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Francis Formula Rectangular Weir Calculator

Francis equation is standard for sharp-crested rectangular measuring weirs.

Calculated Result
1.3886 m³/s

Discharge

Flow Rate in L/s

1388.6 L/s

Flow Rate in cfs

49.04 cfs

Effective Length

2.5 m

Calculation Breakdown

  1. Francis Suppressed FormulaQ = 1.84 · (L - 0.1·n·H) · H^(3/2) => 1.3886 m³/s

Weir Discharge

Interactive visualization based on your current inputs

Value
0.00.30.71.01.4Discharge (m³/s)Head (m)MetricValue

What Is the Francis Formula Rectangular Weir Calculator?

Francis equation is standard for sharp-crested rectangular measuring weirs.

How Does the Francis Formula Rectangular Weir Calculator Work?

The calculation evaluates user-provided measurements using recognized domain equations, converts between measurement units, and adjusts for real-world efficiency factors.

Francis Formula Rectangular Weir Calculator Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

Q = 1.84 (L - 0.1 n H) H^{3/2}

Francis formula for rectangular weirs.

How to Use the Francis Formula Rectangular Weir Calculator

  1. Enter your primary measurements in the input fields above.
  2. Select your preferred units (e.g. metric or imperial) if applicable.
  3. Review or adjust operational assumptions such as field efficiency.
  4. Click Calculate to instantly generate the full results breakdown and visual chart.
  5. Use the Reset button at any time to clear the form and test a new scenario.

Step-by-Step Example Calculation

Weir Flume

Input Values:

crestLengthM:2.5
headOverCrestM:0.45

Understanding Your Result

Your calculated result represents the realistic operational capacity or baseline output under the specified conditions. Comparing theoretical and effective outputs reveals the direct impact of turns, overlap, and practical downtime.

Factors That Affect the Result

Field terrain, operator experience, equipment maintenance, overlap margin, and weather conditions can significantly influence real-world output.

When Should You Use This Calculator?

Use this calculator whenever you need quick, verified estimates for job planning, budgeting, equipment sizing, or project timelines.

Assumptions & Limitations

  • For suppressed weirs, end contractions n = 0.

Frequently Asked Questions

Calculation Accuracy & Reference Note

This calculator implements verified, deterministic mathematical equations based on published standards. Results should be treated as professional engineering estimates; always verify critical operations with local equipment manuals and site inspections.

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