Abstract Some features of the movement of table-shaped icebergs during their towing are examined. A table-shaped iceberg, towed in the Barents Sea in 2017, for which surveys of the underwater and surface parts were carried out, was selected for the analysis. As a result of numerical and physical modeling, the hydrodynamic characteristics of the iceberg were obtained for different motion courses - good convergence of the results of these methods was achieved. To determine each component, the numerical simulation, based on the equations of a viscous fluid motion, was carried out. Turbulent fluid flow is described by the Reynolds-averaged Navier-Stokes and continuity equations. The k − ωSST turbulence model is used to simulate turbulence. Numerical differentiation of the equations was performed in the open source CFD software OpenFOAM. It is shown that iceberg has several positions of stable and unstable equilibrium in terms of the rotation around a vertical axis and the influence of an iceberg orientation on additional resistance during rough seas is considered. Obtained results may be used in the table-shaped icebergs towing planning in different regions of the world, as well as in further study of iceberg behavior under load. Introduction Towards the development of the Arctic, there is a difficult ice situation, which requires the development of innovative approaches in its development. Particular attention should be paid to the environmental and industrial safety, since the ingress of hydrocarbons into the marine environment in the Arctic will lead to severe consequences for the ecosystem of the polar seas. Exploration and extraction of resources in the Arctic at great depths (more than 100 m) is challenging due to the unpredictability of ice conditions and high ice loads (Hamilton, 2011). The main threats to offshore oil and gas facilities during the development of the Arctic shelf are ice formations of various origins: icebergs (continental ice) and hummocky formations (deformed sea ice).

Abstract The article examines iceberg movement under the influence of wind force, with detailed analysis of the influence of the iceberg shape (both underwater and above) on the parameters of this movement. For four icebergs, studied during 2016-2017 trials, hydrodynamic characteristics of the under- and above-water parts were determined by the means of numerical and basin modeling. For these icebergs orientation, direction and speed of movement are calculated for different wind speeds and directions. Regression between the maximum value of the hydrodynamic drag coefficient and the geometric parameters is built based on the studied shape of the above-water part of ten icebergs. A formula for calculating the wind load on an iceberg depending on the parameters of its topside, as well as a formula for calculating the drift speed of icebergs less than 75 meters long, are proposed. The formulas are applied to icebergs of the southwestern part of the Kara Sea, which made it possible to estimate their drift speed and wind load under the influence of wind. The obtained results can be used in modeling of the iceberg drift, as well as for assessing the wind impact during iceberg towing. Introduction For development of the Arctic shelf an important factor influencing iceberg safety is the possibility to assess in sea conditions one or another characteristic of an iceberg based only on the above-water part. For this research it is useful to refer to previously studied icebergs with a known shape of the surface and underwater parts. Informative data on the Russian Arctic icebergs are published in (May et al, 2019), (Buzin et al, 2016), (Buzin et al, 2020) and on the derived correlations of the iceberg's above water shape in the papers: • on iceberg stability (Kornishin et al, 2020); • on towing load (Pashali et al, 2018), (Kornishin et al, 2019), (Efimov et al, 2019); • on iceberg detection distance (Pavlov et al, 2018).

Abstract Optimal design of propulsive system for mini polar cruises is of great significance for improving ship energy efficiency and reducing ship vibration and noise. The present study proposes a hybrid diesel engine/battery/shore power propulsive system and a tri-objective optimization considering annual fuel consumption, lifecycle cost and annual pure electric time is carried out. The results show that 0.27% fuel reduction and 37.48% annual pure electric time are gained by sacrificing 7.85% lifecycle cost compared with the conventional diesel electric propulsive system. Introduction For passenger ships, comfort is an important design index of the propulsive system (Cinquemani and Braghin 2017). In particular, the design requires of propulsive system for mini polar cruises are very different from those of ordinary ships. On one hand, the polar sea conditions are relatively bad, even accompanied by ice floes. In addition, mini polar cruises start and stop frequently, and required power fluctuates drastically. Diesel engines cannot always run in high-efficiency area, which increases fuel consumption and operational costs. On the other hand, the vibration and noise of mini polar cruises will not only reduce the comfort, but also affect creatures underwater and destroy the polar environment (Gardiner 2020, Shijin, Yaqiong et al. 2020). Not only can annual pure electric navigation improve the comfort of the ship, but also reduce the vibration and noise of the ship, reduce the disturbance to creatures underwater, and achieve zero emissions. Therefore, the design of propulsive system for mini polar cruises needs to take into account fuel consumption, operational costs and annual pure electric time. With the development of shipping industry, environmental pollution and operational costs are increasing year by year (Wang, Yan et al. 2016, Yuan, Wang et al. 2018). To improve ship energy efficiency, the (International Maritime Organization (IMO) 2010) has proposed a number of stringent regulations, including ship energy efficiency management plan (SEEMP) and energy efficiency design index (EEDI). Thus, many approaches (Zhu, Chen et al. 2018, Zhang, Zhang et al. 2019, Nuchturee, Li et al. 2020) to improving ship energy efficiency have been proposed in recent years. Among them, hybrid electric propulsive systems (HEPSs) have attracted more and more attention due to its potential of saving fuel and reducing emission (Yuan, Wang et al. 2020). Since the HEPSs include at least two energy sources, optimal design is beneficial to improve the performance, for example, economy, environmental protection, and comfort. Existing research takes annual fuel consumption, greenhouse gas emissions or lifecycle cost as optimization objectives. In (Yuan, Wang et al. 2018), the solar power generation system was applied to a 5000-vehicle space pure car and truck carrier. Through the analysis of experimental data, they concluded that the HEPS can save 4.02% of fuel and 8.55% of carbon dioxide emission every year. In (Zhu, Chen et al. 2018), taking fuel consumption, greenhouse gas emission, and lifecycle cost as optimization objectives, the optimal design were obtained for the HEPS of an anchor handling tug supply vessel. In (Giap, Lee et al. 2020), the indirect-coupling and direct-coupling configurations of hybrid solid-oxide fuel cell and gas engine propulsive systems were proposed for crude oil tanker. The results showed that direct-coupling configurations can reduce more exergy destruction. In (Wu and Bucknall 2020), aiming at the constraints of power and energy density of fuel cell and lithium-ion battery in HEPS of coastal ships, an overall design method combining outer power multi-objective optimization and inner dynamic programming was proposed. It was verified that this method can reduce at least 65% of lifecycle greenhouse gas emissions.

