WMLES in PyFR

[Eduardo Molina]

Hi all,

I would like to implement a basic Algebraic Wall Model in PyFR. The model consists of 2 simple equations for the turbulent boundary layer: one for the shear stress and another for the heat flux (in case of an isothermal BC).  As a 1st attempt, we can restrict the Wall Model to probe the LES quantities within the first element off the wall. Another modification is that the we might need a slip condition that will let the velocity to be driven by the imposed shear stress.

Regarding elements types at the boundary, I don't know how PyFR is structured but I was thinking that quad/hexa(boundary layer) is a good start. 

This will be my first interaction with PyFR and I think that the best way to learn a new code is by coding/adding things.... 

Thus, I really appreciate if someone could help pointing me where I can start the implementation and where I can find LES test cases other than the ones already available in GitHub.

Best,

Eduardo

[Semih Akkurt]

Hi Eduardo,

I think determining first layer of elements from the wall of interest is the best place to start for this. Native PyFR mesh file (.pyfrm) uses hdf5 format. Datasets starting with 'bcon_' stores the connectivity of a boundary to the nearby cells. If you check a bcon_ dataset in a pyfrm file you will see something like this;

DATASET "bcon_wall_p0" {

...

      DATA {

...

      (3): {

            "quad",

            185,

            2,

            0

         },

...

It tells you that boundary face 3 shares the face 2 of element number 185 of the quad elements. Based on this you may want to store the element-local indices of solution points that you are interested in. Once you construct this you'll have a corresponding data set for the boundary you are working on. solvers/euler/kernels/bccflux.mako is a good example of how boundary conditions are implemented in PyFR.

quad element local solution point indices for p=2, face indices, and mesh point indices

 2________2________3

  |                             |

  |    6        7        8    |

  |                             |

3|    3        4        5    |1

  |                             |

  |    0        1        2    |

  |________________ |

 0            0                1

and for hex elements this repeats itself in z direction 

Best,

Semih

[Vincent, Peter E]

Hi Eduardo,

Further to Semih’s reply, I just wanted to pick up on:

where I can find LES test cases other than the ones already available in GitHub.

The best place to look is in the supplementary material of our publications e.g.

https://www.sciencedirect.com/science/article/pii/S0021999116307136

and

https://arc.aiaa.org/doi/10.2514/1.J055304

Thanks

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

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