DOCSLIB.ORG

Nature of Marine Winds, Waves and Swells Over West African Coasts – Case Study of Victoria Island Beach in Lagos, Nigeria

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Nature of Marine Winds, Waves and Swells Over West African Coasts – Case Study of Victoria Island Beach in Lagos, Nigeria Nature Of Marine winds, Waves and Swells over West African Coasts – Case study of Victoria Island beach in Lagos, Nigeria By S. O. Gbuyiro and E. Olaniyan Marine Unit, Nigeria Meteorological Agency, Lagos - Nigeria INTRODUCTION • SEA STATE IS CONTROLLED BY ATMOSPHERIC WINDS WHICH COME IN CONTACT WITH THE OCEAN SURFACE. • WIND IS THE PRIMARY CAUSE OF OCEAN WAVES DUE TO INTERRACTION BETWEEN ATMOSPHERE AND SEA SURFACE . • WIND WAVES COMPRISE OF A SMALL PORTION OF THE TOTAL OCEAN WAVE SPECTRUM WITH TYPICAL WAVE PERIODS OF ABOUT 1 SEC TO 20SECONDS. TYPES OF WAVES AND THEIR SOURCES OF GENERATION • INTERNAL GRAVITY WAVES - CAUSED BY WIND STRESS . ** THE COMMONEST SINCE NEARLY ALL OF OUR OCEAN INTERACTION OCCUR AT THE OCEAN SURFACE. • SEICHES – STANDING WAVES CONSISTING OF TWO PROGRESSIVE WAVES TRAVELLING IN THE OPPOSITE DIRECTIONS. • TSUNAMIES- CAUSED BY EARTHQUAKES. • TIDES - CAUSED BY GRAVITATIONAL PULL BY THE MOON AND SUN ON OCEAN WATER AND CENTRIPETAL FORCES PRODUCED BY A ROTATING EARTH. WAVES CHARACTERISTICS •• BASINBASIN GEOMETRYGEOMETRY INVOLVINGINVOLVING ---- BASING LENGTH -- WATER DEPTH • WAVE LENGTH (L) * WAVE DEPTH (D) • WAVE PERIOD (P) • WATER DEPTH TO WAVE LENGTH RATIO (D/ L) • WIND SPEED * WIND DURATION • FETCH AREA / FETCH DISTANCE IMPACT OF WAVES • TRANSPORTATION & SHIPPING - INVOLVING BOATS AND SHIPS. • ENGINEERING WORKS: COASTAL STRUCTURES • WATER RECREATIONAL ACTIVITIES ALONG THE COASTAL ZONES. • FLOODING AND EROSION ALONG COASTAL SETTLEMENTS WHY THE STUDY • ROLE OF ST HELENA HIGH PRESSURE SYSTEMS. • TO IDENTIFY THE CAUSE OF OCEAN SURGES DURING THE WINTER OR DRY SEASON. • CONSTANT VICTORIAL ISLAND BEACH EROSION AND FLOODING DUE TO STORM AND OCEAN SURGES WHICH IS A THREAT TO ECONOMIC ACTIVITIES (12000 KM2 , 6 MILLION POPULATION & US 3 BILLION SPENT ON SAND FILLING YEARLY. 140 1991 120 1994 100 80 60 40 20 Width of beach (m) 0 Npayad niomr Palace fghouse SLO IMB Ehotel Maroko Locations Fig 1.Locations beach width from 1991 t0 1994 in Victoria Island STUDY AREA • The Nigeria’s coastal zone which also suffer from the coastal problems mentioned above lies within latitudes 4º 10’ to 6º 20’N and longitudes 2º 45’ to 8º 35’E spanning about 850 km of low-lying coastline. • The coastal zone can be divided into four distinct geomorphic parts. These consist of • (1) The barrier-lagoon system stretching for almost 250km from the Nigerian/Benin border • (2) The Mahin transgressive Mud coast stretching for almost 75km. • (3) The Niger delta covering almost 20,000 square kilometres is the