Search Results (10)

Given the typical characteristics of self-propulsion and jack-up wind turbine installation vessels (WTIVs), including their full and blunt hull form and complex appendages, this paper combines the model test method with the RANS-based CFD numerical prediction method to experimentally and numerically study the resistance of the optimized hull at different spudcan retraction positions. The calm water resistance components and their mechanisms of WTIVs based on T-BOW were obtained. Furthermore, using the multivariate nonlinear least squares method, an empirical formula for rapid resistance estimation based on the Holtrop method was derived, and its prediction accuracy and applicability were validated with a full-scale ship case. This study indicates that the primary resistance components of such low-speed vessels are viscous pressure resistance, followed by frictional resistance and wave-making resistance. Notably, the spudcan retraction well area, as a unique appendage of WTIVs, exhibits a significant “moonpool additional resistance” effect. Different spudcan retraction positions affect the total calm water resistance by approximately 20% to 30%. Therefore, in the resistance optimization design of WTIVs, special attention should be paid to the matching design of the spudcan structure and the hull shell plate lines in the spudcan retraction well area. Full article

Over the years, air lubrication technology has been widely applied to maritime vessels, demonstrating its significant energy-saving and emission-reducing effects. However, the application of this technology in inland waterway transportation faces unique challenges due to the shallower water depths, particularly during low water periods. Under such conditions, the formation of the air layer and its associated drag-reduction effects may undergo alterations. Conducting research on air lubrication technology in shallow water conditions holds great practical significance for promoting its application in inland waterway vessels. Therefore, a numerical study is undertaken to examine the impact of water depth on Air layer Drag Reduction (ALDR) to promote the use of ALDR technology on inland canal boats with shallow water depths. The object was a specific river-sea direct ship model, and a groove was created at the bottom of the model with air injection. At two distinct speeds, numerical simulations were run for four different depths: deep water, moderate water, shallow water, and ultra-shallow water. A comparative examination of the air layer morphology on the ship bottom and drag reduction was conducted to investigate the impact of water depth on ALDR and confirm the viability of using ALDR technology on shallow-water navigation boats. The results indicate that due to the change in the velocity and pressure fields at the bottom of the ship, the efficiency of drag reduction and the form of the air layer on the ship’s bottom are significantly impacted by variations in water depth in restricted waters. However, the total resistance can still be significantly reduced by setting grooves on the hull with air injected in shallow waterways. Reduced frictional resistance no longer predominates the overall resistance reduction in shallow water; the proportion of the decrease in viscous pressure resistance rises and can reach up to 4.8 times the decrease in frictional resistance. The research confirms the application prospects of this technology on inland waterway transport ships. Full article

Polyurethane is a common polymeric coating, providing abrasion resistance, chemical durability, and flexibility to surfaces in the biomedical, marine, and food processing industries with great promise for future materials due to its tunable chemistry. There exists a large body of research focused on modifying polyurethane with additional functionalities, such as antimicrobial, non-fouling, anticorrosive action, or high heat resistance. However, there remains a need for the characterization and surface analysis of fluoro-modified polyurethanes synthesized with commercially available fluorinated polyol. In this work, we have synthesized traditional solvent-borne polyurethane, conventionally found in food processing facilities, boat hulls, and floor coatings, with polyurethane containing 1%, 2%, and 3% perfluoropolyether (PFPE). Polyurethane formation was confirmed by attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, with the urethane band forming at 1730 cm⁻¹ and the absence of free isocyanate stretching from 2275–2250 cm⁻¹. X-ray photoelectron spectroscopy (XPS) was used to confirm perfluoropolyether polymerization with an increase in the atomic percentage of fluorine. Wettability and hydrophobicity were determined using a dynamic water contact angle with significant differences in advancing the water contact angle with the inclusion of perfluoropolyether blocks (PU–co–1PFPE 131.5° ± 8.0, PU–co–2PFPE 130.9° ± 5.8, and PU–co–3PFPE 128.8° ± 5.2) compared to the control polyurethane (93.6° ± 3.6). The surface orientation of fluorine supported the reduced critical surface tensions of polyurethane modified with PFPE (12.54 mN m⁻¹ for PU–co–3PFPE compared to 17.19 mN m⁻¹ for unmodified polyurethane). This work has demonstrated the tunable chemical qualities of polyurethane by presenting its ability to incorporate fluoropolymer surface characteristics, including low critical surface tension and high hydrophobicity. Full article

