1. What is Francis's Formula for Rectangular Weir?

Francis's formula is used to calculate the discharge over a rectangular weir, considering the initial and final heights of liquid. It provides an accurate estimation of flow rate for rectangular weirs in various hydraulic applications.

2. How Does the Calculator Work?

The calculator uses Francis's formula:

Where:

• \( Q \) — Discharge (m³/s)
• \( L \) — Length of weir (m)
• \( H_i \) — Initial height of liquid (m)
• \( H_f \) — Final height of liquid (m)

Explanation: The formula accounts for the difference in liquid head above the weir crest, providing an accurate discharge calculation for rectangular weirs.

3. Importance of Discharge Calculation

Details: Accurate discharge calculation is crucial for hydraulic engineering, water resource management, irrigation system design, and flood control measures.

4. Using the Calculator

Tips: Enter weir length in meters, initial and final liquid heights in meters. All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a rectangular weir?
A: A rectangular weir is a flow measurement structure with a rectangular notch through which water flows, used to measure discharge in open channels.

Q2: When is Francis's formula applicable?
A: Francis's formula is applicable for rectangular weirs with suppressed end contractions and under free flow conditions.

Q3: What are the limitations of this formula?
A: The formula assumes ideal flow conditions and may require corrections for approach velocity, weir crest shape, and other real-world factors.

Q4: How accurate is Francis's formula?
A: Francis's formula provides good accuracy for most practical applications but may require calibration for specific weir configurations.

Q5: Can this formula be used for other weir shapes?
A: No, Francis's formula is specifically designed for rectangular weirs. Other formulas exist for triangular, trapezoidal, and other weir shapes.