Abstract In this paper, a diesel/battery hybrid electric propulsion system (HEPS) of a polar icebreaker is proposed to achieve local low noise, and reduce fuel consumption and exhaust emission. The HEPS model is established with the inverse simulation method and the parameters are optimized with two indexes, annual fuel consumption and total cost during the entire life cycle, by NSGA-II algorithm. Compared with the single-objective optimization solutions, the bi-objective optimal design has better comprehensive performance with 2.78% less fuel consumption and 29.07% cost saving respectively. Further, the Pareto-solution set are concentrated in two areas and generate a "gap" depending on the number of battery modules. The battery capacity of the solutions before the "gap" could be fully utilized, while the battery of the solutions after the "gap" is out of service in the open water region. Additionally, the solution subset after the "gap" leads to rapid increasing fuel consumption. Introduction Currently, polar transportation and scientific research activities have been frequently carried out (Parsons et al., 2011; Zhang et al., 2019). The icebreaker is the key equipment to complete polar navigation, and plays a pivotal role in icebreaking, escorting and emergency rescue. However, it encounters various problems such as high fuel consumption, exhaust emissions and noise (Lindstad et al., 2015). The propulsion system of a polar icebreaker in service is mainly diesel electric propulsion system, of which the diesel generator sets continuously provide power during the mission voyage, resulting in that zero emission and ultra-low noise operation is difficult to achieve in the port and polar region and affecting the ecological environment and riding comfort (Xu et al., 2017). The environmentally friendly hybrid propulsion system of ships with energy storage battery has been developed rapidly due to its great potential in energy saving and emission reduction. While the high cost of rechargeable battery should be considered, the better economic and environmental benefits could be achieved with optimization method. At present, the research on HEPS design aiming at fuel consumption and cost is more common in the small and medium ships like ferry and tugboat. It was noted that (Zhu et al., 2020) the fuel consumption and emissions of short haul RORO ferry were taken as the optimization objectives, and the Rule-Based control and Grey Wolf Optimization were adopted to achieve 2.91% and 7.48% fuel consumption reductions respectively. Afterwards, a bi-level optimization method with multi-objective particle swarm optimization as the upper level and an adaptive equivalent consumption minimization strategy as the lower level was proposed (Zhu et al., 2018). The method was applied in an anchor-handling tug supply vessel, and resulted in 3.37% less fuel consumption and 13.95% less net present cost compared to the conventional optimization solutions. However, to the best of the authors' knowledge, the optimal design of diesel/battery HEPS for icebreaker has not been reported in literature due to the complexity of polar navigation, and the existing research focuses on the traditional diesel electric propulsion system. The electric propulsion system of the icebreaker 'Shirase' was combined with the industrial motor control and intelligent power network control technologies to improve the economy and fuel efficiency of the propulsion system when the ice load changed rapidly (Ajioka and Ohno, 2013). Apart from that, the propeller and the diesel engine of icebreaker could operate in the high efficiency zone by optimizing the sizing and speed of propeller (Yang et al., 2011). The working mode of the engine can be switched to improve the operational efficiency with the uncertain load.

Abstract This study investigates analytically the influence of the length to draft and beam to draft ratio of a ship on the drift forces acting on a body in relatively short waves (small wavelength to ship length ratio). For validation, the proposed method is applied to predict the drift forces acting on simple geometries and real ships, yielding satisfactory predictions of the drift forces in both longitudinal and lateral directions. The proposed method can be applied to preliminary design tasks as it can capture the effect of the variation of a body's dimensional ratios and the influence of incident wave direction. INTRODUCTION Recent years have seen diverse demands on the prediction of the steady second order wave forces and moments exerting on floating marine structures with or without forward speed. The side drift force and the drift yaw moment (and to a lesser degree the steady forces and moments in the other degrees of freedom) are essential for the simulation of ship's maneuverability in waves (IMO, 2013), for the design of mooring lines and the simulation of dynamic position of offshore support vessels and floating marine structures, etc. In the forward speed problem, the prediction of added resistance in waves is very important for propulsive performance analysis in realistic environmental conditions (ISO 15016, ISO 19030), thus, in relation to fuel consumption and greenhouse gas emission analysis. Though alternative analytical and numerical methods are available for use in practice (e.g., for 2D problem Papanikolaou and Nowacki, 1980; for 3D problem Zaraphonitis and Papanikolaou, 1992), an efficient (fast, accurate and transparent) method, using minimum hull form information, is often desired. Under such background, analytical solutions based on potential flow theory (Molin, 1979; Chatjigeorgiou and Mavrakos, 2006; Duan et al., 2015; Liang and Chen, 2017), and empirical methods, often demonstrate an advantage in these tasks. For instance, in the prediction of added resistance, a popular approach is to apply potential flow nearor far-field methods, together with some semi-empirical correction for relatively short waves (Fujii and Takahashi, 1975), where the near- or far-field methods face challenges. Another approach is a pure empirical method, as developed by Liu and Papanikolaou (2020a, 2020b). To improve the performance of these methods, it is important to carefully examine the empirical correction components and establish a rational relationship between the empirical formula and hull form parameters.

