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In order to solve the problem of false terrains caused by environmental interferences and tunneling effect in the conventional multi-beam seafloor terrain detection, this paper proposed a seafloor topography detection method based on fast two-dimensional (2D) Censored Mean Level Detector-statistics Constant False Alarm Rate (CMLD-CFAR) method. The proposed method uses s cross-sliding window. The target occlusion phenomenon that occurs in multi-target environments can be eliminated by censoring some of the large cells of the reference cells, while the remaining reference cells are used to calculate the local threshold. The conventional 2D CMLD-CFAR methods need to estimate the background clutter power level for every pixel, thus increasing the computational burden significantly. In order to overcome this limitation, the proposed method uses a fast algorithm to select the Regions of Interest (ROI) based on a global threshold, while the rest pixels are distinguished as clutter directly. The proposed method is verified by experiments with real multi-beam data. The results show that the proposed method can effectively solve the problem of false terrain in a multi-beam terrain survey and achieve a high detection accuracy.

The broadband noise can be dominant or important for total characteristics for marine propeller noise representing the minimum base of self-noise. Accurate prediction of such noise is crucial for survivability of underwater military vessels. While the FW-H Formulation 1B can be used to predict broadband trailing edge noise, the method required experiment measurements of surface pressure correlations, showing its limitations in generality. Therefore, in this study, the methods are developed to utilize wall pressure spectrum models to overcome those limitations. Chase model is adopted to represent surface pressure along with the developed formulations to reproduce pressure statistics. Newly developed method is validated with the experiments of airfoils at different velocities. Thereafter, with its feasibility and generality, the procedure incorporating computational fluid dynamics is established and performed for a propeller behind submarine hull. The results are compared with the experiments conducted at Large Cavitation Tunnel, thus showing its usability and robustness.

The wave power extraction by multiple Wave Energy Converters (WECs) deployed in a Y-shaped Water Channel Resonator (WCR) has been investigated. A WCR consists of a long water channel, and a V-shaped wave guider installed at the entrance of a water channel. If the period of the incident waves coincides with the natural periods of the fluid in a WCR, resonance occurs, as a result, the internal fluid in a WCR is greatly amplified. To estimate the wave power by multiple WECs placed at the antinodal points in a WCR, the heave motion response, time-averaged power, and capture width ratio were calculated for several design parameters. Also, the systematic model tests were conducted in a 2D wave tank. The numerical results are in good agreement with the experimental data. It was verified that a WCR helps the WECs to produce electricity more effectively by amplifying the wave energy in a WCR.

Simulation-based hull form optimization is a typical HEB (high-dimensional, expensive computationally, black-box) problem. Conventional optimization algorithms easily fall into the “curse of dimensionality” when dealing with HEB problems. A recently proposed Cross-Entropy (CE) optimization algorithm is an advanced stochastic optimization algorithm based on a probability model, which has the potential to deal with high-dimensional optimization problems. Currently, the CE algorithm is still in the theoretical research stage and rarely applied to actual engineering optimization. One reason is that the Monte Carlo (MC) method is used to estimate the high-dimensional integrals in parameter update, leading to a large sample size. This paper proposes an improved CE algorithm based on quasi-Monte Carlo (QMC) estimation using high-dimensional truncated Sobol subsequence, referred to as the QMC-CE algorithm. The optimization performance of the proposed algorithm is better than that of the original CE algorithm. With a set of identical control parameters, the tests on six standard test functions and a hull form optimization problem show that the proposed algorithm not only has faster convergence but can also apply to complex simulation optimization problems.

Maneuvering motions of a ship in calm water are studied through the concept of MMG model. Governing forces are defined by the use of available empirical formulae that require only main ship particulars as input variables. In order to validate the calculation tool, a full-scale sea experiment was carried out in Osaka Bay using a 17-m twin-screw passenger ferry. Test execution and data measurement were performed through the utilization of an autopilot control unit and satellite compass. The result of a straight running test confirms the acceptable accuracy in addressing the surge motion problem. Reasonable agreement between simulation and experiment is also confirmed for 5 ∘ / 5 ∘ and 10 ∘ / 10 ∘ zig-zag tests despite the strong environmental disturbance. The current model can generally represent the subject ship maneuvering motions and is promising for the application to other ship hulls.

Wave energy is one of the most available sources of renewable energy in the world. It has been previously proven that the flapping foil can generate thrust forces using energy from the surface waves and an empirical formula was proposed to predict the thrust forces generated by a flapping foil consist of NACA0015 section (Kumar and Shin, 2019a). However, the proposed empirical formula was restricted to the head waves i.e. 0° azimuth angle which was not useful for the flapping foils encountering with oblique and following waves. Therefore, in this study, the thrust empirical formula was modified to include the effects of azimuth angles based on the experimentally obtained data. And the modified empirical equations were validated by the combination of foils experimentally.

Polar regions face increasing challenges resulting from the interactions between global climate change, human activities, and economic and political pressures. As the sea ice extent trends diminish, maritime operations have started increasing in these regions. In this respect, an international concern has arisen for the shrinking of sea ice, preserving the environment, and passengers’ and seafarers’ safety. The International Maritime Organization has enforced the Polar Code (PC) for the ships navigating in these challenging Arctic and Antarctic waters. Polar regions are similar in some aspects but exhibit significant differences in geographical conditions, maritime activities, and legal status. Therefore, the PC that applies to both regions should be reconsidered, accounting for the differences between the areas for further development. This study considers the Arctic and Antarctic geographical differences relevant to the PC’s scope. The emphasis is placed on the changes regarding the sea ice extent and sea ice condition differences in the two regions, which are essential in maritime safety. This study also addresses the aspects of the PC that need improvement.

