Bruno, Thanks for responding!
On Tuesday, August 16, 2016 at 11:16:41 AM UTC-5, Bruno Turcksin wrote: > > Spencer, > > I think that passing around the entire system is the way to go but what I > would do is to use component mask ( > http://dealii.org/developer/doxygen/deal.II/DEALGlossary.html#GlossComponentMask) > > and block mask ( > http://dealii.org/developer/doxygen/deal.II/DEALGlossary.html#GlossBlockMask) > to work on a subset of the whole system. Instead of having a bunch classes > working on small blocks that will be added together at the ends, you have > an entire system but each class works on a small block without knowing what > the others do. For example, the velocity class can have access to the > global dof_handler and a FEValuesExtractors for the velocity. It doesn't > need to know what is its block number or how many blocks there are. > Are there examples of how to do what you describe? Looking at the documentation, it is not apparent how to do this. > > Best, > Bruno > So supposing I have the public interface of my velocity class (specified by an abstract velocity interface class from which this velocity model derives) having the following member functions: TrilinosWrappers::MPI::Vector & get_velocity() FESystem<dim> & get_fe_velocity() DoFHandler<dim> & get_dof_handler_velocity() how would I go about using the Block or Component Mask to return the proper things? For velocity, I can return solution.block{velocity_block} which gives a TrilinosWrappers::MPI::Vector and I could possibly change the interface to return an FiniteElement<dim> instead of FESystem<dim> so that I could return fe_system.base_element(velocity_block) but the mask just allows me to extract dofs into a vector, how do I get that back into a dofhandler? My velocity model is created using the factory method which keep to the abstract velocity interface class and I have several other velocity models that all obey this interface above. The other transport class expect this interface, so it would be very cumbersome to change it for this specific block structure since the others do not use it. Internally it has a block structure but externally, it represents only a velocity which is one of the blocks. > On Tuesday, August 16, 2016 at 11:34:24 AM UTC-4, Spencer Patty wrote: >> >> Dear All, >> >> I have a class which represents a velocity field (I am using a variant of >> the pressure correction navier stokes model with two phases) and a class >> which represents a transport model along a provided velocity field. I am >> adding in some terms into the velocity model (currently surface tension but >> soon to be added is the canham-helfrich or willmore energy) accounting for >> the physics and force balance on the boundary between the two phases. The >> approach that we are using is to create a block structure inside the >> velocity class to incorporate these other physics into the model. We have >> a splitting of velocity separate from the pressure terms and have separate >> dofhandlers for these two groups but now we are lumping all the components >> that need to be simultaneously solved for with the velocity into the >> velocity dofhandler and fesystem. For instance we have the block >> components in the velocity fesystem: >> >> dim components of velocity, normal velocity, curvature and willmore >> energy >> >> so that our velocity fesystem looks like >> >> FESystem<dim> ( >> >> FESystem<dim>(FE_Q<dim> >> (parameters.degree_of_fe_velocity),dim), 1, // velocity >> >> FE_Q<dim>(parameters.degree_of_fe_velocity), >> 1, // normal velocity >> >> FE_Q<dim>(parameters.degree_of_fe_velocity), >> 1, // curvature >> >> FE_Q<dim>(parameters.degree_of_fe_velocity), >> 1 // willmore force >> >> ) >> >> I have figured out how to construct the block sparsity patterns and >> matrices etc and solve for this, but at the end of the day this class >> represents a velocity not a velocity plus other stuff. This class >> interfaces with the other class representing transport and I need to be >> able to provide a velocity, dofhandler and fesystem in such a way that I >> don't break encapsulation ie the other class doesn't need to know that >> internally there was a block system and other components... >> >> The other class expects to be able to query a >> TrilinosWrappers::MPI::Vector, FESystem<dim> and DoFHandler<dim> >> representing the velocity finite element solution. >> >> Supposing internally to the velocity class I have >> >> solution, a TrilinosWrapper::MPI::BlockVector >> fe_system, the FESystem<dim> described above and >> dof_handler, the associated DoFHandler<dim> which is sorted >> DoFRenumbering::hierarchical and DoFRenumbering::component_wise. >> >> Supposing velocity_block represents the block number associated to the >> velocity components, I noticed that solution.block{velocity_block} would be >> a TrilinosWrapper::MPI::Vector of the velocity as desired and it is >> possible to extract the sub FiniteElement >> fe_system.base_element{velocity_block} corresponding only to the velocity, >> but the dof_handler has no such existing capability and if I pass it as is >> with the extracted FiniteElement into an FEValues, an assertion is >> triggered when we call fe_values.reinit(cell) saying that the given finite >> element does not match the dofhandler's finite element... I don't want to >> pass the entire system since that requires the other class to know that it >> only needs the first block components etc. >> >> My question is this: What would be a best approach to dealing with this? >> Is there currently a way to extract a "diagonal block" from the system and >> reduce the solution, fesystem and dofhandler to only represent that part? >> Do I need to create a new FESystem, DoFHandler and vector to provide the >> functionality I need ? >> >> I hope this is clear enough and enough(and not too much) background to >> understand what I am asking. Thanks for any help! >> >> Spencer Patty >> >> >> >> >> >> -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. 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