How is wetted perimeter calculated for common channel shapes?

Rectangular: P = b + 2y; Trapezoidal: P = b + 2y√(1+z²); Triangular: P = 2y√(1+z²); Circular (partially full): P = D × θ/2 where θ is the central angle in radians = 2×arccos(1 - 2y/D). Here b=bottom width, y=flow depth, z=side slope (H:V), D=pipe diameter.

What is the most hydraulically efficient channel shape?

The most efficient cross-section maximizes flow for given area (minimizes P for given A). For a rectangular channel: b = 2y (width = twice depth). For trapezoidal: z = 1/√3 (60° sides) with b = 2y/√3. The semicircle is the absolute most efficient shape, but practical channels use trapezoidal sections with z = 1.0–1.5 for constructibility.

Wetted Perimeter Calculator

Calculate the wetted perimeter and hydraulic radius for common open channel cross-sections including rectangular, trapezoidal, triangular, and circular shapes.

2D stress state at a point. All stresses in MPa.

σx — Normal Stress X (MPa)

σy — Normal Stress Y (MPa)

τxy — Shear Stress (MPa)

⚙ Mechanical Note: Results are based on standard textbook formulas and ISO/AASHTO references. Always verify critical designs with applicable codes (ISO 898, AASHTO 1993, AISC, Eurocode 3) and a qualified engineer.

How to Use

Enter the values for the patient or scenario you are assessing. Calculate the wetted perimeter and hydraulic radius for common open channel cross-sections including rectangular, trapezoidal, triangular, and circular shapes. Use the wetted perimeter result to inform your clinical assessment.

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Frequently Asked Questions

How is wetted perimeter calculated for common channel shapes?

What is the most hydraulically efficient channel shape?