Docking Structures & Wave Energy
Nick RippWilliam Marcouiller
Introduction
• Flow past obstacles
• Relate to dock and bridge piers
• High and low energy waves
• Sediment disruptions
• Design strength for piers anddock legs
www2.icfd.co.jp
Motivation
Experiment
• Simulate incident waves• Estimate wave energy before and after structural
contact by measuring wave height• Determine if major differences occur• Why or why not?
– Geometric violations– Reflections and diffractions– Intensity of wave energy
• Apply to real settings
Experiment
• Physical modeling: similitude requirements– Geometric similarity (linear dimensions)– Kinematic similarity (motion between particles)– Dynamic similarity (vectorial forces)
• Perfect similitude requires that the prototype-to-model ratios of the inertial, gravitational, viscous, surface tension, elastic, and pressure forces be identical.
Setup
2 feet
11 feet
‘Coastal Structures’
Objects used:
4x4 inch rectangular wooden support orthogonal to flow
4x4 inch rectangular wooden support oblique to flow (≈45⁰)
4 inch diameter cylindrical aluminum support
4x4 Orthogonal Square
4x4 Oblique Square
4 inch Diameter Cylinder
No Obstacles
4x4 Orthogonal Square Analysis
4x4 Oblique Square Analysis
4 inch Diameter Cylinder
2 Obstacles
Orthogonal Block Oblique Block
vs
2 Obstacles
Cylinder
Analysis
Controlled period
Measured depth
Observed wave height
Approximate energydensity after collision with obstacle
2 seconds
6 inches (.1524 meter)
6 inches (.1524 meter)
28.5 N-m/m2
Analysis
Since the waves were partially spilling over, a more accurate calculation of energy density is given by the University of Delaware Wave Calculator. It found the energy density to be approximately 18.2 Nm/m2.
Analysis
Calculated wave length
Calculated wave height
Wave steepness
2.4 meter
.1219 meter (breaking)
.05079
Conclusion
• If wave energy varies significantly in the direction normal to wave propagation, wave energy can be transmitted laterally due to wave diffraction in addition to the direction of wave propagation
• Wave diffraction also occurs in the sheltered region behind barriers and obstacles
• Wave reflection occurs when waves come into contact with obstacles
Conclusion
• Encourage dock industry to produce innovative designs that have less of an impact on the coastal environment
• Educate coastal landowners• Restricting the amount of
coastal area disturbed minimizes impacts
Bibliography
Acknowledgments
Professor Chin Wu
Minnesota DNRhttp://www.dnr.state.mn.us/waters/watermgmt_section/pwpermits/docks.html
http://files.dnr.state.mn.us/waters/watermgmt_section/pwpermits/dock_platform_general_permit_q_and_a.pdf
Mohn, Magoon, Pirrell. (2003). Advances in coastal structure design. ASCE
Wisconsin DNRdnr.wi.gov/
University of Delaware: Wave Calculator
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