Proceedings of the Fifth International Conference in Ocean Engineering (ICOE2019)

The design of breakwater in deep water involves consideration of all the aspects of structural stability, economic viability and the construction feasibility. The main objective of this study was to assess the hydraulic stability of the breakwater against design and overload waves and assess the toe stability for possible low water levels using 2D (Flume) physical model study. The breakwater is located at −18.0 m chart datum (CD) and crest and the toe is at +7.6 m CD and −7.0 m CD respectively. The breakwater was hydraulically stable for the series of waves applied for the structure including overload waves while showing negligible damage to the 2–4 T toe for low water levels (+0.11 m CD and −1.39 m CD). The simulation of different toe elevations with low water levels is shown in Fig. 10.

The various geo-synthetic components such as geo-tubes, geo-bags, geo-mattresses, geo-containers, geo-grids, geo-cells find extensive applications in coastal engineering practice. It is more sought after due to the ease of construction, quick implementation and reduced cost as the supply of natural rocks is eluded. Innovative geo-synthetic materials of numerous units were compounded to form a sea wall cross section, to be constructed at Pallana coast (9° 17′ 55.19″ N and 76° 23′ 18.55″) of Allepey, Kerala, to prevent wave run up during high tide level. The Pallana beach is also characterized with poor soil subgrade properties and hence the proposal to construct a geo-synthetic seawall in contrast to the conventional measures. The cross section is designed to ensure stability against overturning, sliding, overtopping and scour protection. The major concerns such as UV radiation, stability against wave action, settlement of the structure and protection against scour are to be addressed prior to the implementation of the design on site. The objective of the paper is to arrive at the significant geo-technical parameters responsible for the geo-technical stability of the structure over time. The pore-water pressures beneath the structure, rapid drawdown, transient stability and sensitivity analysis are computed for the above said structure using GeoStudio software application, which employs finite element method. A visualization of the geo-technical performance can be arrived that aids to verify the design parameters adopted.

Gabion-based coastal structures are being adopted frequently in recent times due to its energy dissipation characteristics and reduction in construction time. The coastal defense has become an essential aspect for maritime facilities and for the places prone to erosion. Reef breakwaters (also called Low crested structures) are seen to cause less environmental impact which makes them popular in recent past. The present investigation involves the study of hydrodynamic stability aspects of gabion-based reef breakwaters. Though these coastal protection structures are meant for wave attenuation, a study on the stability aspects of the structure to resist wave action is essential. This knowledge on the hydrodynamic stability is essential to come out with the design basis for construction of such coastal structures in a wave environment. This investigation on gabion-based reef breakwaters is performed using physical model tests with varying wave parameters and reef geometries. The study is aimed at fetching knowledge on the determination the weight of the gabions to resist the wave action by obtaining a relation between the weight of the gabion, geometrical parameters and to that of the wave parameters. This determination of the weight of the gabions to resist wave action is essential if gabion-based structures are deployed as low crested coastal structures or reef breakwaters. This paper is based on the experimental study conducted in the shallow water wave flume facility in the Department of Ocean Engineering, IIT Madras.

This paper reviews the salient features about development of port infrastructure at VOC Port, either modernising inner harbour or development of outer harbour. In order to increase the current cargo handling capacity from 64 Million Tonnes to 125 Million Tonnes, two alternatives are considered: Alternative I—Deepening of inner harbour basin up to (−)16.50 m CD and strengthening of existing berths for handling 6th generation Container vessels of 8000–12,500 TEU capacity and Post Panamax 95,000 DWT carriers and tankers having maximum draft of 15.20 m. Alternative II—Deepening and development of outer harbour with extension of Northern Break water and Southern Break Water, and Construction of new berths inside Break waters. The implementation of Alternative I and Alternative II will take 5 years and 10 years respectively. For prompt development, Alternative I is found to be most feasible. The total capital cost arrived for implementation of Alternative I is found to be 20% cheaper than Alternative II. The dredging quantity is more for Alternative I, but the dredge materials are utilised for reclamation. The schemes for upgradation/retrofitting of existing berths for deeper draft without affecting the cargo handling are also discussed.

Offshore structures are subjected to nonlinear and irregular wave forces. These structures try to attain their stability in the neighbourhood of their designed equilibrium point through their responses. The excitation forces consist of harmonic inertial wave components and drag dominated forces which changes according to water plane area. Being a multi-degree of freedom system, coupling among these degrees of freedom poses difficulties in obtaining the response. Therefore, these nonlinear structures require investigation in a stochastic framework for understanding their behaviour (sub-harmonic motions, chaotic responses). This paper models the slow drift motion of tension leg platform using a nonlinear stochastic differential equation. These stochastic differential equations are attempted using stochastic methods such as higher order Milstein scheme in an Ito framework. The impact of varying uncertainty on the nonlinear dynamics of system is studied

Most of the fishing harbors along the Indian coast are located within the tidal inlets, barring a few on the open coast. Fishing harbor on an open coast needs protection in the form of breakwaters or training walls for providing tranquility conditions and safe vessel maneuvering and landing facilities. Practically, all inland fishing harbors suffer siltation problems. The studies on the development of a new inland fishing harbor on River Chapora (15° 36′4 6.22″ N and 73° 44′ 51.34″ E) in the state of Goa in India with such problem were carried out, the results of which are reported in this paper.

