Core formulas
| Term | Formula or definition | Units / condition |
|---|---|---|
| Velocity | V = Q/A | m/s when Q is m³/s and A is m² |
| Pressure head | H = p/(ρg) | m of the stated fluid |
| TDH | Elevation + delivery pressure head + losses − available inlet pressure head | m or ft |
| Hydraulic power | P = ρgQH | W |
| Reynolds number | Re = VD/ν | Dimensionless |
| Darcy loss | hf = f(L/D)V²/(2g) | m or ft |
| NPSHA | Absolute suction head above vapor-pressure head | m or ft absolute |
Hydraulic terms
- Flow
- Volume passing a point per time.
- Head
- Energy per unit weight expressed as fluid-column length.
- System curve
- Required system head as flow changes, combining static and flow-dependent components.
- Duty point
- The operating intersection of pump and system curves.
- Pump efficiency
- Hydraulic power delivered to the fluid divided by pump shaft input power.
- NPSHR / NPSH3
- Manufacturer/test-based suction performance value; it is not the same as a complete reliability margin.
- Friction factor
- Dimensionless Darcy factor determined by Reynolds number and relative roughness.
Reference boundary. Do not convert an indicative value into a universal design, health or legal requirement. Check the cited source, laboratory context, certified claim and applicable jurisdiction.
Sources
- Hydraulic Institute — Pump FAQs
- Hydraulic Institute — Pump Principles and NPSH
- U.S. Army Corps of Engineers — EM 1110-1-4008
- U.S. Department of Energy — Pumping System Assessment Tool User’s Manual