Broad Crested Weir Calculator

Enter value and click on calculate. Result will be displayed.

Formula:
q = Cd × b × h2 × (2g (h1 - h2)) 1/2

Width of the Weir :
m
Head 1 on the Weir (h1) :
m
Head 2 on the Weir (h2) :
m
Discharge Constant (Cd) :
Result:
Water Flow Rate (q) :

What is a Broad Crested Weir Calculator?

A Broad Crested Weir Calculator is used to determine the flow rate over a broad crested weir, a type of hydraulic structure that measures the flow of water. Unlike sharp-crested weirs (where the water flows over a thin crest), broad crested weirs have a wider crest, which affects how the water flows and the calculations for discharge. The formula for flow rate Q over a broad crested weir is:

Q=C⋅L⋅H3/2

Where:

  • Q = Flow rate (discharge) in cubic meters per second (m³/s)
  • C = Discharge coefficient (depends on the weir’s design and the flow conditions)
  • L = Length of the crest (in meters)
  • H = Head (height of the water above the weir crest) in meters

Why use a Broad Crested Weir Calculator?

  • Hydraulic Engineering: It helps in the design and analysis of weirs used in dams, rivers, and water treatment plants.
  • Flood Management: Broad crested weirs are used in flood control systems to manage water flow, and the calculator helps in determining the appropriate discharge for specific conditions.
  • Efficient Design: By using the calculator, engineers can optimize the design of weirs to ensure proper water flow, prevent overflow, and maintain safe water levels.

How does a Broad Crested Weir Calculator work?

  1. Input: You provide the length of the weir crest L, the head H, and the discharge coefficient C, which is often provided based on standard design values or empirical data.
  2. Process: The calculator uses the formula Q=C⋅L⋅H3/2 to calculate the flow rate.
  3. Output: The calculator gives the flow rate Q in cubic meters per second (m³/s), which tells you the volume of water passing over the weir in a given time.

For example, if L=2 m, H=0.5 m, and C=3.0, the flow rate would be:

Q=3.0⋅2⋅(0.5)3/2=3.0⋅2⋅0.3536=2.12 m3/s

When should you use a Broad Crested Weir Calculator?

  • Hydraulic Design and Analysis: When designing water management structures like weirs, dams, and spillways that need to measure or regulate flow.
  • Flood Control: To calculate and manage water flow during heavy rainfall or flooding events, ensuring that excess water is safely diverted.
  • Environmental Engineering: In projects related to water resources and river management, where precise flow measurements are needed.
  • Water Treatment Plants: For calculating flow rates in water treatment systems, ensuring proper water level management and preventing overflow.