# Hydraulic Diameter

## Table of Contents

The hydraulic diameter is a characteristic length scale for fluid flow in non-circular pipes. It replaces the diameter of a circular pipe with an equivalent diameter based on the cross-sectional area and wetted perimeter of the non-circular pipe. It is defined as:

$$ D_h = \frac{4A_c}{P} $$

Where:

- \( \small D_h\ \) is the hydraulic diameter,
- \( \small A_c\ \) is the cross-sectional area of the flow, and
- \( \small P\ \) is the wetted perimeter of the cross-section.