Partial Pipe Flow Calculator Water

Manning's Equation:

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

Manning's Roughness Coefficient (n):

Cross-sectional Area (A):

m²

Hydraulic Radius (R):

Slope (S):

m/m

Flow Rate (Q):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Manning's Equation?

Manning's equation is an empirical formula that calculates the flow rate of water in open channels and partially filled pipes. It relates the flow rate to the channel's cross-sectional properties, slope, and roughness characteristics.

2. How Does the Calculator Work?

The calculator uses Manning's equation:

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

Where:

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

Explanation: The equation accounts for the energy loss due to boundary roughness and the geometry of the flow section.

3. Importance of Flow Rate Calculation

Details: Accurate flow rate calculation is crucial for designing drainage systems, irrigation channels, sewer systems, and various hydraulic engineering applications to ensure proper water conveyance and prevent flooding.

4. Using the Calculator

Tips: Enter Manning's roughness coefficient (typical values: 0.012-0.015 for concrete, 0.025-0.035 for natural streams), cross-sectional area, hydraulic radius, and slope. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What are typical Manning's n values?
A: Concrete pipes: 0.012-0.015, Cast iron: 0.013-0.017, Natural streams: 0.025-0.035, Vegetated channels: 0.03-0.05

Q2: How is hydraulic radius calculated?
A: Hydraulic radius R = A/P, where A is cross-sectional area and P is wetted perimeter (length of channel boundary in contact with water)

Q3: When is Manning's equation applicable?
A: For turbulent flow in open channels and partially filled pipes with uniform flow conditions

Q4: What are the limitations of Manning's equation?
A: Not suitable for pressurized flow, non-uniform flow, or laminar flow conditions. Accuracy depends on proper selection of n value.

Q5: How does slope affect flow rate?
A: Flow rate increases with increasing slope, as steeper slopes provide greater gravitational driving force for water movement.