Gravity Flow Through Pipe Chart

Manning's Formula:

\[ Q = \frac{1}{n} \times A \times R^{\frac{2}{3}} \times S^{\frac{1}{2}} \]

Manning's Roughness (n):

Cross-sectional Area (A):

m²

Hydraulic Radius (R):

Slope (S):

m/m

Flow Rate (Q): m³/s

1. What is Gravity Flow Through Pipe?

Definition: This calculator estimates the flow rate in a pipe under gravity conditions using Manning's equation.

Purpose: It helps engineers and designers calculate water flow in open channels or partially full pipes.

2. How Does the Calculator Work?

The calculator uses Manning's formula:

\[ Q = \frac{1}{n} \times A \times R^{\frac{2}{3}} \times S^{\frac{1}{2}} \]

Where:

\( Q \) — Flow rate (m³/s)
\( n \) — Manning's roughness coefficient
\( A \) — Cross-sectional area of flow (m²)
\( R \) — Hydraulic radius (m)
\( S \) — Slope of the energy grade line (m/m)

Explanation: The formula calculates flow rate based on pipe characteristics and slope.

3. Importance of Flow Rate Calculation

Details: Accurate flow rate estimation ensures proper pipe sizing, adequate drainage, and efficient system design.

4. Using the Calculator

Tips:

Typical Manning's n values: 0.013 for concrete, 0.015 for PVC, 0.024 for corrugated metal
Hydraulic radius (R) = Area / Wetted perimeter
Slope is the vertical drop divided by horizontal distance

5. Frequently Asked Questions (FAQ)

Q1: What's a typical Manning's n for concrete pipes?
A: About 0.013 for smooth concrete, up to 0.015 for rough finishes.

Q2: How do I calculate hydraulic radius?
A: For full circular pipes, R = D/4 where D is diameter. For partial flow, R = A/P where P is wetted perimeter.

Q3: What units should I use for slope?
A: Slope is dimensionless (m/m or ft/ft) - the vertical drop divided by horizontal run.

Q4: Can this be used for pressurized pipes?
A: No, Manning's equation is for open channel or gravity flow conditions.

Q5: What's the maximum accuracy I can expect?
A: Manning's equation typically has ±10-20% accuracy due to variability in roughness coefficients.