Object and purpose of research. This work was an experimental check of the possibility to improve the efficiency of low-frequency vibration damping for structural plates with high initial losses of vibration energy. Materials and methods. Vibration dampers used in this study were resonant anti-vibration straps partially tuned to the frequency of intense plate vibrations. Main results. This work demonstrated the possibility of additional efficient vibration damping of a plate with high initial losses of energy at the lower frequencies of its bending resonances. Conclusion. It is shown that vibration dampers suggested by the authors are highly efficient, as well as feature lighter weight and lower thickness than conventional vibration dampers.

Object and purpose of research. This paper justifies the prospects of compensated gross tonnage (CGT) as a main indicator for output potentials of Russian shipyards. Materials and methods. This paper analyses foreign and Russian publications for the most popular ship types built and delivered in recent years, as well as those under construction now, with an insight to Russian economy needs in ships and other marine technology. Main results. CGT indicator commonly used for marketing and statistical purposes, is the most unbiased measurement unit for the potential of separate shipyards and the entire marine industry. This paper suggests СGT as a main statistical indicator for potential of Russian marine industry as a whole and its specific commercial yards. Conclusion. This paper analyses the prospects of CGT as main indicator for production potential of shipbuilding enterpris-es. The methodology of this research can also be applied to Russian shipyards, so as to figure out their true potential and work-load, as well as to determine current underload of existing shipyards.

Object and purpose of research. Laser bathymetry, improvement and development of optical methods and instrumentation for marine environment studies. Materials and methods. Software in support of analytical methods for laser bathymetry taking into account hydrolidar parameters and probing routes. Main results. Efficiency improvement for calculation methods and demonstration of practical value for laser bathymetry in marine environment studies based on the developed physical & mathematical model. Conclusion. Calculation methods of laser bathymetry presented in this paper open new opportunities in lidar studies of marine environment at offshore oil fields of Northern seas.

Object and purpose of research. This paper discusses hydromechanics properties of propeller and their scaling laws. The purpose of this study was to analyse existing methods of scaling model test data through their comparison with full-scale test results, identify possible sources of considerable error that might be present in them, as well as update the method of model test data scaling taking into account hydrodmechanic interaction between propeller and hull in terms of their model data extrapolation to the full scale. Materials and methods. The paper discusses general relationships between hydromechanic parameters of hull and propeller, that arise, in their turn, from the fundamental laws of mechanics. These relationships were used to analyse interconnected laws governing the full-scale extrapolation of model test data for hull resistance, propeller thrust and propeller torque. Main results. The study identified some incorrect hypotheses in current scaling methods for hydrodynamics of propeller in behind-hull conditions, that might bring about considerable error in full-scale estimates of operational advance coefficient, thrust coefficient, efficiency and RPM. Conclusion. This paper suggests alternative techniques for determination of operational advance coefficient and other hydromechanics parameters of full-scale propeller, so as to obtain the estimates that take into account physical peculiarities of scale effect and also correlate with the results of full-scale trials.

Object and purpose of research. This paper discusses structures of high-power electric propulsion systems for ships. The purpose was to give a summary of design solutions made in development of these systems. Materials and methods. This paper relies on academic and technical data, as well on the long-term author’s experience in marine electric propulsion R&Ds. The solution suggested by the author is based on the comparative analysis of design solutions adopted in the development of structures for high-power marine electric power and propulsion systems. Main results. Summary on design solutions for high-power electric propulsion systems of such ships as icebreakers, oil tankers, LNGCs and cruise liners. Conclusion. Results obtained by author were used in the design of the electric propulsion system of the «Lider» nuclear icebreaker and further could be used in design of Arctic vessels.

Object and purpose of research. This paper discusses cavitation erosion on propeller blades. The purpose of this work is to review and analyse modern studies on cavitation erosion, as well as to apply these research results for better under-standing of cavitation damage risk on full-scale propellers. Materials and methods. The paper reviews recent studies on cavitation erosion, as well as the author’s own findings in cavitation erosion on full-scale steel propellers, analyzing the energy needed to create cavitation damage of recorded size. This energy was calculated as per the model based on the results of metallurgical studies discussing the effect of shot blasting upon steel properties. Comparison of these results with those obtained as per classic formulae for the collapse energy of cavita-tion bubble made it possible to estimate the conditions of cavitation erosion on propeller blades. Main results. The review of recent studies on cavitation erosion has shown that current progress in the technologies of experimental studies and computer-based simulations made it possible to considerably improve the knowledge about cavitation erosion process as compared to the level of the 20th century. This review shows that cavitation erosion studies followed three practically independent paths: experimental studies and computer-based simulation of flow around propeller blades with locali-zation of peaks for one or several criteria reflecting the intensity of cavitation energy fluctuations; the studies intended to esti-mate the pressure exerted by collapsing cavitation bubbles and emerging cumulative jets; and finally, the studies on the proper-ties of materials affected by cumulative jets and collapsing bubbles. At this point, it would be practicable to merge these three paths using the results of full-scale cavitation erosion analysis for propellers. KSRC findings in cavitation damage of full-scale steel propeller has shown that cavitation damage recorded in these studies might occur due to a certain combination between the required energy, bubble-blade interaction pressure and the size of affect-ed area on steel blade surface, and this combination, in its turn, might take place when cavitation bubbles consisting of vapour fraction with partial air content hit the blade surface and collapse. Conclusion. This paper shows the capabilities of modern research methods in obtaining new data on the inception mecha-nism of cavitation erosion. Still, to develop the methods for prediction of cavitation erosion (in particular, on propellers), it is necessary to merge the results obtained in different branches of cavitation studies. The basis for this merging could become a power-based analysis of cavitation processes, with help of the cavitation erosion model suggested in this paper and based on the similarity between cavitation erosion and shot-blasting.

