Dear All,
I am simulating Fluid Structure interaction. I have followed tutorial
https://www.youtube.com/watch?v=oOGkvrnKS-c
This tutorial was set as following ....
For Structure,
Time step size = 10 s
Number of time step = 1
For Fluent,
Time step size = 1 s
Number of time step = 10
Coupling System
End Time step = 10s
....................................................................................................................
In my simulation, when i set time step like this. It has error.
But when I change Fluent to
Time step size = 10 s
Number of time step = 1
The error disappears....., but I have to create VDO that Fluent must has many time steps which a small step size.
Could you please advise.....?
Best Regards,
Yannapol S.
hi dear Yannapol
i see your massage, i cant help u im begginer, i want simulate a turbine and a must use "bald Generation" and "Grid Mesh" and "CFx" have u a tutorial that can help me?
best regards
reza
depending on the largest frequency and smallest frequency of the system. the time step depends of the largest frequency (always more than 10 steps a period), the number of the time step depends of the smallest frequency
Hello, Yannapol!
I guess, the same tutorial is represented in this pdf
http://www.ansys.com/staticassets/ANSYS/Conference/Confidence/San%20Jose/Downloads/multiphysics-systems-coupling-2.pdf
And I am surprised that you are setting up time steps separately for Structural, for Fluent and for System Coupling. Time stepping is controlled only by System Coupling module. So, usually you do set the time step at least several times less than the shortest periodic event in your process (e.g. if you have a turbine rotating and it has 12 blades, then your time step should be at most 1/12 of the time of one full rotation of the turbine). The number of steps again depends on your process. Using the same turbine example, I would have at least 3 (better 5) rotations of the turbine (so, 3*12 = 36 steps).
Again, as I remember, the time stepping is controlled by System Coupling, but if you decide to set up time steps in structural and Fluid, they HAVE TO BE exactly the same for both of them otherwise, the whole principle of Fluid-Structure Interactions will be broken.
I hope this helps.
Best wishes.
Usually the time step of any CFD problem should be decided based on the flow physics involved in the phenomena. Usually, the time step should be smaller than the time required in changing of flow physics. For example, the time step can be less than the value of the inverse of vortex shedding frequency, if one captures the vortex shedding phenomena.
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