Abstract In this paper, based on open-source CFD tool OpenFOAM, a hybrid method coupling the FNPT-based (fully nonlinear potential theory) QALE-FEM (quasi arbitrary Lagrangian Euler finite element method) and the viscous flow method is applied to simulate the motion of trimaran in the stern waves. With the hybrid method and the corresponding solver QaleFoam, the linear and nonlinear incident waves are generated by the external wave tank of FNPT-based QALE-FEM and propagate to the internal domain by a transition zone. In the internal domain, the interaction between the wave and trimaran model in simulated by the viscous flow method. The wave generation is carried out first. Then, the motion of trimaran at different sailing speeds in the stern waves of different wave steepness is simulated, and the effect of the stern wave on the motion and moving forward of trimaran are analyzed. INTRODUCTION The study of ship's motion in waves is the key factor affecting the comfortability and safety of the navigation, which has been widely investigated in recent years (Yu et al., 2017; Chen et al., 2018; Diao et al., 2019; Begovic et al., 2020; Tang et al., 2021). As a kind of highperformance ships, the hydrodynamics of trimaran has been studied by both numerical method and tank test (Chen et al., 2019; Zong et al., 2019a; Tang et al., 2017), and the characteristics of trimaran's motion and added resistance in waves has attracted more and more attention in the past decades. Because the trimaran has the advantage of low resistance in calm water, large deck area, good transversal stability, et al. Hence, the study about the seakeeping performance of trimaran in longitudinal waves plays an important role in the further application of trimaran, especially the motion response in the head wave and the stern wave included. The study about trimaran hull form begins at the end of the 20 th century (Pattison et al., 1994), and the motion of trimaran in waves of different headings is preliminarily studied (Kurultay, 2003). With the technological development of numerical simulation and tank tests, in recent years, the study about the seakeeping performance of trimaran has been widely carried out by researchers. Tang et al. (2019) carried out the tank test to study the wave loads, slamming, and the corresponding effect on the vibration of the trimaran. Zong et al. (2019a; 2019b) studied the scheme of T-foil control of trimaran by experiment method, aims to reduce the longitudinal motion of trimaran in the head wave. Deng et al. (2019) predicted the resistance of trimaran in calm water and the motion of trimaran in the head wave, by the analysis of the computed result, both the effect of hull attitude on the resistance in calm water and the effect of wave amplitude on the added resistance in waves. Ghadimi et al. (2019) investigated the seakeeping performance of trimaran in the head wave and bow quartering wave by the commercial computational fluid dynamics code Flow-3D, and the numerical method is validated by comparison with the experimental result. Duan et al. (2019) validated the prediction of motion and added resistance of trimaran by 2.5D method of potential flow method. Li et al. (2020) carried out a numerical study on the effect of wave steepness on the hydrodynamic coefficients and motion in the head waves. Sun et al. (2020) studied the flow interaction between the center hull and side hull by the PIV method. Tang et al. (2020) carried out a numerical study of trimaran motion and wave load prediction based on the time-domain Rankine-Green matching method. Liu et al. (2020) carried out the tank test to study the effect of the fixed appendage and the actively controlled appendage on the reduction of the trimaran's vertical motion.

Abstract An economical method, Sampling & Pull-Up Test (S&PUT), was proposed for investigation of the mechanical properties of the seabed for foundation design of bottom-mounted offshore wind turbine towers. After two kinds of prototype apparatus were manufactured, field experiments were carried out to investigate the feasibility of the proposed test method. The test results demonstrated that, for sounding performance, the PUTs were suitable, as the depth profiles of the wing resistances by PUTs and those of the cone resistances by CPTs were in harmony. Whereas the sampling performance was not satisfactory yet, as the sampling recovery ratios were found not greater than 80%. Introduction An economical method for investigating the mechanical properties of the surface ground on the seabed is required for foundation design of bottom-mounted offshore wind turbine towers. The authors proposed a new sampling and pull-up test, denoted as a S&PUT for short, that can perform sampling and sounding simultaneously (Tani et al., 2020a). Using a hydraulic jack and a vibro- or a percussion hammer, a test device with a sounding probe for pull-up tests (PUTs) and cone penetration tests (CPTs) is statically or dynamically and continuously driven into the ground simultaneously with samplers equipped alongside rods. The purpose of this test method is to collect continuous samples not only of soft ground but also relatively hard ground, while conducting sounding tests to evaluate a depth profile of stiffnesses and/or strengths at the same location. Although limited to soft ground, CPTs can be performed, when the probe is driven statically at a constant rate. On the other hand, PUTs can be done even in harder ground, once the probe is installed dynamically at depths. FORMATTING SAMPLING AND PULL-UP TEST (S&PUT) Fig. 1 compares the concept of S&PUTs and that of standard penetration tests (SPTs) which are most widely used for geotechnical investigations. The basic concept of these two test methods is identical in that, both sampling of disturbed soil samples and sounding for evaluation of the mechanical properties can be done at the same time in the same location. Thereby, similar results of geological columns that are the depth profiles of soil types and sounding measurements can be obtained effectively by both test methods. However, there are four-fold differences as below. The first is that, S&PUTs can be conducted much faster than SPTs. In SPTs, the works of driving the sampler while counting the number of blows, SPT-N values, for sounding, retrieval of the sampler for sampling, and drilling/boring to the next depth must be repeated every 1 meter in depth. Since installation and removal of a self-elevating platform (SEP) or a simple scaffolding to place the drilling machine are time consuming, it usually takes several days to a few weeks to do a SPT at each site. On the other hand, in S&PUTs, the works of driving/penetration and retrieval/pulling-up of the probe and the samplers are done only once. Since the operation of a pile driving barge to be used is simpler and quicker than that of a SEP, the time required to do a S&PUT at each site is estimated not longer than several hours or a day.