Object and purpose of research. This paper discusses electric propulsion system of leader icebreaker. Its purpose was to develop mathematical and computer-based model of electric propulsion drive powered by asynchronous motor with three stator windings for further investigation of steady, transitional, asymmetric and emergency operation scenarios of electric power and propulsion system for the leader icebreaker. Materials and methods. Hardware and methods for computer-based simulation of complex engineering structures. Main results. Development of the mathematical model representing asynchronous motor with three windings in phase coordinates. Computational studies on direct startup of 15 MW propulsion motor, as well as on steady and transitional operational conditions of ship electric power system consisting of 36 MW synchronous genset, two-winding transformers and electric propulsion drive with 15 MW asynchronous motor in phase coordinates with three stator windings and three-level frequency converter. Calculation of voltage non-sinusoidality ratio for MSB buses with operation of 15 MW propulsion motor driven by 36 MW synchronous genset. Conclusion. Mathematical model of asynchronous motor suggested in this paper could be used to calculate steady and transitional operation scenarios of marine power systems with frequency-controlled three-winding asynchronous motor, as well as to calculate electromechanical and electromagnetic processes and refine frequency control algorithms. This is especially relevant because each of the asynchronous electric machines used in the electromechanical assemblies of leader icebreaker propulsion motors has three stator windings, and this icebreaker is the first experience of applying a 15 MW marine electric drive.

Object and purpose of research. This papers discusses PSVs (or, in RS classification, Supply Vessels): special ships that provide offshore drilling rigs with drilling supplies, fuel, water, provisions, spare parts for equipment, as well as deliver personnel shifts to/from the platform and perform the functions of duty, rescue, fire, and environmental protection vessels. The purpose of the study is to develop a physical model of PSV functioning and give design recommendations for proper de-termination of its characteristics and properties. Materials and methods. Generalization and analysis of PSV design and operation, as well as analysis of Russian and foreign publications about PSV specifics, supported by systematized statistical materials sufficient for design recommendations. Main results. This work summarized the data on PSV properties, characteristics, design and operation requirements, as well as the ways to implement them in terms of hull shape, general arrangement, mission-specific equipment, conceptual type and power plant, suggesting a vision of PSV as design object. Regressive analysis performed by the authors is supported by a wide scope of design materials that summarizes PSV operation experience and development trends, thus preparing the basis for future PSV designs. Conclusion. PSVs are the main link in the offshore oil and gas production. The ships of this type are becoming more and more popular, especially in their multi-purpose variant. This paper makes it possible to formulate design requirements for them, as well as to trace the ways of their implementation. This paper also suggests the methods for determination of PSV dimensions, conceptual type and mission-specific equipment, as well as main design parameters, properties and transportation and operation capabilities.

The results of the simulation used a propeller disk actuator method that models the propeller effect without modeling a real propeller. Direct optimization will be calculated using the CFD method of each variation of the clearance propeller configuration indicating that the amount of propulsion efficiency produced is very dependent on the clearance propeller. The most optimal propulsion efficiency occurs at a distance of 0.738 m from the steering shaft with a Dprop = 0.88, KT = 0.22, KQ = 0.028, and J = 0.40 besides having an advance velocity visualized with a Va = 10.6 knots which has a 50% propulsion efficiency, which the value will decrease according to the reduction in distance propeller. The less efficiency of the propulsion produced in the clearance propeller between -0.162 - 0.438 m from the steering shaft. This is because the slope angle between the entry of water and the longitudinal axis of the ship's hull on the stern exceeds the required conditions.

I n the work breakdown structure for shipbuilding of machinery outfitting is related to machinery, ducting, hvac & piping, steel work, and insulation. Integrated work breakdown structure is one of the shipbuilding methods involving in management, so that design time is shorter. The d ucting, HVAC & piping is the system based on the contract assignment and drawing approval by classification society. Then, we compare the effect of each Time Estimation. Then, continue with combine product and project structure. Problem start with how do we compare old with new WBS technology, no optimization process, and no working breakdown structure for the outfitting in the engine room. Bar chart, combination of industrial and financial system with design software also program project evaluation and review technique methodology will be used. Results obtained a work breakdown structure for Guidelines. The Aim was for optimization process time. The schedule created compared with the actual schedule that occurs so that we can see there is a difference of time shows that the shipyard applies integration. This also will lead to man-hour optimization. It is concluded that an integrated work breakdown structure can be applied to obtain the shipyard design in a shorter time .

