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-   -   Re LES mode (http://www.cfd-online.com/Forums/main/111919-re-les-mode.html)

harry January 18, 2013 01:10

Re LES mode
 
Hi All,

I recently plan to put a LES model into my multiphase code to simulate gas-solid flow. I never have experience on LES model. I know FVM method for incompressible flow and have experiences in the development of unstructured based code but based on KE model. Is there any open source or free academic code which allows me to quickly take into my code (for gas-solid flow based on discrete element method coupled with a unstructured CFD for incompressible flow)? Your helps would be greatly appreciated.

Cheers,

Harry

afeworkimussie January 18, 2013 04:32

Yea, you can try OpenFOAM's icoFoam solver.

harry January 18, 2013 06:47

Quote:

Originally Posted by afeworkimussie (Post 402589)
Yea, you can try OpenFOAM's icoFoam solver.

thx your reply. open foam is too complicated to me. my current position does not give me much time for my topic. furthermore, open foam may need lots of improvements to solve gas solid flow based on discrete element method.

FMDenaro January 18, 2013 06:51

Quote:

Originally Posted by harry (Post 402620)
thx your reply. open foam is too complicated to me. my current position does not give me much time for my topic. furthermore, open foam may need lots of improvements to solve gas solid flow based on discrete element method.


sorry to say that you can not hope to work in LES without experience with such a constraint ...

sbaffini January 18, 2013 13:59

Is your code 3D and unsteady?

Does it allow non dissipative convective schemes of 2nd or higher order without loosing stability?

Is the time integration of higher order too?

In this case, your first basic implementation may be just as simple as a mixing length eddy viscosity model (a.k.a. Smagorinsky model in LES) with the length provided trough some linear measure of the grid cell volumes. This approach is known as implicit filtering and is the one mostly used in practice.

Then you can further improve it by somehow changing the constant in the model (either by near wall dumping or by the dynamic procedure), or change the model to some more advanced.

However, quoting Filippo, time restrictions are not friends of LES practicioners neither... less than ever are compatible with LES beginners

harry January 20, 2013 20:16

Thank you all for your comments, in particular for sbaffini's details. Here, I would appreciate Sbaffini further comments for the following points.

In my simulations, time step is alway small, say less than 5e-6. Does it mean that I should focus on other things.

1) accuracy of numerical approximation. Do I have to use second order approximation of convective, diffusion and time terms in NS equations?

2) I are going to simulate some domain with a little bit complex boundary, such as pipe. Are there some special attentions to the simple Smagorinsky model? I noticed some papers discussed this issue.

3) How fine the grid would be? Simulation time is so far a big issue to me due to that I mainly employed sequential simulations which last for around one month. More grids, definitely more time, mainly caused by the coupling between particles and gas flow from my side.

So far, I have to persist my own code, which I have testes by many applications in relation to different gas/liquid solid flows, leading to a few journal papers. The problem is that the code uses one order intergration of time and it does not contain some advanced turbulent models. I have a few cases which cannot be reproduced by my model where I believe turbulence plays a key role. I need to test my thoughts with les models or the like.

Best regards,
Harry


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