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OCEN 201 Introduction to Ocean & Coastal Engineering

OCEN 201 Introduction to Ocean & Coastal Engineering. Ocean Environment &Waves Jun Zhang Jun-zhang@tamu.edu. General Information. 71% of the Earth surface is covered by Oceans Major Oceans 1. Pacific Ocean (46%) 2. Atlantic Ocean (23%) 3. Indian Ocean (20%)

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OCEN 201 Introduction to Ocean & Coastal Engineering

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  1. OCEN 201Introduction to Ocean & Coastal Engineering Ocean Environment &Waves Jun Zhang Jun-zhang@tamu.edu

  2. General Information • 71% of the Earth surface is covered by Oceans • Major Oceans • 1. Pacific Ocean (46%) • 2. Atlantic Ocean (23%) • 3. Indian Ocean (20%) • 4. Remaining Oceans (11%) • Average Ocean Depth is 3800 m • Maximum Depth is 11,524 m

  3. Ocean Floor Reading assignment pp17-19 P18

  4. Physical Properties of Ocean Water • Reading assignment pp19-20 • Primary sea water elements • Chlorine (55%) • Sodium (30.6) • Sulfate (7.7%) • Sodium (30.6) • Magnesium (3.7%) • Potassium (1.1%) • Salinity: amount (grams) of dissolved solid materials (salts) in grams contained in a kilogram seawater (ppt). e.g. Sea Water 35 ppt

  5. Ocean Currents Reading assignment pp19-25 Geostrophic Current (pressure gradients & Coriolis force) Ekman Current (Surface wind friction force & Coriolis force)

  6. Tides • Reading assignment pp23-25 • Diurnal tide (once in a tidal day) • Semi-diurnal tide (twice in a tidal day) • Mixed tide (tidal day 24.84 hr) • Tidal day: rotation of the Earth with respect to the Moon, ~24.84 hr

  7. Fields Related to Ocean Wave • Ocean Engineering: Ship, water borne transport, • offshore structures (fixed and • floating platforms).  • Navy: Military activity, amphibious operation, • WW II Allies landing. • Coastal Engineering: Harbor and ports, dredging, coastal • structures, • beach erosion, sediment transport.

  8. Oceanography: Ocean environment, atmosphere, • fishing, oil spilling, mixing, pollutant • transport. • Environmental Eng.: Capping contaminated dredged • material. • Diffusion and dispersion of toxic • material in ocean and costal water.

  9. Regular and Irregular Waves Ocean waves are almost always irregular and often directional (short-crested). Irregular waves can be viewed as the superposition of a number of regular waves. Regular waves have the same frequency, wavelength and amplitude (height).

  10. T Time t

  11. Regular Waves

  12. Ocean (Irregular) Waves Definitions of Zero-Upcrossing & Downcrossing

  13. Wave Pattern Combining Four Regular Waves FFT & IFFT – (Inverse) Fast Fourier Transform. Irregular wave Regular Waves (Frequency Domain Analysis)

  14. Pierson-Moskowitz Spectrum JONSWAP Spectrum

  15. Ocean Wave Spectra: P-M & JONSWAP Types

  16. Actual Versus Design Seas

  17. Wave Pressure and Kinematics • Linear Wave Theory: Simple, good approximation for • 70-80 % engineering applications. • Nonlinear Wave Theory: Complicated, necessary for about 20-30 % engineering applications. • Both results are based on the assumption of non-viscous flow. • Examples, see animations.

  18. ENVIRONMENT OVERVIEW • Picture showing wind, wave, current, and seafloor for semisubmersible FPS

  19. Linear Wave Theory ----- Dispersion Relation

  20. Using the Dispersion Relation to Find T or L

  21. Use of Dispersion Relation

  22. Definition of Deep, Intermediate and Shallow Water Waves

  23. Linear Wave Theory ----- Phase velocity (celerity) Linear Wave Theory ----- Group (energy) velocity Wave energy propagates at Cg

  24. Linear Regular (Periodic) Wave ----- Elevation & Potential

  25. Linear Regular (Periodic) Wave Energy Density: Average energy per wavelength and per unit width.

  26. Nonlinear Wave Theory • Stokes Expansion • Hybrid Wave Model • Boussinesq Equation (shallow water) • Finite amplitude wave theory

  27. Web-site for animations http://cavity.ce.utexas.edu/kinnas/wow/public_html/waveroom/index.html and Course OCEN 675 http://cavity.ce.utexas.edu/kinnas/wow/public_html/waveroom/index.html

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