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Old   April 8, 2010, 05:41
Question need help about UDS & VOF
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mengyue
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hi guys, i am simulating a system, the fluid involved in this system is water,water vapor and air, because of gradient of vapor mass fraction, there exists phase change.
i don't plan to use the species model available in FLUENT, in my model, i define there phases, which are water,vapor(phase-3) and air, and also, i introduce a UDS to model the diffusion of vapor in the air, the scalar is vapor mass fraction, is that right?
I define the uds for phase-3, and i think i need define vapor/air diffusivity for this uds. but now i am confused with it. in the material pannel, each material has a "UDS Diffusivity", and which one i should introduce my udf for diffusivity? when i introduce udf to vapor, there are some error tips in FLUENT:

Error:
FLUENT received fatal signal (ACCESS_VIOLATION)
1. Note exact events leading to error.
2. Save case/data under new name.
3. Exit program and restart to continue.
4. Report error to your distributor.
Error Object: ()
but when i define the same udf for other materials(air and water), there are not errors.
Can someone tell me the reason... i think my udf should define for vapor, not the other materials...

Regards!

PS:the code is:

DEFINE_DIFFUSIVITY(diffusivity, cell, third, i)
{
Thread *mix_th, *sec_th;
real diff;
real v;
mix_th = THREAD_SUPER_THREAD(third);
sec_th = THREAD_SUB_THREAD(mix_th, 1);

if ((C_VOF(cell, sec_th)==1))
diff = 0.0;

else
diff = 3.02761*pow(10.0,-5.0)*C_MU_EFF(cell, mix_th);
return diff;
}



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Old   April 8, 2010, 08:48
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Dose anyone help me? thanks...and where is sega?
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Old   April 9, 2010, 00:09
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Dose anyone help me? Thanks....
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Old   April 9, 2010, 06:39
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Sebastian Gatzka
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Quote:
Originally Posted by mengyue1 View Post
Dose anyone help me? thanks...and where is sega?
sega is here!
But I think I'm not use here ...
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Old   April 13, 2010, 21:44
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Oh, well, thanks all the same。。。
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Originally Posted by sega View Post
sega is here!
But I think I'm not use here ...
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Old   April 12, 2012, 09:59
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I solved such problem by this way:

1. Make UDM containing the data gotten via C_VOF.
Simle cycle C_UDMI(...)=C_VOF(...)
2. Remove C_VOF(...) from DEFINE_DIFFUSIVITY
3. Use data from UDM in DEFINE_DIFFUSIVITY.

It seems to me - this error appears in some cases when macros C_VOF try to work. For example in solid area.
Best regards...
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Old   February 7, 2014, 10:51
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hi,
did you manage to solve the problem...I have the same problem as you.
thanks for your help in advance!
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Old   February 7, 2014, 18:40
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I didn't try to do smth more exept described above method - this method works.
May be Fluent 15 is better?
Best regards!
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