There is an increasing risk of dike failures along the coasts worldwide due to increase in relative MSL (Mean Sea Level) rise and increase in storm intensity. Wave run-up plays a key role in planning and design of coastal structures. Numerous research works were carried out on wave run-up and wave overtopping in the last few decades. However, limited information is available on the effect of the curvature in coastal dikes on wave run-up and overtopping. This research focuses on influence of curved dikes on wave run-up using numerical models. The numerical models used for this research are DualSPHysics and OpenFOAM. Analysis covers both wave run-up estimation and the underlying wave transformation processes at the curvature. The numerical analysis results show a complex behavior in wave transformation processes for curved dikes. Hence, this research aims to contribute a more precise analysis and understanding the influence of the curvature in the dike line and thus ensuring a higher level of protection in the future development of coastal structures.

The aim of the collaborative project PADO (“Processes and implication of dune breaching at the German Baltic Sea Coast”) is the investigation of dune breaching and the resulting flooding of the hinterland based on a large-scale research dune. During the physical model test, which was located at the beach of Rostock-Warnemuende, the dune was destroyed by a storm surge in November 2018. The measured data served as basis for the set-up of a numerical coastal erosion model with XBeach. The application of the latest XBeach-X release with the default settings results in an underestimation of the mean wave height at the model entrance. Moving closer to the shore, the underestimation decreases leading to a good agreement with observed wave heights in the nearshore zone, especially after the first third of the simulation. Furthermore, the model computes dune erosion due to collision and overwash which is in line with the observation. The predicted final dune erosion is in good agreement with the post-storm measurements of the dune topography and, hence, only minor calibration is needed.

Climate change is becoming a prevailing issue for the many countries around the world. The Republic of Mauritius being part of the Small Island Developing states has a higher probability of encountering larger damages from gradual sea level rise and more intense storms. The purpose of this study was to provide a solution to enhance the protection of the coast line of a specific region on the island, namely, “La Prairie” from wave attacks during severe climatic events. It has been observed that the existing structure is not working as it should be and during the wave attacks that part of the island is not accessible. A design assessment of the existing hard structure was carried out followed by the design of an emergent breakwater as an alternate structure. This structure was then modeled using MATLAB software and a comparison of armor porosity and structure height was done to get a more cost-efficient structure for construction. This paper also contains a cost estimate and a detailed section of the proposed structure. With the application of the proposed solution this specific part of the island would then be protected from wave attacks and hence accessible to the public.

Articulated Leg Platform (ALP) is a compliant offshore structure. The static and dynamic stability of ALP depends on buoyancy force, mainly generated by buoyancy chamber. It is highly flexible in surge and sway direction. Due to high flexibility in these degrees of freedom, sometime response exceeds working comfort. Depending on nature of excitation, it can create unfavorable working condition on the platform too. Response control device can help to reduce the response of platform and can create favorable working conditions. ALP is mathematically modeled as an inverted pendulum. Excitation force on ALP is generated due to fluid structure interaction due to random waves. Generally, structure dimensions are such that Morisons equation is valid for obtaining the excitation forces. Probabilistic approach, which can handle non linearity, is suited to obtain response of such a problem. Stochastic averaging technique along with Fokker Planck equation is one such technique which can handle ALP problem easily, subjected to normalized forces which are small enough to minimize the error. An optimal feedback control along with stochastic averaging technique for ALP is developed, in order to control the response of ALP under wave loads.

Floating Production Storage and Off-loading (FPSO) systems are being utilized world widely by offshore industries. The surge response of FPSO subjected to severe sea states needs to be suppressed in order to keep a particular station for operational purposes. The oil cargo tanks of FPSO can be used as passive dampers for minimizing the surge displacement response of FPSO. These cargo tanks can act as Tuned Liquid Dampers (TLDs) if the natural frequency of the liquid oscillation in containers is tuned to the surge natural frequency of FPSO or tuned to the excitation frequency. The containers can be partitioned into several tanks (as Multiple Tuned Liquid Dampers, MTLDs) with different lengths and liquid depths. The natural frequencies of MTLDs can also be distributed over a range around the natural frequency of FPSO. The present study attempts to comprehend the response control of FPSO under surge motion and so the FPSO is modeled as a single degree of freedom under random sea state. The containers can be modeled as either linear TLDs or nonlinear TLDs. Each linear TLD can be modeled by an equivalent Tuned Mass Damper (TMD) analogy based on linear wave theory. In order to account the nonlinear liquid motion in TLD, an impact damper analogy is used along with the TMD analogy. The study includes the efficiency and robustness of MTLD and it compares the response control obtained by using linear MTLDs and nonlinear MTLDs.

Offshore water depths varying from 30 to 50 m have a tremendous potential to harvest wind energy ≥6 MW. The roughness of the sea makes it very difficult for the installation of substructures from small tripod or jacket structures to floating substructures. More generic, we have to wait for calm sea period in the offshore for the installation of any such structures. It has created a need for research in investigating installation of structures in all-weather condition. Hence in order to increase the potential of installation of offshore structure, understanding the structural behavior during installation is vital. For understanding aforementioned structural behavior in installation, jacket structure which is very common fixed substructure is chosen and studied for all type of waves. In order to study such substructure, heaviest jacket for the given aspect ratio (HyConCast) is chosen. The concept of HyConCast jacket has advantages of combined ductile iron casting knots and precast concrete pipes which is the reason for the heavy mass of the structure. Because of its high mass compared to other offshore structures, its dynamic and excitation responses in regular waves during installation are unknown. In this chapter, the results from experimental study on response of the jacket model for different upending stages under regular waves are discussed.

