Discharge Over Broad-Crested Weir With Velocity of Approach Calculator

Discharge Over Broad-Crested Weir Formula:

\[ Q = 1.705 \times C_d \times L_w \times ((H + h_a)^{3/2} - h_a^{3/2}) \]

Coefficient of Discharge (Cd):

Length of Weir (Lw):

Head of Liquid (H):

Head Due to Velocity of Approach (ha):

Discharge Weir (Q):

m³/s

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1. What is Discharge Over Broad-Crested Weir?

Discharge over a broad-crested weir refers to the rate of flow of liquid over a weir with a broad crest. This type of weir is commonly used in hydraulic engineering for flow measurement and control in open channels.

2. How Does the Calculator Work?

The calculator uses the discharge formula:

\[ Q = 1.705 \times C_d \times L_w \times ((H + h_a)^{3/2} - h_a^{3/2}) \]

Where:

\( Q \) — Discharge Weir (m³/s)
\( C_d \) — Coefficient of Discharge
\( L_w \) — Length of Weir (m)
\( H \) — Head of Liquid (m)
\( h_a \) — Head Due to Velocity of Approach (m)

Explanation: The formula accounts for the combined effect of static head and velocity head on the discharge rate over a broad-crested weir.

3. Importance of Discharge Calculation

Details: Accurate discharge calculation is crucial for designing hydraulic structures, managing water resources, flood control, and irrigation system design.

4. Using the Calculator

Tips: Enter the coefficient of discharge, length of weir in meters, head of liquid in meters, and head due to velocity of approach in meters. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a broad-crested weir?
A: A broad-crested weir is a type of weir with a horizontal crest that is sufficiently long in the direction of flow to allow the streamlines to become parallel and the pressure distribution to become hydrostatic.

Q2: What is the typical range for coefficient of discharge?
A: The coefficient of discharge for broad-crested weirs typically ranges from 0.8 to 1.0, depending on the weir geometry and flow conditions.

Q3: Why is velocity of approach important?
A: Velocity of approach affects the discharge rate because it contributes additional energy to the flow, which must be accounted for in accurate discharge calculations.

Q4: When should this formula be used?
A: This formula is specifically designed for broad-crested weirs where the flow is subcritical and the weir crest is sufficiently broad to establish parallel streamlines.

Q5: What are the limitations of this formula?
A: The formula assumes ideal flow conditions and may need adjustments for very high velocities, submerged weir conditions, or non-standard weir geometries.