second largest delta in the world spanning a coastline of almost 450km. • (4) The Strand coast east of the Niger delta stretches for about 85km from the Imo river eastwards to the Nigerian/Cameroon boundary. Fig2 Showing the Nigeria coast (a) and enlarged box (b) Victoria Island DATA AND METHODOLOGY • Daily Winds, for 1998 to 2002 winter months (November - March) at 10m level over the Atlantic Ocean, between lat.10oS - 20oS and long 10oE - 20oW, were extracted from the general circulation model (GCM) of METEO-FRANCE. • The extracted winds between lat. 10oS - 20oS and long 0o -10oE, served as input data for a parametric wave model. This model has been adapted FROM LYON (1994) AND WHITFORD(2001) to suit local conditions. • The out put variables (wave height, wave period and swells etc) were then obtained. RESULTS a. Winds from the fetch area (lat. 10 degree South - 20 degree South and long. 0 –10 degree East) generally lie between 7-20 knots in strength. The weakest and strongest winds were observed in January and March. (Figs; 3a&b ) b. The corresponding generated significant wave heights were less than 0.3 meters and more than 2.2 meters with period ranging between 2.0 and 7.5 seconds. It takes the lowest generated wave about 10-12 days and the highest 3-4 days to reach the coast as swells. (fig 4a&b). And c. Swells of about 0.47 meters in height resulting from winds of about 10 knots grazed the coast frequently during the period a. Rate of erosion from 1998 –2002 was observed to be 27m/year. 16 RESULTS 14 12 20 18 10 16 Winds (kts) 14 8 12 Winds(kts) 6 10 8 4 1-Jan 15-Jan 29-Jan 12-Feb 26-Feb 12-Mar 26-Mar 6 1-Jan 15-Jan 29-Jan 12-Feb 26-Feb 12-Mar 26-Mar Days Days Fig. 3b. Time seriess of the fetch wind for 2002 F ig . 3a . T im e s e rie s o f th e fe tc h w ind for 2001 1.8 Hsm sw ell 1.6 Hsm swell 1.4 2.5 1.2 2 1 1.5 0.8 1 Wave/Swell (m) 0.6 Wave/swell (m) Wave/swell 0.5 0.4 0 0.2 1-Jan 15-Jan 29-Jan 12-Feb 26-Feb 12-Mar 26-Mar 0 1-Jan 15-Jan 29-Jan 12-Feb 26-Feb 12-Mar 26-Mar Days Days Fig.4b. Generated wave and the Fig.4a. Fetch significant wave and corressponding coastal swells for 2002 the corressponding coastal swells for 2001 20 25 18 16 20 14 15 12 10 Numbers 10 Numbers 8 6 5 4 0 2 7.22 8.75 10.4 11.3 12 13.3 15 17.8 0 5 7.78 10 11.7 13.3 15 Winds (knts) Fig5b. The frequency of occurence of wind(knts) the wind 2001 - 2002 period Fig5a. The frequency of occurence of the wind for 2001 period CONCLUSION This type of temporal observation in the marine wind and associated coastal swells from the generated wave can be important in the determination of surge occurrence in the unusual months. With the continuous coastal erosion caused primarily by the wave and the inundation of the coast during ocean surges in winter, this work will contribute to integrated coastal management. Thank You.
