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Pipe Flow Calculator

Not intended for real-world applications.

Flow (L/s)

500

Diameter (mm)

450

Standard: 150, 225, 375, 450, 525, 600, 675, 750, 825, 900, 1050, 1200, 1500

Slope (%)

1.0

e.g. 1% => 0.01 slope

Manning's n

0.013

Common ~0.012–0.014

Normal Depth (y): -- m

Hydraulic Design Methodology

This tool calculates flow in partially filled pipes using the Manning equation. The process involves:

  1. Determining the cross-sectional area ($A$) and wetted perimeter ($P$) for a partial pipe depth.
  2. Using Manning's equation to compute flow rate ($Q$):
$$Q = \frac{1}{n} \; A \; R^{\frac{2}{3}} \; \sqrt{S}$$

Here:

  1. Iteratively finding the normal depth ($y$) for a given flow ($Q$). If $Q$ exceeds full-pipe capacity, the flow is surcharged.