Discharge Through Drowned Portion Calculator

Formula Used:

\[ Q2 = Cd \times (Lw \times h2) \times \sqrt{2 \times g \times (HUpstream - h2)} \]

Coefficient of Discharge (Cd):

Length of Weir Crest (Lw):

Head on Downstream of Weir (h2):

Acceleration due to Gravity (g):

m/s²

Head on Upstream of Weir (HUpstream):

Discharge through Drowned Portion (Q2):

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1. What is Discharge through Drowned Portion?

Discharge through Drowned Portion is a measure of the quantity of fluid flow over unit time, representing the quantity of water in between the downstream and the crest of the water in hydraulic structures.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ Q2 = Cd \times (Lw \times h2) \times \sqrt{2 \times g \times (HUpstream - h2)} \]

Where:

\( Q2 \) — Discharge through Drowned Portion (m³/s)
\( Cd \) — Coefficient of Discharge (ratio)
\( Lw \) — Length of Weir Crest (m)
\( h2 \) — Head on Downstream of Weir (m)
\( g \) — Acceleration due to Gravity (m/s²)
\( HUpstream \) — Head on Upstream of Weir (m)

Explanation: This formula calculates the discharge through the submerged portion of a weir, accounting for the difference in water levels upstream and downstream.

3. Importance of Discharge Calculation

Details: Accurate discharge calculation is crucial for hydraulic engineering, water resource management, flood control, and irrigation system design.

4. Using the Calculator

Tips: Enter all values in appropriate units. Ensure upstream head is greater than downstream head for valid calculation. Standard gravity value is 9.8 m/s².

5. Frequently Asked Questions (FAQ)

Q1: What is the Coefficient of Discharge?
A: The Coefficient of Discharge is the ratio of actual discharge to theoretical discharge, typically ranging from 0.6 to 0.9 for weirs.

Q2: When is a weir considered drowned?
A: A weir is considered drowned when the downstream water level rises above the weir crest, affecting the discharge characteristics.

Q3: What are typical values for weir crest length?
A: Weir crest length varies depending on application, typically ranging from 0.5 meters to several meters in large hydraulic structures.

Q4: Are there limitations to this formula?
A: This formula assumes ideal flow conditions and may need adjustment for very high velocities, sediment-laden water, or non-standard weir shapes.

Q5: How accurate is this calculation?
A: Accuracy depends on precise measurement of head values and appropriate selection of discharge coefficient for the specific weir configuration.