The objective of this study is to design a hull-mounted sonar dome of a ship using OpenFOAM with a bulbous bow effect at cruise speed in calm water. Verification and validation for the original sonar dome simulation are conducted. Next, the 1.44 million grid size is selected to study different dome lengths. By protruding the dome forward 7.5% of the ship’s length, the optimal 17% resistance reduction is achieved and is mainly caused by the pressure resistance decrease. The optimal sonar dome not only functions in the same way as a bulbous bow, but the viscous flow behaviors are also improved. The protrusion corresponding to 90 deg phase lag reduces the bow wave amplitude. The flow acceleration outside the boundary layer and ship wake velocity are higher coinciding with the much lower total resistance. A smaller flow separation and thinner boundary layer are also observed behind the sonar dome because its back slope is less steep. The high pressure covers a smaller area around the bow, and the smaller bow wave crest does not hit the ship’s flare to form high pressure. Consequently, the lower high pressure on the dome front and higher low pressure on the dome back result in the decreases in pressure resistance. The vortical structures are also improved. Full article

The consideration of shallow water effects has gained in importance regarding inland operations. The interaction between the keel and the riverbed affects the hydrodynamic characteristics of marine vessels. The highly complex nature of the interference phenomenon in catamarans makes the shallow water problem more complicated as compared to monohulls. Hence, catamarans are very sensitive to speed changes, as well as to other parameters, such as the shallow water effects. This makes the design of catamarans more challenging than their monohull equivalents. At lower Froude numbers, the higher importance of the frictional resistance makes the greater wetted surface of the catamaran a disadvantage. However, at higher speeds, there is the potential to turn their twin hulls into an advantage. This study aims to investigate the wave-making resistance of a zero-carbon fast passenger ferry operating in shallow water. The URANS (unsteady Reynolds-averaged Navier–Stokes) method was employed for resistance simulations. Then, the double-body approach was followed to decompose the residual resistance into viscous pressure and wave-making resistance with the help of the form factors of the vessel calculated at each speed. The characteristics of the separated wave-making resistance components were obtained, covering low, medium, and high speeds. Significant findings have been reported that contribute to the field by providing insight into the resistance components of a fast catamaran operating in shallow waters. Full article

The paper presents a multi-fidelity extension of a local line-search-based derivative-free algorithm for nonsmooth constrained optimization (MF-CS-DFN). The method is intended for use in the simulation-driven design optimization (SDDO) context, where multi-fidelity computations are used to evaluate the objective function. The proposed algorithm starts using low-fidelity evaluations and automatically switches to higher-fidelity evaluations based on the line-search step length. The multi-fidelity algorithm is driven by a suitably defined threshold and initialization values for the step length, which are associated to each fidelity level. These are selected to increase the accuracy of the objective evaluations while progressing to the optimal solution. The method is demonstrated for a multi-fidelity SDDO benchmark, namely pertaining to the hull-form optimization of a destroyer-type vessel, aiming at resistance minimization in calm water at fixed speed. Numerical simulations are based on a linear potential flow solver, where seven fidelity levels are used selecting systematically refined computational grids for the hull and the free surface. The method performance is assessed varying the steplength threshold and initialization approach. Specifically, four MF-CS-DFN setups are tested, and the optimization results are compared to its single-fidelity (high-fidelity-based) counterpart (CS-DFN). The MF-CS-DFN results are promising, achieving a resistance reduction of about 12% and showing a faster convergence than CS-DFN. Specifically, the MF extension is between one and two orders of magnitude faster than the original single-fidelity algorithm. For low computational budgets, MF-CS-DFN optimized designs exhibit a resistance that is about 6% lower than that achieved by CS-DFN. Full article

