For at tage hensyn til vekselvirkningen mellem trykvariationer ved pumpen og pumpens sliphastighed beregnes korrelationsfunktionen (X0) mellem pumpehastighed, trykdifference mellem pumpeindgang og -afgang og absolut pumpeafgangstryk på følgende måde:
To account for the interaction of pressure variations at the pump and the pump slip rate, the correlation function (X0) between pump speed, pressure differential from pump inlet to pump outlet and absolute pump outlet pressure shall be calculated as follows: