California State University, Sacramento CE 135 HYDRAULICS LAB
Dept. of Civil Engineering Instructor MEH
SLUICE GATE EXPERIMENT: PREPARATION
OBJECTIVES:
Study the application of one-dimensional method of flow analysis involving continuity,
energy and momentum. Specifically, to
Examine the characteristics of subcritical and supercritical open channel flows
Determine the specific energies at various flows
Study some patterns of forces in open channel flow
APPARATUS:
Rectangular, glass-walled horizontal flume (0.5 m wide) with
Sluice gates at the upstream and downstream sections
Point gages and manometer assemblies for water depth measurements
Automatic temperature sensor
PROCEDURE:
SET UP EXPERIMENT
Open the surge tank valve. Open both the head and the tail (sluice) gates of the half-meter
open channel unit.
Determine the longitudinal profile along the centerline of the floor of the flume to get point
gage zeros. (If not clear from a prior experiment.)
Remove air from all manometric tubing. Locate the pressure taps in the gate and on the
floor of the flume and match them to the manometer columns.
Close the drain valve; start the large pump; and open the intake valve.
MEASURE SLUICE GATE VARIABLES
Establish a steady flow in the flume of about 400-700 gpm
Lower the upstream sluice gate until it impinges on the flow
Keep track of the height of the gate
As the gate impinges on the flow, the water will back up in the flume on the upstream side of the gate. The flow out of the gate opening will be supercritical; the flow behind (upstream of) the gate will be subcritical. Slowly lower the gate until the flume is nearly full. Wait for the flow to reach the steady state for each of your selected gate openings.
Measure and record the flow depths of the water surfaces with the point gages both upstream and downstream of the gate. For the supercritical section, you are trying to measure at the vena contracta.
Also note the height of the gate above the wall of the flume.
Change the gate level and repeat the process until you have at least 6 measurements with upstream flow depths spanning the range available in the flume.
Keep the same flow rate for all runs
MEASURE PRESSURE FORCES & SURFACE PROFILE
Establish a flow of about 600 gpm
Close the sluice gate enough for the upstream water level to be above taps A-F
[Note: remove air from the manometer tubes A-F, which could not be done before
the water level was raised.]
For pressure data record the manometer readings for positions A-F and 1
For surface profile data, record the point gage readings for positions 1-14 or so
Shut off the flow
Turn off the pump; close the intake valve; open the drain valve on the head tank
SLUICE GATE EXPERIMENT: RESULTS
Format: Memo Report [Include your team logo somewhere in the report.]
SUMMARY
Present the key results and describe any major deviations from the printed procedures and why you did them.
You do not need to turn in the lab procedure sheet with your report, but it is ok to add it as an attachment. You may use a computer sketch of the apparatus in the body of the report, but the attachment must be hand drawn.
RESULTS:
Using the continuity equation between the upstream and downstream flows (latter at the vena contracta) compute the velocities on both sides of the gate for each pair of flow depths. Compare the specific energy plot for the observed depths and computed velocities with the theoretical plot at the same flow rate, Q.
Compare the measured contraction coefficient with that given in a published reference.
Using your depth measurements upstream and at the vena contracta, along with the continuity and energy equations, compute the flow rates for each run and compare it with the rate given by the flow meter.
Compute the force on the gate using (a) the measured pressures, (b) hydrostatic assumption, and (c) the momentum equation. Compare the three values in terms of accuracy and convenience.
Plot the pressure distribution on the upstream side of the sluice gate from the measured pressures (taps A-F) plus pressures at the water surface & bottom of the gate ).
Plot the distributions for the hydrostatic assumption on the same chart and compare the those patterns.
Plot the water surface profiles from the point gage and piezometer readings for the single Q you used. Comment on any differences you observe between the point gage data and the piezometer data.
ATTACHMENTS:
Attach your sketch of the experimental set-up and copies of your input data and calculated results.
Write out the key equations used in calculating the results, with one sample calculation for each equation.
REFERENCE:
Roberson, John, & C. Crowe, ENGINEERING FLUID MECHANICS, 6th Ed., Houghton Mifflin Co., 1990, Ch. 6 & 15
CE 135 HYDRAULICS LAB MEH
OPEN CHANNEL FLOW WITH SLUICE GATE
INPUT (OBSERVED) DATA
Lab. Team Name: Team Members:
Water Temperature ________° F Rectangular Flume Width ________ ft
Point Gage at Bottom of Channel: Before Gate ________ At Vena Contracta ________ ft
WATER LEVELS BEFORE & AFTER SLUICE GATE
Flow Rate ____________ gpm Flow Rate ____________ gpm
Run Gate Point Gage Readings Gate Point Gage Readings
No. Opening Before Gate Vena Contracta Opening Before Gate Vena Contracta
(in) (ft) (ft) (in) (ft) (ft)
1
2
3
4
5
6
7
FORCES ON SLUICE GATE AT ONE FLOW RATE
Flow rate, Q ________ GPM Gate Opening __________ inch
Manometer At Channel Bottom ________ inch
Tap Manometer Heads
Tap Elevation No Flow With Flow
---------------- (inches) --------------
Surface Note: This table assumes tap A is at the top.
F If tap A is at the top, you can change the
E listing of the letters.
D
C
B
A
FLOW PROFILE WITH SLUICE GATE
INPUT (OBSERVED) DATA
CONSTANT DATA
Profile Run Flow Rate: ________ gpm Rectangular Flume Width: ________ ft
Sluice Gate Level: ________ ft
VARIABLE DATA
Flow Profile Along Rectangular Channel:
Zeroing Datums Reading With Flow
Tap Distance to Point Gage (ft) Manometer Point Gage Manometer
No. Tap (ft) Bottom Slight Flow Head (in) at Surface (ft) Heads (in)
1
2
3
4
5
6
7
8
9
10
11
12
13
14