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Floworks stops before physical time is reached

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321GO

321GO

Automotive
Jan 24, 2010
345
I'm doing a time dependent study for a brake disc under pulsating heat energy loading.

Basically 3 sec. heat input -> 3sec. cool down -> 3sec. heat input, and so on. Solutions finish condition is solely on physical time in the calculation control setup.

With rotation enabled(even as low as 1rad/s), FW progresses with equal time steps until correct physical end time is reached, so all good.

But, when i disable rotation, FW suddenly "jumps" half way in the sim. to the physical end time, with the notification that physical end time is reached.

Obviously this is not correct and this is confirmed when i plot the results (Temp vs time). The pulsating load is not even recognizable(basically one continous load application)?!

I never had this "problem" before.


I realy cannot figure this one out, anybody?
 
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The "problem" seems to lie in the assembly somehow. The problem dissapears if i analyse the brakedisc as a sole part.

Then the solver proceeds normally with the pre-determined timesteps of 0.1s.

As soon as i add another component(the rim) and analyse as an assembly, things go wrong, i.e. the timesteps are disregarded at some stage in the simulation. It looks like the solver for some reason increases the timesteps dramatically (0.5s->1.5s->5s->15s) in assembly setup, as apposed to the pre-determined timesteps of 0.1s for the part setup.

Simply put.. i don't get it.
 
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I seem to have figured it out myself, for those that may be running into this in the future also.

Insufficient mesh density seemed to be the problem. Pls see the attachment.

With low mesh density, the solver simply "cuts out" some time in the simulation and seems to extrapolate results linearly for some reason and in the process disregarding the toggled load steps.

 
 http://files.engineering.com/getfile.aspx?folder=5ce7bc4c-961c-46af-b6fc-63f4ef468954&file=1.pdf
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It's a finite difference solver so in order for it to get meaningful solutions the mesh has to be fine enough to pick up fine detail in the model. Prepping a model for FloWorks should concentrate on removing unnecessary fine detail.

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