The 12th Symposium on High Speed Marine Vehicles will be held in Naples in October 2020. As in previous years, the Symposium will provide an opportunity to present and discuss developments in the design, construction and operation of high speed marine vessels. Papers are invited on all aspect of high speed vessels with a wide interpretation of ‘high speed’. Subsequent to the conference, selected papers may be considered for publication in the “International Journal of Small Craft Technology”. Authors of such papers will be given the opportunity to update their papers before publication in the Journal.
IMPORTANT
The Conference, in its e-edition, will not need a steady Hall. Participants wishing to reach Naples anyway, will be very welcome and their physical participation will be organised in the best way.
Thanks to the reduction of costs of the e-conference, also registration fee is reduced compared to our original fees.
Final Submission of papers is posponed to 21st July 2020.
Prof. Antonio FIORENTINO, University of Naples Federico II
Prof. Rita MASTRULLO, Head of Department of Industrial Engineering, University of Naples Federico II
Chaired by Trevor BLAKELEY, Royal Institution of Naval Architects, UK
It is well known that the dynamic of the stepped hull in real scale is rather complex and it’s not easy to predict that using empirical or mathematical approaches, and by numerical and experimental way as well. Moreover, there is huge lack in literature of data related to sea trials of stepped hull. Furthermore, the reliability of full-scale CFD simulations is not widely proven and validated especially for high speed and planing hull. For these several reasons, in this paper the authors are focused in the comparison of the results carried out from model experimental tests performed in model basin, model CFD Simulation, full-scale CFD simulations at the and sea trial data.
The performed simulations in model-scale have been compared to tank tests for validation purposes and, after, the full-scale simulations results have been compared to the scaled experimental tests and to the sea-trial results. A specific analysis is dedicated to the resistance components, in particular residuary resistance and friction resistance. The two resistance components, derived from CFD analysis, are compared to the calculated values using the International Towing Tank Conference (ITTC) formulas, and critical analysis was performed. The Stepped Hull considered is a Mito 31 outboard Rigid Inflatable Boat (RIB) built by MV Marine Srl Company.
Luxury high speed boats are increasingly being used for entertainment purposes however, not only humans, but also animals are negatively affected by high speed boats, and time is running out fast for people to do something about it.
In this study, a review of current negative effects of high speed boats to the environment are presented. Then, two main source of negative effect of high speed boats, the harmful gas emissions and noise are investigated. Noise radiated from a high speed super yacht model for different conditions are predicted by CFD analysis. In the CFD analysis, the yacht model is simulated for 5 different crusing speeds. Unsteady flow around the yacht is simulated using Reynolds Averaged Navier Stokes (RANS) with SST (Menter) k-w turbulence model. Resistance values are obtained and noise levels around the yacht are predicted by Ffowcs Williams-Hawkings noise model. Required propulsion power are estimated using resistance and propulsion values for different speeds. Harmful gasses (especially NOx and SOx) released from the yacht and pollute the air are investigated from the similar studies which have similar conditions. In particular, the change of noise level and harmful gases released into the environment, when the speed of the yacht increases are examined and discussed.
Consequently, it is believed that this study would lay an important foundation for the widespread investigation for the negative effects of the high speed boats in the future.
It is well known that during the life-cycle the growth of the ship weight is one of the main source of the performance-loss. Stern flaps have been used in many recent designs of transom stern vessels, in particular by the US Navy, to increase top speed or to realize improvements in fuel economy over the operating range. Furthermore, stern flap implementation has also become a practical retrofit on existing platform because significant improvements can be achieved at minimal cost.
According to the US Navy experience, in order to analyze this aspect, the Ship Design Office of the Italian Navy General Staff has been performed a preliminary evaluation of the application of this device on own Destroyer hull (De La Penne Class), using the CFD U-RANSE approach and through experimental test campaign performed at Model Basin of CNR-INM (Council of National Research – Institute of Marine Engineering). This preliminary study was conducted in model and full scale: several flap angles have been tested with a fixed NACA profile. The results have shown that the major improvements, in terms of power reduction, have been obtained for the interest speed range (Fr∇ =0.94 -1.18).
