KEVOS® MAKEOS · Hydraulics
Orifice and Restrictor Flow
How much liquid flows through this orifice at this pressure drop, or what drop does a flow cause?
Flow through a sharp-edged orifice, jet or restrictor from the discharge coefficient, diameter and pressure difference, or the pressure drop for a given flow.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Calculate | choice | Find the flow for a pressure drop, or the drop for a flow. |
| Orifice diameter | mm | Smallest diameter of the orifice. |
| Discharge coefficient | Discharge coefficient (about 0.6–0.65 for sharp-edged orifices, up to about 0.95 for rounded nozzles); measured values are best. | |
| Pressure drop | bar | Pressure difference across the orifice (flow mode). |
| Flow (pressure-drop mode) | L/min | Flow through the orifice (pressure-drop mode). |
| Fluid density | kg/m³ | Density of the fluid at the working temperature (mineral hydraulic oil about 870 kg/m³, water about 998 kg/m³). |
Method and formulas
- Q = Cd × A × √(2Δp ÷ ρ), with A = πd²/4, Δp in Pa.
- Δp = ρ ÷ 2 × (Q ÷ (Cd A))².
- Example: a 2 mm orifice at 50 bar passes 12.529 L/min of oil.
Limitations
- Turbulent flow through a short orifice; at low Reynolds numbers (cold oil, tiny holes) Cd falls.
- Cavitation at large pressure drops limits the flow.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size a damping or flow-control orifice
- Estimate leakage through a hole
- Check pressure drop across a jet or nozzle
Who it is for
- Hydraulic and process engineers
- Maintenance engineers
- Design engineers
What you get
- Flow
- Pressure drop
- Jet velocity
Interpreting the result
- Use a measured Cd for accurate flow control; small manufacturing changes alter Cd.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3024–3027, 352–368. Topic reference; no source tables or recommended settings are reproduced.
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