Cipolletti (often misspelled “Cappoletti”) weir identification: which description best characterizes this standard weir type used to compensate end contractions?

Introduction / Context:
The Cipolletti weir is a standardized trapezoidal weir shape intended to offset end-contraction effects so that its discharge formula resembles that of a fully contracted rectangular weir. Many exam banks misspell it as “Cappoletti.”

Given Data / Assumptions:

• Sharp-crested weir operated free (ventilated nappe).
• Standard approach and measurement practices.
• Fixed trapezoidal side slopes chosen to compensate contractions.

Concept / Approach:

Cipolletti weirs are trapezoidal: the central portion acts like a rectangular section while the sloping sides provide additional area proportional to head, approximating the discharge of an equivalent contracted rectangular weir. Pedagogically, this is described as a combination of rectangular and triangular (V-notch-like) effects, hence “combination weir.”

Step-by-Step Solution:

Verification / Alternative check:

Handbooks present Cipolletti as a trapezoidal weir; the “combination” phrasing is widely used to distinguish it from pure rectangular or pure triangular notches.

Why Other Options Are Wrong:

(a) Arbitrary proportion; (b) is a pure V-notch; (c) states “1H:2V” in some banks, which is not the classical Cipolletti slope; (e) refers to a different weir class.

Common Pitfalls:

Memorizing an incorrect side slope or confusing Cipolletti with sharp 90° V-notches.

Final Answer:

a combination weir whose geometry blends rectangular and triangular features