i am using cfx to calculate npsh requierd in a centrifugal pump but i meet a problem when i define the inlet statique pressure. i must fixe flow rate outlet and pressure total inlet with varring de statique pressure inlet ti obtain npsh requier

but i can't find at same time for boundary inlet total pressure and statique preesure

how can i do please

thanks

you cannot put a static pressure with total pressure at inlet.

It is sufficient to vary the total pressure at inlet to obtain the NPSH af the pump.

NPSH= (Ptot inlet - Pv) / ( ro * g)

thank you very much I have followed this procedure but when i reached the pressure vapor, normaly, i must FIND a drop of HMT with decreasing Pt but HMT remains constant it is not logical how can i do