Length of Weir for Broad-Crested Weir with Velocity of Approach Calculator

Formula Used:

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

Discharge Weir (Q):

m³/s

Coefficient of Discharge (Cd):

Arc Length of Circle (la):

Head Due to Velocity of Approach (ha):

Length of Weir (Lw):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the Length of Weir Formula?

The Length of Weir formula calculates the required length of a broad-crested weir considering the velocity of approach. It provides an accurate measurement for hydraulic engineering applications where weir discharge and approach velocity are significant factors.

2. How Does the Calculator Work?

The calculator uses the formula:

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

Where:

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

Explanation: The formula accounts for the discharge rate, discharge coefficient, and the combined effect of arc length and velocity head to determine the required weir length.

3. Importance of Weir Length Calculation

Details: Accurate weir length calculation is crucial for proper hydraulic structure design, ensuring efficient water flow control, flood management, and accurate flow measurement in open channels.

4. Using the Calculator

Tips: Enter discharge in m³/s, coefficient of discharge, arc length 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 hydraulic structure with a wide crest that allows water to flow over it, commonly used for flow measurement and control in open channels.

Q2: Why is velocity of approach important?
A: Velocity of approach affects the discharge characteristics over the weir and must be considered for accurate flow calculations.

Q3: What are typical values for coefficient of discharge?
A: The coefficient of discharge typically ranges from 0.6 to 0.9 for broad-crested weirs, depending on the weir geometry and flow conditions.

Q4: When should this formula be used?
A: This formula is specifically designed for broad-crested weirs where the velocity of approach is significant and cannot be neglected.

Q5: Are there limitations to this equation?
A: The formula assumes ideal flow conditions and may require adjustments for real-world applications with complex flow patterns or non-standard weir geometries.