A Boundary Element Method for Motions and Added Resistance of Ships in Waves

The accurate prediction of ship resistance in waves is nowadays of increased importance since it greatly influences ship performance regarding sustainable service speed and fuel consumption in seaways. Added resistance is considered as the longitudinal component of the second order mean force acting on a ship in waves and can be calculated from the first order ship motions by integrating the corresponding second-order pressure on the body surface. The purpose of this paper is to present a methodology for the prediction of motions and added resistance by a three dimensional Rankine panel method and to discuss and validate its results by comparing them with experimental data. The prediction in the short wave range, where forces due to wave reflection dominate, has been made applying semi-empirical corrections proposed by Kuroda. Experimental data for the heave, pitch, and added resistance of an ITTC benchmark KRISO container ship have been compared with numerical ones, and the applicability of the proposed method is discussed

Autonomous Underwater Intervention: Experimental Results of the MARIS Project

open11noopenSimetti, E. ;Wanderlingh, F. ;Torelli, S. ;Bibuli, M. ;Odetti, A. ;Bruzzone, G. ; Lodi Rizzini, D. ;Aleotti, J. ;Palli, G. ;Moriello, L. ;Scarcia, U.Simetti, E.; Wanderlingh, F.; Torelli, S.; Bibuli, M.; Odetti, Angelo; Bruzzone, G.; Lodi Rizzini, D.; Aleotti, J.; Palli, G.; Moriello, L.; Scarcia, U

Underwater intervention robotics: An outline of the Italian national project Maris

The Italian national project MARIS (Marine Robotics for Interventions) pursues the strategic objective of studying, developing, and integrating technologies and methodologies to enable the development of autonomous underwater robotic systems employable for intervention activities. These activities are becoming progressively more typical for the underwater offshore industry, for search-and-rescue operations, and for underwater scientific missions. Within such an ambitious objective, the project consortium also intends to demonstrate the achievable operational capabilities at a proof-of-concept level by integrating the results with prototype experimental systems

Hydrodynamic Optimisation of High-Speed Trimaran Hull Forms

none2noneBRIZZOLARA S; D. BRUZZONEBrizzolara, Stefano; Bruzzone, Dari

Time domain evaluation of ship motion with desingularized methodology

This paper presents an application of a panel method based in the time domain for the calculation of wave induced motions of a ship advancing in waves. The fluid domain boundaries are described using a grid of flat quadrilateral panels and the numerical solution is obtained by a desingularized approach in which, considering a desingularizing distance, a distribution of Rankine singularities has been applied upon the free-surface and inside the body. The method is aimed to deal with non linear effects even though in first applications body motions and wave amplitudes are assumed small and linear hypothesis has been exploited. The boundary conditions have been applied referring to the mean body wetted surface and to the calm water free surface. The solution is determined using an Eulerian time-stepping integration scheme in which the velocity potential computed at a given time-step allows to update the free surface boundary conditions to be imposed at the following time step. Once the current value of potential is obtained, the pressure on the mean hull surface can be calculated to evaluate the forces and moments acting on the body. The adequacy of the results has been verified applying the code to different typologies of hull and comparing the numerical output with experimental data freely available in literature. In this work, two ships have been chosen as test cases, the DTMB 5512 and the S175 hull. In addition, a comparison with other numerical methods has been carried out

Hydrodynamic assessment and optimization of new fast foil assisted SWAMH

This paper presents the hydrodynamic assessment and optimization of a new hybrid vessel concept, characterized by an underwater Small Waterplane Area Mono Hull (SWAMH) assisted by a tandem hydrofoil system. It has been designed by a widely known Italian shipyard specialized in the design and construction of foil assisted fast marine vehicles. The results here presented include the prediction of tandem wings performance and set-up by means of a threedimensional panel method for lifting bodies. In this way it has been possible to isolate the interference effect between the forward and aft wing system and the interference effect caused by the hull on the wings. The wave and total resistance of the underwater hull has been predicted using a linear free surface numerical panel method, developed by the authors and successfully applied also in this case in terms of correlation with experimental model tests. Finally an integrated optimization algorithm exploiting the mentioned CFD methods has been applied to obtain an optimized underwater hull form, able to minimize the wave resistance and the far field waves generated by the vessel at the design speed. The optimum hull form so obtained, is presented and its main characteristics discussed. \ua9 2007 American Bureau of Shipping

Resistance and seakeeping numerical performance analyses of a semi-small waterplane area twin hull at medium to high speeds

The hydrodynamic analysis of a new semi-small waterplane area twin hull (SWATH) suitable for various applications such as small and medium size passenger ferries is presented. This may be an attractive crossover configuration resulting from the merging of two classical shapes: a conventional SWATH and a fast catamaran. The final hull design exhibits a wedge-like waterline shape with the maximum beam at the stern; the hull ends with a very narrow entrance angle, has a prominent bulbous bow typical of SWATH vessels, and features full stern to arrange waterjet propellers. Our analysis aims to perform a preliminary assessment of the hydrodynamic performance of a hull with such a complex shape both in terms of resistance of the hull in calm water and seakeeping capability in regular head waves and compare the performance with that of a conventional SWATH. The analysis is performed using a boundary element method that was preliminarily validated on a conventional SWATH vessel

Time domain prediction of motions of marine vehicles in waves

This paper presents an application of a boundary element method for the calculation of wave induced motions for a ship advancing in waves. The relevant surfaces have been described using a structured grid of flat quadrilateral panels. A desingularized approach has been adopted by placing Rankine singularities at a small distance from every panel center: inside the body and over the the free surface. The boundary element conditions are collocated at the panel centers. The boundary value problem is solved at each time step in terms of velocity potentials by using an eulerian time stepping scheme. The boundary conditions have been applied on the mean body wetted surface and the free-surface is considered at the calm water level. The velocity potential computed on the free-surface at a certain time-step allows to update the kinematic and dynamic boundary conditions. Once the current value of potential is obtained, the pressure on the mean hull surface has been calculated and forces and moments are given by the integration of pressure on the body. The major advantage of choosing the desingularized approach consists in reducing the computational effort, especially when non linear effects are considered. The adequacy of the numerical procedure and of the results has been verified for two and three dimensional cases. Different typologies of marine vehicles have been considered comparing the numerical output with experimental data, freely available in literature. In this paper examples for two cases are presented: the well-known modified Wigley hull, for which experiments on added mass and damping are also available, and the DTMB 5512 ship which was extensively tested at the University of Iowa