Chaired by Paola GUALENI, University of Genova, IT
Abstract: Ship parametric roll is one of the main reasons for marine accidents and is introduced into the second-generation intact stability criteria by the International Maritime Organization (IMO) recently. In order to study the inner mechanism and predict the possibility of the ship parametric roll in head waves, a time-domain model based on the IRF (Impulse Response Function) concept and the weakly nonlinear assumptions is constructed to predict large-amplitude ship motions and investigate the phenomenon of parametric roll as well as the key affecting factors in this paper. The F-K forces and the restoring forces are calculated on the instantaneous wet surface while the radiation and diffraction forces are kept linear and tansformed from frequency-domain results. The model is validated with experimental results of S175 to prove its feasibility in motion prediction firstly. Based on this, a ro-ro ship is selected as an example for the investigation of the parametric roll resonance. The effects of wave height, wave length, ship length, ship speed and the relation between wave frequency and roll nature frequency on parametric roll in head waves are discussed.
Key words: Parametric roll; head waves; time-domain model; large-amplitude motion; affecting factors; numerical study
Abstract. The International Maritime Organization (IMO) is working on the finalization of the Second Generation Intact Stability Criteria (SGISC) intended to be included in Part A of the 2008 International Code on Intact Stability in the following years. The SGISC consider five modes of dynamic stability failure in waves: parametric roll, pure loss of stability, surf riding/broaching to, dead ship condition and excessive acceleration.
In this paper, a set of semi-displacement, round bilge and transom stern hull forms, i.e. typical naval hull forms, is examined in different loading conditions. Although naval ships are not directly impacted by SGISC, they are sensitive to dynamic stability failure phenomena due to their geometry and range of service speeds.
A brief presentation of first and second vulnerability levels for parametric roll, pure loss of stability, dead ship condition and excessive acceleration failure modes is given, jointly with some remarks on the physical background. The procedure to assess vulnerability criteria has been implemented in Matlab©, referring to the latest drafts of the criteria (SDC 7/5, 2019). The limiting KG curves associated with this set of criteria have been obtained for the various condition of loading, for each vessel. The minimum allowable KG curve associated with the excessive acceleration criterion has been compared with the maximum allowable KG curve, to investigate the consistency of the safe operational area.
Surf-riding/broaching failure mode is one of the Second Generation Intact Stability Criteria (SGISC) dealt by IMO. The SGISC are structured with a multi-tiered approach: Level 1, Level 2 and Direct Stability Assessment (DSA). When a ship does not verify one level, the next once must be applied, or the ship design must be modified. If ship changes are not feasible, Operational Measures (OM) can be provided to avoid dangerous situations and reduce the likelihood of stability failures. The OM are divided into Operational Limitations (OL) related to areas or routes and related to maximum significant wave heights and Operational Guidance (OG).
The surf-riding criterion has been applied on the parent hull of the Systematic Series D, a fast semi-displacement naval hull with forms typically vulnerable to surf-riding phenomenon. The 90 m length ship results vulnerable to Level 1 and 2, therefore Operational Measures have been discussed and provided for a hypothetical route in the Mediterranean Sea (Area 26).
Following the OL, in considered Area 26 the ship operations are limited when significant wave heights exceed 3.8 m. The simplified OG define critical ship speeds to be avoided for each considered sea state.
Chaired by Stefano BRIZZOLARA, Virginia Tech, USA
Hydroelastic effects during slamming of high-speed marine vehicles affect the development of the pressure along their bottom. The aim of this study is to investigate coupling process of a novel CFD method and a FEM structural solver for simulation of hydroelastic slamming. As slamming is characterised by violent and strongly nonlinear fluid–structure interaction, the flow solver is based on a Lagrangian, volume–conservative, second–order accurate method, meshless FDM. Rhoxyz fluid solver is coupled to CalculiX structural solver, through a partitioned bidirectional coupling tool, preCICE. After the validation of coupling using a dam break experiment, the effect of hydroelasticity in slamming is studied by analysing the pressure and deformations of the structure during water entries of a deformable symmetrical wedge with low angle of deadrise.
