Current Research Experimental and numerical modeling of flow in a levee breach Experiments and...
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Current Research • Experimental and numerical modeling of flow in a levee breach • Experiments and simulation of sandbag motion at a levee breach • Measurement and simulation of dam break flows • Experimental study of erosion due to levee overtopping
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Transcript of Current Research Experimental and numerical modeling of flow in a levee breach Experiments and...
Current Research
• Experimental and numerical modeling of flow in a levee breach
• Experiments and simulation of sandbag motion at a levee breach
• Measurement and simulation of dam break flows
• Experimental study of erosion due to levee overtopping
Graduate students: S. Yusuf, M. Elkholy, C. Riahi-Nezhad, L. Larocque, J. Feliciano, L. Alva-Solari
Experimental and numerical modeling of flow in a levee breach
Objectives
• To obtain detailed 3-D flow field from measurements in a model levee breach
• To measure flow field around submerged structures
• To simulate complex 3-D flow field in a levee breach and a flooded urban area using the VOF model
Breach Dimensions
465 ft
200 ft
45 ftS
W
N
E
Source: IPET Report 2, https://ipet.wes.army.mil
Physical Model
Scale 1:50 (model: real-life system/prototype)
Model Prototype
Breach width 9.3 feet 465 feet
Canal width 4 feet 200 feet
Flooded area 140 Sq. Ft 8 acres
Model Construction
Sampling rate (HZ) …………………..……. 0.1 to 50Sampling Volume (CC) ………………..…. 0.09Dist. To sampling volume (cm) ……….. 5Resolution (cm/s) ….………………………. 0.01Prog. Velocity range (cm/s) ………..….. 3, 10, 30, 100, 250Accuracy ………………………………………… 1% of measured velocity, 0.25 cm/sMaximum depth (m) ………………………. 60
ADV
Source: http://www.sontek.com/download/brochure/adv.pdf
Velocity measured using 16 MHZ SonTek MicroADV
UVP
An Ultrasonic Velocity Profiler (UVP) transducer transmits a short emission of ultrasound, which travels along the measurement axis. When the ultrasonic pulse hits a small particle in the liquid, part of it scatters on the particle and echoes back.
Figure 1: This diagram explains the process of data collection by the UVP. The UVP is placed at an angle and reflection of the particles and from the bottom creates a velocity profile.
(X7, Y4) (X7, Y5)
These plots show the velocity in the x direction.
Vx Vx
Velocity Distribution (X7,Y4) and (X7,Y5)
0 10 20 30 40 50 600
2
4
6
8
10
12
Velocity (cm/s)De
pth
(cm
)
0 10 20 30 40 50 600
2
4
6
8
10
12
Velocity (cm/s)
Wat
er D
epth
(cm
)
-10 0 10 20 30 40 50 60 700
5
10
15
Velocity Y-dir(cm/s)
Dep
th (
cm)
X24-Y9
UVP
ADV
-5 0 5 10 15 20 25 30 35 40 45 500
5
10
15
Velocity X-dir(cm/s)
Dep
th(c
m)
X24-Y9
UVP
ADV
0 5 10 15 20 25 30 35 40 45 500
5
10
15
Velocity Y-dir(cm/s)
Dep
th (cm
)
X24-Y13
UVP
ADV
0 5 10 15 20 25 30 35 40 45 500
5
10
15
Velocity X-dir(cm/s)
Dep
th(c
m)
X24-Y13
UVP
ADV
Velocity Profiles for X24-Y9 and X24-Y13
Breach Geometry in Gambit 2.4.6
Inlet (Blue)Outlet (Red)Houses (solid Blocks)Arrows shows the direction of flow
Mathematical ModelGeneral
• Ansys Fluent 6.3.26 used for modeling of levee breach flows
• Solver: Pressure based
• Multiphase model: VOF (Implicit scheme)
• Turbulence model: k-epsilon
Grid specification• Boundary layer : meshed at the bottom of the channel
• Grid: hexahedral with size = 2 cm
Ongoing and Future Research
• Flow measurements around model buildings using UVP
• Comparison of computed and measured velocity distributions
• Characterization of turbulence over irregular topography
• Inclusion of erosion and deposition of channel bottom and sides
Tracking Sand Bag Motion in a Levee Breach using DPTV
Technique
Objectives• Developing a visual technique for tracking the motion of the sand bags and
plotting their trajectories.
• Determining the three-dimensional velocity components of the sand bags.
• Formulating relationships between the sand bag size and shape and flow
parameters.
• Determining optimum sand bag size, and more efficient procedures for
levee closure.
Trials for breach closure
Source: http://www.usace.army.mil/katrina-images/NO-A-09-04-05_0072.jpg
Recording deviceSpecification GRAS-03K2M/C
Maximum resolution 640(H) x 480(v)
Pixel size 7.4 m x 7.4 m
Maximum Frame rate 200 Fps
Shutter speed 0.02 ms to 10s
Transfer rate 100 Mbit/s
Area coveredat distance of
1.0 m
370 x 270mm2
Angle of view 22 16 27
The Model Sand bags
Plan view
Elevation
14.5 25.4 36.3 54.4 108.8
21.8 26.3 29.6 33.9 42.8
4,000 7,000 10,000 15,000 30,000
Weight (gm)
Equivalent Dia. (mm)
Equivalent prototype weight (Ib)
1:50
3-D Stereoscopic System
Image Plane
Lens Plane
Water surface
Cam
era-
axis
2
f
d
zx
dz
dx
o
a
a1o1 o2 a2x1 x2
x1 x2
SCa
mer
a-ax
is1
Centroiding
Testing of extraction of sandbag in stationary flow
After Extraction
x x xU/S Levee D/S Levee
Bed Elevation Contour Map for the Katrina Model
Ditch
xx
Canal
9.70 – 16.1
16.1 – 19.1
19.1 – 22.3
22.3 – 25.7
cm
Datum: Top of the U/S levee
1 2 3 4 5
Trajectories of 10,000 Ib sandbag at different locations
(Plan view)
1
2 43
5
Trajectories of 10,000 Ib sandbag (vertical direction)
Time (sec)
Location (3)
Time (sec)
Location (1)
Ongoing and Future Research
• Understanding the general mechanics of sand
bag motion.
