[dune-pdelab] Visualization of Gauss point data

[Christian Engwer]

On Wed, Jul 20, 2011 at 04:10:00PM +0200, Nicolas Schwenck wrote:
> Sorry, I still don't get the problem:
> 
> If you solve the elasticity problem as a single field problem
> (solving only for displacement directly) then you don't have stress
> or strain in the weak form and also not in the local operator. So,
> why is it costly to compute the stress in the driver before passing
> to the vtk writer?

it isn't... or actually "it can't be" ;-)

> As Felix already pointed out, a mixed approach would directly give
> you stress and displacement (you could also include strain) as a
> solution vector.
> 
> As Christian E. pointed out the subsampling can help you if your
> visualization tool cannot handle higher order/discontinous basis
> functions.
> 
> Best,
> Nicolas
> 
> 
> 
> On 07/20/2011 03:34 PM, Christian Simon wrote:
> >Dear Nicolas,
> >
> >yes, the deformation is my primary variable. In order to compute
> >the the deformation, I need to compute the stress (it is necessary
> >in the residuum). So I have the stress only in the local operator.
> >
> >Thanks in advance,
> >Christian
> >
> >
> >
> >-----Nicolas Schwenck <nicolas.schwenck at iws.uni-stuttgart.de>
> >schrieb: -----
> >
> >    An: dune-pdelab at dune-project.org, Christian Simon
> >    <christian.simon at twt-gmbh.de>
> >    Von: Nicolas Schwenck <nicolas.schwenck at iws.uni-stuttgart.de>
> >    Datum: 20.07.2011 15:08
> >    Betreff: Re: [dune-pdelab] Visualization of Gauss point data
> >
> >    On 07/20/2011 02:45 PM, Christian Simon wrote:
> >>    Dear all,
> >>
> >>    I moved this question from the dune mailing list to the
> >>    dune-pdelab mailing list.
> >>
> >>    Here is the problem:
> >>    I computed stresses at the Gauss points resulting from the
> >>    deformation gradients in my local operator. Now I wonder, how I
> >>    can visualize these stresses via vtkwriter directly from the
> >>    local operator, which is on element basis, without a second
> >>    calculation of the variable in the driver *_Q2.hh or somewhere
> >>    else? Or is there a way to assign these stress values to a vector
> >>    container and visualize it in the driver *_Q2.hh?
> >>
> >>    Maybe it is possible to extrapolate these values to the nodes
> >>    within the operator and assign the values to a vector container,
> >>    which in turn can be visualized by the vtkwriter?
> >>
> >>    Is this there a solution for this problem?
> >>
> >
> >    Dear Christian,
> >
> >    Just to clarify:
> >
> >    Do you have the deformation as primary variable for which you
> >    solve and with this solution you reconstruct the stress?
> >
> >    If that is true I don't get why do you have the stress in the
> >    local operator.
> >
> >    Or do you use a mixed approach, where you solve for the stress and
> >    deformation? But then you still would get the solution not in the
> >    operator but in the driver as a solution vector.
> >
> >    Best,
> >    Nicolas
> >
> >    --     _____________________________________________________________________
> >
> >    Dipl.-Ing. Nicolas Schwenck
> >
> >    IWS, Universität Stuttgart     phone: +49 711 685 64736
> >    Pfaffenwaldring 61     fax:   +49 711 685 60430
> >    D-70569 Stuttgart
> >
> >                email: nicolas.schwenck at iws.uni-stuttgart.de
> >                    url: www.hydrosys.uni-stuttgart.de
> >    _____________________________________________________________________
> >
> 
> 
> -- 
> _____________________________________________________________________
> 
> Dipl.-Ing. Nicolas Schwenck
> 				
> IWS, Universität Stuttgart 		     phone: +49 711 685 64736
> Pfaffenwaldring 61			     fax:   +49 711 685 60430
> D-70569 Stuttgart
> 
>             email: nicolas.schwenck at iws.uni-stuttgart.de
>                 url: www.hydrosys.uni-stuttgart.de
> _____________________________________________________________________
> 
> 

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