Load more

Recommended publications
  • NANOOS Asset List 1 National Oceanic and Atmospheric
    NANOOS Asset List 2008 NANOOS Asset List 1 National Oceanic and Atmospheric Administration 1.1 The CoastWatch West Coast Regional Node http://coastwatch.pfel.noaa.gov Daily – Monthly composites of satellite observations Sea Surface Temperature (GOES & POES) Ocean Color (MODIS and SeaWiFS) Ocean Winds (QuikSCAT) 1.2 The National Data Buoy Center http://seaboard.ndbc.noaa.gov/maps/Northwest.shtml 6 Minute – Hourly buoy observations Meteorological Observations (Air Temp., Pressure, Wind Speed and Direction) Ocean Observations (Water Temp., Wave Height, Period and Direction) 1.3 The Center for Operational Oceanographic Products and Services http://tidesandcurrents.noaa.gov http://opendap.co-ops.nos.noaa.gov/content 6 Minute near-shore station observations Meteorological Observations (Air Temp., Pressure, Wind Speed and Direction) Ocean Observations (Water Temp., Water Level) 1.4 NOAAWatch http://www.noaawatch.gov Information related to ongoing environmental events NOAAWatch themes include Air Quality, Droughts, Earthquakes, Excessive Heat, Fire, Flooding, Harmful Algal Blooms (HABs), Oil Spills, Rip Currents, Severe Weather, Space Weather, Tsunamis, and Volcanoes 1.5 National Weather Service http://www.weather.gov Environmental observations and forecasts Coastal and Marine Forecasts Weather Warnings 1 NANOOS Asset List 2008 Surface Pressure Maps Coastal and Marine Observations (Wind, Visibility, Sky Conditions, Temperature, Dew Point, Relative Humidity, Atmospheric Pressure, Pressure tendency) GOES Satellite Observations (Visible,
    [Show full text]
  • Part II-1 Water Wave Mechanics
    Chapter 1 EM 1110-2-1100 WATER WAVE MECHANICS (Part II) 1 August 2008 (Change 2) Table of Contents Page II-1-1. Introduction ............................................................II-1-1 II-1-2. Regular Waves .........................................................II-1-3 a. Introduction ...........................................................II-1-3 b. Definition of wave parameters .............................................II-1-4 c. Linear wave theory ......................................................II-1-5 (1) Introduction .......................................................II-1-5 (2) Wave celerity, length, and period.......................................II-1-6 (3) The sinusoidal wave profile...........................................II-1-9 (4) Some useful functions ...............................................II-1-9 (5) Local fluid velocities and accelerations .................................II-1-12 (6) Water particle displacements .........................................II-1-13 (7) Subsurface pressure ................................................II-1-21 (8) Group velocity ....................................................II-1-22 (9) Wave energy and power.............................................II-1-26 (10)Summary of linear wave theory.......................................II-1-29 d. Nonlinear wave theories .................................................II-1-30 (1) Introduction ......................................................II-1-30 (2) Stokes finite-amplitude wave theory ...................................II-1-32
    [Show full text]
  • Sea State in Marine Safety Information Present State, Future Prospects
    Sea State in Marine Safety Information Present State, future prospects Henri SAVINA – Jean-Michel LEFEVRE Météo-France Rogue Waves 2004, Brest 20-22 October 2004 JCOMM Joint WMO/IOC Commission for Oceanography and Marine Meteorology The future of Operational Oceanography Intergovernmental body of technical experts in the field of oceanography and marine meteorology, with a mandate to prepare both regulatory (what Member States shall do) and guidance (what Member States should do) material. TheThe visionvision ofof JCOMMJCOMM Integrated ocean observing system Integrated data management State-of-the-art technologies and capabilities New products and services User responsiveness and interaction Involvement of all maritime countries JCOMM structure Terms of Reference Expert Team on Maritime Safety Services • Monitor / review operations of marine broadcast systems, including GMDSS and others for vessels not covered by the SOLAS convention •Monitor / review technical and service quality standards for meteo and oceano MSI, particularly for the GMDSS, and provide assistance and support to Member States • Ensure feedback from users is obtained through appropriate channels and applied to improve the relevance, effectiveness and quality of services • Ensure effective coordination and cooperation with organizations, bodies and Member States on maritime safety issues • Propose actions as appropriate to meet requirements for international coordination of meteorological and related communication services • Provide advice to the SCG and other Groups of JCOMM on issues related to MSS Chair selected by Commission. OPEN membership, including representatives of the Issuing Services for GMDSS, of IMO, IHO, ICS, IMSO, and other user groups GMDSS Global Maritime Distress & Safety System Defined by IMO for the provision of MSI and the coordination of SAR alerts on a global basis.
