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