• Formulating relationships between the sand
bag size and shape and flow parameters.
• Determining the optimum size of sand bags
and procedures for levee breach closure.
Experimental and Numerical Investigations of Dam-Break
Flows
Objectives• To measure the instantaneous velocity over time for a dam break experiment.
using an Ultrasonic Velocity Profiler (UVP)
• To conduct LES simulation of a dam break wave.
• To compare the measured and simulated flow field
Figure: Experimental dam break set up. Notice the left hand side of the dam is filled with water up to 25 cm.
• Flume: 7.67 m long, 25 cm deep, 18 cm wide, and 3.5% slope.• UVP placed at 45 deg. (schematics shown below). • UVP start measuring velocity as dam is lifted
Experimental Set up
UVP Probe
UVP probe facing upward to determine water level over time
UVP Probe
UVP probe facing downward to find the velocity profile at the bottom of a dam break wave
Experiment 1 Experiment 2
• A numerical grid with two separate volumes (water and air) was generated using Gambit, a grid generating program.
• The numerical simulation was conducted using FLUENT. • Large Eddy Simulation (LES) and Volume of fluid (VOF) models
were used.
Numerical Set-up
The grid used in the numerical simulation. The blue grid indicates the water and the other portion is the air at the initial location.
Volume: WATERVolume: AIR
Experimental Results• The UVP continuously measures the velocity over time and generates a
velocity profile at a specified time step.• Multiple trials were conducted to compare the repeatability of the
experiment.
0 10 20 30 40 50 60 70 80 90 100
5
10
15
20
25
30
35
40
45
50
55
Velocity (mm/s)
Dis
tanc
e to
flu
me
bed
(mm
)
Velocity Profiles Repeatability (1.0s)
trial 1
trial2
This graph shows the velocity profile measured using a UVP. The two lines represent two separate trials of the experiment.
T=1.0s
Comparison • A comparison between the numerical simulation and the
experiment velocity profile on the upstream side of the dam break
• Additional measurements throughout the model• Experimental measurements of flow field including
erosion and deposition following dam failure.• Simulation of flow field following dam failure
including erosion and deposition of bottom material
Ongoing and Future Research
Levee Breach due to Overtopping
Objectives
• To understand and identify the parameters that govern the erosion and headcut formation during the overtopping of a levee.
• To conduct laboratory experiments overtopping small-scale dikes in a flume.
• To collect and evaluate the data and improve/modify breach models.
Dike and Flume Dimensions
DIKE DIMENSIONS
Height 0.22 m
Top 0.09 m
Side slope 2H:1V
FLUME DIMENSIONS
Length 6.5 m
Width 0.46 m
Height 0.26 m
Material D50 Specific Gravity LL PL
Sand 30 400 μm 2.69 --- ---
Kaolin 0.6 μm 2.59 81.1% 33.6%
Silt 106 22 μm 2.65 --- ---
Silt 250 49 μm 2.65 --- ---
Material
Soil Composition
No SOIL BX30 Kaolin Silt 106
Silt 250 γd ωo
No Passes with Roll
Flow Rate (L/s)
Exp 1 Soil 1 85% 15% --- --- 113 lb/ft3 12% 10 0.24
Exp 2 Soil 2 70% 15% 15% --- 126 lb/ft3 10% 15 0.24
Exp 3 Soil 3 80% 10% 10% --- 126 lb/ft3 10% 18 0.24
Exp 4 Soil 4 --- 10% 72% 18% 108 lb/ft3 13.5% 15 3.9
Compaction
DATA
Weight of the roll
20.5 Kg
Soil Layer Thickness
0.05 m
No Passes per Layer
10, 15, 18
Compaction obtained
80% to 95% of γd
Instrumentation
Description QuantityWater level gauge downstream 01Water level gauge upstream 01Video cameras 04UVP sensor for velocity measurement (being implemented)
04
Data acquisition (being implemented) 01Weir 01Timer 01
Instrumentation
UVP Sensor Upstream
UVP Sensor Downstream
Top Video Camera
Front Video Camera
Video Camera
Data Acquisition
Levee Breach Experiments 1, 2 & 3
1
2
3
EROSION ON THE DOWN STREAM FACE
OF THE DIKE
HEADCUT
HEADCUT UNDERMININGRESERVOIR
FLOW
FLOW
FLOW
MAIN ELEMENTS OF THE PROCESS:- SOIL PROPERTIES- GEOMETRY- FLOW CHARACTERISTICS
Headcut Experiment 4
FRONT VIEW
TOP VIEW
0.02 m
0.02 m
1.5H:1V
HEADCUT GEOMETRY
Headcut Experiment 4 (Front View)
30s0s 1’
2’ 2’30” 2’52”
2’53” 3’ 4’
Ongoing and Future Work
a. Systematically vary non-dimensional numbers involving soil properties, levee geometry and flow properties in experiments.
b. Understand and evaluate the scale effect.c. Focus on the effect of cohesion on the breach
process.d. Conduct experiments at larger scales.
