2-way FSI does not start due to setup issues

ManateeManatee Member

I want to look at the 2-way interaction between a pulsatile fluid flow and an elastic wall, in particular its deformation.



To start with, I wanted to look at 10 seconds of pulsation so I used Hybrid Initialisation on Fluent and set my parameters in Run calculation to:

Number of Time Steps: 1000

Time Step Size: 0.01

Max Iterations/Time Step: 5

Reporting Interval: 1

Profile Update Interval: 1

(not sure what the last two do)


Running this by itself with the UDF I wrote works fine. However, I cannot get my System Coupling to work or even start! I read you should match your time step values when you do system coupling so I set Transient Structural to:

Number of Steps: 1000

Step End Time: 0.01

Initial/Minimum/Maximum Time Step: 0.01


and System Coupling to:

End Time: 10

Step Size: 0.01

Minimum Iterations: 1

Maximum Iterations: 10

But I get this error message: The fluid solid interface load is not valid for multi-step analysis


So I change Transient Structural to:

Number of Steps: 1

Step End Time: 10

Initial/Minimum/Maximum Time Step: 0.01

But I get this error message: End time must be greater of equal to start time (9.999999999) plus step size (0.01): 10.00999999999


So I change Transient Structural to:

Number of Steps: 1

Step End Time: 11

Initial/Minimum/Maximum Time Step: 0.01

But I get this error message: The specified end time cannot be greater than the end time specified by Transient Structural: 10


So now I set Transient Structural to:

Number of Steps: 1

Step End Time: 20

Initial/Minimum/Maximum Time Step: 0.01

and System Coupling to:

End Time: 15

Step Size: 0.01

Minimum Iterations: 1

Maximum Iterations: 10


I click on Update Project on the Workbench and get the error message:

Participant Solution encountered a fatal error: Message: The Mechanical beginning time 0 is different from the system coupling service beginning time 10.


So I really don't understand what the software wants from me. Doesn't it run all the modules parallel and thus needs the same values for all the setups? How do these end and start times relate to each other?

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