Abstract The present paper focuses on numerical and experimental studies on the resistance for the accelerated forward motion of a catamaran vessel, that is planned to operate on a fixed journey schedule, while it includes significant acceleration and deceleration phases. In general, the numerical predictions by use of an unsteady CFD solver and a newly introduced simplified quasi-steady approach showed good agreement with the experimental data. INTRODUCTION Studies on the unsteady forward speed motion of ships are not widely published and mostly related to investigations of the maneuvering of ships, thus of the unsteady ship motions in the horizontal plane and the coupled surge, sway and yaw motions (Abkowitz, 1964). For conventional ships and particularly large-scale ships (mega tankers, bulk carriers and containerships) and fast marine vehicles, studies on the unsteady forward speed motion are of interest in relation to the simulation of the propeller-engine interaction. The estimation of the associated fuel consumption and of the time the ship to reach a certain speed or to come to full stop becomes important, along with the estimation stopping distance (see, e.g., Mizythras et al., 2018, Zeraatgar & Ghaemi, 2019). Some specific studies in the area are also of interest for naval ship applications, which will be not treated in this paper. With the introduction of fast, zero emission passenger ships, operating in urban areas on a fixed time schedule (waterborne shuttle), a new type of application for the simulation of the accelerated forward speed motion has emerged. As elaborated by Papanikolaou and Xing-Kaeding (2019), the frequent stops and the tight time-schedule planned for a battery-driven fast catamaran may be associated with significant acceleration rates in the range of up to 0.20g, which puts severe challenges on ship's battery capacity, the power of the e-motors and propulsion system, with manifold side-effects on ship design and operation (Papanikolaou, 2020).

Abstract The resistance performance of ships has great significance in saving energy consumption and realizing the development of the green ships. In this paper, a 42m trawler is selected as the research object, and the effects of bulbous bow with different length, width and height on the hull resistance performance are studied by comparing the results of numerical simulation and model test. Through multi scheme optimization, several groups of spherical bow lines with better resistance performance are obtained, and the reliability of the spherical bow optimization method used in this paper is fully verified by model test. It provides a detailed reference for the design of the bow shape of fishing vessels in the future. INTRODUCTION Trawlers are the most numerous of all kinds of fishing vessels. The research on trawlers with excellent resistance performance is of great significance to the energy saving and emission reduction of fishing vessels, and it is also conducive to the development of green ships (Guo, 2012). The bow line has a great influence on the ship resistance, If the size, shape and position of the bulbous bow match the hull line reasonably, it will play a significant role in reducing the total resistance of the hull (Yan, 2018). The main reason is that in a certain speed range, if the bulbous bow size is selected properly, the wave generated by bulbous bow and the wave generated by the hull may have a favorable interference effect, the wave height of the composite wave will be reduced, and the wave making resistance of the bow will be significantly reduced, thus reducing the total resistance of the hull (Ying, 2007). At present, the commercial software STAR-CCM+ is widely used in the research of resistance performance in the world, but its element division, calculation parameters setting and other factors will affect the final calculation results (Zhang,2020). The deviation of free surface modeling, turbulence modeling, boundary conditions and model discretization from the reality also makes the calculation accuracy uncertain (Wilson et al., 2001). In order to solve this problem, this paper selects a 42 m trawler which is a classic type of offshore fishing vessel in Zhoushan Islands of China for research. According to Zhao (2012) and Zhang (2018), the length of bulbous bow has obvious influence on ship resistance. Based on that research, this paper compares other optimization schemes, and carries out numerical simulation on the resistance of several trawler models with bulbous bow of different sizes to study the influence of bulbous bow of different length, width and height on the ship resistance performance. The numerical simulation is mainly based on STARCCM+ software, the resistance of the ship model reduced according to the scale ratio is simulated by computer, and the pool test is carried out by the ship model of corresponding size (Niklas, 2019), and the calculated resistance value is compared with the test value, so as to verify the feasibility and reliability of the resistance calculation by STAR-CCM+ software.

Abstract Resistance and flow around the high-speed catamarans are influenced by water depth, which were studied less than that in unlimited water depth. Numerical simulations on flow around a high-speed catamaran both in unlimited and shallow water depth are carried using STAR-CCM+ software. Numerical method is verified based on experimental results according to the ITTC approach first, following numerical simulations on catamarans in shallow water in the same approach. The numerical results show that shallow water effects are obvious on resistance and flow characters of catamaran, and change of residual resistance is the main factor affecting total resistance in shallow water. The favorable interference on resistance occurs in supercritical water depth and the hull trims by stern and rises vertically in each Froude number. The transverse wavelength, angle between the intersection and centerline, and divergence wave angle in the subcritical region all increase with the depth Froud number. In supercritical region, only divergent waves remain, and the angle of divergent waves obviously decreases according to FrH. INTRODUCTION High-speed catamaran was developed in the 1970s, which has been widely used in recent years for its good stability and resistance performance at high speed. However, when a high-speed catamaran enters a finite depth of water, both the resistance performance and the flow field around the ship are affected by shallow water. Comparing with the research on ship resistance performance and flow field of an infinite water depth catamaran, there are relatively few investigations under shallow water conditions. In this paper, the resistance of a catamaran in shallow water is predicted by a numerical method based on the RANS solution, which provides basis for the prediction of shallow water resistance and the design of power system. Besides, it provides a certain reference for revealing the shallow water effect of the catamaran resistance.