M any design codes for structures in tropical waters are still based on the code for the North Sea, even though both have different environmental conditions. This research was conducted to assess the influence parameters of the tropical water environments and to determine the empirical estimates of the parameters that have a major effect on the corrosion that occurs in tropical waters. The result of this study will produce a practical equation function to estimate the corrosion loss based on the parameters of temperature, current velocity, and dissolve Nitrogen (DIN) for two different levels, low concentration level DIN, and high concentration level DIN. The function can analyze the estimation of corrosion that occurs in two different locations in the chain, the splash zone area, and immersed area. The corrosion rate (mm / year) obtained from the empirical estimation is then validated with the actual measurement data from the field obtained from the available literature. The empirical estimation results show a good fit when compared with data from existing actual measurements. Furthermore, the validated estimation results and actual data are compared with the existing class/code rules wear allowance. The corrosion rate results in particular conditions that exceed the corrosion wear allowances in the rules for data on tropical waters.

The use of sound absorbers on many ships made from glass wool. Glass wool has a negative impact on health, which can irritate the skin and disrupt the respiratory system. Therefore, it is necessary to have an alternative sound insulation material that is eco-friendly which has capabilities comparable to glass wool, and can also be used as heat insulation on ships. These alternative ingredients are materials from natural fiber. This research made sound absorbers using coconut fiber by soaking fiber into an alkali NaOH solution. Materials are selected based on density, economic value, and ease in the manufacturing process. The sound absorbers are modified using coconut fiber which is given a soaking treatment of alkaline NaOH solution and distilled water with a percentage of 15%. Soaking aims to remove lignin content and improve the mechanical properties of coconut fiber. In this research, 9 variations were made with different compositions. Tests are based on ASTM E84 to determine the flashpoint value and the safe flame spread on the ship. From the test results, it was found that coconut coir material was given a soaking treatment of alkaline NaOH solution with a percentage of 15% for 2 hours with a density of 0.3 gr/cm3 and thickness 30 mm and using a polyurethane adhesive. The time to reach the flashpoint is 20.45 seconds and the average temperature of flame spread is low when compared to other specimens including glass wool. The conclusion obtained is that the sound absorbers are safe when used on a ship.

Object and purpose of research. This paper discusses passenger catamarans. Its purpose is to find methods and means to improve seakeeping and propulsion performance in waves, reduce external structural loads, improve comfort and reduce material consumption of catamaran by means of optimally shaped bows and passive motion stabilizers. Materials and methods. The study is based on the methods of ship theory and ship motions, as well as on numerical calculation methods. Main results. Based on the calculation data analysis, this paper suggests principal technical solutions offering high comfort and cost-effectiveness of catamaran. Conclusion. These results could be used for design optimization of comfortable and efficient passenger catamarans.

Object and purpose of research. This paper discusses structural materials under cyclic load. The purpose is to determine the minimum fatigue life corresponding to a certain non-exceedance probability of this value. Materials and methods. The study was performed on three structural materials: steel 15ХМ, steel 08Kh18N10Т and titanium alloy PТ-7М. Initial estimate of fatigue life distribution parameters relied on the data about guaranteed maximum and minimum values of temporary resistance and relative cross-section tapering. The assessment was performed as per a common curve “conditionally elastic stress amplitude versus number of cycles to failure” taking into account the mechanical prop-erties of given material. The values of minimum fatigue life were obtained as per two different methods: statistical simulation of the random values following the Weibull distribution law and the analytical expression for probability density of the lows for given distribution function of random value and fixed scope of sampling. Main results. The lows yielded by statistical simulation are more conservative than those yielded by the analytical formula. The margin in terms of the number of cycles to failure stipulated as 10 in several regulatory documents seems to be somewhat unsubstantiated. This margin is too great in the low-cycle domain and too small in the high-cycle one. Conclusion. This paper postulates the existence of guaranteed maximum and minimum values for mechanical properties of structural materials, namely temporary resistance and relative cross-section tapering. These values were applied to well-known analytical curves of fatigue, which finally yielded possible variation ranges for fatigue life at various amplitudes of conditionally elastic reduced stresses, assuming the existence of a certain shift in the sensitivity limit of fatigue life distribution. These data were further used to establish standard deviations and mathematical expectations for the number of cycles to failure.

Object and purpose of research. This paper discusses surface layer at water-air boundary. The purpose of this work to investigate, in controllable conditions, the dynamics of surface layer properties depending on temperature variations. Materials and methods. Contact multi-channel tools for temperature and humidity control, as well as infrared tools for water surface temperature monitoring. Simulation of different thermal conditions at water-air boundary and low-intensity hydrophysical disturbances on the free surface. Main results. The study yielded simulation data and experimental confirmation of humidity fluctuations in the surface layer at different temperatures at water-air boundary in the conditions of low-intensity disturbances. Conclusion. This study yielded the data on qualitative changes in surface layer humidity based on the calculations as per simultaneously measured temperatures of water in the surface layer and near water-air boundary.

Air pollution that stems from vessels has become a critical problem especially for people living in cities with heavy maritime traffic. Istanbul City is an important metropolis of the region and the world. This study proposed strategies to reduce air pollution in the Strait of Istanbul by extending the International Maritime Organization and European Union strategies’ scope. The strategies’ priority levels were analyzed employing the fuzzy analytical hierarchy process method by asking opinions from experts who live in the Strait of Istanbul as a marine pilot or vessel traffic operator with at least 10 years of existing work experience. The analysis results determined which types of ship that passes the strait are more sensitive to the above mentioned strategies using the fuzzy technique for order preference by similarity to ideal solution method. Accordingly, the strategies under the “Declaration of the Strait of Istanbul and the Marmara Sea as a Sulfur Emission Control Area” and “prohibition of the use of heavy fuel on ships” have been the highest priority strategies in reducing air pollution in the strait. The direct passing ships achieved the highest sensitivity level to the strategies held in this study according to the selected experts.

