Concrete Drain Pipe Gravity Flow
Non-full and full gravity flow in a concrete drainage pipe. Area ω, wetted perimeter χ, hydraulic radius R, Chezy coefficient C = R^(1/6)/n, velocity and discharge.
| Bore D (mm) | Fill H/D | Slope i (‰) | Rough n | Depth H (mm) | θ (°) | Surf. width (m) | Area ω (m²) | Wetted χ (m) | Radius R (m) | Chezy C | v (m/s) | Q (m³/s) | Qh (m³/h) |
|---|
Max velocity
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m/s
Total flow ΣQ
—
m³/s
Non-full: H = D·H/D, G = (D/2 − H)/(D/2), θ = acos(G)·180·2/π. Surface width = sin(θ/2)·D/1000. Area ω = (D/2000)²·π/360·θ − (D/2000 − H/1000)·surface/2. Wetted χ = π·D/1000·θ/360, R = ω/χ, C = R^(1/6)/n, v = C·√(R·i/1000), Q = ω·v (n = 0.014, i in ‰). Full: ω = π·D²/4·10⁻⁶, χ = π·D/1000, otherwise identical.