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April 22, 2012, 14:23 |
High skin friction coefficient,
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#1 |
New Member
Join Date: Mar 2012
Posts: 12
Rep Power: 14 |
Hello all,
I tried to do the tutorial of the cornell website for the turbulent flow, with the pipe dimenstion 8mX0.1m. and the inlet velocity of 1 m/s. choosing k-epsilon turbulence flow. but choosing material as water ( density-1000 kg/m3, and viscosity 0.0007 pa.s). I tried to make the mesh fine, to have low yplus ( I obtained yplus about 0.3 for fully developerd flow). but i wonder why the skin friction coefficient is 3.5 while in the moody diagram the maximum value is 0.1? why my result doesn't match with moody diagram. i attached the skin friction plot here. thanks skin friction.jpg |
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April 22, 2012, 15:46 |
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#2 |
Senior Member
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,758
Rep Power: 66 |
Did you remember to set your reference values? A reference velocity is used to calculate the skin friction coefficient. Not sure what the default in Fluent is. You should set it your bulk velocity (average cross sectional velocity) I believe. Also check to make sure the reference density is correct.
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April 22, 2012, 19:13 |
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#3 |
New Member
Join Date: Mar 2012
Posts: 12
Rep Power: 14 |
Aaaahh!! you are right!!! thank you sooo much for the response, I put many times and trying different meshes!! now i tried to put reference values and it seems it's ok. thanks again
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skin friction coefficient, turbulence |
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