Under relaxation with PISO ?
 

hi all,

I've had a look on the PISO and SIMPLE algorithm and, as far as I understand the SIMPLE algorithm expects under-relaxation factors while PISO doesn't.
So here are my questions:
Do I have to set under-relaxation factors in SIMPLE each time I use it ? or can I omit them without risking divergence ?
Moreover, can I use them with PISO even though it doesn't expect any ?

Thank you for lightening my mind!