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May 9, 2014, 23:48 |
Power Law Velocity Profiled UDF
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#1 |
New Member
Patrick Wayne
Join Date: Nov 2013
Posts: 3
Rep Power: 13 |
Hello,
I'm going crazy trying to figure out how to program a 1/7th power law velocity profile (FD) for my inlet on simple duct flow in Star-CCM+. I have very little experience in programming in general and even less experience in field functions, so I really don't know what to do. I tried going off of something in the "Help" section: [(($$Position[1] <= 0.0025) ? 1.0752*1.143*pow(($$Position[1]/0.0025),0.143) : 1.0752*1.143*pow(((0.005-$$Position[1])/0.0025),0.143)), 0, 0] Basically, it's u(y) = u_bar*(y/delta)^(1/7) for y <= 0.0025 m. and u(y) = u_bar*((h-y)/delta)^(1/7) for y > 0.0025 m. I know this is wrong because my simulation won't run with this. Can anyone help me? Thanks, P. Wayne p.s. The entire height of the duct is only 5 mm.....just in case you were wondering Last edited by pwayne; May 9, 2014 at 23:54. Reason: Forgot Something |
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May 11, 2014, 07:43 |
Error Message?
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#2 |
New Member
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Could you please post the error message from Star-CCM+ in order to understand what is not working.
Cheers |
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May 12, 2014, 13:53 |
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#3 |
New Member
Patrick Wayne
Join Date: Nov 2013
Posts: 3
Rep Power: 13 |
I'll upload that as soon as possible. What I remember is that it says a floating point error has occured in regards to the segregated flow solver. Maybe that helps?
P.Wayne |
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May 12, 2014, 20:50 |
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#4 |
Senior Member
Join Date: Nov 2010
Location: USA
Posts: 1,232
Rep Power: 25 |
Your field function looks fine. The problem probably lies with the mesh or BCs.
Does it blow up immediately or after some iteration? |
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May 12, 2014, 21:10 |
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#5 |
New Member
Patrick Wayne
Join Date: Nov 2013
Posts: 3
Rep Power: 13 |
It blows up just after the first iteration. It's a relief to know the function is fine though, so thank you. I'll work on the Mesh, BCs, then we'll see what happens. I didn't gfet a chance to work on it today, but I'll dive into it tomorrow.
P.Wayne |
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Tags |
duct flow, field functions, power law, udf, velocity profile |
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