Bulk carriers and general cargo vessels have the largest number and tonnage among different types of ship fleets. According to the United Nations Conference on Trade and Development data in 2019, the tonnage of the global bulk carrier and general cargo vessel is 842,438,000 and 74,000,000 metric tons, respectively. The main cargo weight measurement method for bulk carriers and general cargo vessels is the draught survey calculation. In this study, a fuzzy analytic hierarchy process questionnaire was prepared based on previous studies and experts’ opinions. Responses from the experts were consolidated to determine the priority vector of the criteria of draught survey error sources. Expert evaluations showed that the major reasons of draught survey inconsistencies are problems occurring at draught reading and ballast measurement stages. Accordingly, the most effective alternatives to minimize the errors were found to be training and documentation, which are closely related to education. This study aims to determine the draught survey error causes and their priorities along with different means to reduce the errors from the experts’ opinions. This study will contribute to the literature by shedding light on draught survey errors in which studies in the academic literature are very limited.

Future planning is difficult in several industries, including the maritime sector, especially with the current pandemic because of numerous active dynamic factors. Thus, this study aimed to determine the freight demand estimates based on the Twenty-foot Equivalent Unit-based monthly number of containers handled in Turkish ports by comparing the prediction accuracy and reliability of artificial neural network (ANN) models with various algorithms using the “exponential smoothing” and “Box-Jenkins” time series methods. The monthly container volume handled in Turkish ports between January 2005 and December 2018 was used, and augmented Dickey-Fuller tests were conducted with the EViews 5 software. Results from several tests revealed that the 12-time delay ANN model, which was developed with the original series, provided the highest accuracy. In this study, the demand forecasts for the container volume that would be handled in Turkish ports were conducted for the year 2022 with the developed model, and a methodological approach was presented for the forecast models in different maritime industry fields.

In the processing of oil and gas, a pressure vessel is an important piece of equipment. It needs a method to prevent the failure of the pressure vessel. The Risk-Based Inspection (RBI) is a systematic approach to the inspection management method for equipment based on the level of risk. RBI is expected to provide sufficiently accurate recommendations to prevent equipment failures. In this research, the objects to be carried out are the 10V2102 condensate separator and the 10V2103 condensate storage vessel. According to RBI analysis, the risk category of the current RBI date is low risk for the condensate separator 10V2102 and condensate storage vessel 10V2103. Meanwhile, the inspection date of Condensate Separator 10V2102 is 2 April 2026 and 11 February 2027 for Condensate Storage Vessel 10V2103 and selected inspection methods are Visual Testing, Ultrasonic Testing (UT), Radiography Test (RT), Eddy Current Test, and Magnetic Particle Inspection.

Object and purpose of research. This paper discusses marine ducted propeller and the ways to ensure its target performance parameters. The purpose of this study was to mitigate unsteady forces on the propeller behind the duct struts. Materials and methods. Analytical estimates of propeller parameters and in-house KSRC methods for numerical simulation of ducted propeller behaviour. Main results. Calculations of effective wake behind duct struts taking into account the flow around hull and its append-ages. Calculations of unsteady forces for a standard propeller operating in this wake. Design of a propeller with increased blade skew. Calculations of unsteady forces for the new propeller in the initial wake. Wake field parameters contributing to mitigation of unsteady forces. Calculations for the new strut shape for wake optimization. Calculations of unsteady force amplitudes for standard propeller in the new wake. Conclusion. Ducted propeller discussed in this study was meant to illustrate how propeller wake properties, like unsteady forces, can be optimized without changing propeller geometry, only by means of curved duct struts.

Object and purpose of research. This paper discusses insufficient flow rate in a standard swirl atomizer of ma-rine water-mist Fi-Fi systems. The purpose of this study was to find the reasons for this insufficient flow rate and the ways to improve it. Materials and methods. This research was a computer-based simulation (in commercial ANSYS CFX package for engineering analysis) based on modern methods of computational fluid dynamics (CFD). Main results. An upgraded swirler for high-flow atomizer preventing cavitation in its inner channels. Conclusion. These results make it possible to design atomizers and sprinklers of marine water-mist Fi-Fi systems with cavitation-free swirler channels.

An accurate evaluation of three-dimensional (3D) Time-Domain Green Function (TDGF) in infinite water depth is essential for ship’s hydrodynamic analysis. Various numerical algorithms based on the TDGF properties are considered, including the ascending series expansion at small time parameter, the asymptotic expansion at large time parameter and the Taylor series expansion combines with ordinary differential equation for the time domain analysis. An efficient method (referred as “Present Method”) for a better accuracy evaluation of TDGF has been proposed. The numerical results generated from precise integration method and analytical solution of Shan et al. (2019) revealed that the “Present method” provides a better solution in the computational domain. The comparison of the heave hydrodynamic coefficients in solving the radiation problem of a hemisphere at zero speed between the “Present method” and the analytical solutions proposed by Hulme (1982) showed that the difference of result is small, less than 3%.

