WavesContinuous rise and fall in the sea level and waves are formed as a result of multiple factors that may be industrial, such as the movement of ships or the occurrence of explosions or natural as a result of earthquakes, tides, or winds.pptx

Continuous rise and fall in the sea level and waves are formed as a result of multiple factors that may be industrial, such as the movement of ships or the occurrence of explosions or natural as a result of earthquakes, tides, or winds

1. Harbor Engineering Dr.-Ing. Reda Diab 1 Harbor Engineering & Marine structures هندسة الموانيء و المنشات البحرية By Dr.-Eng. Karim Nassar Lecture No. 3

2. Chapter (1) Introduction to Harbor Engineering Chapter (2) Harbor Hydrodynamics Chapter (3) Wave Mechanics Chapter (4) Port Planning Chapter (5) Breakwaters Chapter (6) Berths Chapter (7) Introduction to Coastal Engineering محتويات هندسة الموانيء و المنشات البحرية

3. Chapter (3) Wave Mechanics 1- Introduction to waves 2- Linear wave theory (Airy theory) 3- Waves propagation 4- Waves forces

4. 1- Introduction to waves a- Wave definition and importance c- Wave parameters d- Ocean wave types e- Wave forecasting b- Wind waves

5. a- Wave definition and importance Continuous rise and fall in the sea level and waves are formed as a result of multiple factors that may be industrial, such as the movement of ships or the occurrence of explosions or natural as a result of earthquakes, tides, or winds ارتفاع و انخفاض مستمرين في سطح البحر مكونة قمم Crests و قيعان troughs و تتكون الامواج نتيجة لعوامل متعدده قد تكون صناعيه مثل حركة السفن او حدوث انفجارات او طبيعيه نتيجة للزلازل او المد و الجزر او الرياح crest trough trough crest اهمية دراسة الامواج The planning and design of Harbours, Location and the entrance of harbours, the planning and design of berths, breakwaters, and navigation channels, shore protection measures. (تدخل في تخطيط منشات الحماية الشاطئية)

6. b- Wind waves

7. Wind waves Wind waves are generated by wind. Wind stress on water surface, transfers the wind energy to water and create waves. Winds acting over a fetch of ocean, build waves from ripples to waves (fully developed seas ) to swell and finally to surf . braking Surf Ripples The waves energy and so the wave height depends on the wind energy transferred which is a function of: Wind speed, wind duration and fetch. Fetch area

8. Generating area (FETCH): the continuous area in which waves (SEAS) are generated by a wind having a fairly (constant) direction and speed. هي منطقة ممتده داخل البحر تتولد فيها الامواج عن طريق رياح لها اتجاه وسرعة (ثابتان). Fetch length: the horizontal distance (in the direction of wind) over which a wind generates ripples and seas. Fetch duration: the time it takes for the wave to travel the whole fetch length

9. Seas – refer to short-period irregular waves still being created by winds in the area of generation. Swells – refer to more regular waves that have moved out of the generating area. Surf - waves that have reached the coast, grow in height, and break. braking Surf (irregular waves) (regular waves) swash Swash - is a turbulent layer of water that washes up or down on the beach after an incoming  wave  has broken. عبارة عن طبقة مضطربة من المياه تنجرف لأعلى أو لأسفل على الشاطئ بعد انكسار الموجة القادمة.

10. c- Wave parameters

11. Wave characteristics: H = wave height a = wave amplitude = H/2 L = wave length T = wave period wave speed (celerity), C = L / T wave steepness = H / L Wave frequency ( = 1 / T Wave number (k) = 2 Still water depth (d) Group velocity (c g ) = n*C , n= Wave energy (E) = =1.025 t/ Wave power (P) = c g * E   ------ (t/m) ------ m/sec * t/m ------- (t/sec) (m) (m) (sec) (m/sec) ( )   (m/sec) a a Number of waves per one second (m)

12. d- Ocean wave types 1- According to wave period. 2- According to water depth.

13. 20s 1- According to wave period.

14. 2- According to water depth. d d d 1 2 3

15. e- Wave forecasting 1- Calculating H & T of waves using wind data [fetch (f), and speed (U)]. 2- Wave Height Statistics .

16. 1- Calculating H & T of waves using wind data [fetch (f), and speed (U)]. From SPM:   H o --- wave height in deep water ( ft ). (significant wave height) T --- wave period (sec). U --- wind speed ( ft /sec). F --- fetch length ( ft ). g --- gravitational acceleration (32.2 ft /   Ft = 0.3048 m Nautical mile = 1.82 km = 1820 m = 5971.12 ft Knots = 0.5 m/sec = 1.64 ft /sec

17. Example (1): Knowing that the wind speed is 35 knots. Find the significant wave height and the wave period for a fetch length 250 nautical mile. Fetch (F) = 250 nautical mile = 250* 5971.12= 1492780 ft Wind speed (U) = 35 knots = 35 * 1.64 = 57.4 ft /sec   = 17.52 ft     = 9.3 sec  

18. 2- Wave Height Statistics .   Wave height (meter) 1 2 3 4 5 6 Number of waves (n) 15 30 50 11 10 4 Root mean square of wave heights N = 15 + 30 + 50 + 11 + 10 + 4 = 120 3.1m   N = total number of waves =   1.41H rms = 4.37m   1.87H s = 8.17m   0.886H s = 3.87 m   0.707H rms = 2.19m   Significant wave height Maximum wave height Average wave height Most probable wave height 6. H/ H rms  

19. Example (2): The significant wave height in a particular site was found from observations to be 2.0m, if the total number of waves taken to be 1450 waves. Find the followings: 1- H rms , H mp , and H max . 2- How many waves are expected to measure 2.5m. 3- What height is reached by half of the waves? 1.41H rms     0.707H rms = 1.0m   1.87H s = 3.74m   H/ H rms   2.5/1   n = 66 waves H/ H rms   H/1   H = 1.18 m

20. فى النهاية اذكركم بالدعاء لأخوانكم فى غزة