The marine outfall system is used for disposal of effluent into the ocean. There is a strong belief that the ocean is an ultimate sink for the disposal of wastewater making sure that the disposed of effluent is within the standard disposal limits. For the large-quantity effluent discharge, multiport diffuser type marine outfall system is effective. The multiport diffuser is a series of main outfall pipe connected to the diffuser system with multiple nozzle ports connected in parallel to each other with an optimum spacing. In this study, the performance of the single round nozzle for buoyant fluids at a stable water condition in the unstratified water depth is carried out. The same is carried out for the multiple port round nozzle by varying the spacing distance between the consecutive ports. The numerical simulation for the single round nozzle for varying port outlet velocities is carried out achieving acceptable densimetric Froude number enhancing the performance of the round nozzle’s diffusion rate for the positively buoyant, neutrally buoyant and negatively buoyant effluent, and its respective plume characteristics are studied.

Steel liners are used in the construction of bored cast in situ RCC piles especially in water borne transport infrastructure. Embedment length of the liner is the length between dredge level/bed levels to the termination level of the liner. Sufficient embedment length for steel liner ensures the quality of the pile. The minimum embedment depth of liner is calculated as per IS 2911 using the same procedure as given for piles. A parametric study is carried out to develop design charts for embedment length of liner for different water depths in sand, clay and rock and the details are given in this paper. The comparison between twice the fixity depth and embedment depth is also given.

Formation of shoals in an estuarine environment creates significant problems such as reduction in depth in navigational channels, decreased discharges and degradation of water quality. One of the widely used solutions to reduce sedimentation is the implementation of a sediment trap by creating a trench or a pit in the submerged bottom at specific locations. A sediment trap is defined as a section of the estuarine bed deepened to a depth greater than its surroundings. The lower velocity allows sediments to deposit in the trap rather than move past over it. Implementation of a silt trap at specific locations in a highly dynamic domain like Hooghly estuary helps to optimize the dredge quantity or the maintenance dredging can be localized to a specific location (the trap) rather over a wide submerged area. This study involves optimization of the location and shape of a silt trap near the Haldi-Hooghly confluence point, West Bengal, India. The trap was designed to reduce the dredging quantity in the downstream Jellingham channel which is a part of the navigational channel en route to Haldia Dock Complex in the Hooghly estuary. Based on a comprehensive numerical study, an option of irregular polygon shaped silt trap of a surface area of 250,000 m2 positioned in such a way to trap the sediments from both the Hooghly and the Haldi rivers near the Haldia anchorage was finalized which was found to perform efficiently in reducing the dredge quantity in the Jellingham channel. The details of the study are reported in this paper.

Due to climate change, the semi-arid region received rainfall of 1 in 100 year return period which causes a flood in the region. In the present study, analysis of July 2017 flood of the semi-arid region of Banas River basin caused due to heavy rainfall has been carried out. The Dantiwada and Sipu dams on Banas River and tributary of Banas River received heavy inflows during this period. This resulted in short duration huge releases from the dams. These releases were more than carrying capacity of the river which resulted in flooding of adjoining areas. 226 numbers of villages including two major districts were inundated. 224 people lost their lives, and around 34,000 people have been evacuated. Total damages worth of Rs. 1653 crore (16.53 billion Rs.) has been reported. In the present study, reasons for flooding, damage assessment, and measures to check flooding using 1D hydrodynamic modeling have been presented. MIKE Hydro River has been used for the computation of water surface elevation along 123 km river reach. The 1D hydrodynamic model developed from cross-sections extracted from the DEM. The outcome of the present study recommends careful operation of Dantiwada and Sipu dams as well as the relocation of people living in the floodplain areas of Banas River.

Ambica is one of the major rivers in the Indian state of Gujarat. The river originates from Saputara Hill ranges in the Nasik district of Maharashtra. Ambica has a drainage area of about 2715 km2, and it travels 136 km before joining with the Arabian Sea. The objective of the study is to understand the hydrodynamics of the tidally influenced river Ambica and to assess the effect of the proposed tidal barrage on the salinity intrusion characteristics. A two-dimensional depth-averaged hydrodynamic model has been developed, using Delft3D modeling scheme, to fulfill the objectives. The open ocean boundary of the numerical model is forced with tidal constituents and the upstream boundary of the river forced with discharge. The numerical model has been simulated for two different cases: (i) with and (ii) without the proposed tidal barrage. Results of the numerical model show the inundation and saline water ingression characteristics along river stretch for various discharge conditions.

A new semi-analytical solution to the one-line model is presented in this work which can be used for the description of complicated coastal systems. An application of the semi-analytical model to Borth case study in Wales, UK, is presented. Additionally, Calangute beach in Goa, India, will be discussed as a future case study where the model will be applied.

The west coast of India from Kanyakumari (Cape Comorin) to Trivandrum bordering Arabian sea is a thickly populated one. Fishing is the main occupation of the hamlets. The coast is prone to southwest (June–September) and northeast monsoon (October–December) waves in every year. The southwest monsoon is severe along the coast creating heavy erosion resulting loss of valuable lands, roads, worship places and houses. Mandaikadu is one such affected coast located on the west coast of Indian Ocean. Studies in the form of field observations, bathymetry and numerical model studies were carried out. Based on the findings, groin field with six numbers were proposed, and field observations indicate littoral drift is directed towards west direction. The details of studies and effect of groins were highlighted in the paper.