This paper aims to numerically estimate the dynamic ice load on a conical structure. The Discrete Element Method (DEM) is employed to model the level ice as the assembly of numerous spherical particles. To mimic the realistic fracture mechanism of ice, the parallel bonding method is introduced. Cases with four different ice drifting velocities are considered in time domain. For validation, the statistics of time-varying ice forces and their frequencies obtained by numerical simulations are extensively compared against the physical model-test results. Ice properties are directly adopted from the targeted experimental test set up. The additional parameters for DEM simulations are systematically determined by a numerical three-point bending test. The findings reveal that the numerical simulation estimates the dynamic ice force in a reasonably acceptable range and its results agree well with experimental data.

In the conventional experiment to assess the towing operations, the towing stability of the towed vessel has been evaluated under the condition without lateral motion of the tug-boat. However, the tug-boats may have a lateral force to change the direction of the towed vessel. In this study, experiments have been conducted considering unsteady conditions in the towing system. First, a towing test system in a Circular Water Channel (CWC) using the conventional experimental method is built. Second, the towing characteristics of the towed vessel are investigated using the conventional method, and they are compared with other research results and stability discriminant criteria. Third, the lateral motion of the tug-boat was modeled as a sinusoidal motion using a forced oscillation device changing frequency and amplitude. Finally, the discussion is given in terms of both towing- and course-stability of the towed vessel according to the lateral motion of the tug-boat.

Performance of a NACA 634-021 hydrofoil in motion under and in close proximity of a free surface for a large range of angles of attack is studied. Lift and drag coefficients of the hydrofoil at different submergence depths are investigated both numerically and experimentally, for 0° ≤ AoA≤30° at a Reynolds number of 105. The results of the numerical study are in good agreement with the experimental results. The agreement confirms the new finding that for a submerged hydrofoil operating at high angles of attack close to a free surface, the interaction between the hydrofoil-motion induced waves on the free surface and the hydrofoil results in mitigation of the flow separation characteristics on the suction side of the foil and delay in stall, and improvement in hydrofoil performance. In comparing with a baseline case, results suggest a 55% increase in maximum lift coefficient and 90% average improvement in performance for, based on the lift-to-drag ratio, but it is also observed significant decrease of lift-to-drag ratio at lower angles of attack. Flow details obtained from combined finite volume and volume of fluid numerical methods provide insight into the underlying enhancement mechanism, involving interaction between the hydrofoil and the free surface.

This paper presents a direct numerical simulation of turbulent flows over a bump in an open channel to examine the turbulence characteristics near divergent waves emanating from the bump and to investigate the interaction of the turbulences with the divergent waves. To verify the reliability of the simulations, the mean velocity profile and root-mean-square of velocity fluctuations are compared with previous data. The anisotropic invariant maps show that the ratio of the streamwise to spanwise velocity fluctuations plays an important role in characterizing the anisotropic nature of the separated shear layer behind the bump in the vicinity of the free surface. The vortex identification discloses a large-scale streamwise vortical structure from the mean velocity field and a cluster of small coherent structures from the instantaneous velocity field, which are responsible for the anisotropic characteristics of the turbulence beneath the free surface.

Managing with the presence of sea ice is the primary challenge in the operation of floating platforms in the Arctic region. It is widely accepted that offshore structures operating in Arctic conditions need station-keeping methods as well as ice management by icebreakers. Dynamic Positioning (DP) is one of the station-keeping methods that can provide mobility and flexibility in marine operations. The presence of sea ice generates complex external forces and moments acting on the vessel, which need to be counteracted by the DP system. In this paper, an icevaning control algorithm is proposed that enables Arctic offshore vessels to perform DP operations. The proposed icevaning control enables each vessel to be oriented toward the direction of the mean environmental force induced by ice drifting so as to improve the operational safety and reduce the overall thruster power consumption by having minimum external disturbances naturally. A mathematical model of an Arctic offshore vessel is summarized for the development of the new icevaning control algorithm. To determine the icevaning action of the Arctic offshore vessel without any measurements and estimation of ice conditions including ice drift, task and null space are defined in the vessel model, and the control law is formulated in the task space. A backstepping technique is utilized to handle the nonlinearity of the Arctic offshore vessel’s dynamic model, and the Lyapunov stability theory is applied to guarantee the stability of the proposed icevaning control algorithm. Experiments are conducted in the ice tank of the Korea Research Institute of Ships and Ocean Engineering to demonstrate the feasibility of the proposed approach.

This paper predicts the speed-power-rpm relationship in regular head waves using various indirect methods: load variation, direct powering, resistance and thrust identity, torque and revolution, thrust and revolution, and Taylor expansion methods. The subject ship is KVLCC2. The wave conditions are the regular head waves of λ/LPP = 0.6 and 1.0 with three wave steepness ratios at three ship speeds of 13.5, 14.5 and 15.5 knots (design speed). In the case of λ/LPP = 0.6 at design speed, two more wave steepness ratios have been taken into consideration. The indirect methods have been evaluated through comparing the speed-power-rpm relationships with those obtained from the resistance and self-propulsion tests in calm water and in waves. The load variation method has been applied to predict propulsive performances in waves, and to derive overload factors (ITTC, 2018). The overload factors have been applied to obtain propulsive efficiency and propeller revolution. The thrust and revolution method (ITTC, 2014) has been modified.

