Integrating Fans in butterfly

SaketSarupria · November 7, 2017, 9:34am

Hello all,

Wondering if there is a way to integrate fan axial, swirl and radial flow in the simulations via butterfly. At the moment I am interested in modelling hvls fans in public space (outdoor case). Would be good to get a perspective of what’s possible and what not using current version of butterfly.

Thank you!!

Regards
Saket

TheodorosGalanos · November 7, 2017, 9:59am

Hi @SaketSarupria

It is definitely possible to do fan simulations in OF, in three different ways:

Using the fan or fanPressure boundary conditions in OF itself (see https://github.com/OpenFOAM/OpenFOAM-5.x/tree/master/src/finiteVolume/fields/fvPatchFields/derived/fan and https://github.com/OpenFOAM/OpenFOAM-5.x/tree/master/src/finiteVolume/fields/fvPatchFields/derived/fanPressure). This is the easiest and probably less accurate way of doing it. In this case you are substituting the fan itself by the pressure drop that one might see when a fan is active.
Using the Multiple Reference Frame (MRF) functionality in OF. This is a more accurate but also more cumbersome to set up. I have found that this is the an extremely good trade-off between accuracy and simulation time.
Running a transient simulation with the Rigid Body Motion (RBM) functionality of OF. This is the most accurate, but by far the most cumbersome and time consuming method. A single fan, in a small room, that run for approximately 10 seconds (real time simulation) took around 2 weeks of run time (with very high quality settings)!

The first of those options is actually available in BF as we speak, through the custom boundary condition object. It would be very educational for you to try and set up a case in this fashion. You can find tutorials for both of these boundary conditions in the OF tutorial folders (just search the keywords).

The MRF option is not yet easily available through BF, although not impossible to set up. It is still a vanilla steady-state simulation, with the same models, but has an additional implication during meshing (creating cellzones) and running (using fvOptions). It will be something we plan to add in BF in the future.

The transient case is the hardest and probably the last one to be attempted.

The one issue I found with RBM (and MRF) inside OF was that snappyHexMesh would cause a few problems while meshing the cases, since there are very specific requirements for the rotating regions. I would routinely resolve these with another mesher (cfMesh), I will need to revisit soon and see if this still stands now.

Hope this helps.

Kind regards,
Theodore.

minggangyin · November 7, 2017, 10:21am

@TheodorosGalanos Thanks for your answer.I am also interesting for this issue. You gave me a very clear direction for simulating Fan in butterfly.I also wish the function will be some component for butterfly.

ebifbezif · July 12, 2018, 4:00am

Hi,

Did you successfully achieved this simulation? The case I’m working on might be close to this one.

Regards

SaketSarupria · December 10, 2018, 9:32am

Hi @TheodorosGalanos,

Were you able to work on integrating the MRF functionality in butterfly. Is it possible for you to you give some tips and hints on how to set up a simple case like you did about integrating heat loads in buoyantBoussinesqSimpleFoam.

Thanks you very much for your time.

Regards
Saket