🌊 Submerged Orifice & Weir Flow Calculator
Calculate open-channel flow over rectangular, V-notch, and trapezoidal weirs, or through submerged sluice gates. Outputs Q, Cd, and specific energy.
🏗️ Weir / Gate Schematic
📝 Configuration
Key Equations:
Rectangular: Q = Cd(2/3)b√(2g)H1.5
V-notch: Q = Cd(8/15)√(2g)tan(θ/2)H2.5
Trapezoidal: Q = Cd(2/3)√(2g)H1.5(b+H tan(θ/2))
Sluice: Q = Cd b a √(2g(H−htail))
Rehbock: Cd = 0.602 + 0.083 H/P
Rectangular: Q = Cd(2/3)b√(2g)H1.5
V-notch: Q = Cd(8/15)√(2g)tan(θ/2)H2.5
Trapezoidal: Q = Cd(2/3)√(2g)H1.5(b+H tan(θ/2))
Sluice: Q = Cd b a √(2g(H−htail))
Rehbock: Cd = 0.602 + 0.083 H/P
📊 Results
Configure inputs and click Calculate to view results.
📘 Calculation Methodology
Mathematical Model
Weir flow equations derive from integrating velocity profiles over the notch/crest. Discharge coefficients account for approach velocity, nappe contraction, and viscous effects.
Worked Example
A rectangular weir with b = 1 m, P = 0.5 m, and H = 0.3 m: Rehbock gives Cd ≈ 0.652, yielding Q ≈ 0.148 m³/s.
Assumptions
- Free discharge (no submergence correction for weirs).
- Sluice gate uses simple energy-based orifice equation.
- Rehbock Cd valid for H/P < 3.
- V-notch assumes fully developed nappe.