A key factor that governs the wave interferences of a submerged body is the dimensionless Froude number. Computational Fluid Dynamics (CFD) is used to describe the resistance force coefficients and the generated waves of two SUBOFF submarine models. Grid independence studies are performed on two cases, totally and shallowly submerged cases, with four sets of computing meshes. The highest peaks are marked by red points at given wavelengths, a line is fitted to those points with a least-squares approximation, and the half wake angle at multiple Froude numbers is defined between the fitted line and the centerline of the free surface. The results show that when the depth of the target is 1.1D, constructive interferences occur at Fn = 0.3 and 0.5, while destructive interference occurs at Fn = 0.35 with distortion of the waveform. The half wake angle is less than 19.47° because of the interference between the bow and stern wave systems.

Numerical simulations of the Vortex-Induced Vibration (VIV) about a large-scale flexible pipe subject to shear flow were carried out in this paper. Efficiency verification was performed firstly, validating that the proposed fluid–structure interaction solution strategy is competent in predicting the VIV response. Then, the VIV characteristics related to multi-mode and spanwise hybrid waveform about the flexible pipe attributed to shear flow were investigated. When inflow velocity rises, higher vibration modes are apt to be excited, and the spanwise waveform easily convertes from a standing-wave-dominated status to a hybrid standing–traveling wave status. The multi-mode or even multiple-dominant-mode is prone to occur, that is, the dominant mode is often followed by several apparent subordinate modes with considerable vibration energy. Hence, the shedding frequencies no longer obey Strouhal law, and vibration trajectories become intricate. According to the motion analysis concerning the coupled cross-flow and in-line vibrations, as well as the corresponding wake patterns, a tight coupling interaction exists between the structural deformation and the wake flow behind the flexible pipe. In addition, the evolution of the vortex tube along the pipe span and a strong 3D effect are observed due to the slenderness of the flexible pipe and the variability of the vortex shedding attributed to the shear flow.

Growth promoting and immune stimulating effects of common mallow (Malva sylvestris) aqueous methanolic extract (AME) in O. mykiss were examined. Two different concentrations of common mallow AME [0.1 (CM1) and 0.5 (CM5) g kg-1 of feed] commixed a basic diet and a control diet without the common mallow extract were fed to rainbow trout for 30 days to evaluate growth rate and immune responses. At the end of the study, fish growth performance was determined as significantly higher in the group fed with 0.1 g kg-1 common mallow AME compared with control diet fed group (P

The length-weight relationships (LWRs) of fish are helpful in fisheries science. A total of 504 yellowspotted puffer (Torquigener flavimaculosus) specimens (257 female and 247 male) were caught from the Yumurtalık coast of Turkey (Eastern Mediterranean Sea) between 2018 and 2019 by using a trammel net set with a depth range between 5 and 42 m. The sex ratio was found 1:1.08 for males and females, respectively. The length-weight relationship was described for combined both sexes by the following formula W = 0.00130×L3.094 (r2 = 0.918) with a positive allometric growth. Fulton condition factor (CF) was calculated as 1.713 ± 0.145 for combined sexes. This study presents the first results available for the length-weight relationships and condition factor of T. flavimaculosus according to both sexes in the Yumurtalık coast of Turkey.

The objectives of this study were to investigate the effects of Oliveria decumbens as a medicinal herb with reported immunostimulatory potential on the growth, immunity status and health of Nile tilapia (Oreochromis niloticus). In an eight- week trial, fish (45 ± 5 g) were randomly divided into 13 treatments as follows: in 10 treatments fish were fed on diets containing 0 (control), 0.01, 0.1 and 1% of O. decumbens extract and essential oil and their 1:1 combinations. Also, in three treatments fish received plant hydrolate at doses of 312.5, 625 and 1250 ppm as bath treatment. At the end of experiment, blood samples were taken for immunological and biochemical measurements. All treated fish showed comparable growth performance to those received control diet. The highest levels of respiratory burst activity were observed in extract 1% group. Similarly the serum lysozyme levels were significantly affected by essential oil and extract supplemented diets. Fish received plant hydrolate at dose 312.5 ppm showed the highest significant protein level. Also, the globulin levels were increased in group fed on diet containing extract 1%. Plant supplementation had no negative effects on the fish health biochemical indices including cholesterol, triglyceride, alkaline phosphatase and aminotransferase enzymes. In conclusion, the results of this study showed that application of O. decumbens derivatives improved the immunity of Nile tilapia without adverse effects on fish growth and health.

Subsistence inland fisheries are underreported in developing countries like Pakistan. This study attempted to find out fish consumption determinants of traditional subsistence fishers in Charsadda district of Khyber Pakhtunkhwa (KP) Province of Pakistan. Data were collected between March and December 2019 through 36 predetermined questions applied to 286 randomly selected households. The data were analyzed through multiple linear regression model. Study found that average fish consumption of the sample households was 3.3 kg per capita per annum, which is higher than Pakistan’s national average of 1.9 kg per capita per annum. The most viable reasons of fish consumption among the sample households were that most of them were; subsistence fishers, lived closed to water bodies and had easy access to fishing grounds. Majority of them consumed fish once a month in summer season but consumption increased in winter season. The regression results indicated that fish price, proximity to rivers, and family size have negative, whereas number of fishing equipment’s, education and family income have positive effect on fish consumption. Actions are needed to improve fish production in local rivers through hatcheries development and aquaculture encouragement, so that fish meat become affordable to other areas located far away from water bodies.

