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jumpTable: Can someone explain how to use it?

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Old   April 12, 2013, 20:15
Default jumpTable: Can someone explain how to use it?
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Pei-Ying Hsieh
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Dear OpenFOAMers,

Could someone explain how to use jumpTable in cyclic fan BC? In the TJunctionFan example, I saw:

p
{
type fan;
patchType cyclic;
jump uniform 0;
value uniform 0;
jumpTable polynomial 1((100 0));
}
----------------
Does the "polynominal 1((100 0));" mean pressure jump of 100 Pa with 0 velocity? What if I have a 5th order polynominal, like Del_P = a0 + a1*U + a2*U^2 + a3*U^3 + a4*U^4 + a5*U^5. How to specify this? I tried
5((a0 a1 a2 a3 a4 a5)); but, got an error.

Thanks!

Pei-Ying
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Old   April 13, 2013, 00:23
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Fumiya Nozaki
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Reading the source code(fanFvPatchFields.C), the meaning of "f" dictionary changed from v2.2.0:

To set "Del_P = a0 + a1*U + a2*U^2 + a3*U^3 + a4*U^4 + a5*U^5"
  • Older versions than 2.2.0
    Code:
    p
    {
    type fan; patchType cyclic; f 6(a0 a1 a2 a3 a4 a5); value uniform 0;
    }
  • Version 2.2.0 and newer
    Code:
    p
    {
    type fan; patchType cyclic; jump uniform 0; value uniform 0; jumpTable polynomial 6( (Del_p(U0) U0) (Del_p(U1) U1) (Del_p(U2) U2) (Del_p(U3) U3) (Del_p(U4) U4) (Del_p(U5) U5) );
    }
    I think to use the older version settings gives unexpected results.

Please correct me if I'm wrong.

Hope this helps,
Fumiya
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Old   April 13, 2013, 07:27
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Pei-Ying Hsieh
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Hi, Fumiya,

You are a great help!

I looked at the source code in fanFvPatch. Could not figure out how to use the polynominal method. So, I ended up using reading the csv method to read in the curve.

And yes, in the source code, it looks like it tries to be backward compatible with OF-2.1.x, but, when I tried it "f 6(a0 a1 a2 a3 a4 a5)", the case diverged in 4 steps. Maybe there is a bug.

Pei-Ying
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