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Topical Presentation to Visiting Student from Cheju National University, Korea

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  1. Notional Taiwan Ocean University Coastal Engineering- Introductions Topical Presentation to Visiting Student from Cheju National University, Korea by Tzang, Shiaw-Yih Ph.D. Associate Professor Dept. of Harbor & River Eng. 9:00AM~12:00PM; Aug, 25th, 2005

  2. Outlines • Definition in coastal Area • Coastal Hydraulics • Small – amplitude (SA) wave theory • Wave deformation • Wave Classification in the Ocean • Coastal Structures • Design Formula • Countermeasures for Coastal Protection • Failure events around NTOU seawalls by Typhoon Herb(1996)

  3. Reference • Dean, R. G. and R. A. Dalrymple (1991) "Water Wave Mechanics for Engineers and Scientists", World Scientific (Advanced Series on Ocean Engineering, Vol. 2). • Silvester, R. (1974)Coastal Engineering, Ⅰ, Ⅱ, Elsevier Scientific Publishing Co. • Horikawa, K. (1978) "Coastal Engineering - An Introduction to Ocean Engineering“ University of Tokyo Presses. • Ou, S. H., Hsu, T. W. and Chang, H, K. (2001). Sustainable Diamond Coast – Prevention of Coastal Damages and Integrated Planning on sustainable Utilization of Coastal Ocean Space (in Chinese), Water Resources Bureau, MOEA, ISBN 957-02-8964-3. • Svendsen, IB. A.and I. G. Jonsson (1976) "Hydrodynamics of Coastal Regions", Lyngby, Den Private Ingeniørfond, Technical University of Demnark.

  4. Definition inCoastal Area Geographical Configuration: Source: U.S Army Coastal Engineering Manual

  5. Definition inCoastal Area Coastal Processes: Source:Svendsen & Jonsson(1976) "Hydrodynamics of Coastal Regions", Lyngby, Den Private Ingeniørfond, Technical University of Demnark.

  6. or L ( T ) ( ) h H a x , t x t or ( ) h Coastal Hydraulics –SA Wave Theory (1) Wave definition: H:Wave height η:Water Surface elevation L:Wave length a:amplitude Source: Dean R.G. and R. A. Dalrymple (1984) “Water Wave Mechanics for Engineers and Scientists”

  7. L (or T) z KFSBC DFSBC (x, y) H x (or t) LBC LBC h BBC Boundary value program specification for periodic water waves Coastal Hydraulics –SA Wave Theory (2) Assumptions: Potential Flow, In viscid Fluid ⇒ (Laplace Equ. for Velocity Potential ) Source: Dean R.G. and R. A. Dalrymple (1984) “Water Wave Mechanics for Engineers and Scientists”

  8. Coastal Hydraulics –SA Wave Theory (3) Expressions: (Progressive wave ) (wave number) (angular frequency)

  9. Water particle velocities in a progressive wave Coastal Hydraulics –SA Wave Theory (4) Exponentially decay with depth: Direction of progressive wave propagation z x=L x=L/2 x u w w u Source: Dean R.G. and R. A. Dalrymple (1984) “Water Wave Mechanics for Engineers and Scientists”

  10. A z Water particle of interest B ξ ζ x ( x1 , z1 ) Coastal Hydraulics –SA Wave Theory (5) Elliptical form of water particle trajectory: Source: Dean R.G. and R. A. Dalrymple (1984) “Water Wave Mechanics for Engineers and Scientists”

  11. In deep water : shallow water: Coastal Hydraulics –SA Wave Theory (6) Dispersion equation: • σ& k or T & L are correlated, rather then independent • In deep water, longer waves propagate faster

  12. Coastal Hydraulics –SA Wave Theory (7) Particle Trajectory: Source: Dean R.G. and R. A. Dalrymple (1984) “Water Wave Mechanics for Engineers and Scientists”

  13. Wave Classification in the Ocean (1) A. By Period

  14. Depth water: , shallow water: , intermediate: Wave Classification in the Ocean (2) B. By Water Depth Wind wave : swell:

  15. Caisson Caisson Coastal Structures – Design Formula (1) Structure Type: Totally reflected incident waves Vertical Composite Rubble – mound foundation Partially dissipating Waves Rubble Mound Rubble - Mound

  16. P 1 h * Water Surface h 0 d h P u ¢ h P 2 P 3 Coastal Structures – Design Formula (2) Goda’s Formula: Deried from • 4th-order standing wave theory • Lab experiments • Case study on failure events Source:Goda, Y.“Random Seas and design of maritime structure,” university of Tokyo Press(1985)

  17. Coastal Structures –Countermeasures for Coastal Protection Seawall:protective structure of stone or concrete; extends from shore into the water to prevent a beach from washing away. Breakwater:A structure that extends parallel to the shore at a defined offshore distance. Breakwaters trap sand behind them and also stop waves from breaking on the beach. Groin:structures built perpendicular (at a right angle) to the shoreline. Groins can trap sand moving alongshore and also stop sand from leaving. Works like a headland! Source:http://lighthouse.tamucc.edu/Main/GroinAndBreakwaterDefinition

  18. Failure events around NTOU seawalls by Typhoon Herb (1996)(1) Typhoon path classification: 7 Special Case Paths of Typhoon Herb (1996 ) (Old 7 Paths) Source:Central Weather Bureau of R.O.C.

  19. Pa-Chi-Men breakwater of port of Keelung Lod Pool breakwater of port of Keelung NTOU Seawall National Taiwan Ocean University Failure events around NTOU seawalls by Typhoon Herb (1996)(2) Failure Documents: Geographical locations:

  20. Failure events around NTOU seawalls by Typhoon Herb (1996)(3) NTOU Seawall:

  21. Failure events around NTOU seawalls by Typhoon Herb (1996)(4) Pa-Chi-Men Breakwater of Port of Keelung:

  22. Failure events around NTOU seawalls by Typhoon Herb (1996)(5) Log Pool Breakwater of Port of Keelung:

  23. Thanks for your attention !!