## Fluids

Topics relate to Fluent, CFX, Turbogrid and more

#### given a source，the temperature is diffculty to converge

• lvxk
Subscriber

Hello，teacher，Recently,i met a problem ，I want to set a source term to control the temperature of aim place，First，i made a simple case that i used the PI Algorithm to control the source，give a source ，it will be compute the temperature at once，then the UDF about the adjust Function will make a estimete，if the temperature is low，it will be add the source ，vice versa，but when the number of meshes more than one hundred，it is hard to estimate the temperature，and furtherly it not easy to adjust the source ，so i give a relaxation factor，when i give the source，it will be make 100 iterations to compute the temperature，then，to adjust the source term，but it not solve the problem cause of every calculation before adjustment is not converge，i am looking forward to receive your reply，thank you so much！

• DrAmine
Ansys Employee
Does it converge without sources?
• lvxk
Subscriber
it will be converge when i give source a constant´╝îbut it needs manys iteration´╝îbut when i add the UDF´╝îit is diffcult to converge´╝î
• lvxk
Subscriber
the question is whether it is normal that it needs many many many iterations to compute the temperature when i give the source with a constant´╝ƒ

• Rob
Ansys Employee
It depends on how frequently, and how large a change the UDF makes. The solver iterates towards a solution, if the boundary settings change quickly relative to the progress towards the converged solution it'll take a long time to settle down. Also, define "many many": a tutorial may converge in 2-300 iterations, a real model may require 1500 or so.