In the tradition dating back from the 1970ties, time-domain strip approaches have been used to investigate the seakeeping performance of planing High Speed Craft, HSC. The geometrical starting point is prismatic hulls and main issues addressed, have been design-loads and a representative design-acceleration. Usually, design is interpreted as some sort of maximum or limiting value. This has been a rationale for focusing on the craft in head seas. A strip method is based on the assumption that the governing hydromechanics can be described in 2-D cross-cuts. Some shortcomings from that assumption have been dealt with in different ways turning the method to something often referred to as 2 1/2 D. The time-domain has opened for a strip approach catching the non-linear motions and accelerations characterising the HSC´s run in waves and the different published methods have shown to be useful design tools for relatively prismatic hull shapes. Warp, the longitudinal variation of deadrise, influence the seakeeping characteristics and could be a valuable component for the designer. Warp introduces three-dimensionalities challenging the strip approach. The present study examines a strip-method in order to evaluate its validity range with respect to warp. Results from simulations and published model test results for three warped hulls and their parent prismatic hull, in calm water, regular and irregular waves are presented. The results are discussed and generalised to how warp influences the practical applicability of the time-domain strip method.
The repeated wave slamming experienced by high-speed planing craft can cause structural damage and discomfort or injury to passengers and crew. The design guidelines related to structural and seakeeping considerations are still mainly determined through semi-empirical criteria that can lack physical meaning or are limited in application. The research presented here is party of a study to understand the fundamental physics of water-impact for high-speed planing hulls. The slamming loads and resulting hull motions were measured during multiple wave impact events. Sets of towed scale model experiments were conducted in regular waves to capture repeated sequences of wave impact events. These experiments, of both a 1.2 meter (4-ft) and 2.4 meter (8-ft) length planing hull model, were conducted in the 115.8 meter (380-ft) long tow tank at the United States Naval Academy. Heave, pitch, accelerations, water profile (both encountered and stationary), bottom pressures, and high-speed video were recorded during each test run. Both the large and small model were tested at the same Froude number, while the large model was also tested at a lower speed (though still in the planing region). The pressure signals during individual slam events have been isolated and the regularity of the pressures signals during the repeated wave slams will be presented.
Rosen (2005) has developed a method for reconstructing the 2D pressure distributions on the hull bottom during a hull-water impact. Morabito (2014) has developed an empirical method for calculating the pressure distribution during planing at steady speed. This method can be extended to the impact problem by substitution of an equivalent planing velocity. This paper will present the recreated pressure distributions from the measured pressures and Rosen’s PDR method with the predicted pressures from the extension of Morabito’s planing pressures method.
Chaired by Ermina BEGOVIC, University of Naples Federico II, IT
The main component of high-speed craft (HSC) roll damping is due to the hydrodynamic pressure developed on the hull surface: this is very different from the case of displacement hulls. However, the estimation of roll damping of HSC, by means of roll decay tests for example, is often treated in the same manner as for larger and slower ships. Being able to model correctly the roll motions of HSC is of paramount importance: in the prediction of the lateral component of acceleration of an impact at a roll angle, or during a manoeuvre at the pre-planing regime speed.
Practical seakeeping mathematical models of HSC focuses only on the vertical impacts dynamic in head waves, neglecting roll. This works shows a method meant to include hydrodynamic pressure induced roll damping in time domain simulations. The results of the study will be validated by means of free sailing model tests on a HSC at beam and quartering irregular seas performed at the Seakeeping and Manoeuvring Basin (SMB) of MARIN.
The prediction of planing hull motions and accelerations in a seaway is of paramount importance to the design of high-speed craft to ensure comfort and, in extreme cases, the survivability of passengers and crew. The traditional approaches to predicting the motions and accelerations of a displacement vessel generally are not applicable, because the non-linear effects are more significant on planing hulls than displacement ships. No standard practice for predicting motions or accelerations of planing hulls currently exists, nor does a nonlinear model of the hydrodynamic forces that can be derived by simulation. In this study, captive and virtual planar motion mechanism (VPMM) simulations, using an Unsteady RANSE finite volume solver with volume of fluid approach, are performed on the Generic Prismatic Planing Hull (GPPH) to calculate the linearized added mass, damping, and restoring coefficients in heave and pitch. The linearized added mass and damping coefficients are compared to a simplified theory developed by Faltinsen [6], which combines the method of Savitsky [12] and 2D+t strip theory. The non-linearities in all coefficients will be investigated with respect to both motion amplitude and frequency. Nonlinear contributions to the force response are discussed through comparison of the force response predicted by the linear model and force response measured during simulation. Components of the planing hull dynamics that contribute to nonlinearities in the force response are isolated and discussed.
