Ship Hull Research Articles

Hydroelasticity of a 21000TEU containership subjects to freak waves by fluid-flexible structure interaction simulations

In this paper the CFD-FEM two-way coupled method is used to simulate the motions and wave loads on a 21000TEU containership subjected to freak waves. A numerical wave tank is established for the generation of long-crested freak waves by wave focusing method based on superimposing sinusoidal component waves. The ship hull is modeled with a backbone beam which reproduces the vertical bending vibration modal behaviour of real ship. The simulated freak waves are checked and the evolution of freak waves during propagation is analyzed first. The ship responses in regular waves at different wave heights and ship speeds are compared. The extreme responses of ship motion and sectional loads in freak waves are analyzed and compared with those in regular waves. The influence of ship forward speed and wave height of freak waves on ship motion and load responses are analyzed and discussed.

End-to-end deep learning method to reconstruct full-field stress distribution for ship hull structure with stress concentrations

An image-based deep learning framework is developed to reconstruct full-field stress distribution of ship hull structure from discrete measurements in this paper. The work is motivated by the lack of data to assess the strength state of vessel. The proposed deep learning framework is based on a conditional generative adversarial network (cGAN) which contains a generator and a discriminator. They are mutually trained in a supervised manner based on an adversarial mechanism. The hull structure of interest is selected to be an opening deck of a bulk carrier. A novel image encoding algorithm is also designed to fuse global stress distribution and high gradient stresses at hatch corner regions into an image. A total of 3400 stress fields are generated and simulated using finite element method (FEM) to provide a sufficiently large dataset for training and testing the network. It is shown that the proposed deep learning approach can efficiently reconstruct the full-field stress distribution of hull structure. Furtherly, the influence of measurement noise on reconstruction accuracy is discussed. The results demonstrate that the well-trained network can directly generate robust solutions to full-field stress distribution under given discrete measurements.

An Analysis and Comparison of the Hydrodynamic Behavior of Ships Using Mesh-Based and Meshless Computational Fluid Dynamics Simulations

This paper presents a comparison of two turbulence models implemented in two different frameworks (Eulerian and Lagrangian) in order to simulate the motion in calm water of a displacement hull. The hydrodynamic resistance is calculated using two open-source Computational Fluid Dynamics (CFD) software packages: OpenFOAM and DualSPHysics. These two packages are employed with two different numerical treatments to introduce turbulence closure effects. The methodology includes rigorous validation using a Wigley hull with experimental data taken from the literature. Then, the validated frameworks are applied to model a ship hull with a 30 m length overall (LOA), and their results discussed, outlining the advantages and disadvantages of the two turbulence treatments. In conclusion, the resistance calculated with OpenFOAM offers the best compactness of results and a shorter simulation time, whereas DualSPHysics can better capture the free-surface deformations, preserving similar accuracy.

Research on Course-Changing Performance of a Large Ship with Spoiler Fins

The poor maneuverability inherent to large ships is a non-negligible problem that restricts the development of the shipping industry, as large ships can only cruise at an excessively conservative speed when they encounter complicated traffic conditions; nevertheless, ship collision accidents still occasionally occur. In the present study, the novel concept of spoiler fins for modern large ships is proposed. In order to assess their effectiveness in enhancing ship maneuverability, a KRISO container ship (KCS) was selected to carry a pair of spoiler fins, after which a simplified simulation approach for saving the calculation resource was designed for ship collision avoidance conditions, and a full-scale numerical model, including the ship hull, fin, and fluid field domain, was established. Transient-state hydrodynamic forces were calculated during collision avoidance maneuvers using the CFD method; the pressure and velocity contours around the ship were demonstrated; and the ship motion trajectories under different initial ship speeds were simulated and predicted through the adoption of overset mesh and 6-DOF dynamic mesh techniques. Eventually, the improved course-changing performance, dependent on the spoiler fins, was validated.