    [Show full text]
  • Sea State Effect on the Sea Surface Emissivity at L-Band
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by UPCommons. Portal del coneixement obert de la UPC IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. 41, NO. 10, OCTOBER 2003 2307 Sea State Effect on the Sea Surface Emissivity at L-Band Jorge José Miranda, Mercè Vall-llossera, Member, IEEE, Adriano Camps, Senior Member, IEEE, Núria Duffo, Member, IEEE, Ignasi Corbella, Member, IEEE, and Jacqueline Etcheto Abstract—In May 1999, the European Space Agency (ESA) temperature images will provide looks of the same pixel under selected the Earth Explorer Opportunity Soil Moisture and incidence angles from 0 to almost 65 , which requires the Ocean Salinity (SMOS) mission to obtain global and frequent soil development of soil and sea emission models in the whole moisture and ocean salinity maps. SMOS single payload is the Microwave Imaging Radiometer by Aperture Synthesis (MIRAS), range of incidence angles, and suitable geophysical parameters an L-band two-dimensional aperture synthesis radiometer with retrieval algorithms. multiangular observation capabilities. At L-band, the brightness The dielectric permittivity for seawater is determined, among temperature sensitivity to the sea surface salinity (SSS) is low, other variables, by salinity. Therefore, in principle, it is possible approximately 0.5 K/psu at 20 C, decreasing to 0.25 K/psu at to retrieve SSS from passive microwave measurements as long 0 C, comparable to that to the wind speed 0.2 K/(m/s) at nadir. However, at a given time, the sea state does not depend only as the variables influencing the brightness temperature (TB) on local winds, but on the local wind history and the presence signal (sea surface temperature, roughness, and foam) can be of waves traveling from far distances.
    [Show full text]
  • Marine Forecasting at TAFB [email protected]
    Marine Forecasting at TAFB [email protected] 1 Waves 101 Concepts and basic equations 2 Have an overall understanding of the wave forecasting challenge • Wave growth • Wave spectra • Swell propagation • Swell decay • Deep water waves • Shallow water waves 3 Wave Concepts • Waves form by the stress induced on the ocean surface by physical wind contact with water • Begin with capillary waves with gradual growth dependent on conditions • Wave decay process begins immediately as waves exit wind generation area…a.k.a. “fetch” area 4 5 Wave Growth There are three basic components to wave growth: • Wind speed • Fetch length • Duration Wave growth is limited by either fetch length or duration 6 Fully Developed Sea • When wave growth has reached a maximum height for a given wind speed, fetch and duration of wind. • A sea for which the input of energy to the waves from the local wind is in balance with the transfer of energy among the different wave components, and with the dissipation of energy by wave breaking - AMS. 7 Fetches 8 Dynamic Fetch 9 Wave Growth Nomogram 10 Calculate Wave H and T • What can we determine for wave characteristics from the following scenario? • 40 kt wind blows for 24 hours across a 150 nm fetch area? • Using the wave nomogram – start on left vertical axis at 40 kt • Move forward in time to the right until you reach either 24 hours or 150 nm of fetch • What is limiting factor? Fetch length or time? • Nomogram yields 18.7 ft @ 9.6 sec 11 Wave Growth Nomogram 12 Wave Dimensions • C=Wave Celerity • L=Wave Length •