This paper reviews a state-of-the-art zero emission propulsion system for a battery-powered small craft. The main aspects considered are the available propulsion systems, energy storage, and dock battery charging. This underlying activity is part of the KISS project, a research and development program in the frame of the EU-funded “Piano Operativo Regionale CALABRIA FESR-FSE 2014–2020 ASSE I–PROMOZIONEDELLA RICERCA E DELL’INNOVAZIONE”, which is aimed at designing and building a physical prototype. Its hull form is based on previous research conducted by the authors, and the powering performances were preliminarily predicted by CFD simulation. The KISS project represents a successful example of an electric small craft with performances and a mission profile comparable to competitors with conventional propulsion. Such a target has been achieved by a concurrent design that considers the hull form, engine, propulsion system, and energy storage onboard. Safety issues and the regulatory frame are also highlighted. Full article

Dicyclopentadiene (DCPD) modified unsaturated polyester resins (UPRs) are mostly used for hulls, decks, and bathroom facilities. Main advantages of these polymers over orthophthalic or isophthalic polyesters are their relatively low shrinking, reduced styrene emission, lower cost, and fast curing in thin layers. On the other hand, once cured, these materials are more brittle and have lower glass transition temperatures and lower chemical resistance due to their different chemical constitutions. DCPD UPRs with standard grades are usually produced with high-quality DCPD (over a 85% purity) using the so-called “water process”, a synthesis consisting of two reaction steps. An adduct of maleic anhydride with DCPD is firstly formed with water, and then, it reacts with the other esterification monomers such as acids and glycols. DCPD raw materials used in this study were prepared by a unique distillation process developed by ORLEN Unipetrol and University of Chemistry and Technology, Prague. This technology allows producing a wide spectrum of DCPD quality by adjusting the content of another norbornene dimer: methyl dicyclopentadiene (MeDCPD). The influence of MeDCPD on unsaturated polyester properties was examined throughout this study. It has been discovered that in low concentrations, MeDCPD had a slight influence on flexural mechanical properties whereas its concentrations up to 65% led to a softer and brittle material. Nevertheless, by adjusting the unsaturation degree, it has been shown that MeDCPD may be successfully implanted in UPR formulation. Full article

The particle swarm optimisation (PSO) algorithm has been widely used in hull form optimisation owing to its feasibility and fast convergence. However, similar to other intelligent algorithms, PSO also has the disadvantages of local premature convergence and low convergence performance. Moreover, optimization data are not used to analyse and reduce the range of values for relevant design variables. Our study aimed to solve these existing problems in the PSO algorithm and improve PSO from four aspects, namely data processing of particle swarm population initialisation, data processing of iterative optimisation, particle velocity adjustment, and particle cross-boundary configuration, in combination with space reduction technology. The improved PSO algorithm was used to optimise the hull form of an engineering vessel at Fn = 0.24 to reduce the wave-making resistance coefficient under static constraints. The results showed that the improved PSO algorithm could effectively improve the optimisation efficiency and reliability of PSO and effectively overcome the drawbacks of the PSO algorithm. Full article

In this study, a high-speed planing trimaran hull form is designed, and the effects of different displacements and gravity longitudinal layouts on the performance of the trimaran planing hull in calm water are experimentally investigated in the towing tank of the China Special Vehicle Research Institute. Based on previous work, an innovative inner tunnel appendage hydroflap is mounted in the inner aft tunnel, located 1/8 L from the transom in the longitudinal direction with attack angles of 0° and 4°, respectively. Furthermore, a regular stern flap is mounted on the transom close to the chine. The towing test results show that, as the gravity center moves forward, the high-speed region resistance of the planing trimaran increases and the longitudinal stability is also strengthened. Further, the total resistance of the planing trimaran with a heavier displacement is larger while the average mass resistance declines; i.e., the resistance efficiency is improved. The results also indicate that the inner tunnel hydroflap and stern flap enhance the aft hull hydrodynamic lift and tunnel aerodynamic lift. As a result, mounting aft hull lift enhancement appendages can affect the bottom and inner tunnel pressure distribution and then cause a slight resistance decrease in the low-speed region. The value relationship of resistance between groups of appendages for the attached hull and bare hull is reversed at a speed of about Froude number 3.0. Although the aft hull lift enhancement appendages result in a higher resistance cost in the high-speed region, the longitudinal stability is effectively promoted and the occurrence speed of porpoising results in a delay of 1 to 2 m/s. Full article