Risers are vertical offshore circular conduits that connects the reservoir beneath the water surface to a fixed or floating platform at the water surface, when the riser are subjected to sea currents the flow started to separate from its outer surface and vortices are formed in the downstream leads to vortex shedding. So there is need to spoil vortex shedding and suppress Vortex-induced vibration (VIV) to prevent damage on structures and on the other hand there is equal chance for utilization of energy as sustainable source from the ocean currents. The present numerical study is the done on larger diameter circular conduits which is used to draw cold water from deeper water depths for floating barge desalination plant deployed by National Institute of Ocean Technology (NIOT) would be susceptible to vortex-induced vibrations. Two such conduits held together in tandem arrangement using spacer is studied extensively for higher Re of O (106) in this work. The aspect ratio (L∕D) of the cylinder is an important parameter to be considered. In this study modeling of cylinder for aspect ratio of 9 is chosen to capture the 3D effect along the length of the cylinder. The present work is focused on studying flow behavior around the conduits and its vortex shedding using commercial CFD software STAR-CCM+. The numerical simulation was carried out at Re of O (106) for tandem arrangement of 2D center to center spacing of Re ranging from 0.8 × 106 to 3.2 × 106. In this orientation the effect of lift, drag and pressure variation along the length and also on circumference of conduits was analyzed and it is correlated with the various flow velocities of circular conduits.

Offshore wind turbine (OWT) substructures are exposed to extreme waves under severe environmental conditions especially in intermediate and shallow waters. These extreme waves are highly nonlinear, which cause high intensity short duration impact forces on OWTs. The main objective of the study is to investigate numerically and experimentally wave impact forces on a vertical slender cylinder which resembles a monopile substructure for offshore wind turbines subjected to focused breaking waves in intermediate water depth. Both laboratory measurements and numerical simulations are performed in order to obtain more insights into the breaking wave impact problem. The total response forces on a monopile substructure were measured at higher resolution in a well-controlled programmable wave flume. In addition, acceleration of the monopile, the wave surface elevations around the breaking region were measured for different intensities of breaking wave impacts. Further, the evolution of focused breaking waves along the tank and their characteristics were examined. Numerical experiments are carried out in a computational fluid dynamics based three-dimensional numerical wave tank, REEF3D. The model is based on the incompressible Reynolds-averaged Navier–Stokes equations together with the k  − ω for turbulence and the level set method for free surface. The experimentally measured main wave crest of the breaking focused wave group is fairly well captured in the numerical simulation.

Harmful algal bloom (HAB) events can have severe consequences such as mass fish kills and problems to public health. The Albion Fisheries Research Centre has an ongoing HAB monitoring programme at established coastal sites in Mauritius including Grand Baie, Albion, Le Morne and Blue Bay. The commonly observed benthic dinoflagellates are from the genera Amphidinium sp., Coolia sp., Gambierdiscus sp., Ostreopsis sp., Prorocentrum sp. and Synophysis sp. These are the causative agents of fish toxicity such as ciguatera. The monitoring data at the four monitoring sites for the period 2013–2017 were analysed to evaluate the temporal, spatial and seasonal variations in the densities of harmful marine microalgae species. Recurrent high densities were recorded at all the sites during the years. The genera Prorocentrum and Ostreopsis were observed at relatively higher densities throughout the years at the four study sites whilst the other genera occurred only occasionally. An increase in the mean cell densities of Ostreopsis sp. and Prorocentrum sp. were observed from 2013 to 2016 followed by a decline in the abundance in 2017 at most of the study sites. The cell densities of these two genera were found to be higher during summer seasons, and their occurrences were more significant at two sites, namely Blue Bay and Le Morne which are located in the South Coast of the Island. This warrants further studies to determine the influence of oceanographic parameters, seawater quality and environmental conditions on the cell densities of harmful marine microalgae in Mauritius.

The Gulf of Khambhat is an inverted funnel-shaped indentation on the Arabian Sea of India. The maximum water depth of Gulf of Khambhat region is 35 m. Tidal range is high with semi-diurnal type. The current is very strong with magnitude of 2.5 m/s which occurs during mid-tide. Gulf of Khambhat (21° 03′ 41.49″ N, 72° 25′ 18.26″ E) receives enormous sediment from the discharge of three major rivers: Narmada, Tapti, and Sabarmati. The shoal movement as well as shoal enhancement has been observed in this region. At certain locations, the depth of water is reduced from 20 to 2 m in ten years. The dredging at an area of about 300 by 300 m from −2 to −20 m and disposal in deep contour is proposed, and the siltation rate in the dredge area and disposal area is studied. MIKE 21 HD flow module is used for tidal propagation, and for the siltation analysis, MIKE 21/3 integrated module is used. Desk studies are done analyzing satellite imageries. The results of analyses indicate that the sediment flow at dredge location is dominated by tidal current and the river flow is having no significance at the site which is located 24 km from confluence point. It can be observed that the bed level accretion works out to 180 cm per year. The disposal location was also identified where the siltation rate is assessed as 7 cm per year. The details of studies are furnished in the paper.