Chaired by Carlo BERTORELLO, University of Naples Federico II, IT
In this paper we investigate the efficacy of augmenting, or replacing, an active height control system for a submerged hydrofoil with a passive system based on springs and dampers.
A state-space model for submerged hydrofoils is formulated and extended to allow for a suspension at the front wing, aft wing or both wings. The model is partially verified by obtaining results in the fixed-wing limit and comparing these
with experimental data from the MARIN Foiling Future Demonstrator.
In the current study we limit ourselves to translational springs, only allowing suspension motion in the heave direction. This results in unfavorable behavior: either the motions increased or the system becomes unstable. It is therefore recommended for future research to try rotational springs.
The present study is concerned with the numerical simulation of Fluid-Structure Interaction (FSI) on a deformable three-dimensional hydrofoil in a turbulent flow. The aim of this work is to develop a strongly coupled two-way fluid-structure interaction methodology with a sufficiently high spatial accuracy to examine the effect of turbulent and cavitating flow on the hydroelastic response of a flexible hydrofoil. A 3-D cantilevered hydrofoil with two degrees-of-freedom is considered to simulate the plunging and pitching motion at the foil tip due to bending and twisting deformation. The defined problem is numerically investigated by coupled Finite Volume Method (FVM) and Finite Element Method (FEM) under a two-way coupling method. In order to find a better understanding of the dynamic FSI response and stability of flexible lifting bodies, the fluid flow is modeled in the different turbulence models and cavitation conditions. The flow-induced deformation and elastic response of both rigid and flexible hydrofoils at various angles of attack are studied. The effect of three-dimension body, pressure coefficient at different locations of the hydrofoil, leading-edge and trailing-edge deformation are presented and the results show that because of elastic deformation, the angle of attack increases and it lead to higher lift and drag coefficients. In addition, the deformations are generally limited by stall condition and because of unsteady vortex shedding, the post-stall condition should be considered in FSI simulation of deformable hydrofoil. To evaluate the accuracy of the numerical model, the present results are compared and validated against published experimental data and showed good agreement.
Retractable hydrofoils may enhance performances of seaplane during take-off and landing runs by lowering the speed when the hull is leaving or touching water surface. Hydrofoils are designed to complement airlift with additional hydrodynamic lift elevating the hull above the water at a speed lower than take-off speed; this minimizes slamming phenomenon on the hull, improving seakeeping capability of the seaplane, since water impacts are minimized compared to conventional configuration and, as a consequence, forces and accelerations on airframe, crew and passengers are reduced. This is of foremost importance on ultralight seaplanes, where wave forces acting on the relatively small aircraft mass provide high accelerations and significant roll, pitch and yaw forces that are higher on light aircraft compared to heavy seaplanes. As matter of facts, clear advantage of this configuration is the increase of sea state when a light seaplane can safely fly, providing additional useful days along the year. Important benefit is the improvement of seaplane performances during take-off and landing, reducing duration of the most critical flight phases, increasing overall safety and reducing pilot workload. Further benefits are envisioned, with optimization of wing, empennage and fuselage to minimize aero-drag and, as snow-ball effect, mission fuel consumption and energy power requirements. Life-cycle cost receives benefits too, since less water spray is ingested by engine and less water droplets impinge on fast revolving propeller, thus reducing expensive power plant maintenance cost over the entire service life.
Chaired by Claudio PENSA , University of Naples Federico II, IT
Abstract
The increasing demands in high-speed transportation have brought the multi-hull forms into the forefront. Many applications have already been realized in civil transportation and naval purposes. The design features and performance characteristics of these vessels differ from mono-hull due to the wave interference phenomenon. Nowadays, evaluation of ship hydrodynamics with CFD has become very popular and successful results have been achieved. Based on this, it is aimed to contribute to the prediction of wave interference effects of a trimaran surface combatant, advancing in deep, unbounded and calm water, by applying the CFD method. A trimaran model with a scale of 1/125 was chosen for the numerical investigation. Primarily, a V&V study was conducted by using proper techniques. Then, the form factor of the trimaran was calculated with two different methods: Prohaska and double-body. The hydrodynamic analyses were performed under incompressible, viscous and fully turbulent flow conditions. Computational results were compared in terms of resistance components and interference factors. The form factor prediction methods were discussed regarding wave interference.
