No Slide Title
2/15/2000Channel Flow.ppt1Flow in ChannelsAST 324Carl E.
Anderson2/15/2000Channel Flow.ppt2Lesson Objectives1.Understand the
effects of waterway slope, shape, and roughness on the flow
velocity of water.2.Know how to determine the area and hydraulic
radius of the three major channel cross section shapes used in
waterways.3.Be able to use the Manning Equation and the Continuity
Equation to predict flow- velocity and flow-rate in a
waterway.2/15/2000Channel Flow.ppt3Think of water flowing down
achannel as a soapbox racer goingdown a racetrack. The only
forcecausing motion is gravity.
What factors would cause the racer(water) to move down the
track(channel) faster?2/15/2000Channel Flow.ppt4If you wanted to
find a tire that would get better traction, what characteristics
would you look for?2/15/2000Channel Flow.ppt5Open Channel
FlowCross-SectionAreaWetted PerimeterQ=AV2/15/2000Channel
Flow.ppt6MANNING EQUATIONV = velocity of flow in feet per second
(meters per second)C = Constant = 1.49 for English units (1.00 for
metric units) R = Hydraulic Radius in feet (meters)
2/15/2000Channel Flow.ppt7MANNING EQUATIONS = channel slope in
ft/ft or m/mn = Manning roughness coefficient
2/15/2000Channel Flow.ppt8MANNING EQUATIONMore roughness in the
channel (n) will slow down the waterSmaller R (flow depth) will
slow down the waterSmaller slope (S) will slow down the water
2/15/2000Channel Flow.ppt9MANNING ROUGHNESS COEFFICIENTSSmooth
concreten = 0.012Corrugated pipen = 0.025Smooth soiln =
0.03Cultivated soiln = 0.042/15/2000Channel Flow.ppt10CHANNEL
HYDRAULIC RADIUSR = A / P (the average flow depth)A = Area of the
flow cross-section in sq. ft (sq. m)P = Length of the line of
contact between the channel and the water on the area in feet
(meters)2/15/2000Channel Flow.ppt11Manning EquationSimple Example:
Rectangular cross-section
A = BDP = B + 2DFor B = 5 ft., D = 2 ft. A = 10 ft.2P = 9 ft.R =
10 / 9 = 1.11 ft.BD 2/15/2000Channel Flow.ppt12MANNING EQUATION
2/15/2000Channel Flow.ppt13Manning EquationSimple Example:
continued Rectangular cross-section
A = 10 ft.2P = 9 ft.R = 10 / 9 = 1.11 ftForS = 1% = 0.01 ft/ftn
= 0.04BD 2/15/2000Channel Flow.ppt14Manning EquationSimple Example:
continued Rectangular cross-section
Q = AV = (10)(3.99) = 39.9 CFS2/15/2000Channel
Flow.ppt15PRINCIPLES OF WATER FLOWA = BD + ZD2P = B + 2D(Z2+1)1/2R
= A/ PTrapezoidal Open ChannelBDZ12/15/2000Channel
Flow.ppt16PRINCIPLES OF WATER FLOWA = pD2 / 4P = pDR = A/ P = D/
4DRound pipe flowing full
2/15/2000Channel Flow.ppt17Example for Trapezoidal ChannelB = 10
feetD = 3 feetn = 0.04S = 0.1% = 0.001 ft/ ftZ = 2 feet horizontal
for each foot vertical on the side slopes.Estimate the Velocity and
Capacity2/15/2000Channel Flow.ppt18Example for a full pipeD = 12
inches = 1 foot p = 3.1416n = 0.015S = 0.1% = 0.001 ft/ ftEstimate
the flow velocity and the capacity of this pipe.2/15/2000Channel
Flow.ppt19Parabolic Channel Cross-sectionPTAD
