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January 23, 2011, 10:33 |
Velocity gradient tensor
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#1 |
New Member
kumaran
Join Date: Jan 2011
Posts: 4
Rep Power: 15 |
Hello there,
could anyone suggest how to extract second invariant of the velocity gradient tensor from fluent? I am using Fluent v12 Thanks |
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January 24, 2011, 08:06 |
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#2 |
Member
Nikolopoulos Aristeidis
Join Date: Jan 2011
Location: Athens, Greece
Posts: 62
Rep Power: 15 |
Yes i know how you should do it!
I did it for calculation of frictional solid viscocity in Euler -Eule granular material simulation. If you want the IId in a UDF you should obtain the derivatives of velocity in each direction (C_DUDX(cell, thread), C_DVDX(cell, thread), C_DWDX(cell, thread) etc. (check the command in the UDF manual). and then just use the formula. ND_ND parameter will help you in order to obtain a code that works for 2-D and 3-D. If you want the IId just for plotting define a custom field function (Fluent -> Define -> define a custom field function ) Be careful in this: Are you sure that you want to calculate the second invariant of gradU??? Or you want the second invariant of the deviatoric part of rate-of-strain tensor? |
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January 25, 2011, 08:56 |
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#3 |
New Member
kumaran
Join Date: Jan 2011
Posts: 4
Rep Power: 15 |
hello Nikolopoulos,
thank you for your response. I am looking for the IId of gad U to look at the coherent vortices in 3D. i am not that familiar with the UDF.. do you mind sharing the UDF file that has the skeleton? so that i can try to modify it ? Thanks |
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January 26, 2011, 02:31 |
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#4 |
Member
Nikolopoulos Aristeidis
Join Date: Jan 2011
Location: Athens, Greece
Posts: 62
Rep Power: 15 |
Do you want it only for post process?
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January 26, 2011, 03:15 |
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#5 |
New Member
kumaran
Join Date: Jan 2011
Posts: 4
Rep Power: 15 |
hi,
yes. i want only for post process to see the streamwise vortices in teh midsection of the domain Thanks |
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January 25, 2012, 04:00 |
udf for velocity tensor
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#6 |
New Member
studen
Join Date: Jan 2012
Posts: 12
Rep Power: 14 |
hi kumaran and nick, i also need to see the velocity tensor for my simulation can u pls share the udf file.
regards and thnks in advance |
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