Abstract A design methodology of a stern-fit flap is proposed for a high speed vessel with a tunnel-shaped stern. Along with conventional stern flaps, the resistance of stern-fit flaps is evaluated by model tests and numerical simulations to compare their performance in resistance reduction. An optimization of flap geometry using a quasi-random algorithm is conducted with the chord length and the flap angle as design variables to investigate their hydrodynamic difference induced by the surface shape. It turns out that stern-fit flaps have an overall advantage over conventional flaps in resistance reduction, which mainly results from the difference of the localized flow around the flaps. INTRODUCTION Due to its simple structure and efficient performance, a stern flap is widely used for medium or high speed vessels to reduce their drag by inhibiting the stern wave and adjusting the navigation attitude. The early application of stern flaps is used to control the navigation attitude of planning boats in the 1970s ( Brown , 1971; Savitsky and Brown , 1976) The idea of stem flap designed for high-speed displacement ships is originated from stem wedge research conducted in the 1980s ( Karafiath et al. , 1999). Basically, stern flaps can be classified into flat plate ( Yaakob et al. , 2004; Klara et al. , 2019) and curved plate ( Cusanelli and Hundley , 1999; Cumming et al. , 2006; Song et al. , 2019) according to their shape. Chen (2019) compared the performance of KCS ship in terms of resistance reduction with flat flaps and curved flaps using numerical simulation, which indicated that curved flaps can achieve better resistance performance than flat flaps. Curved flaps are usually constructed by a simple extension of the transom edge from its location to a specified position away from the stern ( Cusanelli and Hundley , 1999; Yaakob et al. , 2004; Cumming et al. , 2006; Chen, 2019). The typical feature of this conventional stern flap is that the flap angle a (Fig. 1) relative to the horizontal is constant along its leading edge when the ship is floating positively. It is apparent that the specification of angle a does not necessarily depend on the stern shape. Thus another angle θ is defined as an angle between the sectional profile of the flap and the extension of the local buttock in its longitudinal section. Fig. 1 illustrates the angle θ relative to the extension of the centerline buttock, and the relation between θ and a is θ = α + β where β is an angle between the horizontal and the extension of the buttock. As the angle β relative to the extension of the buttock is determined by the stern shape, the angle β equivalently represents the geometrical characteristic of the stern. Note that an angle is considered as positive when the referenced axis rotates anticlockwise to its location. In general, the conventional stern flap can reach a good performance in drag reduction after a design optimization when β is almost constant along its transom edge especially for a flat stern. However, for a stern with a complex surface whose β changes significantly along the transom edge, the flap designed by the conventional method will not perform as good as expected, because the flap portion with the large β probably result in drag increase while the flap portion with the small β may lead to failure to suppress waves.

Abstract By Python, we in this paper use machine learning algorithms to establish five different ship resistance prediction models for the Taylor standard set of residual resistance coefficient. In the case of the same other parameters, the straight-line interpolation is used to calculate the residual resistance coefficients of six groups of Taylor standard set with different breadth-draft ratios, and the LSTM model with the highest prediction accuracy is used to carry out the residual resistance prediction, and the prediction results are compared with the results of other researchers. The results show that the LSTM model has higher accuracy and better generalization performance for resistance prediction of Taylor series ships, which verifies the feasibility of the fast prediction method of ship resistance based on LSTM model. More importantly, it provides a fast method to predict the ship resistance by establishing the machine learning model. INTRODUCTION Prediction of ship resistance is one of the important contents of accurate prediction of ship rapidity, and it is also the difficulty and emphasis of ship hydrodynamics research (Huang, 2014). Researchers usually use approximate methods such as model series data, empirical formula, and parent ship estimation method to predict ship resistance. In the wake of developments in science and technology, computational fluid dynamics (CFD) technology has been more and more used in ship hydrodynamic calculation. Compared with the traditional resistance prediction methods, CFD technology has higher accuracy and is widely used. The prediction accuracy of approximate methods needs to be improved, and the CFD technology needs more time and requires high computational resources. Furthermore, in the initial design stage of the ship, the known parameters of the ship form are limited, and the hull line is still to be determined, so it is impossible to use ship model test or numerical simulation to determine the resistance. At this time, how to use the limited hull parameters to estimate the ship resistance effectively is particularly vital.

Abstract Optimization design of hull based on the computational fluid dynamics (CFD) is widely used in simulation-based design (SBD). And with the limit of computer ability, complex hull optimization such as hull appended with an actual propeller have not launched a full investigation. In this paper, we conduct design optimization of Japan Bulk Carrier (JBC) with an actual propeller (AP) based on CFD considering ship resistance and propeller wake distortion. In-house software OPTShip- SJTU is used for the present hull form optimization. Firstly, hull form modification module is applied to change the stern shape of the JBC. The in-house hydrodynamic CFD software naoe-FOAM-SJTU is applied to calculate the hull resistance and AP wake distortion. And the dynamic overset grid method is used to achieve the interaction between hull and propeller so that the optimization can take the high-fidelity flow interaction into consideration. The results demonstrate that the OPTShip-SJTU solver can be extended to optimize the coupled hydrodynamic performance in hull form optimization. The optimization results indicate a V-shaped hull can suppress the flow separation around the stern and benefit the propeller wake distortion. At the same time, the results remind us that it is necessary to consider the resistance and wake distortion together in hull optimization studies. INTRODUCTION Hull hydrodynamic performance is an important index for ship design. For hull form optimization, it is a measure to optimization the hull hydrodynamic by modifying the shape of the hull. With the development of computational ability and the computational fluid dynamic techniques, the Simulation-Based Design (SBD) framework has been developed quickly and applied to the hydrodynamic optimization of hull form, such as the resistance, seakeeping, ship maneuver, and so on( Miao, et al., 2020; Yang, et al., 2015; Tahara, et al., 2011). Hull form optimization has four steps: (1) the deformation of the initial hull (2) the hydrodynamic calculation of sample hulls (3) the surrogate model construction (4) the best hull form searching base on the optimization algorithm: For the resistance and wake distortion optimization, many scholars focus on the optimization of hull resistance and propeller wake distortion. In the aspect of hull resistance optimization, the single hull (Liu, et al., 2018)and the catamaran resistance ( Zha, et al.,2014). is optimized and compared with the experiment results using the naoe- FOAM-SJTU. In the aspect of propeller wake distortion optimization, the Wide Chord Tip propeller is studied and maximizes the performance of the propeller by adjusting expanded areas of the propeller blade. Results show that the propeller efficiency can be increased up to over 2% (Lee, et al., 2010). Consider the resistance and the propeller wake distortion simultaneously, many scholarship focus on the initial hull hydrodynamic performance with an actual propeller (Korkmaz, 2015; Deng, et al., 2015). The multi-objective genetic algorithm is taken as the optimization technique leading to the optimal hull forms which have better resistance and propulsion performances (Liu, et al.,2018). For closing the reality condition, the design optimization for self-propulsion of a bulk carrier hull is investigated based on the discrete adjoint method and the actuator disk method (He, et al., 2019).

