7910

• UCREFRP Catalog Number: 7910
• Author: Bovee, K. D. and R. T. Milhous.
• Title: Hydraulic Simulation In Instream Flow Studies
• USFW Year: 1978.
• USFW - Doc Type: Theory And Techniques, Instream Flow Information Paper No. 5.
• Copyright Material: NO

on the state of flow is represented by the ratio
between inertial and gravity forces. This ratio
is given by the Froude number, defined as
F = V
497
where,
V = mean velocity
g. = the acceleration of gravity
0 = the. hydraulic depth

If F is less than unity, gravity forces predominate, so the flow
has low velocity and is described as tranquil or streaming. If F is
greater than unity, the effects of inertia are more pronounced, so the
-flow has high velocity and is described as shooting, rapid, or torren-
tial. When F is equal to unity, flow is defined as critical.
Most instream flow studies are concerned primarily with the sub-
critical state of flow, although hydraulic simulations for certain
recreational activities may deal with supercritical states of flow.
COMMONLY USED. EQUATIONS FOR THE ANALYSIS OF OPEN CHANNEL FLOWS
The water surface elevation in a stream defines the cross-sectional
area of flow. If the velocity is also known, the discharge can be
calculated using the equation of continuity:
Q AV
where,
(1)
Q = discharge in cubic feet per second (cubic meters per second).
A = area of the cross section of flow in square feet (square
meters).
V = average velocity of flow through the cross section in feet per
second (meters per second).
Over the years, considerable empirical and theoretical
been conducted on the relationship between channel features
velocity in the channel. The first velocity equations were
relationships based on the observed behavior of flow in open
Around 1770, a French engineer, Antoine Chezy, developed the
velocity equation, which is now known as the Chezy equation:
V = C (RS)h
where,
research has
and the
empirical
channels.
first
(2)
P