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OCE421

Marine Structure Designs

Lecture 1

Fall, 2006

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OCE421: Marine Structure Designs,

Fall 2006 Prerequisite: OCE307

Instructor: Dr. James Hu, Prof. in OE

Office: Sheets Building, Rm. 220

Phone: 874-6688

Email: hu@oce.uri.edu

Class Hours: M,W 2:00 -3:15 pm Class Room: Room 117, Sheets Building

Office Hours: By appointment

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Teaching Assistant

Mr. Nate Greene

Office Hours: TBA

Office: 202 Sheets

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Mailing List

www/oce/uri/edu/

mailman/listinfo/oce421

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Primary Textbook

U.S. Army Corps of Engineers, (1984)

Shore Protection Manual, Vol.1 and 2,

Vicksburg, MS: Coastal EngineeringResearch Center. (it is now out-of-print)

Coastal Engineering Manual(CEM)

http://ocean.oce.uri.edu/cem/

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Grading Policy

Homework Assignments: 10%

Mid-term Exam: 30% (10/23/2006)

Quizzes: 30%

Project Report and Presentation : 30%

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Homework Assignments

5-6 homework assignments

No late homework accepted

Using MATLAB extensively

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Project guideline, Fall 2006

2-person or3-person teams allowed

Project proposal: due Nov. 1

Final report: due Dec. 4

Presentation: Dec. 6 and Dec. 11

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Project proposal

must include:

general statement (statement of problem)design site description

proposed coastal structure

map and bathymetry plot near the design sitewave data base to be used

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Final Project Report

must include:

general statement (statement of problem)

design site description

proposed coastal structure

planning analysis

map and bathymetry plot near the design site

design wave and design water depth

complete structural design

cost analysis

alternative design and cost analysis

environmental impact analysis (optional)

concluding remarks

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Effects of Water Waves

Waves are the major factor in

determining the geometry and composition of

beaches

significantly influence the planning and design

of harbors, waterways, shore protection

measures, coastal structures, and other coastal

works.

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Physical Description

of a water wave

its surface form

the fluid motion beneath the wave

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Progressive/Standing Wave

A waveform which moves relative to afixed point is called aprogressive wave; the

direction in which it moves is termed the

direction of wave propagation. If a waveform merely move up and down at

a fixed position, it is called a standing wave

or a clapotis.

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Oscillatory/Nearly Oscillatory Waves

Water waves are considered oscillatory ornearlyoscillatory if the water particle motion is described

by orbits that areclosed ornearly closed for each

wave period. The linear theory describespureoscillatory waves.

Most finite-amplitude wave theories describenearly oscillatory waves since the fluid is moved a

small amount in the direction of wave advance byeach successive wave. This motion is termedmass transport of the waves.

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Wave Classification by Wave Period

One way to classify waves is by wave

period, or the wave frequency. Of primary

concern are gravity waves which haveperiods from 1 to 30 seconds.

A narrower range of wave periods, from 5

to 15 seconds, is usually more important incoastal engineering problems.

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Gravity Waves

Surface tension forces may be neglected.

Gravity is the dominant restoring force.

Oscillatory water motion is the result of the

interaction between gravity and inertia

forces.

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Seas and Swell

Gravity waves can be separated into two

states:

Seas - when the waves are under the influenceof wind in a generating area, and

Swell - when the waves move out of the

generating area and are no longer subjected tosignificant wind action.

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Wave Parameters and Characteristics

A (simple) wave is completely specified by waveheight, the water depth, and the wave period (orwave length).

Other characteristics of interest:

Wave surface profile

Forward speed (celerity)

Particle velocities, accelerations, and motion paths Dynamic pressure field

Kinetic and potential energy

Wave power and momentum flux

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Monochromatic and Irregular Waves

Monochromatic wavesa single

(deterministic) wave height and period.

Irregularwavesstatistical (probabilistic)distribution of wave heights and periods;

and wave spectrum(wave power versus

wave frequency)

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Design Wave Conditions

(for a specific location) Various design requirementsdifferent

types of design wave information are

needed Effective wave measurement, analysis, and

prediction techniques are needed.