Pump and system-curve analysis — finding the operating point where pump and system curves meet, and optimising efficiency and variable-speed control.
Hydraulic Modelling — in depth
A pump runs where its curve crosses the system curve. We build both — static lift plus friction for the system, head-flow for the pump — to find the duty point, confirm it sits near best efficiency, and model variable-speed operation so the pump tracks demand efficiently across the full flow range.
What matters in practice
Static head plus friction vs flow.
Head-flow characteristic.
Where the curves intersect.
Speed-adjusted efficient running.
| Item | Use | Note |
|---|---|---|
| Duty point | Selection | Curve crossing |
| Efficiency | Energy | Near BEP |
| NPSH | Cavitation | Margin |
| VSD | Turndown | Efficient |
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Fundamentals, design drivers and practical guidance
Pump and system-curve analysis — finding the operating point where pump and system curves meet, and optimising efficiency and variable-speed control.
Reynolds & Bauhm builds and calibrates hydraulic models for pressurised and open-channel systems, sizing pumps at their best-efficiency point, checking surge and NPSH, and proving conveyance under design conditions — so plant hydraulics are engineered, not assumed.
Hydraulic modelling underpins reliable water and wastewater conveyance: it predicts how flow, head and pressure behave through pipes, channels, pumps and structures, so a design can be proven on paper before steel and concrete commit it. Whether the question is pump selection, surge, or whether a channel will surcharge, the model turns governing equations into actionable design margins.
Pressurised networks are solved from continuity and energy, with friction losses from Darcy-Weisbach or Hazen-Williams and minor losses at fittings; the system curve so produced is intersected with the pump curve to fix the duty point. Getting this right avoids the classic failures — a pump run far from its best-efficiency point, cavitation from inadequate NPSH, or a network that cannot deliver design flow at the far node.
What our engineers assess on every scope of this type
| Parameter | Typical basis | Why it matters |
|---|---|---|
| Regime | Froude number | Locates jumps; sets freeboard |
| Friction | Darcy-Weisbach / Hazen-Williams | Sets head loss along pipes |
| Duty point | System curve x pump curve | Fixes flow and head delivered |
| NPSH | Available > required | Prevents cavitation damage |
| BEP | Operate near best efficiency | Saves energy, extends pump life |
| Open channel | Manning's equation | Sizes channel for design flow |
Common questions on hydraulic modelling
The network's system curve — static lift plus friction and minor losses — is intersected with the manufacturer's pump curve. The crossing point gives the delivered flow and head; the design aims to place it near the pump's best-efficiency point.
Net Positive Suction Head available must exceed that required by the pump, or the liquid flashes to vapour and the impeller cavitates, eroding it and collapsing performance. The check is part of every pump-system analysis.
It is governed by Manning's equation and specific energy rather than pressurised pipe losses, and must account for sub- and super-critical flow, hydraulic jumps and freeboard so the channel passes design storm flow without surcharging.
Calibration and disciplined inputs — realistic roughness, accurate geometry and correct boundary conditions. A model is only as good as those assumptions, which is why Pump & System Curves is built and checked against known operating data where available.
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