Keywords: CFD, Form factor, Trimaran, Wave interference.
Abstract
Fast marine vehicles have become more important than ever before due to increasing need and population. In maritime sector, special ship types such as catamaran and trimaran have already been designed and/or built to the civil and naval areas of use. The hydrodynamic performance of these vessels is an interesting problem for naval architects due to the wave interference between the hulls. From this point of view, a generic high-speed catamaran hull form (Delft catamaran 372 or DC372) has been chosen for the numerical prediction of manoeuvring coefficients. To achieve this, the pure yaw captive manoeuvre simulations of the DC372 have been performed in deep water conditions for two different advance speeds by using CFD method. The unsteady RANS equations have been solved under incompressible, viscous and fully turbulent flow conditions. The uncertainty in the computations has been determined using proper techniques. Manoeuvring coefficients have been calculated by processing time dependent force/moment signals obtained numerically with the help of Fourier analysis. It is found that the manoeuvring coefficients of fast catamaran are highly dependent on the advance speed.
Keywords: CFD, Pure yaw, Delft catamaran, Dynamic manoeuvre.
The field of a sea based modern shipping activities is constantly seeking for its improvements in order to achieve the economically justified operational patterns. In the same time, the sea transportation activities also need to satisfy currently imposed and, as well as, upcoming in the near future, safety and ecologically friendly footprint characteristics when it comes to the emission of the green house gasses and hard particles (IMO, 2015). Fulfilment of the stated requirements consequently asks for the determination of certain vessels operational parameters such is the total resistance of a vessel which estimation is frequently carried out for predefined calm and deep water environmental scenario. Current work is dealing with investigation of the total resistance parameter in calm and deep water for the preselected types of the trimaran ship hull configurations. The total resistance is estimated according to ITTC recommended procedure. through applicability of the robust and reliable method which is capable to address the problem of wave resistance prediction in calm and deep water. The method has origin in ordinary and modified Michell thin-ship wave theory by taking into account the viscous effects (Skejic and Jullumstrø, 2012). The differences between the utilized theories are discussed from the qualitative and quantitative point of view of the obtained results in comparison to the open source available theoretical experimental data and from the perspective of common engineering practice. Finally, based on the above description, the performed total resistance studies are used as a base for formulation of the optimization procedure which may be used in the trimaran vessel preliminary designs in the range of the forward speeds commonly expected during the normal operational life of the investigated trimaran vessel.
Skejic, R. and Jullumstrø, E. (2012) Power Performance and Environmental Footprint of High-Speed Vessels in Calm Deep Water. OMAE 2012, Brazil.
Chaired by Marco ALTOSOLE, University of Naples Federico II
The aim of the research is to study an azimuthing contra-rotating propeller with a power of 2000 kW. The topic is very useful because the azimuth thruster solutions currently do not find commercial applications in naval units for passenger transport because not very hydrodynamic efficient. The thruster system is studied especially to be installed on High Speed Crafts (HSCs) for passenger transport with a cruising speed of about 35-40 knots. The study is interesting because among the advantages that these solutions provide are the possibility of transmitting very high torques and to guarantee a much longer life cycle. In more detail, the propulsion is design by using a C-drive configuration, with a first mechanical transmission realized by using bevel gears mounted in a frame inside the hull, and a second transmission realized by bevel gears housed in a profiled hull at the lower end of a support structure. In the profiled hull will be installed the shafts of the propellers, in a contra-rotating configuration. In order to optimize the system before its industrial use, a close power loop test bench has been studied and designed to test high power transmissions. The test configuration allows to implement a back-to-back connection between two identical azimuthing contra-rotating propellers. Moreover, the particular test bench allows to size the electric motor simply based on the dissipated power by the kinematic mechanisms. Since the efficiency of these systems are very high, it is not necessary to use large electric motors, thus managing to contain the operating costs of the testing phase. The most significant disadvantage is the need to have two identical transmissions with consequent increase in installation costs. Through the back-to-back test bench it is possible to study the increase in efficiency compared to traditional systems.
