SimScale CAE Forum

Visualising a vortex


#1

Hi guys,
I thought the other day that I saw vorticity as a data type in post processing, however now I can’t find it? looking at another vortex experiment it looks like they contour by vorticity… otherwise, what would be the best way to visualise vortices? I’m currently using steam tracer, however, sometimes it looks too busy but if I reduce the number of streams it doesn’t show enough (I know I’m picky).

Maybe my turbulence model isn’t correct for what I need?

I’m trying to show something like this:

Kind regards,
Darren Lynch


#2

Just done some google digging, maybe I’d be better with LES turbulence modelling?


#3

Hi Darren,

The vorticity result control item is located under Result Control -> Field Calculations -> Velocity. If you do not find it there, could you share what your simulation type is? (For example: turbulent steady-state with k-omega model)


#4

Hi @sjoshi, thanks for your response. I’m doing a compressible simulation, I only see surface control items there. Maybe its not implemented in compressible?

Im doing a compressible, steady state, with K-omega SST turbulence model.

Kind regards,
Darren Lynch


#5

Hi Darren,

The image shown in the link is most likely an iso-surface of Q-critertion.

If you download the simulation, you can get the Q-criterion with OpenFOAM using the command ‘Q’. Another way to determine the vortices in OpenFOAM is with the ‘Lambda2’ command.

I haven’t seen this function objects implemented in SimScale, but they would be a nice feature to have.

Cheers.


#6

Hi @pfernandez, thank you. I just found a paper detailing these two functions, I’ll check them out… I presume I cannot do this in Paraview as a post process?

Kind regards,
Darren Lynch


#7

You can visualize Q in Paraview exactly as you do with pressure and velocity. What you can’t do, as far as I know, is calculate Q within Paraview; for that, you will need to use the function objects of OpenFOAM. This will generate a new file inside the time step folder with the value of ‘Q’ in each cell, just as ‘p’ and ‘U’.


#8

Hi @pfernandez, so my only option here is using the vorticity when it comes to compressible or use open foam direct… in which case do I have to resolve my simulation to get Q? I suppose what I’m asking, is Q a calculated parameter from the other variables (‘U’, ‘P’ etc) or is it measured during the simulation at each step? Can I reupload it with Q to simscale?

Kind regards,
Darren Lynch


#9

Q is calculated from the other parameters. So, you can solve your case in simscale, download the results, and then get Q using the field function.

I know you can upload an OpenFOAM mesh, what I never tried uploading a case with results. I don’t think that’s possible at the moment; but maybe someone from SimScale can correct me if I’m wrong.


#10

A little addition: Adding the Q-criterion as a result control item is tracked! I actually also needed it a couple of weeks ago with a marine propeller case for which I needed to do local post-pro as well. Should not take long to have it in production!


#11

Cheers @dheiny, any chance of Q-criterion and vorticity in compressible flow too? As far as I can see compressable lacks vorticity, or is there a reason for this?

Kind regards,
Darren