Under relaxation factor for unsteady NS scheme?

zonexo

hi,

I am working on a unsteady fractional step FVM unsteady scheme and at times my solution blows up.

I've read that in SIMPLE scheme, there's something called under-relaxation factor which prevents divergence of variables. I believe the default values in Fluent is 0.3 & 0.7 for p and u,v.

However, can i use it for my unsteady scheme? i've used it in an steady problem and it works. but if it's an unsteady problem, it 'll cause time inaccuracy, right?

Thanks!