Open Pipe Flow from Jet Trajectory
Estimate flow from a horizontal open pipe by measuring how far the jet lands (Purdue method).
A tape measure and a carpenter's square give ±10% flow on a flowing-full pipe — the classic well-driller's acceptance test.
Formula
Note: Assumes the pipe flows full and horizontal; partially-full pipes need the USBR coordinate correction.
Open Pipe Flow from Jet Trajectory is a free purdue method for pump engineers, plumbers and plant designers — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About Open Pipe Flow from Jet Trajectory
Estimate flow from a horizontal open pipe by measuring how far the jet lands (Purdue method). The calculation implements V = X·√(g/2Y); Q = A·V (projectile motion of the jet) (Purdue Univ. Ext. — measuring irrigation flows). A tape measure and a carpenter's square give ±10% flow on a flowing-full pipe — the classic well-driller's acceptance test.
How to use Open Pipe Flow from Jet Trajectory
- 1Enter Pipe inner diameter in mm.
- 2Enter Horizontal distance X in mm (Where the jet top crosses Y below pipe crown).
- 3Enter Vertical drop Y in mm (Standard: measure X at Y = 100 mm (4 in)).
- 4Read Jet velocity, Estimated flow instantly — no submit button needed.
- 5Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Open Pipe Flow from Jet Trajectory?
- ✓Implements the standard formula — V = X·√(g/2Y); Q = A·V (projectile motion of the jet)
- ✓Reference cited on-page: Purdue Univ. Ext. — measuring irrigation flows
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Live worked example: the substitution recomputes from your numbers
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the Open Pipe Flow from Jet Trajectory use?+
It computes V = X·√(g/2Y); Q = A·V (projectile motion of the jet), per Purdue Univ. Ext. — measuring irrigation flows. The formula is displayed under the result along with a worked example substituted with your own inputs.
What should I keep in mind when using this calculator?+
A tape measure and a carpenter's square give ±10% flow on a flowing-full pipe — the classic well-driller's acceptance test. Note: Assumes the pipe flows full and horizontal; partially-full pipes need the USBR coordinate correction.
Can I use this for pump selection?+
Use it to establish the duty (flow, head, NPSH, power) and then pick a pump whose curve passes through that point near best efficiency. The tool gives you the engineering numbers a supplier will ask for.
Is the Open Pipe Flow from Jet Trajectory free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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