CIVE 612 OPEN-CHANNEL FLOW
Spring 2009
ASSIGNMENT 2
Due 19 February 2009
Read Sections 2.5 – 2.7 and Chapters 3, 4, and 5 in Chaudhry (2008).
Work problems 5.1 and 5.5 (assume a wide rectangular channel in this problem) in Chaudhry (2008) and
the problems given below. You are responsible to work and understand all of these problems, but turn in
only problem 5.1 and problem 3 below for grading.
1. The flow in a river at an upstream gauging station is measured to abe 1600 m3/s. At a distance 5.2
km downstream, another gauging station indicates that the flow rate is 1050 m3/s at the same instant
of time. The river channel is relatively uniform along the reach between the gauging stations with an
average top width of 300 m. At what rate is the water surface elevation changing (in m/hr) if the
average lateral flow is (a) negligible along the reach, and (b) equal to about -.020 m2/s. Provide
sketches and explain why your calculated result makes physical sense and discuss the limitations of
your analysis.
2. Using the equation for conservation of linear momentum (as derived in class) but neglecting the term
for lateral flow momentum, develop the following equation that is often used for modeling steady
gradually-varied flow in a channel with uniform cross-section geometry:
2
0
1F
r
SS
dx
dh f
−
−
=
If the geometry is not uniform, show that the equation can be expressed as
w
f
CT xd
dA
CSS
dx
dh
−
∂
∂
•+−
=1
)(
0
Γ
Γ where gA
u
C2
=
3. Derive an expression for
x
A
∂
∂, like Eq. (13) derived in class, for a channel with trapezoidal geometry
with asymmetric side slopes.
