Length Of Crest Given Discharge Over Weir Calculator

Formula Used:

\[ L_w = \frac{Q_w}{h_c \times \sqrt{2 \times g \times (H - h_c)}} \]

Length of Weir Crest (Lw):

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1. What is Length of Crest Given Discharge Over Weir?

The Length of Crest Given Discharge Over Weir calculation determines the required length of a broad-crested weir to handle a specific discharge flow rate. This is essential in hydraulic engineering for designing efficient water control structures.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ L_w = \frac{Q_w}{h_c \times \sqrt{2 \times g \times (H - h_c)}} \]

Where:

\( L_w \) — Length of Weir Crest (m)
\( Q_w \) — Discharge Over Broad Crested Weir (m³/s)
\( h_c \) — Critical Depth of Weir (m)
\( H \) — Total Head (m)
\( g \) — Gravitational acceleration (9.80665 m/s²)

Explanation: The formula calculates the required weir crest length based on the discharge rate and hydraulic characteristics of the flow over the weir.

3. Importance of Weir Crest Length Calculation

Details: Accurate weir crest length calculation is crucial for proper hydraulic structure design, ensuring adequate water flow control, flood management, and efficient irrigation systems.

4. Using the Calculator

Tips: Enter discharge in m³/s, critical depth in meters, and total head in meters. All values must be positive, and total head must be greater than critical depth for valid results.

5. Frequently Asked Questions (FAQ)

Q1: What is a broad-crested weir?
A: A broad-crested weir is a hydraulic structure with a horizontal crest that is sufficiently long in the direction of flow to support hydrostatic pressure distribution.

Q2: Why is critical depth important in weir calculations?
A: Critical depth represents the depth where flow energy is minimized for a given discharge, making it a key parameter in open channel flow calculations.

Q3: What factors affect weir discharge capacity?
A: Weir discharge capacity is influenced by crest length, head over the weir, weir shape, and approach conditions.

Q4: When is this formula applicable?
A: This formula applies to broad-crested weirs with streamlined flow conditions and negligible velocity of approach.

Q5: What are typical weir crest length values?
A: Weir crest lengths vary widely depending on application, from less than 1 meter for small irrigation channels to several meters for large flood control structures.