V-Notch - The Hong Kong Polytechnic University Department...

The Hong Kong Polytechnic University
Department of Civil and Structural
Engineering
Fluid Mechanics
Laboratory Report
V-notch
Subject: Fluid Mechanics, CSE202
Lecturer: Dr. K.W. Chau
Team members
1. Dai Yifeng, 07000414x
2. Shao Qian, 07001042x
3. Hu Jiaqi, 07002407x
4. Gang Rui,07002339x
Introduction
In hydraulic engineering, weirs are commonly used to regulate flow in rivers and

other open channels. Where the relationship between the water level upstream of the
weir and the discharge is known, the discharge at any time may be found by noting
the upstream water level. Fig. 1 shows a V-shaped notch weir, in vertical plate. Such
notches usually have sharp edges so that the water springs clear of the plate as it
passes through the notch.
Objective
To determine the relationship between the discharge and the water level of a V-notch
weir.
Theory
The discharge of a V-notch weir is given by
Q = C
d
2
5
tan 2
15
8
H g θ
where Q = discharge (m
3
/s), C
d
= coefficient of discharge, θ = half-angle of the V-
notch, H=water level measured from the vertex of the V-notch.