    [Show full text]
  • Waves and Structures
    WAVES AND STRUCTURES By Dr M C Deo Professor of Civil Engineering Indian Institute of Technology Bombay Powai, Mumbai 400 076 Contact: [email protected]; (+91) 22 2572 2377 (Please refer as follows, if you use any part of this book: Deo M C (2013): Waves and Structures, http://www.civil.iitb.ac.in/~mcdeo/waves.html) (Suggestions to improve/modify contents are welcome) 1 Content Chapter 1: Introduction 4 Chapter 2: Wave Theories 18 Chapter 3: Random Waves 47 Chapter 4: Wave Propagation 80 Chapter 5: Numerical Modeling of Waves 110 Chapter 6: Design Water Depth 115 Chapter 7: Wave Forces on Shore-Based Structures 132 Chapter 8: Wave Force On Small Diameter Members 150 Chapter 9: Maximum Wave Force on the Entire Structure 173 Chapter 10: Wave Forces on Large Diameter Members 187 Chapter 11: Spectral and Statistical Analysis of Wave Forces 209 Chapter 12: Wave Run Up 221 Chapter 13: Pipeline Hydrodynamics 234 Chapter 14: Statics of Floating Bodies 241 Chapter 15: Vibrations 268 Chapter 16: Motions of Freely Floating Bodies 283 Chapter 17: Motion Response of Compliant Structures 315 2 Notations 338 References 342 3 CHAPTER 1 INTRODUCTION 1.1 Introduction The knowledge of magnitude and behavior of ocean waves at site is an essential prerequisite for almost all activities in the ocean including planning, design, construction and operation related to harbor, coastal and structures. The waves of major concern to a harbor engineer are generated by the action of wind. The wind creates a disturbance in the sea which is restored to its calm equilibrium position by the action of gravity and hence resulting waves are called wind generated gravity waves.
    [Show full text]
  • Air-Sea Interaction and Surface Waves
    712 Air-Sea Interaction and Surface Waves Peter A.E.M. Janssen, Øyvind Breivik, Kristian Mogensen, Frédéric Vitart, Magdalena Balmaseda, Jean-Raymond Bidlot, Sarah Keeley, Martin Leutbecher, Linus Magnusson, and Franco Molteni. Research Department November 2013 Series: ECMWF Technical Memoranda A full list of ECMWF Publications can be found on our web site under: http://www.ecmwf.int/publications/ Contact: [email protected] ©Copyright 2013 European Centre for Medium-Range Weather Forecasts Shinfield Park, Reading, RG2 9AX, England Literary and scientific copyrights belong to ECMWF and are reserved in all countries. This publication is not to be reprinted or translated in whole or in part without the written permission of the Director- General. Appropriate non-commercial use will normally be granted under the condition that reference is made to ECMWF. The information within this publication is given in good faith and considered to be true, but ECMWF accepts no liability for error, omission and for loss or damage arising from its use. Air-Sea Interaction and Surface Waves 1 Introduction Presently we are developing a coupled earth system model that allows for efficient, sequential interaction of the ocean/sea-ice, atmosphere and ocean waves components, and, therefore it becomes feasible to introduce sea state effects on the upper ocean mixing and dynamics (Mogensen et al., 2012). By the end of 2013, a first version of this system will be introduced in operations in the medium-range/monthly ensemble forecasting system. The main purpose of this operational change is that coupling between atmosphere and ocean is switched on from initial time, rather than from day 9-10 in the forecast.