The accurate estimates of the maximum length of fish within a population are significant issues. Because the parameters related to maximum length, weight and age of fish communities in the ecosystem are constantly used in population dynamics and stock estimation studies, recording of such data is vital for determining the life history of fish. In this connection, a single specimen of Scomber japonicus was captured off Kabatepe Bight (Gallipoli Peninsula) with handline by a commercial fisherman on 21 September 2013. This specimen was 370.00 g in total weight and 34.6 cm in total length (32.0 cm in fork length), corresponding to the second maximum size recorded for Turkish waters. This study aims to contribute to the scientific literature.

In this study, the in vitro effects of some metal ions (Ag + , Cd 2+ , Cu 2+ , Fe 2+ , Ni 2 + and Pb 2+ ) on freshwater fish Capoeta umbla liver and gill glucose 6-phosphate dehydrogenase (G6PD) have been investigated. For this purpose, C. umbla liver and gill G6PD enzymes were purified, with a specific activity of 31.52 and 22.83 EU/mg protein, 3353.2 and 736.5 fold in a yield of 19.28% and 23.15%, respectively. In order to control the enzyme purification SDS-PAGE showed a single band for the enzyme. In addition, in vitro effects of metal ions on enzyme activity were researched. As a result, Ag + , Cd 2+ , Cu 2+ , Ni 2+ and Pb 2+ inhibited fish liver G6PD; Ag + , Cd 2+ , Fe 2+ , Ni 2 + and Pb 2 + inhibited fish gill G6PD. Besides, it was found that the most effective inhibitor of G6PD enzyme within metal ions used was Ag + . Our results also demonstrate that these metals might be dangerous at low micromolar concentrations for fish G6PD enzyme.

"The main purpose of this paper is to present a short review of the actual progress on the floating offshore wind turbines. Floating offshore wind turbines have several advantages: overcoming the depth constraint, floating offshore wind turbines can be installed further offshore and therefore on the one hand have little or no visual impact from the coast, and on the other hand to take advantage of more constant and stronger winds, thus increasing the production efficiency of electricity. They are assembled to port and then transported to site with an ordinary tug, which can also bring them ashore for heavy maintenance or final dismantling. Floating wind power is the future of offshore wind power."

"Onboard vessel heavy rotating equipment and environmental conditions (sailing in waves) are a major source of onboard vibrations that may affect the vessel structure and equipment. Vibrations are propagated through the vessel structure from the engine room all the way up to the superstructure affecting the installed masts. All the equipment installed on the superstructure and the mast, such as antennas, navigation lights, radars etc, are affected by these vibrations which can lead to malfunctioning equipment with major implications in the sailing fitness of the vessel itself. This paper presents the analysis of a tug superstructure and mast vibrations problems caused by the main engine and the propeller rotation. Solutions to optimize the structure and to improve the transmission model of these vibrations are also described."

"Regarding the increasing demands for a low noise environment onboard ships, the classification societies introduced the measurement of noise levels onboard every ship not only for the first ship, no matter the type and size above 1600 gross tonnage. That why is necessary a good collaboration of all the parties involved in the construction of ships from designers, shipbuilders, till owners. This article describes the measurements technique used for obtaining the noise levels onboard a cargo vessel, to obtain the approval of Classification society-"

The estimation of the hydrodynamics characteristics of the small ships rudders is an important issue in the initial design process. The manoeuvring performance depends on the type and geometry of the rudder. The control forces and moments generated by the rudder deflection can be calculated on the basis of the hydrodynamics characteristics of the rudder. A short description of the Mordvinov theoretical model is presented in this paper, in order to determine the hydrodynamics characteristics of a small ship rudder, with the propeller and hull influences. On the basis of the control forces and moments, the optimum position of the rudder stock and the selection of the steering gear can be performed. Using the Mordvinov method, the computer code PHP NM-MAN-HC was develop at the Research Centre of the Naval Architecture Faculty of “Dunarea de Jos” University of Galati. This computer code is integrated in the software platform PHP (Preliminary Hydrodynamics Performance) and is used for didactic applications and practical research activities in the small ship design process

"As part of the continuum growth of the shipping industry, new challenges arise for the engineers. The development of floating structures capable of withstanding accidental loads, such as grounding and ship collisions, become nowadays an integral part of the design process. The current paper presents a methodology for impact analysis using FEMAP software capabilities in two distinct stages. The first stage consists of the impact analysis using a rigid indenter displaced at different speeds. The second stage of the study evaluates the impact analysis considering both the indenter and the structure deformable. Mesh influence tests, as well as the influence of the type of elements used in the analysis, have been taken into consideration in the present study."

"The junction flow between an hydrofoil and a plate is manifested by the generation of vortex structures as a result of the interaction between the boundary layer on the plate and the boundary layer on the profile. Two benchmark tests have been identified in the literature: one for the flat plate, and the other for the NACA 0012 profile. The Verification and Validation study for both hydrofoil and flat plate was performed by testing all turbulence model implemented in Ansys Fluent and results are compared with the experimental ones."

"The purpose of this paper is to verify the induced stresses of a framework element from central area of the chemical tanker ship type. This static calculation was performed by the finite element method with Femap software as modeler and NX Nastran as solver."