Direct numerical simulations of turbulent boundary layers developing over synthesised calcareous marine biofouling surfaces

ABSTRACT The topographical complexity and multi-scale nature of biofouling makes the use of current drag-topography correlations over regular topographical arrangements impractical. In order to address this problem, we synthesise biofouling-type surfaces of tubeworm-type populations in various percentage coverages and distributions. To acquire the resulting flow field we utilise topography-resolving direct numerical simulations. The surface synthesis is performed by an in-house surface generation/analysis package, AdRoS, in which individual biofouling organisms are used as building blocks to synthesise surfaces that resemble those found on ship hulls. Our synthesis algorithm allows for a parametric study to be performed with respect to selected parameters characterising the topography. In this work we focus on the frontal solidity, λ f , in order for its impact to the mean flow to be investigated. Results indicate that both the boundary layer growth-rate, as well as the roughness function, Δ U + , scale with the frontal solidity, λ f , in a proportional fashion, indicating the significance of the frontal solidity parameter. The organism-characteristic height, h , proves to also have a significant impact to the mean flow and even counter-act against the frontal solidity. Interestingly, typical flow separation patterns such as those found on isolated wall-mounted objects were detected, which were found to be mitigated or amplified depending on the planar, λ p , and frontal, λ f , solidity.

Evaluation of the Effect of Static and Flowing Conditions on the Corrosion Behavior of the Hull of Marine Ships

Marine ship hulls' corrosion resistance behavior under static and flowing conditions was investigated. The metal of the hull panels of marine ships was chemically and mechanically examined and analyzed, revealing that carbon steel type DIN 1.0501 C35 is employed in constructing the hull of ships in the port of Basrah in Iraq. A corrosion resistance test for this metal was carried out in laboratory-prepared seawater under static and flowing conditions at a flow rate of 1500 liter/hour and various immersion times (12, 24, 48, 120, 168, 336) hours. The temperature was kept constant at 30°C, and a fixed salt concentration of (3.5% sodium chloride). The corrosion rate of C35 carbon steel was calculated using the weight loss method is an effective method for calculating the corrosion rate of carbon steel. The samples were examined using a scanning electron microscope (SEM) for corrosion analysis. Conclusions from this research indicate that an increase in the flow rate resulted in an elevation of the corrosion rate, doubling the corrosion rate compared to samples under static conditions. The corrosion rate exhibited a significant increase during the first 24 hours, followed by a gradual decrease with increasing immersion time. The corrosion rate increased by 682.9%. The speed of corrosion was fast initially, but the weight loss slowed after 24 hours of immersion. A scanning electron microscope (SEM) examination revealed that the flow environment was aggressive for carbon steel. It was much more severe, and the pits and grooves were more significant than the static condition.

Hot embossed micropatterned slippery Al 5083 alloys in stagnant and laminar saltwater

Slippery AA 5083 alloy surfaces were fabricated by using ground (mean roughness-Ra = 45±2 µm), polished (Ra = 9±3 µm) and hot embossed micro-patterned specimens, and coating them with silicone oils of varying viscosities (1000−100000 cSt). The surface energy of aluminium alloy (AA) 5083 was estimated to be 850±210 mJ·m−2 using Schultz model. The ground/polished specimens were coated with 12±1 µm and 24±0.3 µm thick oil. They showcased slippery character, wherein apparent water static contact angles (SCAs) of 94±1° to 104±1°, slide-off angles (SAs) of 4±0° to 21±2° and contact angle hysteresis (CAH) of <10° were observed. Also, CAH and SAs revealed an increasing trend with an increase in the oil viscosity, irrespective of the coating thickness or the substrate roughness. In addition, the water droplets bounced-off the oil coated (24 µm thick) surfaces up to Weber no. (We) of 3.91. Furthermore, micro-patterned specimens were fabricated by hot embossing at 300 °C, 17+1 MPa, 5 min and comprise of hexagonally arranged pillars and holes with 6.5−7.1 µm diameter and 9.5−13.6 µm pitch. A key finding is that micro-pillars offered the highest tolerance to shear drainage of oil under saltwater (3.5 wt% NaCl) for up to 7 days, in both stagnant and flowing laminar (Reynolds no.‐Re =247) conditions, as compared to micro-holes and unpatterned surfaces. Interestingly, the slippery properties of oil coated unpatterned AA5083 have retained after 7 days of submersion, showing SCAs ≥ 97±3° and SAs ≤ 14°, despite the negative spreading coefficient of oil on AA5083 under water. Such slippery durable micro-pillared and micro-holed AA5083 surfaces could be highly beneficial for mitigating biological corrosion of ship hulls in marine environments.

