Adam Koenig Final Presentation - University of Hawaii

crookedjourneyMechanics

Oct 24, 2013 (3 years and 9 months ago)

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Adam Koenig, Wichita State University


Mentors:

Dr. Ron Riggs, University of Hawai’i,
Manoa

Dr.
Sungsu

Lee,
Chungbuk

National University

Krystian

Paczkowski
, University of Hawai’i,
Manoa



HARP REU Program, August 3, 2011

Overview


Background and Motivation



Benefits of CFD Approach



Description of Utilized CFD Tools



Simulation Description



Results



Conclusions and Recommendations

Background and Motivation


Experiments have collected data on tsunami bore
formation
1,2



Tsunami blockage and funneling is less studied



Such data would be useful for establishing design
parameters for structures in and around streets that
would be affected by this channeled flow, especially if
flow is accelerated

Goals


Numerically simulate tsunami bore channeled
through a city street



Identify effects and phenomena caused by buildings
obstructing bore flow



Quantify relationships between tsunami bore
parameters and flow properties in the street


Benefits of CFD approach



Much more inexpensive than experimental tests



No scaling problems



Greater flexibility in test parameters

Software/Models


This study uses
OpenFOAM

v 1.7.1, a free, open
-
source CFD
software package for a wide range of fluid problems



Solver:
InterFoam
, a solver for two incompressible,
immiscible fluids that uses a VOF method to generate a
volume where the sharp interface between phases would
exist



Turbulence: k
-
ε

model,
a RANS based turbulence model
with transport equations for turbulent kinetic energy and
turbulent dissipation

Hardware




JAWS system at Hawaii Open Supercomputing Center


320 Dell
PowerEdge

1955 blades with four 3.0 GHz
processors per blade


Cisco SDR
infiniband

(10Gbit/sec) interconnect

Domain Description


The domain of this test consists of a 120
×
290
×
30 ft
rectangular prism with two half
-
buildings obstructing
the end


The half
-
buildings are each 45 feet wide and 90 feet
long

Domain Description


The inlet consists of a 3.6 ft high patch spanning the
back wall of the domain


The inlet speed was controlled by setting a constant
velocity condition across the surface of the inlet. Tests
showed that there was no difference in the channel
flow of a total pressure inlet was used.


The inlet speed was adjust to give the desired Froude
number of the bore. The study focused on bore
Froude numbers between 2 and 3 from experimental
data
1,2
.


The Mesh


The mesh consists of two groups of hexahedral cells
stacked in the domain


Mesh density is 1.25 ft/cell in horizontal directions


Vertical density is 0.9 ft/cell up to the height of the
inlet, and 1.65 ft/cell from top of the inlet to the top of
the domain


This meshing allows for acceptable resolution
throughout the domain with improved resolution in
majority of flow area

The Mesh

Limitations/Difficulties


Zero velocity boundary condition in wall above inlet


Data is only valid until reflected bore strikes back wall


Reason for long domain


Open boundary resulted in flow anomalies and crashed
simulations



Gap Aspect Ratio


Dimensions chosen to fit regular two
-
way street and
building size based on Empire State Building


Actual aspect ratios would vary considerably

Simulation Example

Observations


Water pools in front of obstructing buildings at height
significantly greater than bore height



Original bore reflected back out to sea as a hydraulic
jump



Remaining water cascades between buildings into the
street

Results

0
0.5
1
1.5
2
2.5
3
3.5
4
0
0.5
1
1.5
2
2.5
3
3.5
4
Pool Height (m)

Bore Froude Number

Pool Height vs. Bore Froude Number

Results

0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0
0.5
1
1.5
2
2.5
3
3.5
4
Outlet Height (m)

Bore Froude Number

Outlet Height vs. Bore Froude Number

Results

0
0.5
1
1.5
2
2.5
3
0
0.5
1
1.5
2
2.5
3
3.5
4
Pool to Outlet Height Ratio

Bore Froude Number

Pool to Outlet Height Ratio vs. Bore Froude Number

Results

0
1
2
3
4
5
6
7
8
9
0
0.5
1
1.5
2
2.5
3
3.5
4
Outlet Velocity (m/s)

Bore Froude Number

Outlet Velocity vs. Bore Froude Number

Outlet Velocity
Bore Velocity
Results

0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0
0.5
1
1.5
2
2.5
3
3.5
4
Reflected Froude Number

Bore Froude Number

Reflected Froude Number vs. Bore Froude Number

Conclusions


Pooling height, outlet height, and outlet velocity all
positively correlated to bore Froude number.


Height ratio independent of bore Froude number


Outlet velocity never exceeds bore velocity, but
numbers are very close at low Froude numbers


Possibly a consequence of inlet height and sheet flow in
bore


Reflected bore relatively constant for tested range, but
possible negative correlation

Recommendations for Future Work



Study effect of gap aspect ratio on flow property
relationships



Determine whether inlet height affects funneling
behavior and whether inlet height affects bore shape


Acknowledgements


Krystian

Paczkowski
, for his insight into the inner
workings of
OpenFOAM

software


Dr. Susan Brown, for continuous assistance with data
storage issues


Dr. Ron Riggs and Dr.
Sungsu

Lee, for their guidance and
insight into fluid behavior problems


This material is based upon work supported by the National
Science Foundation under Grant No. 0852082. Any opinions,
findings, and conclusions or recommendations expressed in
this material are those of the author(s) and do not necessarily
reflect the views of the National Science Foundation.

Works Cited


1
Robertson
, I. N., H. R. Riggs, and A. Mohamed.
"Experimental Results of Tsunami Bore Forces on
Structures."
Proceedings of the 27th International
Conference on Offshore Mechanics and Arctic
Engineering
.
Estoril
, Portugal. Print.


2
Robertson
, I. N., H. R. Riggs, K.
Paczkowski
, and A.
Mohamed. "Tsunami Bore Forces On Walls."
Proceedings of the ASME
2011 30
th

International
Conference on Ocean, Offshore, and Arctic
Engineering
. Rotterdam, The Netherlands. Print.

Questions?