Rehbocks Formula for Discharge over Rectangular Weir Calculator

Rehbocks Formula:

\[ Q = \frac{2}{3} \left(0.605 + 0.08 \frac{S_w}{h_{Crest}} + \frac{0.001}{S_w}\right) \sqrt{2g} \cdot L_w \cdot S_w^{3/2} \]

Height of Water above Crest of Weir (S_w):

Height of Crest (h_Crest):

Acceleration due to Gravity (g):

m/s²

Length of Weir Crest (L_w):

Discharge (Q):

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1. What is Rehbocks Formula for Discharge over Rectangular Weir?

Rehbocks Formula is an empirical equation used to calculate the discharge over a rectangular weir with suppressed ends. It provides a more accurate estimation of flow rate by accounting for various hydraulic parameters and weir geometry.

2. How Does the Calculator Work?

The calculator uses Rehbocks Formula:

\[ Q = \frac{2}{3} \left(0.605 + 0.08 \frac{S_w}{h_{Crest}} + \frac{0.001}{S_w}\right) \sqrt{2g} \cdot L_w \cdot S_w^{3/2} \]

Where:

\( S_w \) — Height of Water above Crest of Weir (m)
\( h_{Crest} \) — Height of Crest (m)
\( g \) — Acceleration due to Gravity (m/s²)
\( L_w \) — Length of Weir Crest (m)

Explanation: The formula accounts for the relationship between water height, crest dimensions, gravitational acceleration, and weir length to determine the discharge rate.

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 all values in appropriate units (meters for lengths, m/s² for gravity). Ensure all values are positive and within reasonable physical limits for accurate results.

5. Frequently Asked Questions (FAQ)

Q1: What is a suppressed end weir?
A: A suppressed end weir is one where the weir extends across the full width of the channel, preventing end contractions and side flow effects.

Q2: When should Rehbocks Formula be used?
A: This formula is particularly useful for rectangular weirs with accurate head measurements and when precise discharge calculations are required.

Q3: What are the limitations of Rehbocks Formula?
A: The formula assumes ideal flow conditions and may require adjustments for very high or very low flow rates, or for non-standard weir configurations.

Q4: How does weir height affect discharge?
A: Higher weir crests generally result in lower discharge rates for the same upstream water level, as they create more resistance to flow.

Q5: Can this formula be used for other weir shapes?
A: No, Rehbocks Formula is specifically designed for rectangular weirs with suppressed ends. Other weir shapes require different discharge formulas.