Abstract In this paper, numerical simulations were performed for a high-speed deep-V planing hull, called Generic Prismatic Planing hull (GPPH). The resistance performance of the planing hull was studied. All the simulations were carried out using a dynamic overset grid package, which was developed by the authors based on the open-source CFD library OpenFOAM. The simulation results of resistance, sinkage, trim and wetted length were studied and compared with experimental measurements. The simulated pressure distributions, velocity field and wave patterns were also investigated to improve the physical understanding of planing crafts. INTRODUCTION Planing craft is a type of marine vehicle, whose weight is predominantly supported by hydrodynamic lift, rather than hydrostatic lift (buoyancy), which results in lower resistance compared with displacement ships at high speed. Because of this characteristics, the planing craft now has widespread applications in recreational and military use as well as for search and rescue operations. Therefore, continuous investigations have been performed to provide a better physical understanding of the planing craft, and to improve efficiency, safety and performance of it. The previous studies about planing craft mainly focused on the hydrodynamic forces and motions in calm water (Taunton, Hudson and Shenoi, 2010; Judge, Mousaviraad, Stern, et al., 2020a); slamming loads in waves (Bi, Shen, Zhou and Su, 2019; Judge, Mousaviraad, Stern, et al., 2020b); structural responses due to slamming loads (Begovic, Bertorello, Bove, et al.,2020; Rosen, Garme, Razola, and Begovic, 2020); and deck house or appendage design (Park, Park, Jang and Im, 2014; Molchanov, Lundmark, Furth and Green, 2019; Zou, Ma, Ji and Kang, 2018). The current study mainly discussed about hydrodynamic analysis of the high-speed planing crafts operating in calm water. As was reviewed in Yousefi, Shafaghat and Shakeri (2013), the related hydrodynamic analysis techniques include analytical techniques, experimental techniques and numerical techniques. Since the 1960s, analytical hydrodynamic analysis methods for planing crafts have been proposed in numerous literatures (Clement and Blount ,1963, Savitsky 1964, Savitsky and Brown, 1976). Despite the lack of accuracy, these works have made a great contributions to the understanding of the planing crafts for the following researchers. Ghassemi and Ghiasi (2008) proposed a combined analytical method to predict the total resistance of planing crafts at high speed, in which the resistance of the planing hull in calm water was divided into the induced resistance, frictional resistance and spray resistance. Sun and Faltinsen (2012) proposed an analytical 2D+t method to simulate the hydrodynamic forces on a semidisplacement high-speed craft. As concluded by the authors, these analytical methods were efficient and can give reasonable predicted results over a wide range of Froude numbers. Experimental techniques were always considered as the most reliable methods and were used to validate numerical techniques (Taunton, Hudson and Shenoi, 2010; Zou, Han, Zhang and Ji, 2017; Marco, Mancini, Miranda, et al., 2017). But different facilities and differences in towing set-ups also resulted in obvious discrepancy in the measurements of variables, such as resistance, sinkage, trim and wetted keel length (Judge, Mousaviraad, Stern, et al., 2020a).

Abstract In this paper, the air lubrication drag reduction is applied to the highspeed SWATH (small water area twin hull), and the effect of injection position on the drag reduction and wetted surface area reduction is studied. Before the numerical simulation, the convergence of the computational grid is tested first. The tank test of a high-speed SWATH with air lubrication is carried out, which is used to validate the accuracy of the numerical method. Then, the hull moving in calm water with various injection positions and air flow rates are simulated to study the effect of air flow rate and injection position on the drag reduction and wetted surface area reduction. It could be seen the high airflow rate is beneficial for the drag reduction of SWATH. The distance between surface and injection position has a negative influence on the drag reduction and wetted surface area reduction. INTRODUCTION The basic structure of the small water area twin hull ship (SWATH) is two slender underwater bodies and struts, which has a large wetted surface area, and its development trend is high-speed and large-scale. Therefore, Reducing resistance especially friction resistance during high-speed navigation is important for SWATH. The air lubrication method is proved to be effective to reduce the resistance of ships (Jang et al. 2014; Butterworth et al. 2015). The air lubrication method achieves drag reduction by the injection of air under the hull to cover the surface with a fluid less viscous than water. The early research of the air lubrication method is using the method on a simplified plate. Elbing et al. (2008) conducted experimental research on changing the aeration rate on a 2-dimensional simplified flat plate, using strip aeration troughs. The aeration rate was changed from 0.01m 2 /s to 0.015m 2 /s. When the aeration rate is insufficient or there is some upstream disturbance, the air layer Decomposition may occur. Amromin (2016) studied the influencing factors of the stable gas layer boundary with a flat plate as the object. Makiharju et al. (2018) used vent holes to carry out the abovementioned plate test to study the influence of vent holes layout on air layer coverage and obtain a cm-level air layer. Slyozkin et al. (2014) used experimental methods to change the incoming flow velocity and ventilation of the flat plate model to study the propagation process of gas in the bottom of the ship.

