SimScale CAE Forum

Create Slice to monitor flow field during solving


#1
  • Which feature do you need?
    I would like to ability to add a slice that can be monitored as the solver is running for a CFD study.
  • What is the problem that you want to address with this feature?
    This will allow users to check to see if there are any obvious issues with their setup (flow going the wrong direction, forgetting to add a boundary condition, etc.)
  • What is the expected outcome?
    Fewer mistakes during setup and less wasted time on poor setup.

Platform Update 12/2018
#2

Hi Eweber,

I am not from the SimScale Team but the mentioned reasons for adding this feature is not a good one. In general, for CFD and actually for OpenFOAM this is not a big deal and I guess SimScale could implement this feature. However, I don’t know the software architecture which is behind and thus, the implementation could be a bit more challenging but making less mistakes would be not a good point. If you set some BC wrong, the solver will blow up fast. Okay there are the cases when users set up a set of boundary conditions which will lead to an numerical solution (Ax=b) but with an arbitrary number of possibilities. I am not sure if such a feature could provide the necessary information for unskilled people. In addition, I think SimScale applies appropriate or default BC if the user forgot some of them because no BC no numerical solution, no solving. In addition, you should specify which kind of quantity you would like to monitor? An averaged value, or something else. Keep in mind that slicing etc, will always induce errors and other stuff and averaging as an own topic. Area averaging, volume averaging (but with a slice?) and so on :slight_smile:

I just wanted to make some more statements. In general I guess it is nice to have especially for faster post-processing like - run-time processing. But there are so many possibilities with FOAM. :slight_smile:

Kind regards,
Tobias Holzmann


#3

Tobias,

I appreciate the comments. I work for a Solidworks reseller and do quite a bit with Solidworks Flow simulation. When the study is solving we are able to monitor vectors and slices of the flow field. While it doesn’t really do much for us while it is solving most of the time, it has saved me from allowing a study to run when the setup has a simple mistake such as putting a pressure outlet on a face that should actually be a flow rate inlet. Another example would be mistyping a value of a BC. The difference with SimScale is you are paying for core hours where a simple mistake like this could be very frustrating. I will admit it is a stupid mistake but I have made it on occasion. With a mistake like this the solver will not fail but will give you a result that is not as you intended.

It is probably not an easy change as you can only monitor the log files and residuals in the Simulation designer and clips are added in the post-processor. So, they would have to add a new category to create clipping planes in the Simulation designer.

It is just something that would be nice to have but certainly not necessary.


#4

If this was desired, we could save the last solved timestep in the post processor instead of having to wait until the end. Each time a new timestep is solved it could overwrite the last giving a live view on the solve. I don’t know how well open foam would be geared for doing this but making a new category seems un-necessary if all we need is already present, just the way we deal with results needs to change maybe?

Makes sense in my head, I think this could be valuable. However, if it comes as an expense to compute time maybe it should be result control item.

Kind regards,
Darren


#5

Hi,

openfoam can handle saving the last time step easily and overwrite it. Within the latest version there are even more possibilities like - save each 50th time step and keep only the last 5. Thus, the space usage can be reduced. It is also possible to say that after 200th time steps you really want to keep the time folder (e.g. for transient solvers or even for steady-state simulations).

For steady state it would be, store each 200th iteration but also store the last 5 iterations and overwrite them always till we reach the end. This is not a big deal in openfoam and is already included. The output would be like that (for steady state):

Saved folders at beginning:

0 - 1 - 2 - 3 - 4

After a while

0 - 15 - 16 - 17 - 18

Again more iterations

0 - 100 - 125 - 126 - 127 - 128

And after a long time

0 - 100 - 200 - 300 - 400 - 464 - 465 - 466 - 467

Thanks for remind me @1318980 (Darren) that we have this possibility in FOAM :slight_smile:
I guess this would be one of the best ways.


#6

The way this is done in Solidworks Flow Simulation is it only saves for the last solved iteration. You do not have the ability to show any earier iterations. Having the latest iteration is all that would really be needed in my opinion. This would acomplish what I want.


#8

This feature I added to the “Vote for Features” category titled " Create Slice to monitor flow field during solving" has been implemented with the 12/2018 update (Live Post-Processing). This is exactly what I was looking for.