Effects of Homogeneous and Inhomogeneous Roughness on the Ship Resistance

Ship hull roughness can significantly increase the ship resistance. The roughness caused by biofouling attached to the ship hull is not uniform but has a random distribution. The purpose of this study is to investigate how the inhomogeneous surface roughness distribution affects the ship resistance and the various resistance components. The KRISO container ship (KCS) is considered as a case study. To model the inhomogeneous surface roughness, the ship hull is divided into three segments with equal wetted surface area. Combinations of three roughness heights, denoted as P, Q, and R with ks values of 125 μm, 269 μm, and 425 μm, respectively, are considered to obtain homogeneous and inhomogeneous roughness arrangements (PPP, QQQ, RRR, PQR, PRQ, QPR, QRP, RPQ, and RQP). CFD method is utilized in this study, utilizing RANS equations and k-ω SST turbulence model. A VoF method is used to model the free surface. CFD simulation results show that for the homogeneous roughness, the total resistance coefficient CT increases with increasing ks (PPP &lt; QQQ &lt; RRR), as expected. For the inhomogeneous roughness, the friction resistance coefficient CF increases in the order PQR &lt; PRQ &lt; QPR &lt; QRP &lt; RPQ &lt; RQP, consistent with results from earlier studies. In all the cases, the friction resistance (CF) is the dominant component of the total resistance. As Re increases from 2.2 x 109 to 2.7 x 109, the percentage of the friction resistance decreases, while the percentage of the wave resistance increases. The viscous-pressure resistance decreases slightly as Re increases from 2.2 x 109 to 2.7 x 109.

Novel Statistical Analysis Schemes for Frequency-Modulated Thermal Wave Imaging for Inspection of Ship Hull Materials

Novel Statistical Analysis Schemes for Frequency-Modulated Thermal Wave Imaging for Inspection of Ship Hull Materials

Enhancing Efficiency in Deep-V Planing Hull Ships: A Study on The Design of Spray Strips to Minimize Resistance

Spray strips are deflectors installed on the hull to decrease the wetted surface area (WSA). By reducing the WSA, the overall resistance of the ship is lowered because it lessens the friction of water flowing against the hull. The purpose of this research is to predict the function of spray strips in an effort to improve ship performance. In this study, the numerical methodology employs the Finite Volume Method (FVM) along with the Reynolds-averaged Navier-Stokes equation (RANS) for resolving fluid dynamics issues. The modeling of the two-phase flow involves the utilization of both the Volume of Fluid (VOF) model and the Eulerian model. The results of this study show that spray strips can reduce the total resistance by about 2.7%. Increasing the number of spray strips can reduce the drag shear value by 3.5%. Spray strips are effective in reducing total drag when the Froude number (Fr) is greater than 1 or when the vessel is in the planing phase. The profile shape of spray strips with dimension 2:1 shows the best performance on ship resistance.

Methods of reducing fuel consumption by seagoing vessels in order to reduce emissions of harmful substances into the atmosphere

The aim of the paper is to draw attention to the emissions of toxic compounds into the atmosphere problem by seagoing ships. Annex VI of the MARPOL Convention, which came into force in 2005, concern the prevention of air pollution from ships, forced shipowners to use solutions aimed at limiting the emission of these harmful substances into the atmosphere. One of the instruments enabling the implementation of these guidelines is the design energy efficiency index EEDI, introduced obligatorily for designed and newly built ships. In turn from 2013, the regulations also oblige shipowners to maintain an effective energy management plan during ship's operation, SEEMP (Ship Energy Efficiency Management Plan). The paper presents factors that influence the reduction of fuel consumption by ships, leading to a reduction in emissions of harmful substances into the atmosphere and thus achieving the required EEDI and other indicators. These are factors related to the ship's hull, the main propulsion engine and the propeller-rudder system. The influence of each of these factors on the level of fuel consumption by the ship was indicated. The work highlights the methods of reducing fuel consumption by seagoing ships aimed at reducing emissions of toxic compounds into the atmosphere, which are currently the most popular and effective, and relate mainly to the hull and main propulsion engines.