Abstract As a high-performance ship, trimaran is composed of a main hull and two slender side hulls. It has obvious advantages over monohull and catamaran in rapidity, seakeeping, stealth and general arrangement. Taking a trimaran as the research object, this paper uses the Multidisciplinary optimization platform for ship hydrodynamic performance (SHIPMDO-WUT) independently developed by our research team to carry out optimization. This platform uses Radial Basis Function interpolation method (RBF) to modify the ship hull form. The objective function of the optimization is wave-making resistance coefficient (Cw). In order to explore the influence of hull form and sidehull arrangements on the Cw of trimaran, the optimization is divided into two steps: The first step is only to optimize the side-hull arrangements. The second step is to optimize the hull form and side-hull arrangements comprehensively. The optimization results show that 1) arrangements modifying is significantly affected Cw of trimaran. 2) modifying the hull form will change the best position of side hulls and there is a relationship between arrangements and hull form. INTRODUCTION With the proposal and implementation of energy efficiency design index (EEDI) by IMO, energy conservation and emission reduction has become an important index in ship design. Trimaran, as a kind of highperformance ship, has been widely concerned since it came into being. It has broad application prospects in both civil and military fields for its excellent rapidity and Seakeeping performance. Compared with conventional monohull, trimaran has two side hulls, larger deck area and flexible general layout. In the aspect of resistance performance, two side hulls can form favorable interference with the main hull, so as to effectively reduce wave making resistance. In recent years, in the field of hull form optimization, many scholars have studied the resistance performance optimization of trimaran. Daniel Floden (2004) used Shipflow to optimize the position of side hulls under various speeds, and analyzed the influence of side body position on wave making resistance. Palmers (2015) changed the position of the side hull and used an improved Particle Swarm Optimization algorithm to find the position of the side body with the minimum resistance. Mizine et al. (2008) used Shipflow to predict the wave making resistance of trimaran. The result verified the calculation accuracy of Shipflow, and obtained the influence of the main hull and side hull on the wave making resistance. Mahmood S. et al. (2011) Optimized the trimaran form by only considering the main hull and keeping the side hull unchanged. Yang Chi et al. (2015) considered both the position of side hulls and the hull form of side body. First, CFD calculation was carried out for nine different positions of side hulls to obtain the optimal position of resistance. Then the hull form of side hull was optimized to obtain the optimal profile of side hull at three design speeds (Fn = 0.25, 0.35 and 0.45). Liu Xinwang (2019) optimized the side hull position of trimaran by using the self-developed ship form optimization software, which reduced the total resistance by 44%. Sun Lina (2015) adopted the idea of hierarchical optimization, firstly optimized the position of side, and then completed the optimization of hull form under various speeds based on the optimal position. Zong Zhi (2018) used six parameters to optimize coefficient of total resistance (CT) of a trimaran, three to control the hull form of the main hull, two to change the position of side hulls and the rest one being length ratio of new side hull to original side hull. CT of the optimized trimaran decreased by 21.34%.

Abstract Flapping-foil thrusters arranged below the hull of the ship are examined for the exploitation of energy from wave induced motions by direct conversion to useful propulsive power. In the framework of Seatech H2020 project (https://seatech2020.eu/) flapping-foil thruster propulsion innovation is examined, in combination with standard propulsion system based on optimally controlled Dual Fuel engine, aiming at an increase in fuel efficiency and radical emission reductions of NOx, SOx, CO2 and particulate matter. In this paper the combined performance of the above systems is examined for a short-sea shipping scenario in the North Sea and two ship types. The analysis is based on a simplified approximation using data from systematic series. The results show that: (i) flapping-foil thrusters can directly convert kinetic energy from the ship motions into thrust to augment the overall propulsion in waves, (ii) additional thrust generated by the foils will enable the engine to operate in part-load without compromising vessel speed, resulting in an additional positive effect on its emission profile, and (iii) the foils can improve the dynamic stability of the ship. INTRODUCTION Research and development results concerning flapping foil thrusters, supported by extensive experimental evidence and theoretical analysis, have shown that such systems, operating under conditions of optimal wake formation, can achieve high levels of propulsive efficiency; see, e.g., Triantafyllou et al (2000, 2004), Taylor et al (2010). Additional data concerning thrust coefficient, foil flexibility and Reynolds number effects can be found in the experimental systematic study by Vermeiden et al (2012). Based on the above results, the last period biomimetic propulsors with the ability to convert wave energy directly into thrust augmentation is subject of intensive investigation. For ships the application of bow mounted flapping-foil thrusters positioned below the waterline, which exploit the energy from the wave induced motions to generate a net positive thrust augmenting the ship propulsion, could lead to significantly reduced engine loads. A schematic presentation of biomimetic foil thruster arranged at the bow of the ship, with support for elevating/lowering the system in the water is shown in Fig. 1. In real sea conditions, the ship's propulsive power demand typically increases above the corresponding value in calm water for the same speed and at the same time experience undesirable wave induced, oscillatory, heave and pitch motions. The application of flapping foil thrusters, coupled with optimally controlled Dual Fuel engine technology, is expected to yield significant fuel savings and emission reductions.

Abstract When exposed to harsh conditions like sour environment, the resistance of low carbon line pipe steels to hydrogen embrittlement is of the upmost importance. There are several factors that are playing a role on the sour resistance of line pipe steels. The control of secondary phase inclusions is one of the most known factors. For example, elongated MnS or hard non-metallic inclusions like Al 2 O 3 act as stress concentrators via the accumulation and recombination of hydrogen atoms. A banded microstructure like ferrite-perlite bands is also known to increase the susceptibility to hydrogen cracking. And finally, the corrosion of the steel at the steel-fluid interface plays also a role on the sour performances and is often less discussed in the literature than the previous two parameters. This paper highlights the importance of the corrosion layer developed during sour exposure on the overall Sulfide Stress Cracking (SSC) resistance of 4 line pipe steels designed as per API 5L annex H. The impact of Ni and Cr alloying is investigated here in terms of diffusible hydrogen and surface evolution. The former is studied via permeation and interrupted testing with direct hydrogen measurements while the latter is studied via EPMA, SEM and XRD. The overall sour performances are evaluated by four-point bending and uni-axial constant load tests following NACE TM0316 and NACE TM0177 standards. In this study, Ni and Cr alloying have different effects. Nickel alloying improves the compacity and the coverage of the corrosion layer which acts as a barrier by limiting the hydrogen concentration inside the steel and improves the overall sour resistance. However, this was not observed in the Cr alloyed steel. With the test conditions of the present study, the Cr-alloyed steel did not develop a homogeneously distributed iron sulfide corrosion layer during sour exposure which resulted in a hydrogen level into the metal nearly 5 times higher than the Ni-alloyed steel after 30 days and failures in the SSC A tests.