    [Show full text]
  • 6 Water Waves 35 6 Water Waves
    6 WATER WAVES 35 6 WATER WAVES Surface waves in water are a superb example of a stationary and ergodic random process. The model of waves as a nearly linear superposition of harmonic components, at random phase, is confirmed by measurements at sea, as well as by the linear theory of waves, the subject of this section. We will skip some elements of fluid mechanics where appropriate, and move quickly to the cases of two-dimensional, inviscid and irrotational flow. These are the major assumptions that enable the linear wave model. 6.1 Constitutive and Governing Relations First, we know that near the sea surface, water can be considered as incompressible, and that the density ½ is nearly uniform. In this case, a simple form of conservation of mass will hold: @u @v @w + + = 0; @x @y @z where the Cartesian space is [x; y; z], with respective particle velocity vectors [u; v; w]. In words, the above equation says that net flow into a differential volume has to equal net flow out of it. Considering a box of dimensions [±x; ±y; ±z], we see that any ±u across the x-dimension, has to be accounted for by ±v and ±w: ±u±y±z + ±v±x±z + ±w±x±y = 0: w + Gw v + Gv Gy z y Gx u u + Gu x Gz v w Next, we invoke Newton’s law, in the three directions: " # " # @u @u @u @u @p @2u @2u @2u ½ + u + v + w = ¡ + ¹ + + ; @t @x @y @z @x @x2 @y2 @z2 " # " # @v @v @v @v @p @2v @2v @2v ½ + v + w + u = ¡ + ¹ + + ; @t @x @y @z @y @x2 @y2 @z2 " # " # @w @w @w @w @p @2w @2w @2w ½ + w + u + v = ¡ + ¹ + + ¡ ½g: @t @x @y @z @z @x2 @y2 @z2 6 WATER WAVES 36 Here the left-hand side of each equation is the acceleration of the fluid particle, as it moves @u through the differential volume.
    [Show full text]
  • Realistic Simulation of Ocean Surface Using Wave Spectra Jocelyn Fréchot
    Realistic simulation of ocean surface using wave spectra Jocelyn Fréchot To cite this version: Jocelyn Fréchot. Realistic simulation of ocean surface using wave spectra. Proceedings of the First International Conference on Computer Graphics Theory and Applications (GRAPP 2006), 2006, Por- tugal. pp.76–83. hal-00307938 HAL Id: hal-00307938 https://hal.archives-ouvertes.fr/hal-00307938 Submitted on 29 Jul 2008 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. REALISTIC SIMULATION OF OCEAN SURFACE USING WAVE SPECTRA Jocelyn Frechot´ LaBRI - Laboratoire bordelais de recherche en informatique Domaine universitaire, 351 cours de la Liber´ ation, 33405 Talence CEDEX, France [email protected] Keywords: Natural phenomena, realistic ocean waves, procedural animation, parametric energy spectra Abstract: We present a method to simulate ocean surfaces away from the coast, with correct statistical wave height and direction distributions. By using classical oceanographic parametric wave spectra, our results fit real world measurements, without depending on them. Since wave spectra are independent of the ocean model, Gerstner parametric equations and Fourier transform method can be used with them. Moreover, since they are simple to use and need very few parameters, they allow easy production of ocean surface animations usable in movies and games.
    [Show full text]
  • Swell and Wave Forecasting
    Lecture 24 Part II Swell and Wave Forecasting 29 Swell and Wave Forecasting • Motivation • Terminology • Wave Formation • Wave Decay • Wave Refraction • Shoaling • Rouge Waves 30 Motivation • In Hawaii, surf is the number one weather-related killer. More lives are lost to surf-related accidents every year in Hawaii than another weather event. • Between 1993 to 1997, 238 ocean drownings occurred and 473 people were hospitalized for ocean-related spine injuries, with 77 directly caused by breaking waves. 31 Going for an Unintended Swim? Lulls: Between sets, lulls in the waves can draw inexperienced people to their deaths. 32 Motivation Surf is the number one weather-related killer in Hawaii. 33 Motivation - Marine Safety Surf's up! Heavy surf on the Columbia River bar tests a Coast Guard vessel approaching the mouth of the Columbia River. 34 Sharks Cove Oahu 35 Giant Waves Peggotty Beach, Massachusetts February 9, 1978 36 Categories of Waves at Sea Wave Type: Restoring Force: Capillary waves Surface Tension Wavelets Surface Tension & Gravity Chop Gravity Swell Gravity Tides Gravity and Earth’s rotation 37 Ocean Waves Terminology Wavelength - L - the horizontal distance from crest to crest. Wave height - the vertical distance from crest to trough. Wave period - the time between one crest and the next crest. Wave frequency - the number of crests passing by a certain point in a certain amount of time. Wave speed - the rate of movement of the wave form. C = L/T 38 Wave Spectra Wave spectra as a function of wave period 39 Open Ocean – Deep Water Waves • Orbits largest at sea sfc.
