Co-simulation between two flow simulations
 

Hello

I am wondering if a co-simulation between 2 flow simulations in StarCCM+ is possible.
So far, from what am reading on the user manual, it seems only fluid - solid co-simulation can be done.

My problem is the following: I have one part (let call it Part2) of my geometry which has fixed definition.
However, I have several different Part1 connected to it, that I want to test, which are provided independently to me. My aim is to be able to run Part1 and Part2 together without having to do much actions.
I was wondering if it was possible to do a co-simulation of these two parts, by coupling the outlet of Part1 to Inlet of Part2. For the moment, I am not successful in doing so. I could do it with table exportation, but I would much prefer co-simulation. Does anyone has hint on this?

Thanks a lot

I replied in another thread about this, but I think you are exactly describing the function of co-sim. If you are having issues getting it to work, you may want to contact tech support. They are very responsive to all issues. For reference, a clip from the help files is below...

'STAR-CCM+ allows you to couple two running simulations together in a co-simulation analysis. The STAR-CCM+ to STAR-CCM+ co-simulation capability targets simulations involving conjugate heat transfer (CHT), fluid-structure interaction (FSI) or exchange of scalar/vector fields across a coupling boundary.'

Hello
Thanks for your 2 answers.
I am indeed thinking as you do, that what am describing is exactly what a co-simulation should do, and especially from the line your took from the user manual.
So far, I have trouble to make it work, so as you suggested, I will contact the tech support. I was asking on the forum, in case someone had some info on that.

In the same time, I went to the Steve Portal - Bright Idea, and found some comment such as:
""This may also be feasible once fluid-fluid co-simulation is made available"" which somehow means that a co-simulation fluid-fluid is not yet available.

I will keep updates once I find out the final answer on this point.

fluid-fluid co-simulation
 

Hi everyone,
I managed to do a fluid-fluid co-simulation in a simple region (pipe). Maybe it would be interesting for smb.
There were 3 regions: Inlet,middle,outlet.
Each region had 3 boundaries: velocity Inlet, non-slip wall, pressure-outlet.
It was two loops (velocity and pressure) and several steps.
Velocity loop (transfers the velocity from inlet region to outlet region):

First step solved only first region. Data of velocity profile on outlet boundary was written into a table.
Second step solved only middle region. Data of velocity profile on inlet boundary was observed from table of first step. Data of velocity profile on outlet boundary was written into a table.
Third step solved only outlet region. Data of velocity profile on inlet boundary was observed from table of second step. Data of pressure profile on inlet boundary were written into a table.

Pressure loop (transfers the pressure from outlet region to inlet region):

4st step solved only middle region. Data on pressure-outlet boundary was observed from the table of step 3. Data of pressure profile on inlet boundary were written into a table.
5 step solved only inlet region. Data on pressure-outlet boundary was observed from the table of step 4.

These two loops sholud be done for a several times.
In my simulation it was enough of 3 full loops to get the convergence. I compared the results with non-coupling region and it wasn't any differences.

There is two problems on in this algoritm:
1) It's impossible to transfer the gradients on the co-boundary.
2) If area doesn't propose a parallel flow, this algoritm should be done step by step (without a parallel solution of regions).