This paper is related to the technological development of an innovative small-size Autonomous Surface Vehicle designed to meet the requirement of accessing, monitoring and protecting the shallow waters peculiar of the Wetlands. Surveys in these peculiar environments is reduced due to the absence of suitable tools expressly addressed to work in extremely shallow waters. The first prototype of a fully electric, modular, portable, lightweight, and highly-controllable Autonomous Surface Vehicle (ASV) for extremely shallow water and remote areas, namely SWAMP (Shallow Water Autonomous Multipurpose Platform), was developed by CNR-INM and DITEN-Unige. This catamaran is equipped with four azimuth Pump-Jet modular (PJM) actuators expressly designed for small-size (1 to 1.5 m long) ASV. The main advantage of Pump-Jet thrusters is that they are flush with the hull, thus minimizing the risks of damages due to possible grounding. This system is used to increase the manoeuvrability in narrow spaces and to increase the spacial resolution also in extremely shallow waters. The knowledge of the hydrodynamic characteristics of the thruster and of the vessel allows to partly or fully identifying the vessel for a better controllability. With this aim a series of tests have been conducted in the DITEN towing tank. In particular advance resistance on the SWAMP hull in deep and shallow water and bollard pull and self-propelling tests with the PJM working have been conducted. The results of the tests with the effects of advance speed on the PJM performance is reported in this paper together with the description of the modelling of the thruster itself and the results of at-sea self-propelling tests.
The passenger transportation among Islands or coastal locations is usually realized by High speed ferries. These vessels use traditionally powerful high speed diesel engines, but this transportation has the characteristic of being subject to season, weather condition, period of the years, causing often an underutilization of the power installed onboard, by the fact that the displacement varies significantly and also the amount of runs scheduled per day.
In consideration also of the need to reduce the impact of waves generated by the hull, especially considering the historical or naturalistic scenarios where these vessels operate, the authors investigated the possibility to adopt an hybrid propulsion on an high speed hull, using tank test at a wider range of speed, to optimize usage.
This use of hybrid propulsion is innovative, because usually the hybrid propulsion is used for slow, traditional vessels, according to the limited request of power for propulsion.
In the study proposed there is a “dual use” , that can be obtained navigating in “peak touristic season” using traditional propulsion, with diesel engines, at 22-24 knot, and in “low season” performing the entire trip or part of it, using only batteries or hybrid. With the use of this system the authors studied a solution capable to carry over 300 passengers, verifying also that the weight of the batteries, actually traditional Li-Po batteries, doesn’t impact too much on the total displacement, but also investigating the aspect of the firefighting system on hybrid vessel, aspect that it s innovative, due to the tendency of Li-Po batteries at overheating and exploding in case of fire
Chaired by Simone MANCINI, Force Technology, DK
Full scale seakeeping trials are rare, especially for planing hulls, and are in general focused in studying bottom pressures, accelerations and vibrations. In this paper, a comprehensive description of the experimental setup and analysis of full scale seakeeping trials propulsion data of a 65 ft planing pleasure yacht is presented.
Torque and rpm have been measured on both propeller shafts during seakeeping trials in mild sea conditions, along with hull motions and accelerations.
Correlations between hull motions and propulsion data are discussed, both in the time and frequency domain.
Further tests on a shaft sample have been carried out in order to validate its mechanical properties and hence quantitative results regarding shaft torque.
The main novelty of the present work lays in a detailed analysis of the propulsion system response of a planing pleasure yacht in mild weather conditions.
V-shaped spray interceptors, also referred to as spray deflectors, are a novel concept of spray deflection on planing craft. Conventional spray rails are positioned longitudinally on the bottom of the hull and detach the spray from hull deflecting it towards the sides or slightly down and aftward. The V-shaped spray interceptors, on the other hand, are located in the spray area forward of the stagnation line such that those would deflect the oncoming spray down and aftward, thereby producing a reaction force that reduces the total resistance.
Experimental investigations have shown that compared to the bare hull, a V-shape spray interceptor arrangement reduces the total resistance by up to 25% while conventional spray rail setup only reduced it by up to 18%. The V-shaped spray interceptors have been the subject of a recent numerical investigation, that re-ported a total resistance reduction of 32% (compared to the bare hull), of which 28% was due to reduction of wetted surface and the related viscous drag while remaining 4% was due to aftward deflection of the spray. However, the test vessel was simulated at a fixed running position i.e. the influence of the spray deflectors on the craft’s heave and pitch motions was neglected.
