| An IW is a wave inside an ocean where water bodies exist when they are made up of layersiof differentidensitiesi.The difference in salinity is one of the key reasons of the difference in water temperature.The Internal Waves(IWs)are located on the interface of two different density media.The IWs are also known as gravity waves because these are mainly caused due to the influence of gravity.These waves occur when the interface is disturbed,and disturbances are usually produced by tidal currents pushing layered bodies of water through shallow water barriers,such as on shallow ridges.Nonlinear Internal Solitary Waves(Solitons)are feasibly dangerous to underwater submarine activities,maritime operations,offshore structures,oil and gasipipelines,and jacket platforms.The highly effective mechanism for Internal Solitary Waves(ISWs)generationiis the tidal energy transfer from barotropicito baroclinicion enormous seafloor barriers(continental shelf fractures,canyons,seamounts,and crests).There are several ways to recognize Internal Solitary Waves(ISWs),but each one has advantages and disadvantages of its own.At frequent intervals,Earth observation systems keep a watch on and monitor internal ocean waves.However,the systematic recognition of ISWs remains a difficult task.The main research contents are as follows:Chapter 2,in this chapter of this study,an approach for ISWs recognition is proposed in its entirety.The three basic phases of the approach are input data preprocessing,parameter extraction,and modelling.In order to pre-process for noise,the suggested system will first capture synthetic aperture radar(SAR)pictures.Cloud-related occlusion is solved through augmentation methods like flip and rotation.The segmentationiand featureiextraction of wave characteristics including,amplitude,frequencyi,longitudei,and latitudeiare done by U-Net.Lastly,the Kd V solver is applied to modelling internal ocean waves.ISWs velocity and density graphs are produced using the Kd V solver,which also accepts input for internal wave parameters.On SAR imagery,the machine learning model was evaluated,and it was shown to provide reliable outcomes for ISWs recognition.Chapter 3,ISWs are produced through semi-daily barotropic tidal currents that influence undersea ridges offshore westside Pulau.The southern Andaman seawaters are one of the most substantial areas where they are generated and propagated.This research aims to examine ocean surface characteristicsiof internalitidesiand tidalicurrentsiin the vicinity of the undersea ridge and the nearby Pulau waters using satellite imaging datasets(February to April 2019)and coastal regional ocean circulation modelling model output datasets.The results demonstrate that the internal solitary wave ocean surface characteristics are identified by backscattering of strong radar signals of the two groups of internal solitary wave arches in the dense beam and propagation zone,in which the distance and wavelength of the package group vary by 70-90 km and 8-158 km,respectively.There were 29 Internal Solitary Waves seen in April 2020.The satellite and model datasets imply that the near Pulau ridge is the only place internal waves are generated.The 0.4–6.0 m/s extremely strong semidiurnal barotropic tidal currents are shown here.The Pulau channel is partially entered at high tide by increased barotropic tidal currents traversing the ridge.The model predicts that considerable vertical disturbance of isopycnal and current stratification in the LW region manifests internal tidal wave generation over the ridge.The outcomes of this analysis should reveal how often internal waves occur and their characteristics,including their frequency,wavelength,and current speed,as well as the locations where they occur.This data may be utilized to design offshore infrastructure like petroleum refining,floating aquaculture net cages,and shore areas with extreme resource extraction.Chapter 4,in this chapter presented the design criteria,and risk evaluation for marine structures,over continental shelf and slope that might be affected by currents associated with internal waves.The derivation of design criteria requires long time series of currents at very high sampling rates commonly not available.Therefore,methodologies to derive those time series are required.In this research study,an approach based on numerical modelling is proposed as a proof-of-concept.The Sulu Sea was selected to test the capability of the model to simulate those currents.Model results were compared to data available in the literature.The currents and other properties such as travelling time,wavelength,period,and number of waves per packet are within the range of observations.The major goal of this work was:(i)to prove the ability of a 2D-V non-hydrostatic model to simulate the generation and propagation of solitons and(ii)to investigate the feasibility to generate long time series suitable to deduce relevant statistics and design criteria and ultimately to evaluate the risks posed by such events to marine structures including submarine pipelines.Regarding the second item,the model that was implemented to simulate the generation and propagation of ISW in the Sulu Sea takes about 14 wall clock hours per simulated month using 36 2.9 GHz Intel Xeon E5-2666 v3 processors,which means about 70 days of CPU time to compute a 10-year hindcast that should be enough for the purpose of generating criteria and relevant statistics.These times can be significantly reduced at a certain cost by using either more processors or faster processors.However,this is already a reasonable timescale for a desktop study and therefore it can be concluded that from the computational point of view,this goal is achievable.Chapter 5,in this thesis chapter,a numerical model in slice configuration was applied to the Central Andaman Sea to derive metocean operational and design criteria associated with internal solitary waves.The model was based on a 10-year hindcast,driven by tides at the open boundary,and included realistic stratification and topography.The accuracy of the results was confirmed through comparison with data mostly taken from satellites,particularly in terms of parameters such as phase speed and interpacket distance.The phase speeds ranged from 2.21 m/s in March to 2.5 m/s in November,with corresponding interpacket distances ranging from 99 km to 111 km.The model results indicated that internal solitary waves were more/less frequent in March/August.The maximum current speeds obtained with the model at two arbitrary locations occur in November,reaching a value close to 1.5 m/s.Additionally,the computed velocities associated with return periods of 1,10,50,100,and 1000 years were 1.67 m/s,1.76 m/s,1.8 m/s,1.81 m/s,and 1.84 m/s,respectively. |
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