A stepped notch is a combination of rectangular notches as shown in figure. It is thus obvious that the discharge over such a notch will be the sum of the discharges over the different rectangular notches.
Consider a stepped notch as shown in figure. For the purpose of analysis, let us split up the notch into two rectangular notches 1 and 2. The total discharge over the notch will be the sum of the discharges over the two rectangular notches.
Let,
H1 = Height of the liquid above the sill of notch 1
b1 = Breadth of notch 1
H2, b2 = Corresponding values for notch 2, and
Cd = Coefficient of discharge for both the notches
From the geometry of the notch, we get,
and the discharge over the notch 2,
Now the total discharge over the notch,
Example:
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Example - Discharge over a Stepped Notch
Problem
Find the discharge in m3 /s over a stepped notch shown in figure.
The level of water coincides with the top of the notch. Take Cd for all sections 0.6. All dimensions are in mm.
Workings
Given,
Cd = 0.6
We know that the total discharge over the stepped notch,
Solution
Discharge over the notch = 0.779 m3 /s
Last Modified: 29 Jan 12 @ 04:27 Page Rendered: 2022-03-14 17:43:06