# jumpTable: Can someone explain how to use it?

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 April 12, 2013, 20:15 jumpTable: Can someone explain how to use it? #1 Senior Member   Pei-Ying Hsieh Join Date: Mar 2009 Posts: 271 Rep Power: 9 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

 April 13, 2013, 00:23 #2 Senior Member   Fumiya Nozaki Join Date: Jun 2010 Location: Yokohama, Japan Posts: 169 Rep Power: 7 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

 April 13, 2013, 07:27 #3 Senior Member   Pei-Ying Hsieh Join Date: Mar 2009 Posts: 271 Rep Power: 9 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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