Ebook: HSMV 2020

This book presents the proceedings of the 12th International Symposium High Speed Marine Vehicles held on 15 and 16 October 2020, for the first time as an e-conference.

High Speed Marine Vehicles Conference has almost 30-year history since the first Conference held in Naples in 1991. Since then, it has been an opportunity to present and discuss developments in the design, construction and operation of high speed marine vessels.

The Symposium is addressed to individuals from universities, research organizations, industry, government agencies, certifying authorities as well as designers, operators and owners who contribute to improved knowledge about “High Speed Vessel”.

For this edition, more than 40 abstracts have been submitted and, after a review process, 26 papers have been included in this book. Amongst the topics covered in this year’s event are updated aspects and developments concerning the ship design, numerical and experimental hydrodynamics, seakeeping and manoeuvring, marine structures and machinery.

Thanks are due to the Scientific Committee who shouldered most of the responsibility for reviewing papers and providing constructive comments to improve their quality.

My personal and special thanks to Professor Antonio Fiorentino, founder and Chairman of HSMV, for sharing his invaluable knowledge and experience.

Ermina Begovic

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. This study presents a review of current negative effects of high-speed boats to the environment. In this study, the flow around a benchmark planing Fridsma boat is simulated by CFD and resistance values for different non-dimensional Froude number (Fn) conditions are validated from the experimental results obtained from the literature. Using the same CFD methodology, a catamaran model in which the towing tank test results are available, is simulated for different Fn conditions and resistance values are predicted. In the CFD analysis, unsteady flow around the Fridsma hull model and catamaran model is simulated using overset meshing technique and turbulence is modeled by Reynolds Averaged Navier Stokes (RANS) with SST (Menter) k-omega turbulence model. Resistance values are compared with the experimental data and required propulsion powers are estimated for different Fn conditions. Then, total resistance of the catamaran for full-scale vessel is calculated using an extrapolation method and required propulsion power predictions are conducted. Noise prediction, corresponding to the required propulsion power are presented. In particular, the change of noise level and harmful gases released into the environment, when the speed of the vessel 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 lifecycle the growth of the ship’s weight is one of the main sources 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 the existing platform because significant improvements can be achieved at a minimal cost. According to the US Navy experience, to analyze this aspect, the Ship Design Office of the Italian Navy General Staff performed a preliminary evaluation of the application of this device on own Destroyer hull (De La Penne class), using the CFD U-RANS 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 the 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 = 0.335 – 0.419).

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.

V-shaped spray interceptors 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 they would deflect the oncoming spray down and aftward, thereby producing a reaction force that reduces the total resistance. An experimental study reported that the V-shaped spray interceptors to reduce the total resistance at low planing speed by up to 4%. This paper features a numerical comparison of two planing craft, one equipped with a conventional setup of longitudinal spray rails and the other with a V-shaped spray interceptor. Both configurations were simulated in calm water conditions and were free to pitch and heave in a speed range of Fr_∇ = 1.776 to 3.108. The numerical model was analyzed for grid sensitivity and numerical results were compared with experimental results. The two concepts were compared in terms of total resistance, lift, running position and wetted surface area. Conventional spray rails were shown to account for up to 5.6% of total lift and up to 6.5% of total resistance. The V-shaped spray interceptor was shown to reduce the total resistance by up to 8%. Since the V-shaped spray interceptor was located in the spray area forward of the stagnation line, it deflected the oncoming spray thereby producing a horizontal reaction force (-1.5% of R_TM) in the direction of the craft’s motion. The rest of differences in the total resistance of the hulls equipped with the conventional spray rails and the V-shaped spray rails was due to absence of the resistance of the absent spray rails.

Full scale seakeeping trials are rare, especially planing hull 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.

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 the numerical and experimental way as well. Moreover, there is a huge lack in the literature of data related to sea trials of the 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 on the comparison of the results carried out from model experimental tests performed in the model basin, full-scale CFD simulations, and sea trial tests. The performed simulations in full-scale have been compared to the extrapolated experimental tests and the sea-trial results. Moreover, the dynamic trim angle and the dynamic wetted surface have been taken into account to assess the reliability of the full-scale simulation performed. The stepped hull considered is a Mito 31 outboard Rigid Inflatable Boat (RIB) built by MV Marine Srl Company.

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.

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.

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 at several oscillating frequencies 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. Due to the accurate grid structure used here, numerical ventilation has been prevented and wave deformations have been captured well.

The field of sea based modern shipping activities is constantly seeking for its improvements 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 greenhouse gasses and hard particles [1]. Fulfilment of the stated requirements consequently asks for the determination of certain vessels operational parameters such as 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 [2] 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 considering the viscous effects [3]. 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.

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.

The main component of high-speed craft (HSC) roll damping is related to the hydrodynamic lift developed on the hull surface. This is very different from displacement type hull forms. However, the estimation of roll damping of HSC is often treated in the same manner as for larger and slower ships. Being able to model the roll of HSC correctly is of paramount importance in the prediction of the lateral component of acceleration of an impact at a roll angle in waves, or during a manoeuvre at high speed. These are phenomena that can have severe consequences on the comfort and safety of the crew on-board of HSC.

Three procedures meant to estimate the HSC roll damping were analyzed. The outcomes of these procedures were compared in terms of roll and lateral accelerations statistics of HSC sailing in irregular waves. The HSC motions were predicted by a 2D+t mathematical model. Differently from the majority of the state-of-art HSC seakeeping tools, which focuses only on the vertical impacts in head waves, in this work the roll was included in the simulations. The numerical results of the simulations were validated by means of free sailing model tests at beam and quartering irregular seas carried out at the Seakeeping and Manoeuvring Basin of MARIN.

A time-domain strip method, in the Zarnick tradition, is used to discuss the modeling implications when alongships geometrical variations are studied, eg. warp or motion with frequent bow submergence. Results from simulations and published model test results for three warped hulls and their parent prismatic hull, in calm water and regular waves are presented. It is concluded that warp can be modelled by the strip approach. Non-the less, method development is proposed and the importance of combining different numerical end experimental methods both in research and design is stressed.

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.

Bottom pressures were measured on two prismatic planing hull models operating in regular waves. Testing in regular waves created repeated wave slam events, which provided information on variability of the motions, accelerations, and pressures during wave slamming events. Using a reconstructed pressure distribution based on Rosen’s method [2] and predicted pressure distributions based on empirical equations given by Morabito [3], better understanding of how the hull and water interact during wave slamming can be achieved.

The aim of the research is to develop an azimuthing contra-rotating propeller for commercial applications with a power of 2000 kW. The thruster system is designed especially to be installed on high speed crafts (HSCs) for passenger transport with a cruising speed of about 35–40 knots. The topic is very useful because the azimuth thruster solutions currently do not find commercial applications in naval units for passenger transport. The latter are heavy, not very efficient from a hydrodynamic point of view and suitable for maximum cruising speed of about 18–20 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 realized 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 was 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. 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, was developed by CNR-INM and DITEN-Unige. This catamaran is equipped with four azimuth Pump-Jet Modular (PJM) actuators 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 by allowing the access also in extremely shallow waters with smaller risk of loosing manoeuvrability. 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, bollard pull and self-propelling tests with the Pump-Jet Module working have been carried out. 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.