It is increasingly recognized in the recent past that reinforced concrete (RC) berthing structures are not permanently durable and free from maintenance. A large number of cases of damage and failure in RC berthing structures have been reported worldwide, and rehabilitation of such structures involves phenomenal cost, besides challenging technical problems in identifying appropriate rehabilitation techniques and materials. In order to arrive at a suitable rehabilitation strategy, non-destructive tests (NDT) are carried out to assess the condition of concrete in the distressed RC structural elements. Health monitoring of berthing structures through in situ testing is a specialized job requiring reliable test methods and instruments. The paper discusses in detail the rehabilitation of berthing structures at Cochin, Tuticorin and Chennai Port Trusts. In the case of the Cochin Port Trust, distressed RC structural elements of the North Tanker Berth (NTB) jetties and South Tanker Berth (NTB) jetties exhibited half-cell potentials more than −350 mV indicating that there is a greater than 90% probability that reinforcing steel corrosion is occurring in that area at the time of measurement as per the reference guidelines of ASTM C-876. Based on the analysis of the various NDT tests, viz. ultrasonic pulse velocity (UPV) test, core drilling and carbonation tests and the evaluation of chlorides and pH, a detailed rehabilitation methodology including under water micro-concrete jacketing has been suggested for the distressed RC structural elements of the central platform, Breasting dolphin and the approach trestle of both the jetties. coal jetties 1 and 2 and the oil jetties at Tuticorin Port Trust were rehabilitated after conducting detailed NDT investigation in the RC structural elements of the berthing dolphin, main jetties, approach jetties, mooring dolphin and catwalk of the three jetties. The severe distress in the RC structural elements of the three jetties could be attributed to the failure of the earlier repair carried out using shotcreting. Based on the extensive NDT tests conducted, the condition of the concrete was assessed and a rehabilitation methodology consisting of micro-concrete jacketing and installation of self-regulating anodes was suggested for the various distressed RC structural elements of the three jetties. Modification/rehabilitation of finger jetties was carried out at the Chokhani floating dry dock in Chennai Port Trust. NDT tests were conducted to arrive at the rehabilitation methodology. The heavily corroded pile liners were cut and removed from −0.20 m level by using under water cutting gear. The cracked and spalled concrete was fully removed to expose the full circumference of the steel. The rust in steel was completely removed and cleaned by chemical means. Additional steel was provided for modification of pile for fender arrangement. Sacrificial zinc anodes were installed, and leads were provided for connecting to a monitoring box. Under water micro-concrete was used after coating the rebars with a zinc primer. The UPV tests conducted after repair for a period of nearly 6 years at every 6 month interval indicated that the integrity of the concrete were still good. The half-cell potentials measured at every 6 month interval for a period of 6 years showed values more positive than −200 mV indicating that there is a greater than 90% probability that no reinforcing steel corrosion is occurring in that area at the time of measurement. The half-cell potential values more positive than −200 mV even after six years clearly indicate that the self- regulating anodes were effective in preventing further distress to the RC structural elements.

Oil spill accidents on the marine waters impose great threat to the marine organism, humans and economic. Continuous efforts have been made to achieve effective mitigation measures to avoid the damage to the marine environment. Countermeasures, to combat the spilled oil, are to be taken, by the response action team, with thorough knowledge on the spilled oil conditions, characteristics and projected trajectory of oil sleek movements on the water surface. In the present study, experimental investigations are carried out to understand the interaction between the oil droplets and suspended sediments to form aggregates. Further, the laboratory results on the formed aggregates (OSAs) sizes are used as an input to the numerical model investigation. To demonstrate the use of numerical model to estimate the trajectories of a hypothetical oil spill incident, a 2D oil spill trajectory model is developed for Gulf of Khambhat, West Coast of India. A finite element method-based numerical scheme, TELEMAC-2D, is used for this study, which also capable of estimating the ambient hydrodynamics that drive the spilled oil to spread spatially. In addition to the estimate of spilled oil trajectory, oil-sediment aggregates trajectories are also investigated using the numerical model. From the numerical model results, it is evident that the area influenced by the OSAs is significantly small compared the ambient oil spill conditions, which may be thought of an alternate option for combating any future oil spill incidents.

The measurement of the rheological properties of gas hydrate slurries necessitates the high pressure rheometer that can provide a proper mixing inside the pressure cell during hydrate formation from two multiphase fluids, water and gas. However, the hydrate formation is highly challenging in conventional cup and bob geometry due to its plane surface. To overcome this, the present work focuses on the study of high pressure rheology for hydrate slurries formed from water-heptane (C7H16) system using a high pressure cell in Anton-Paar® (MCR-52) rheometer and a modified Couette geometry which enables the measurement of rheological studies of multiphase hydrate system. It was observed that the hydrate slurries exhibit shear thinning behavior. The present study provides an important information about the rheology of methane hydrate slurries formed from multiphase systems for flow assurance applications.

This paper presents the design of temporary cofferdam structure for new dry dock. For this, construction of temporary dewatering has to be done at the dry dock area for excavation and safeguarding the work area and keeping dry. The temporary cofferdam can be built in such a way that the entire length of pile sheet piles can be installed and removed easily. Hence, cofferdam with steel sheet pile and beams is proposed based on geological and site constraints. In this paper, discussion about a temporary dewatering at the dry dock location is necessary to isolate the proposed work area. This method provides safe environment to work, and materials can typically be reused on other projects. The 2D analysis using Staad pro has been carried out.

The purpose of this paper is to compare the performance of proportional-integral-derivative controller(PID), multivariable PID controller and linear quadratic regulator(LQR) applied to a dynamic positioning system of ship by numerical simulation in MATLAB. A square manoeuvre in different sea state is used to test the performance.

Hybrid functions (hereafter, HBL) has been newly presented as an efficient method to the full Boltzmann integral (FBI) for quadruplet wave–wave interactions at finite depths and also been tested for idealized wave spectra. Herein, the method is implemented in TOMAWAC, the third-generation wave model, and is validated between the existing approximate methods such as discrete interaction approximation (DIA), multiple discrete interaction approximate method (MDIA) and quasi-exact method, namely Gauss quadrature method (GQM), for observed wave spectra. The measured wave spectra obtained from the off-Kochi, along the southwest coast of India at a water depth of 21 m, are analyzed for southwest monsoon period in the year 2016, with an objective to understand the effect of nonlinear coupling due to quadruplet resonant interactions on composite spectra. The swell and sea components of the spectra are separated using peakedness algorithm, and the analysis shows that most of the spectra are swell dominated. The nonlinear coupling between swell and sea spectra is studied thoroughly, and it is ascertained that coupling is generally much larger in the vicinity of closer intermodal distance and mean directions.

