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Old   March 24, 2005, 04:26
Default Changing Temperature & Divergence
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I am analyzing the flow inside the toiletbowl. Here are some few relevant info on the model:

1. 19 inlet boundaries, 2. 2 static pressure boundaries-one at the exit and another at the open-top area (with environment on) 3. im using VOF option, since the water and air in a toiletbowl dont mix. 4. on the scalar bound. tab, every inlet is set to scalar #1, which is the VOF 5. the diff scheme used is MARS 6. the time step used is .004 (highest used before diverge was .005) 7. transient analysis

after running up to about 170 iterations (about .7 secs), the solution diverges. i reduced the time step & the residual tolerance further and yet, still diverges. i looked at the .info file, it shows that the min and max temp are 54K and 14000K respectively, while the average stays at 310K. now the questions i have is:

1. what makes the temp increase as such, when as far as i am aware of, nothing contributes to that increment? in increase of 20K while flushing the bowl just doesnt make sense, does it?

2. why couldnt i run the analysis further? what are the other parameters that i should be aware of in transient analysis, so that the solution doesnt diverge.

and yeah, i kept on getting warning #007, which i think can be neglected, right?

please advice. thanks!

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Old   March 24, 2005, 05:42
Default Re: Changing Temperature & Divergence
Jörn Beilke
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Usually you don't solve for the temperature when doing a VOF calculation. There must be something wrong with the setup.
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Old   March 24, 2005, 10:10
Default Re: Changing Temperature & Divergence
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do you know where can the error possibly be at? i looked at almost every setting but nothing tells me that it is wrong. what may have i overlooked?

thanks for your help!
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Old   March 30, 2005, 01:33
Default Re: Changing Temperature & Divergence
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I have to support Jorn, do you think the temperature difference would make a big effect in splashing? If it does not work, simplify the physics.

btw. it's really interesting problem, is there any journal on it, or is it all company secret? ))

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