Thanks for the email.

The polynomial information is stored inside the .pyfrs files. They can be 
interrogated with e.g. h5py or any other HDF5 wrapper.

Basically, we store the solution value at a set if nodal points within each 
element, which when combined with an associated nodal basis can be used to 
reconstruct the polynomials within each element.

If you are interested we would need to provide some more info about the exact 
file format, since it is not documented anywhere yet. Also, since elements can 
be curved, it can be a challenge to work out which element a given physical 
point is in. And when you have found the element the mapping may need to be 
inverted numerically.

Peter

Dr Peter Vincent MSci ARCS DIC PhD FRAeS
Reader in Aeronautics and EPSRC Fellow
Department of Aeronautics
Imperial College London
South Kensington
London
SW7 2AZ
UK



On 12 Nov 2018, at 15:45, Eduardo Ramos Fernandez 
<[email protected]<mailto:[email protected]>> wrote:

Hi all,

I want to use the solution of a turbulent flow from PyFR as an input for a 
Lagrangian simulation. The problem is computing the trajectories of the 
particles advected by the flow are sensitive to local errors in the fluid 
velocity field and can diverge. The trajectories can be computed one at a time 
since they do not interact and they are not coupled to the solver (flow not 
affected by the presence of particles). Because of that, I dump my flow 
solution from PyFR and convert it to .VTU so I can after read it with the 
Lagrangian software and use VTK libraries to extract velocities at different 
positions. The problem is in the conversion from .pyfrs to .vtu information is 
lost through the -d N linearisation stage and the computational advantage of 
having a coarser mesh it is lost. Furthermore, making N high, when resolving 
particle trajectories, makes the inverse search from particle positions to 
fluid cells really expensive in an unstructured mesh. Would it be possible to 
dump the internal PyFR polynomial information local to each cell so it can be 
used in a post-processing stage? This would be useful for any kind of 
post-processing doing integration over the fields.

Regards,

Eduardo

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