This paper features a numerical comparison of two planing craft, one equipped with a V-shaped spray interceptor arrangement and the other with a conventional setup of longitudinal spray rails. Both configurations are simulated in calm water conditions and are free to pitch and heave in a speed range of (Fr∇ = 1.8 to 4.6). The numerical model is analysed for grid sensitivity and validated against experimental results. The two concepts are compared in terms of total resistance, running position, wetted surface area and hydrodynamic forces acting on the hull.
Hydrodynamics of High Speed Craft is a topic of very high interest for recreational boaters and industry professionals alike. This project aims to be a first step toward conducting such experiments in exposed outdoor environments. This paper will outline a preliminary design and testing plan of a free running model of a high speed craft. The proposed free running model will be subjected to all six degrees of freedom, self-propelled, autonomously controlled, and will be exposed to weather elements.
Chaired by Ugo SALERNO, Chairman&CEO RINA, IT
The rules and regulations inherent to the design pressures and scantlings of high-speed powercrafts are numerous, and regularly reviewed. Recently, the new ISO 12215-5:2019 made notable changes to the way high-speed crafts are analysed, including extending the acceleration experienced up to 8 g in certain circumstances. Nevertheless, despite the multiple iterations and variety of regulatory bodies, the seminal work undertaken on planing crafts throughout the 1960s and 1970s remains the foundation of any rule-based design requirement. Consequently, this paper investigates an array of recently published rules though a comparative design case study, the current state-of-the-art across a number of regulations, and the ultimate impact on scantlings. The study reveals that, despite divergence in intermediate calculations and assumptions, similar requirements are ultimately achieved. Eventually, discussion on the comparison undertaken and future trends in high-speed marine vehicles is provided, tackling the relevance of classical planing theory in light of contemporary innovations.
One of the most important design strategies for increasing the speed and/or efficiency of marine vehicles is that of weight reduction. This can be achieved by optimising structural design via judicious distribution of the most apt materials and via the application of innovative lightweight structures.
Sandwich structures are ideal candidates for structural lightening since they provide excellent mechanical properties at low densities, and a wide range of properties via intelligent selection of face-sheet and core materials, and configurations. Further, sandwich structures selection for marine vehicles needs to consider manufacturing feasibility for large structures, sustainability issues and materials compatibility with the aggressive marine environment.
As a possible alternative to the ubiquitous glass reinforced plastic (GRP) fibre composite sandwich materials used for marine vehicles, all-aluminium sandwich structures have several attractive properties such as light weight, high mechanical properties, sustainability, and corrosion resistance. Common architectures for metallic cores include; honeycomb, foam, corrugated and lattice. Mainly due to economical and manufacturing restrictions, a corrugated core could be most applicable for marine structures.
Hence, this work aims to investigate the mechanical response of aluminium corrugated sandwich structures, with particular attention to bending and low-velocity impact response. Bending stiffness was used as the criteria to select corrugated panels allowing valid comparisons with typical marine GRP sandwich panels. These corrugated structures were first subjected to quasi-static indentation tests to predict the impact response. Low-velocity impact tests were then performed and the corrugated sandwich response was compared with that of other lightweight sandwich structures to assess their energy-absorption efficiency. Corrugated panels were also tested under bending conditions to evaluate collapse mechanisms and the effect of corrugation direction on bending response. The acquired information can be applied to support the design of lightweight corrugated panels to be used for decks, floors, ceilings and other structural elements of marine vehicles.
The AA 50843 aluminium alloy is widely used in high speed marine vehicles thanks to its peculiar properties, such as adequate strength, lightness and excellent welding properties and resistance to corrosion, sea water and salty athmospheres. The aim of this scientific work was to develop and validate a procedure, starting only from hardness measurements, to predict the elastic-plastic behaviour of AA 5083 welded joints under static loading using non-linear FEA analyses. The hardness measurements allowed identifying the different zones and to assess their different mechanical properties, which were considered in the finite element model. Finally, the finite element model results were validated experimentally, comparing the results with the measurements obtained by means of a full-field technique such as the Digital Image Correlation technique.
Prof. Antonio FIORENTINO