Pump Affinity Laws

Compare flow, head, and power scaling from speed and impeller-diameter changes with visual bars.

visual calculatorTurbomachinery & Rotating Flow

Read the flow shape before trusting the number.

This page turns a CFD setup into regime, scale, and dominant-effect cues. Adjust the calculator below and compare the moving graphic with the computed result.

input scale

model

check

pumpaffinity lawsrotating machineryscaling

formula

KaTeX rendered

\begin{aligned}\text{Q2/Q1 = (N2/N1)(D2/D1)\^{}3}\\[0.35em]\text{H2/H1 = (N2/N1)\^{}2(D2/D1)\^{}2}\\[0.35em]\text{P2/P1 = (N2/N1)\^{}3(D2/D1)\^{}5}\end{aligned}

ASCII source

Q2/Q1 = (N2/N1)(D2/D1)^3, H2/H1 = (N2/N1)^2(D2/D1)^2, P2/P1 = (N2/N1)^3(D2/D1)^5

Q1 (m3/s)H1 (m)P1 (W)rpm1rpm2D1 (m)D2 (m)

flow

before0.080

after0.107

head / 100

before0.350

after0.622

power / 10000

before0.420

after0.996

N2/N1

1.3333

D2/D1

1.0000

Q2 (m3/s)

0.1067

H2 (m)

62.222

P2 (W)

9955.56

Affinity laws are first-pass similarity scalings. Cavitation, Reynolds effects, and off-design separation can break them.

pump affinity laws rotating machinery scaling