolutionStep()
> >
> >         apply_velocities_to_fluid()
> >
> >         fluid_solver.SolveSolutionStep()
> >
> >         apply_forces_to_structure()
> >
> >         check_convergence()
> >
> >     structural_solver.FinalizeSolutionStep()
> >     fluid_solver.FinalizeSolutionStep()
> >
> >
> > Of course if someone uses the current Solve() nothing changes and
> > current behaviour is unmodified...
> >
> > any voice against such change? if not i'll go ahead...
> >
> > ciao
> > Riccardo
> >
> >
> >
> >
> > --
> >
> > Riccardo Rossi
> >
> >  PhD, Civil Engineer
> >
> > member of the Kratos Team: www.cimne.com/kratos [1]
> >
> > lecturer at Universitat Politècnica de Catalunya, BarcelonaTech (UPC)
> >
> > Research fellow at International Center for Numerical Methods in
> > Engineering (CIMNE)
> >
> > C/ Gran Capità, s/n, Campus Nord UPC, Ed. C1, Despatx C9
> >
> >  08034 – Barcelona – Spain – www.cimne.com [2]  -
> >
> >  T.(+34) 93 401 56 96 skype: ROUGERED4
> >
> >
> >
> >  [3]
> >
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> >
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-- 


*Riccardo Rossi*

PhD, Civil Engineer


member of the Kratos Team: www.cimne.com/kratos

lecturer at Universitat Politècnica de Catalunya, BarcelonaTech (UPC)

Research fellow at International Center for Numerical Methods in
Engineering (CIMNE)


C/ Gran Capità, s/n, Campus Nord UPC, Ed. C1, Despatx C9

08034 – Barcelona – Spain – www.cimne.com  -

T.(+34) 93 401 56 96 skype: *rougered4*



<http://www.cimne.com/>

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Les dades personals contingudes en aquest missatge són tractades amb la
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dirigint-se a cimne en cimne.upc.edu. La utilització de la seva adreça de
correu electronic per part de CIMNE queda subjecte a les disposicions de la
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Electronic.

 Imprimiu aquest missatge, només si és estrictament necessari.
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