[Marc]

Hello ishaandesai,
in case of a curved geometry it is better to go with a non staircase boundary as Bouzidi, but for the first draft I prefer bounce back. You can send me a link to the Picture. The first step is that every voxel for your inflow has the correct material numer.
Best Marc

[Marc]

Hello ishaandesai,

you have to respect a certian overlap, move your renaming indicators two physDeltaX in fluid direction than you should get rid of this error. Check the coordinates in your error message to see for which cells are no boundaries found and adapt your indicator in the according direction

Best Marc

[Marc]

Dear Behnam,
with all indicators in our code you are able to define boolean arithmeitc, which means that you can combine indicators (+) or intersect them (-). I think your idea is to intersect the cylinder by a cuboid.
The offset means that you deal by the renaming process with a certain offset in an cartesian coordinate. if you just use rename 2,1 all your cells with 2 will disappear. The offset gives you the possibility to create a layer in the directions that you want.

Best,
Marc

[Marc]

Dear steed 188,

I still believe that you want a “normal” pressure outlet condition (Dirichlet pressure=0)? It is possible to set a periodic boundary the only condition is that your outlet has an equal size like your outflow. You have to apply a forcing area instead of the inlet and force your massflow concerning a mean massflow. This is stable for high Re number flows. If you come to the spring School I will show you how to stabilize your case.

Best,
Marc

[Marc]

Dear steed188,

I don’t think so. You should deal with periodic boundaries to stabilize your simulation at high Reynolds numbers.

Best,
Marc

[Marc]

Dear steed188,

I think it depends, if you pass uAv to the convection boundary constructor.
For periodic boundaries you have to use forced dynamics and you don’t nedd additional material number for inflow and outflow. You can have a look at the forced poiseuille flow 2d example.

Best Marc

[Marc]

Hi steed188,

first we several pressure boundary condition approaches local and interpolation. I don’t know which one you use for your case. I prefer interpolation because the non equilibrium bounce back approach will be instable by high Reynolds numbers. If your geometry has an inlet and outlet of the same size, you should use periodic boundaries. I actually working on wall functions. OpenLB will get this feature in the future. If you want to learn more about simulating turbulent flows with LBM, I highly recommend you our spring school in March.

Best,
Marc

[Marc]

Hi Pedro,
we don’t have grid refinement in our Code. SuperLattice and the underlying BlockLattice is used in every example.
Best,
Marc

[Marc]

Hi Pedro,
for such high Reynoldsnumbers you have to be careful with your spacing. A y+ around 2 should fit for a LES Simulation. Which turbulence model did you use for MRT?
I would highly recommend you to come to our springschool in March to learn more about the simulation of turbulent flows.
Best,
Marc

[Marc]

Hi Pedro,
the first step is to delete the line:
delete bulkDynamics;
because you don’t have a pointer anymore.
If you still get an error message, use the original cylinder2d.cpp file and modify just the code line that I send you in the last post. This should compile without errors. Then you can apply your modifications step by step.
Best,
Marc

[Marc]

Hey Pedro,
if you want to use a Dynamics pointer you have to adapt the arguments in the function prepareLattice.
The easiest way to run the model is to change the line:
BGKdynamics<T, DESCRIPTOR> bulkDynamics( converter.getOmega(), instances::getBulkMomenta<T, DESCRIPTOR>() );
to
SmagorinskyBGKdynamics<T, DESCRIPTOR>bulkDynamics( converter.getOmega(), instances::getBulkMomenta<T, DESCRIPTOR>(), 0.15);
Good luck with your turbulence Simulation!
Best,
Marc

[Marc]

Hi Pedro,
there are no books about LBM turbulence as far as I know. I would recommend you books, which introduces the physics and mathmatics behind turbulence on the one side and on the other side books about the LBM method. This books should give you all the knowlegde that you need to deeply understand papers that dealing with LBM turbulence. Some recommendations for you:

Bailly, C., & Comte-Bellot, G. (2015). Turbulence. Cham: Springer.
Krüger, T., Kusumaatmaja, H., Kuzmin, A., Shardt, O., Silva, G., & Viggen, E. M. (2017). The Lattice Boltzmann Method: Principles and Practice. Cham: Springer International Publishing.

Best,
Marc

[Marc]

Hello steed188,

I am also working on turbulence. Which kind of model do you use? At the moment, there is no time average functor implemented in OpenLB, but I think it is a very usefull tool in case of turbulent flows. We can work on the functor together, if you want.

Best,
Marc

[Author]

Posts