    [Show full text]
  • Statistics of Extreme Waves in Coastal Waters: Large Scale Experiments and Advanced Numerical Simulations
    fluids Article Statistics of Extreme Waves in Coastal Waters: Large Scale Experiments and Advanced Numerical Simulations Jie Zhang 1,2, Michel Benoit 1,2,* , Olivier Kimmoun 1,2, Amin Chabchoub 3,4 and Hung-Chu Hsu 5 1 École Centrale Marseille, 13013 Marseille, France; [email protected] (J.Z.); [email protected] (O.K.) 2 Aix Marseille Univ, CNRS, Centrale Marseille, IRPHE UMR 7342, 13013 Marseille, France 3 Centre for Wind, Waves and Water, School of Civil Engineering, The University of Sydney, Sydney, NSW 2006, Australia; [email protected] 4 Marine Studies Institute, The University of Sydney, Sydney, NSW 2006, Australia 5 Department of Marine Environment and Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan; [email protected] * Correspondence: [email protected] Received: 7 February 2019; Accepted: 20 May 2019; Published: 29 May 2019 Abstract: The formation mechanism of extreme waves in the coastal areas is still an open contemporary problem in fluid mechanics and ocean engineering. Previous studies have shown that the transition of water depth from a deeper to a shallower zone increases the occurrence probability of large waves. Indeed, more efforts are required to improve the understanding of extreme wave statistics variations in such conditions. To achieve this goal, large scale experiments of unidirectional irregular waves propagating over a variable bottom profile considering different transition water depths were performed. The validation of two highly nonlinear numerical models was performed for one representative case. The collected data were examined and interpreted by using spectral or bispectral analysis as well as statistical analysis.
    [Show full text]
  • Comparison of Various Spectral Models for the Prediction of the 100-Year Design Wave Height
    MATEC Web of Conferences 203, 01020 (2018) https://doi.org/10.1051/matecconf/201820301020 ICCOEE 2018 Comparison of Various Spectral Models for the Prediction of the 100-Year Design Wave Height Sayyid Zainal Abidin Syed Ahmad1, 2,*, Mohd Khairi Abu Husain1, Noor Irza Mohd Zaki1, Mohd Hairil Mohd2 and Gholamhossein Najafian3 1Universiti Teknologi Malaysia, 54100 Kuala Lumpur, Malaysia 2Universiti Malaysia Terengganu, 21030 Kuala Nerus, Malaysia 3School of Engineering, Universiti of Liverpool, Liverpool, United Kingdom Abstract. Offshore structures are exposed to random wave loading in the ocean environment, and hence the probability distribution of the extreme values of their response to wave loading is required for their safe and economical design. In most cases, the dominant load on offshore structures is due to wind-generated random waves where the ocean surface elevation is defined using appropriate ocean wave energy spectra. Several spectral models have been proposed to describe a particular sea state that is used in the design of offshore structures. These models are derived from analysis of observed ocean waves and are thus empirical in nature. The spectral models popular in the offshore industry include Pierson-Moskowitz spectrum and JONSWAP spectrum. While the offshore industry recognizes that different methods of simulating ocean surface elevation lead to different estimation of design wave height, no systematic investigation has been conducted. Hence, the aim of this study is to investigate the effects of predicting the 100-year responses from various wave spectrum models. In this paper, the Monte Carlo time simulation (MCTS) procedure has been used to compare the magnitude of the 100-year extreme responses derived from different spectral models.
    [Show full text]