Computation of Green's functions for the acoustic scattering by an elastic structure excited by a turbulent flow in water

To model the hydrodynamic noise produced by an elastic ship hull or propeller excited by a turbulent boundary layer, we need an efficient method to compute the acoustic scattering by an elastic body surrounded by a fluid. In 3D, Boundary Element Methods (BEM) are used to reduce the computational costs, for both the fluid and the elastic body. A natural way to compute the boundary integral representation (BIR) of the sound pressure is to use formulations based on the free space acoustic and elastic Green's functions. However, since the turbulent flow along the elastic body is known only statistically, the use of these Green's functions would be too expensive. A remedy is to compute a Green's function adapted to the physical problem, thus satisfying the transmission conditions of the fluid-structure problem. This so-called "tailored Green's function" is determined by solving a coupled acoustic-elastic problem with the BEM, and leads to a simplified BIR of the sound pressure compatible with a stochastic source term. We first validate the computation of the tailored Green's function over a classic spherical geometry. Then we compare the scattering of multiple quadrupoles by elastic or rigid NACA0012 profiles.

Co-occurrence of microplastics and microparticles containing Cu and Zn and other heavy metals in sea-surface microlayer in Osaka Bay, Japan

Antifouling biocides such as Cu, Zn, and organic compounds not only inhibit adhesion of sessile organisms on ship hull but also possess toxicity to non-sessile organisms in marine environment. Thus, we firstly investigated the heavy metals and polymer types of anthropogenic microparticles (MPs) floating in the sea-surface microlayer (S-SML) in Osaka Bay. 7 types of MPs containing different metals (Cu, Cu-Zn, Zn, Ti, Sn, Ba and Fe-Mn-Ni) were found. The polymer type for 97.8 % of Cu and Cu-Zn MPs (41 samples) and 52.6 % of Zn MPs (19 samples) was acrylic resins which are widely used as binders in contemporary antifouling paints for ships; concentrations of 511–54,000 mg/kg for Cu and 95.1–13,200 mg/kg for Zn were found in these MPs. The high metal concentrations found the co-existence of acrylic polymers point towards an origin from antifouling paint particles (APPs). Furthermore, to quantify Cu and Zn concentrations in these MPs based on X-ray fluorescence spectroscopy (μ-XRF), calibration curves obtained from standard paint particles containing different Cu and Zn concentrations and different particle sizes made with similar matrix used in commercial antifouling paint were firstly established, according to which highly reliable Cu and Zn concentrations in MPs were obtained.

CFD studies into frictional effects of ship coatings to enhance condition monitoring & increase efficiency

Abstract Managing biofouling on ship hulls is essential for reducing CO2 emissions in the shipping industry. Biofouling, characterized by the accumulation of organisms on hulls, escalates surface roughness and hydrodynamic drag, subsequently increasing fuel consumption and CO2 emissions. In response, AkzoNobel, Royal Philips, and Damen Shipyards are developing a fouling prevention technology that utilizes Ultra Violet Light Emitting Diodes (UV-LEDs). The use of an array of multiple UV-LED tiles may lead to non-uniformities from gaps between tiles, potentially increasing frictional resistance due to variations in thickness and surface roughness at the tile joints. This study examines the impact of these non-uniformities on skin friction through simulations using the commercial Computational Fluid Dynamics (CFD) software, Star-CCM+. The analysis highlights effective jointing methods that minimize drag forces by optimizing gap-filling techniques, thus comparing favourably to traditional coatings. The findings contribute significantly to advancing a UV-C hull fouling prevention system, promising reduced environmental impacts and enhanced operational efficiency in the shipping industry.

Применение роботов вертикального перемещения для очистки корпусов судов от обрастаний

Traditionally underwater robotics deals with UAVs and ROVs. This paper discusses a new type of robot for this application - vertical climbing robots. This type of robots has traditionally been considered for terrestrial use. However recent developments have confirmed the effectiveness of using such robots for underwater research. The article describes the work carried out in the Laboratory of robotics and mechatronics of the Ishlinsky Institute for Problems in Mechanics RAS on using climbing robots for technological operations in the aquatic. In particular we discuss issues of creating a robotic system for cleaning ship hulls from fouling. This work was carried out jointly with the St. Petersburg State Marine Technical University.

