Hydraulic diameter (Dₕ)
Definition
An effective diameter for non-circular channels, Dₕ = 4A/P (for a rectangle, 2wh/(w+h)). It lets circular-pipe formulas apply to other shapes.
Explanation
The hydraulic diameter Dₕ = 4·Area/Perimeter (for a rectangle, 2wh/(w+h)) reduces a non-circular cross-section to a single equivalent length scale.
It lets you apply circular-pipe formulas — Reynolds number, resistance, pressure drop — to rectangular microchannels.
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Related lessons
Further reading
- Flow, pressure & resistance cheat sheet — SemitreeVerify the current edition.