Sea surface temperature (SST) plays a key role in the dynamics of the global climate system. Adequate understanding of the SST dynamics is crucial for modelling the land–ocean-atmospheric dynamics and for predicting weather. There exist many different approaches and associated methods for studying the dynamics of SST. Among these, methods developed in the context of nonlinear dynamic and chaos theories are particularly suitable and useful, since there is sufficient evidence as to the presence of chaotic behaviour in SST dynamics. Many past studies have applied the concepts of chaos to analyse the SST time series in different parts around the world and reported interesting results. Encouraged by the outcomes of such studies, the present study applies the concepts of chaos theory to examine the dynamic characteristics of SST in the Arabian sea region. In particular, the False Nearest Neighbour (FNN) is employed to a 30-year SST data series from (1987 to 2016). The implementation of the FNN method involves phase space reconstruction of the SST time series using a delay embedding procedure and identification of the false nearest neighbours in the reconstructed phase space using a neighbour search approach. The effect of delay time on the FNN dimension estimation of the SST series is also investigated by considering different delay time values, including those obtained using the Autocorrelation Function (ACF) method and the Average Mutual Information (AMI) method.

Ships or any marine vessels experience loads in form of dynamic wave and wind forces. These affect the motion of ships in both transverse and longitudinal direction. The motions of ship are an important parameter to be controlled as well as to be known in order to prevent any failures like capsizing or structural instability. Therefore, it is of utmost importance to predict the ship motions. This paper attempts to study the ship motions using Kalman filter (KF) considering a regular sea state. Initially, the dynamic longitudinal loads are obtained by the long-term prediction method on basis of ship motion calculations using strip theory. The measurements are then corrupted via noise to simulate practical observations. The unknown parameters like sectional wave exciting force and sectional hydro-mechanic force are then estimated using KF by analysing the problem as a 2D problem using linear Airy wave theory under assumption that the body is a rectangular floating frame. The problem can then be extended to actual load conditions and sea states.

Wave slamming induces extremely high loads to offshore structures and ships whether, due to wave impact on the deck of offshore structure or due to moving bodies such as ships and air crafts hitting the water surface. During slamming wave impact, a localized high pressure will generate at the point of incidence. This very high pressure experienced by the bottom of deck plate is difficult to predict. In this paper, numerical simulation of wave slamming on offshore platform deck structures in incident waves is carried out using weakly compressible smoothed particle hydrodynamics (WCSPH). Pressure values in SPH are very sensitive to errors in the treatment of boundary conditions. Hence, two types of boundary conditions are tried for this slamming problem: repulsive and dynamic boundary conditions. The pressure values on the center regions of the structure are observed from the SPH generated pressure contour lines, to be larger than the values on the surrounding parts.

The loss or drop of pressure or head which occurs in pipelines or in duct flow due to the fluid's viscosity in or inside the surface of the pipeline or duct is known as friction loss (or skin friction). Pressure drop occurs along the flow direction inside a pipe which is triggered by friction due to fluid, both internal within the fluids and with the piping surfaces, piping restrictions or sudden changes in the geometry of the flow path. Surfactants are used in the oil and gas industries for flow assurance purpose since years, but using the same for reducing friction in pipelines is still rare available in the literatures. In addition, surfactants are the chemicals which are used to get adsorbed and coated on the walls of the pipeline for reducing the friction and also affect the drag reduction. Therefore, surfactant as a friction reducing agent is having lot of scope to explore and a necessary requirement for studying to reduce friction in the pipelines. In this work, sodium lignosulfonate (SLS) is used for the studies of friction in the different diameter of pipelines for measuring the head loss. Two pipe diameters which have been used in this study are ¾ inches and ½ inches. The head loss due to friction has been determined using Darcy–Weisbach equation. It has been found that the surfactant helps to reduce the friction in the pipelines. This work provides a precursor for further studies involving surfactant to reduce friction in the pipelines for various industrial processes.

Understanding the formation and dissociation behavior of methane gas hydrate in marine sediments is one of the important precursors for methane gas production from the hydrate deposits. The phase behavior of gas hydrates is influenced by the presence of sediments, composition of salts and water present in it. Krishna–Godavari (KG) Basin in India is one such reservoir which has a huge potential of methane gas hydrates. Here, we have investigated the phase equilibria, and the kinetics of methane hydrate formation, and dissociation in the presence of pure water, and in aqueous solution of 10 wt% (KG) basin sediment. We observed that the phase equilibrium conditions of methane hydrate in presence of 10 wt% sediment solution got shifted to slightly higher pressures at given temperature as compared to that in the bulk phase. It has also been observed that more number of methane gas molecules are consumed in 10 wt% sediment solution in the initial 30 minutes of time than in the pure water system, revealing the promotion effect of sediment surface. The number of moles of methane gas released during the dissociation of hydrate has found to be lesser in sediment solution than in pure water at any given time after initial 55 min of the start of dissociation.

An ultra-low IFT (interfacial tension) is required between the liquid–liquid systems to dislodge the crude oil completely from the pores of the formation. As a huge amount of alkali is used for this purpose, scale formation and formation damage near wellbore region is a common issue. To perform an economically and environmentally viable process, it is obligatory to design the process with low and optimum concentration of alkali. Moreover, if the concentration of alkali is properly designed according to the oil chemistry, the alkali flooding alone could result in a favorable recovery for high acid number crude oil. So, the present study utilized low concentration of NaOH, to understand the behavior of alkali at the IFT of hydrocarbon–water system. Hydrocarbons like heptane and benzene were selected to understand the influence of hydrocarbon type on the IFT reduction. It was found that the IFT between the hydrocarbon–water system continuously decreases with an increase in NaOH concentration; moreover, a minimum concentration of 100 ppm is required to initiate reduction reaction. It is evident to state that IFT is dependent upon type of the hydrocarbon, because the enhanced reduction is observed in aromatics–water system using NaOH due to stronger cation-π interaction.

