Fluid Dynamic Calculators

Weir Spillway

A weir is a barrier placed on the path of a stream through which it flows to a lower level. In this calculation, a weir with a water level h flowing over a threshold with a height P and width b is considered. The weir has 2 options of the crest shape (look at figure). As a result of calculations, the water flow rate Q is determined according to the following formula:

Q = m₀*b*h*(2gh)^0.5

m₀ - flow ratio coefficient, depending among other things, on the total width B of the dam according to the Bazin's formula.

Weir spillway calculation

Weir spillway calculation

INITIAL DATA

h - Water height above the weir (measured at distance of 4h from the weir);

P - Weir height;

B - Total dam width;

b - Spillway width.

RESULTS DATA

Q - Volumetric flow rate.

Metric Imperial

Fluid height (h)

Weir height (P)

Dam width (B)

Spillway width (b)

Rectangular spillway

Triangular spillway

Flow rate (Q)

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BASIC FORMULAS

Flow ratio coefficient:

m₀ = [0.405 + 0,0027 / h - 0.03*(B - b) / B] * [1 + 0.55*(b² / B²) * (h / (H+P))];

Flow rate for rectangular spillway:

Q = m₀*b*h*(2gh)^0,5;

Flow rate for triangular spillway:

Q = 1.4*h^2.5.

INITIAL DATA

h - Water height above the weir (measured at distance of 4h from the weir);

P - Weir height;

B - Total dam width;

b - Spillway width.

RESULTS DATA

Q - Volumetric flow rate.

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