# SU & SP: CFX 4.4 HELP!!!

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 June 19, 2005, 21:19 SU & SP: CFX 4.4 HELP!!! #1 Robin K Guest   Posts: n/a Hi, I want to put source: Source=R3-R2-R1 where R1, R2 and R3 represent different expressions. R1=+ive, R2=-ive, R3=+ive At the moment, I am carrying out the following operation: SP(INODE,IPHASE)=SP(INODE,IPHASE)+R2*VOL(INODE) SU(INODE,IPHASE)=SU(INODE,IPHASE)+((R3-R1))*VOL(INODE). This is causing a divergence. Does anyone have any other way of doing it!...I hope so...? Thanks in Advance, Robin K

 June 27, 2005, 21:30 Re: SU & SP: CFX 4.4 HELP!!! #2 Jeff Guest   Posts: n/a Robin, The form of a source term, when solving for variable phi is as follows: Source = SU + SP * phi Since in your source term, you don't have any variables that are a function of the solved variable, phi, SP should be zero. SU(INODE,IPHASE) = SU(INODE,IPHASE) + R3 - R2 - R1 SP(INODE,IPHASE) = SP(INODE,IPHASE) + 0.0 Use this if your source is mostly positive. If (R3-R2-R1) is very negative, you may want to put this in the SP term by first dividing by phi (since the code will multiply it by phi later). This would be: SU(INODE,IPHASE) = SU(INODE,IPHASE) + 0.0 SP(INODE,IPHASE) = SP(INODE,IPHASE) + (R3-R2-R1)/phi(INODE,IPHASE) This will make the matrix more diagonally dominant when SP gets carried to the other side and incorporated into the matrix diagonal. Jeff

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