Heavy oil reservoirs are one of the largest remaining crude oil reserves in the world. Often, the inherent properties of heavy and extra-heavy oils cause major problems in production and transportation processes. The viscosity of these oils makes their treatment difficult with conventional means. Use of solvents to dissolve the heavy oils has been a traditional method to deal with these problems. Improvement in flow through solvent treatment can be further optimized through the use of nanoparticles. Literature works have suggested that nanoparticles have catalyzing effects which affect the polar species of heavy oils. This study is aimed at examining the effects of metallic nanoparticles in altering the viscous property of heavy fraction. Use of thermal stimulation in association with solvents are explored as a means to achieve viscosity reduction. These applications can be further extended into the areas of flow assurance.

The development of the Mauritius FAD Fishery started in 1985. The designed FAD is the rosary type comprising trawl floats mounted on a single or double-string polyamide rope, anchored in the open sea with polypropylene ropes, at depths ranging from 400 to 3500 m. Yet, FAD losses are high and mostly due to damages caused by navigating vessels and entanglement of fishing lines and hooks with the mooring rope of fishermen boats fishing close to the FADs. Moreover, it was observed that the rosary type FAD sinks to >200 m during strong surface current; hence, the use of trawl floats, which are resistant to pressure and resurfaces during slack current. Consequently, these FADs can neither be fixed to a light device for easy detection at night nor can they be equipped with satellite buoys as these would implode due to high pressure during sinkage. To reduce FAD losses, a sturdy, unsinkable and traceable fibreglass reinforced plastic single buoy FAD has been designed, equipped with a solar-powered flashlight, and a satellite buoy to track and collect biological and oceanography information. The mooring line consists of a mixed of steel wire (Ø 14 mm) and of polypropylene rope (Ø 20 mm). Based on the law of static equilibrium, the buoyant force on the buoy was calculated at 2,441.0 N. Turbulent flow models with speed of ocean current at 1, 2 and 3 knots were used to calculate the overall drag force (52,656.6 N) on both the mooring rope and the submerged portion of the buoy. Additional improvements made on the single buoy FAD were the (a) net-wrapping technique that proved to reduce the surface tension by as much as three times; and (b) shackle connection coupled with the formation of the catenary loop that provided full scope for rotation, thereby, reducing significantly the tensile force on the main line. Assuming a contingency anchorage of 130% on the total drag force, the minimum anchorage weight was 2,080.2 kg for metal and 3,578.4 kg for concrete.

Maritime countries like India face serious coastal erosion issues. Over 1200 km of Indian coastline is identified as eroding. Unavailability and high cost of natural rocks remain as a major hindrance for construction of conventional hard options like breakwaters, seawalls and groynes. This has forced coastal engineers to find nature friendly and economical alternatives. Experiences from Australia, Germany and United States prove the efficacy of geotextile containment systems in coastal protection. This chapter aims at reviewing Indian examples of protection works using geosynthetic and geotextile containment systems from early 1980s. Geosynthetic protection structures include groynes, submerged reefs, seawalls and breakwaters. Benefits and difficulties in implementation of protection works are identified by reviewing prominent works conducted in the east and west coast of India. Experiences at Hamla, Dahanu and Pentha helped in replacing conventional structures with geotubes. Equilibrium beach profile is attained using near-shore geotube reef system at Hamla and Dahanu, Maharashtra, whereas reef constructed using geotextiles at Candolim, Goa suffered serious damage due to vandalism and toe scour. Geosynthetic systems along with gabions and rock armours improve the stability, wave dissipation and reflection characteristics as seen in Pentha, Odisha and Uppada, Andhra Pradesh. Lack of proper design criteria and deliberate destruction by vandals remains as the major threat. Countering these challenges, geosynthetic containment systems offer a cost-effective alternative to conventional coastal protection methods in India.

In general, the groyne sections are made of rubble stones of different sizes. To conserve the ecosystem and also due to the scarcity of natural rocks around certain locations, the reliance on these hard materials for the construction of groyne sections becomes questionable forcing us to look for alternate eco-friendly soft materials, for example, geo systems. In order to evaluate the feasibility and advantages of geo systems for groyne construction and to test their hydrodynamic stability, the core section of rubble stones was replaced by geo-bags filled with sand. The objective of this study is to assess the wave transmission, hydrodynamic stability and wave overtopping of a groyne section with a geo-bags filled core section through physical model studies. The tests were conducted in a wave flume in Department of Ocean Engineering, Indian Institute of Technology Madras, India. A model scale of 1:15 is adopted based on Froude’s scaling law and dimensional limitations of the testing facility. The aforementioned cross sections were tested simultaneously in a wave flume that was partitioned longitudinally. The transmission and hydrodynamic stability of both the sections have been analysed by subjecting the corresponding sections to the action of random waves defined by JONSWAP spectrum through a well-controlled experimental programme. The details of test set-up, testing facility, parameters of model, test procedure, analysis of results and discussion will be reported in this chapter.

This paper presents the design optimization for reinforced concrete structure done in order to minimize the cost of the concrete and steel for pile by selecting different span length in marine approach jetty, POL berth, Mormugao, Goa. Dimensions of approach jetty is 200 m length × 15 m width. The purpose of the approach jetty is to carry vehicles and oil pipelines. Live load of 30 kN/m2/Class 70R (wheeled) from IRC is considered for the jetty design. The proposed location falls under seismic zone III. Piles are founded in sandstone at a depth of (−)32 m CD. Two options (I and II) were explored for the above considerations, and the feasible alternative has been arrived at cost-effective, robust design, and time-sensitive manner.

