Hello,

Do the under-relaxation factors for pressure and velocity always have to sum to unity?

Thanks.

nope

zxaar is correct. And for some more info on URFs check out this answer given by an engineer at Fluent (the fourth comment to be precise):

http://university.fluent.com/blog/in...&pb=1#comments

Hello, I'm a french student. i've got to fill in the Under relaxation factors box. But I don't know what is really these factors. Can somebody help me ?

Thanks !

Cyril

[girishkaundinya]

Originally Posted by Cyril
;125527

Hello, I'm a french student. i've got to fill in the Under relaxation factors box. But I don't know what is really these factors. Can somebody help me ?

Thanks !

Cyril

Because of the nonlinearity of the equation set, it is necessary to reduce the change of a variable from one iteration to the next. This is referred to as under-relaxation. For example, if the pressure under-relaxation factor is 0.3, the change in pressure value from one iteration to the next will be restricted to 30% of the difference between the initial value and the newly calculated value.