SI (m, m/s, m³/s)

Weirs & Orifices

Quick discharge checks for sharp‑crested weirs (rectangular, V‑notch, Cipolletti) and sharp‑edged orifices (free or submerged). Export clean summaries or rating tables.

Inputs — Weir

Weir type

Crest width b (m)

Head over crest H (m)

Discharge coefficient C_d

Typical: Rect/Cip ≈ 0.62 · Triangular ≈ 0.62. Override as needed.

Approach velocity V_a (m/s, optional)

Corrects head by + V_a²/(2g).

Rating table: H_max (m)

Rows

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Free‑flow assumption. If tailwater rises near crest elevation, weir becomes drowned—coefficients and equations change. For sharp‑crested weirs, submergence often begins around tailwater ≥ 0.6·H above crest (check your standard).

Inputs — Orifice

Orifice type

Diameter D (m)

Discharge coefficient C_d

Typical sharp‑edged free orifice C_d ≈ 0.61–0.63.

Head above orifice centerline H (m)

Gravity g (m/s²)

Tank area A_t (m², optional)

For drain‑time: set A_t & initial/final heads.

Initial head h₀ (m, optional)

Final head h₁ (m, optional)

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Formulas (step‑by‑step)

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References & notes: Classical sharp‑crested weir/orifice equations (Torricelli, Francis/Kindsvater‑Shen forms). Default C_d values are indicative only—always calibrate to local standards or lab data when available.