The purpose of offshore seawater intake is to provide a continuous supply of seawater with proper quantity and quality. The large volume and specified water quality requirements, offshore intake wells are preferred. The adequate and economical supply of seawater from the offshore intake well depends on the performance of the pumping system. In a typical intake well, the pumping equipment is placed below the water surface based on the free surface water oscillation inside the well. The loads exerted by the incoming waves and the free surface water oscillation will affect the pumping performance. This phenomenon should be reduced for smooth and efficient pumping operation. To achieve this, some auxiliary equipment like curtain wall is introduced into the intake well. This type of internal structure can regulate the flow and dissipate the incident wave energy up to some extent. Moreover, they can obstruct the formation of vortices and eddying. The present study focuses on the internal hydrodynamics of an offshore intake well with a porous curtain wall. A 1:20 scale model is tested with regular waves in the shallow wave basin and wave run-up, rundown, free surface water oscillation inside the well and the pressure acting on the curtain wall is measured. Then, the influence of the porosity on the free surface water oscillation is investigated by changing the porosity.

International Maritime Organization’s (IMO) recent discussion on the development of second-generation intact stability criterion has emphasized on the instability problems like surf-riding and broaching of ships. Surf-riding and broaching occur when a ship rides in astern seas with the ship velocity close to the wave celerity. It results in loss of stability, sometimes even leading to capsizing. Rudder becomes ineffective in these conditions and ship may lose its manoeuvring abilities. A ship’s vulnerability towards surf-riding and broaching is investigated using a numerical method. The numerical method based on strip theory calculates the Froude–Krylov and hydrostatic force for instantaneous wave profile. The numerical study is conducted on the ITTC A2 fishing vessel in regular astern waves and is compared with the measured ones available from the literature.

Wells turbine (WT) used for harnessing wave energy has narrow operating range and poor starting characteristics. To enhance its starting and running characteristics, guide vanes (GV) are installed upstream and downstream of the rotor. This paper studies the effect of the gap-to-chord ( $$G/l_{r}$$ G / l r ) ratio of the WT GV on the turbine performance numerically. The work incorporates validation of the numerical simulations with experimental results and application of optimization techniques to find the optimal $$G/l_{r}$$ G / l r ratio. A range for $$G/l_{r}$$ G / l r ratio is suitably selected for the analysis and metamodel based on Kriging algorithm is developed. Following this, the optimization algorithm of screening is utilized to find the optimal conditions to achieve the objective function.

This paper discusses the effect of modifying the hangar shape on the dynamic interaction of ship airwake and rotor downwash of the helicopter using computational fluid dynamics (CFD). A traditional 1:100 scaled simplified frigate ship (SFS-2) is modified to obtain trapezoidal and rectangular configurations of the hangar. The coupled interaction of ship airwake formed behind the ship subjected to free stream velocity of 6 m/s with the downwash generated by helicopter rotor hovering at 5000 rpm is simulated using STARCCM + CFD solver. The Reynolds-averaged Navier–Stokes equation is solved with conventional k-ω two-equation turbulence model to simulate the flow. The helicopter rotor thrust coefficient on hovering plane and landing plane is calculated for all the three SFS-2 configurations. The resultant velocity flow field of the ship airwake and rotor downwash is surveyed to compare the turbulence intensities at four equidistant lateral planes along the flight deck for a zero wind-over-deck (WOD) angle. The modified hangar configurations are shown to improve the coupled flow aft of the hangar.

Hydrodynamic drag of ocean-going vessels imposes severe penalty with regard to exhaust emissions and fuel consumption. Stern flaps have been extensively used as a cost-effective energy saving device, largely by the US Navy. Experimental analysis to identify an optimum stern flap fitted at the transom stern end of a generic high-speed displacement vessel operating at Froude number regime of 0.17–0.48 is described. In this study, twelve different stern flap configurations were studied. Identification of optimum stern flap was based on systematic analysis of extensive model test resistance data of various stern flap configurations over twelve different Froude numbers.

This degree project investigated on the corrosion rate of distinct steel reinforcement diameters exposed to urban atmosphere, coastal atmosphere, tidal and submerged zone and compared the corrosion rate for the different exposure conditions. The corrosion rate of steel reinforcement embedded in different concrete cover thicknesses was evaluated and discussed. The methodology involved exposing samples of 6, 8, 10 and 12 mm diameter bare steel reinforcement to urban atmosphere, coastal atmosphere, tidal zone and submerged zone for 60 days. Similarly, 10 mm diameter steel reinforcement embedded in concrete with cover thicknesses of 25 and 50 mm was exposed to tidal actions. The research findings showed that the corrosion rate for steel reinforcement exposed to tidal zone experienced structurally significant metal loss and a corrosion rate of 131.229 μm/yr over the 60-day exposure period, whereas specimens exposed to the submerged zone experienced a corrosion rate of 34.781 μm/yr over that same exposure period. The corrosion rate of steel samples exposed at Mahebourg was 66.940 μm/yr and the corrosiveness for this location was high and classified under category C4 corrosion. However, the corrosion rate for specimens exposed to Vacoas was 48.783 μm/yr and the corrosion activity for Vacoas falls under category C3 corrosion since the corrosiveness was medium. The percentage mass losses for 10 mm diameter bare steel reinforcement exposed to sea tides for 60 days were 0.897%, while for steel reinforcement embedded in 25 and 50 mm concrete cover, the percentage mass losses decreased to 0.092% and 0.017%, respectively. The cost assessment based on the proposed case study was cost-effective when the repairs were performed during construction phase. It consisted of increasing the cover thickness to 50 mm for reinforced concrete piles exposed to splash and tidal zones.