A numerical procedure for calculating ice-induced fatigue damage for ship hulls in level ice

Ship hulls advancing in level ice are exposed to considerable cyclic ice loadings, which might cause fatigue damage, threatening the structural integrity and endangering the crews’ lives. Ice-induced fatigue problem is of significance to ice-going ships. In this paper, a fatigue analysis for ship structures in level ice is performed based on a dedicated 6-degree-of-freedom (6-DOF) numerical model of ice-ship interaction, founded on a circumferential crack assumption. The numerical procedure considers the time-varying instantaneous waterline and the couplings between ship motions and external forces. The local ice loads used for fatigue assessment can be obtained from numerical simulations, and the random load peaks are represented by Weibull distribution. A case study of fatigue calculation for designated transverse frames is carried out, of which the applied stress is converted from ice loads by means of structural beam theory. Eventually, according to a proper S-N curve, the fatigue damages are evaluated on the basis of Palmgren–Miner rule, respectively under the operational scenarios of laterally symmetrical and asymmetrical initial ice edges.

Numerical Simulation and Experimental Study on Dynamic Characteristics of Gas Turbine Rotor System Subjected to Ship Hull Excitation

Numerical Simulation and Experimental Study on Dynamic Characteristics of Gas Turbine Rotor System Subjected to Ship Hull Excitation

Feasibility study on additive-manufactured honeycomb sandwich structural solutions for a Fast Patrol Vessel

This work represents a significant step toward integrating additive-manufactured honeycomb sandwiches into ship hull structures. The sandwich structure consists of two continuous fibre-reinforced thermoplastic faces and a regular honeycomb core made of chopped fibre-reinforced thermoplastic. The primary goal is to create optimal manufacturing and design methods to determine to which extent the sandwich solution that has been analysed may be used as a structural component of a fast patrol vessel. The core of the design procedure is a purposely developed evolutionary multiobjective optimisation routine suited to evaluate the flexural response of the structure under investigation. The analytical formulations utilised to predict the structural response of an additive-manufactured honeycomb sandwich subjected to 3-point bending have been derived using a combined analytical and experimental approach. A fast patrol vessel made of steel has been taken as a reference to demonstrate the capabilities of the proposed solution. A steel primary stiffener and its associated plate have been extracted from the midship section and replaced by an additively manufactured honeycomb sandwich. By maintaining the same structural encumbrances, it has been found that a pseudo-optimal combination of the mechanical properties of the sandwich base materials can accomplish an exceptional weight reduction of three times.

Parameter adaptation of k − ω SST turbulence model for improving resolution of moderately separated flows around 2D wing and 3D ship hulls via EnKF data assimilation

Parameter adaptation of k − ω SST turbulence model for improving resolution of moderately separated flows around 2D wing and 3D ship hulls via EnKF data assimilation

Ship Hull Hybrid Structural Design Accounting for Reliability

The optimum ship hull design solution has always been a concern, and in recent years, genetic algorithms to optimise the ship hull structure have been developed. The genetic algorithm’s fundaments generate alternative solutions and compare them with pre-defined constants and objectives. The development of design solutions evolves through competition and controlled variations. Minimising the ship hull structure weight is essential in reducing the ship’s capital (construction) expenditure and increasing the cargo capacity. The risk of the ship is associated with the loss of the ship, cargo, human life, environmental pollution, etc. It is a governing factor impacted by the chosen structural design solution and the measures taken to reduce the structural weight. A genetic algorithm will be employed to study the weight minimisation of a multi-purpose ship hull structure, controlling the associated risk by accounting for several structural design variables. The risk and best design solution are defined by the probability of compressive collapse of the stiffened plates, integral ship hull structure, and the associated cost due to failure. The Pareto frontier solutions, calculated by the non-dominated sorting genetic algorithm, NSGA-II, will be employed to determine feasible solutions for the design variables. The first-order reliability method will estimate the Beta reliability index based on the topology of the stiffened plates and ship hull structure as a part of the Pareto frontier solutions. The algorithm employed will not account for any manufacturing constraints and consequences due to the encountered optimal design solution.