Abstract The floating transportation of tunnel elements is a crucial link in the construction of submerged pipe tunnels. However, the selection of towing water resistance coefficient is always one of the difficult problems, so that the tank towing test is generally used to determine the value in major projects. This paper takes the long and large tunnel element as the research object, the coefficient of towing water resistance of tunnel elements is regressed according to the towing test data of the physical model of towing tank tunnel elements. The empirical formula of drag coefficient of tunnel elements towing in water is obtained, which is composed of such variables as channel water depth, towing velocity and towing angle. The empirical formula is compared with the experimental value of tunnel elements towage test, and the result is close to the experimental value. It is shown that this empirical formula can calculate the towing water resistance coefficient of tunnel elements towing more quickly and accurately. The empirical formula can provide a new method to estimate the towing water resistance coefficient of towing for the subsequent towing of long and large tunnel element and slender and long floating bodies, and then provide suggestions for towing for project bidding, and provide support for the scheme planning of ship machinery configuration and construction decision making. Introduction Immersed tunnel elements have been increasingly used all over the world with extensive application range. There are over 130 underwater immersed tunnel elements fully operational worldwide right now. The Detroit River Tunnel is the first immersed tunnel element built in accordance with the standard construction method of immersed tunnel element; Japanese government started to build immersed tunnel elements since 1935, and has built a large number of large-scale immersed tunnel elements in the past three decades; the construction of the Maastunnel in Rotterdam, Netherlands started in 1941; the Busan-Geoje immersed tunnel was built in recent years, the maximum weight of a single tunnel element even reached 50000 tons while the maximum immersion depth was 40m. Researchers in Chinese mainland started research on this construction method in Shanghai around 1960. Although compared to other countries, the construction of the immersed tunnel element in China started late, it enjoys fast development and good momentum. The construction of the Pearl River Tunnel was completed in 1994; Ningbo Yongjiang Tunnel and Changhong Immersed Tunnel were completely built in 1995 and 2002, respectively; the construction of Guangzhou Luntou-Biological Island Immersed tunnel element was completed in 2010; Zhoutouzui Tunnel in Guangzhou was opened in 2015; 2017 witnessed the construction completion of Honggu Tunnel in Nanchang and Dongping Tunnel in Foshan; the Hong Kong-Zhuhai-Macao Bridge consisting of bridges, tunnels and artificial islands was officially opened on October 23, 2018, making the travel among Hong Kong, Zhuhai and Macau much more convenient and also promoting the prosperity and development of Hong Kong, Zhuhai and Macao; immersed tunnel element has been adopted by a series of key projects including Shenzhen-Zhongshan Link, Jinguang East Tunnel, the river-crossing tunnel of Yuliangzhou of Xiangyang East-West Axis, Immersed Tunnels Project of Chebei Road-East Xinjiao Road, Dalian Bay Subsea Tunnel, Guangzhou-Shenzhen Riverside Expressway and Guangzhou Ruyifang Station, which proves the broad prospect of immersed tunnel element.

Abstract Compared with central manifold, PLET is much smaller and the load combination is also simpler. The foundation analysis result is shown that shallow foundation can meet all the requirements of LS17-2 project. This paper presents the design methodology of shallow foundation for PLETs. A design example is also be demonstrated in this paper. Introduction The development of LS17-2 gas field consists of subsea production system, one SEMI and subsea pipelines. The subsea production system comprises one west manifold and three east manifolds. LS17-2 SEMI is a SEMI platform and located near Manifold EAST1. Well fluid from west production loop will be transported to LS17-2 SEMI for process through two 10" pipelines and two 10" SCR risers. Well fluid from all east manifolds will converge at Manifold EAST1 and then be transported to LS17-2 SEMI for process through two 12" SCR risers. After processing, qualified natural gas shall be pressurized and transported to subsea pipelines from YC13-1 platform to HongKong through a 18" subsea export pipeline. Condensate oil shall be sent to the storage tank on LS17-2 SEMI and be exported by DP Shuttle oil tanker. Except four manifolds, the subsea production system also comprises twenty-five PLETs to connect manifolds or SEMI. Fig.1 shows the development layout of LS17-2 Gas Field. Most facilities in subsea production system are fixed structures, that is, they need to be fixed onto the seabed or sliding in a small area by the foundation structures which can ensure they will not sink into the seabed by the vertical load and prevent the great displacement by the horizontal load. Driven piles, suction piles and shallow foundations are three common foundation types for subsea production system. Driven piles are suitable for a wide range of soil conditions but restricted by the water depth for the pilling technology and economic. Suction piles can be used in very soft geological conditions and deep water but the cost of design, construction and installation is very high. Shallow foundation is that foundation for which the depth of embedment is less than the minimum lateral dimension of the foundation element. Mudmat with skirts or without skirt is the typical shallow foundation. It is not sensitive to the water depth and easy to be installed. So, it is widely used for the foundation of subsea products in deep water if the geophysical condition is appropriate. For LS17-2 project, a suction pile is selected as the central manifold's foundation, because the soft seabed cannot bear the large external load and self-weight from central manifold. In comparison, PLET is much smaller and the load combination is also simpler. The foundation analysis result is shown that shallow foundation can meet all the requirements of LS17-2 project.