RESULTS (CONT.)

Figure 7: After Software Analysis

PTV Results

• Results used to find the

velocity distribution

over the inlet to the

weir structure.

• Figure 6 & 7 are

examples of PTV

results for pair of video

frames of a low flow

rate test.

• The video of each flow

tested contains of

hundreds of frames.

• Vector fields found for

all frames with the

same flow rate are

merged together to

obtain high density

vector fields of the

visible surface flow.

Case Study: Velocity and Discharge Measurements in a

Combined Weir and Sluice Gate Structure Reinaldo E. Alcalde, Mohamed Jalloh & Dr. David Admiraal

Department of Civil Engineering, University of Nebraska-Lincoln

Discussion

• Lab testing and analysis has been completed for free flow over

inlet weir.

• Flow over weir has linear behavior for flows > 0.07 m3/s.

• PTV results are clear and suitable for further analysis and

comparison to develop approach velocity coefficient.

• More data needed to develop a rating curve for SFWMD.

Future Work

• Characterize flow behavior at submerged weir flow

• Determine head loss coefficient for the sluice gate

• Determine discharge coefficient of weir with abutments with

use of sluice gate

• Determine approach velocity coefficient

• Dr. David Admiraal, UNL Faculty Mentor

• Mohamed Jalloh, UNL Graduate Student

• Sarah McClure, UNL Undergraduate Research Assistant

• Dr. Juan A Gonzalez-Castro, SFWMD

• UNL McNair Scholars Program

Develop alternative rating approach for accurately measuring

flow rates through the G304 and G306 structures at all possible

flow combinations, which includes:

• Free flow over the inlet weir

• Submerged weir flow

• Gate-controlled open channel flow in the culvert

• Gate-controlled pressurized flow in the culvert

With these results, SFWMD will be able to effectively regulate

the flow of water into and out of their man-made wetland.

G304 and G306 Structures

• Used by South Florida Water Management District

(SFWMD) (Figure 1)

• Regulate flow into and out of large man-made wetland

• Consist of weir, sluice gate, and corrugated culvert (Figure 2)

Complex Structural Design

• Flow in structure is perpendicular to supply and discharge

canals.

• Environmental limitations require use of sluice gates to

control flow.

• Renders use of traditional weir, sluice gate, and culvert

equations unsuitable for accurate field estimations of

discharge.

Previous Work

• Alternative rating approach for gate-controlled, full culvert

flows (Gonzalez, 2005)

Challenges in the Field

• Limited control of flow conditions

• Accuracy of measuring flows

• Limited capability to measure velocity distributions upstream

of the weir

BACKGROUND

PURPOSE CONCLUSIONS

ACKNOWLEDGEMENTS

Figure 2: Head box/culvert combination (after Admiraal, 2007)

Figure 1: South Florida Culvert Structure (after Gonzalez, 2007)

Field Measurements

• Used to calibrate model (Figure 3 & 4)

• Obtain a better understanding of actual flow conditions

1:6.26 Scale Physical Model

• Used to simulate wide range of flow scenarios

• To gauge discharges, water levels, and flow velocities, model includes:

A pump to regulate flow

A point gage to determine height of water above the weir

A weight tank for measuring mass flow rate

An HD camcorder to record particle flow over the weir

Particle Tracking Velocimetry (PTV))

• Used to determine magnitudes and directions of flow velocities

• Applied to both field and lab image recordings

• Software: FlowFieldCaptorMD

MATERIALS AND METHODS

Figure 3: Model of Structure, Near

Frame 1 Frame 2 Surrogate Particles Overlap Search Area

Images from FlowFieldCaptorMD (after Admiraal, 2011)

Sluice Gate

Weir

Inlet Tank

Outlet Tank

Culvert

Figure 4: Model of Structure, Far

Figure 6: Before Software Analysis

RESULTS

0

0.01

0.02

0.03

0.04

0.05

0.06

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2

Dis

cha

rge

(m

3/s

)

Head (m)

Discharge vs. Head

Experimental Values

Theoretical Values for Sharp Crested

Weir

Figure 5: Discharge vs. Head for Free Flow