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The paper illustrates the main theoretical and
computational aspects of an automatic computer based procedure
for the parametric shape optimization of a particular
unconventional hull typology: that for a catamaran S.W.A.T.H.
ship. The goal of the integrated computational procedure is to find
the best shape of the submerged hulls of a new U.S.V. (U...
Contexts in source publication
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... of selecting the variation of the hull form is still based on a trial and error scheme, highly reliant on an expert evaluation and interpretation of C.F.D. results, which does not facilitate the convergence on the optimal solution. Small Waterplane Area Twin Hull (S.W.A.T.H.) ships are a special concept of hull typology and configuration (see Fig. 1) featuring two or more slender struts that are actually piercing the free surface, while the major part of the displaced volume is concentrated well below the free surface in torpedo-like underwater bodies. The major advantage of this hull typology is its superior seakeeping ability. Another benefit of this type of vessel is a high ...
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... order to have an excellent fitting between the hull surface modeled inside the C.A.D. software and the discretized one for the computation, it has been divided into 9 different zones, as shown in Fig. 10: one for each side of the two struts and five for the submerged ...
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... regards free surface it has been divided in two zones, as shown in Fig. 11: the first one from the symmetry plane to the waterline of the hull and the other one from the end of the first to the end of the computational domain. ...
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... care has to be paid on the selection of valid points: in fact, as particularly evident from Fig. 12, there are few dozen of points which fall well below the mean trend line traced by the others: these points correspond to fake calculations, in which the C.F.D. solver has predicted an unrealistically low value of the objective function, generally due to a mis-generated panel mesh discretization of the hull geometry. The check of these ...
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... hence a higher wave resistance, the predicted wavy free surface elevation can be compared from one case to another. With this simple criteria often used by designers in trial and error procedures it is possible to visually guess which solution could be better than others on the basis of the free wave pattern colored contours as those presented in Fig. 15 to Fig.17. Differences in the generated wave pattern by two different hull shapes, at a given speed, are justified by the interference effects that each wave train generated along the hull has with the other. In order to realize the effectiveness of the optimization procedure, both initial (first point created by Sobol D.o.E.) and ...
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... content and hence a higher wave resistance, the predicted wavy free surface elevation can be compared from one case to another. With this simple criteria often used by designers in trial and error procedures it is possible to visually guess which solution could be better than others on the basis of the free wave pattern colored contours as those presented in Fig. 15 to Fig.17. Differences in the generated wave pattern by two different hull shapes, at a given speed, are justified by the interference effects that each wave train generated along the hull has with the other. ...
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... of the optimization procedure, both initial (first point created by Sobol D.o.E.) and optimized hull variants are compared against a conventional (drop-shaped) underwater hull form, whose profile resembles the shape of a N.A.C.A. four digits symmetric airfoil, with maximum thickness at about 30% of chord length from the leading edge. Fig. 14 presents the 3D panel mesh generated for the compared hull shapes. Their wave patterns are compared from Fig. 15 to Fig. 17. Table 4 resumes the main features of the four design ...
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... variants are compared against a conventional (drop-shaped) underwater hull form, whose profile resembles the shape of a N.A.C.A. four digits symmetric airfoil, with maximum thickness at about 30% of chord length from the leading edge. Fig. 14 presents the 3D panel mesh generated for the compared hull shapes. Their wave patterns are compared from Fig. 15 to Fig. 17. Table 4 resumes the main features of the four design ...
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In the past few decades, the growing capability of Computational Fluid Dynamics (CFD) has pushed the research in the field of ship hydrodynamics from simple to complex, covering the prediction of ship resistance, seakeeping, self-propulsion and maneuvering. However, the predictions of free maneuvering problems are especially difficult, mostly due t...
Citations
... Examples of direct modification includes Beizer curve [11], non-uniform rational basis spline-NURBS [17,18] and T-splines [12]. Some examples of systematic variation methods applied in hull form optimisation include Lackenby shift [19], parametric modification [20,21] and free-form deformation [22]. ...
... However, all studies above are about SWATH vehicles with vertical struts except Xing (2008), Brizzolara andVernengo (2011a, 2011b) whose works (Brizzolara, 2004;Brizzolara et al, 2011aBrizzolara et al, , 2011bBrizzolara et al, , 2012 mainly focused on the resistance optimization of torpedo hulls of I-SWATH used to unmanned surface vehicles. In this paper, an unconventional SWATH with inclined struts (Qian and Yi, 2015) was proposed and both numerical simulations and model tests were carried out to investigate the influence of submergence depth on resistance performance. ...
An unconventional SWATH vehicle with inclined struts is proposed and the influence of submergence depth on its resistance in calm water is investigated by numerical and experimental method. At different submergence depth, resistance performance of a torpedo hull, which is based on the DAPAR SUOFF model and treated as the underwater hull of SWATH excluding struts, is studied firstly by a more accurate numerical method based on RANS considering water viscosity and free surface. Numerical simulations and model tests are carried out. The numerical method is demonstrated by the good agreement between calculated results with model tests. The submergence depth actually has a distinct influence on the total resistance of (bare) torpedo hull mainly by affecting residual resistance at low speed and near the free surface. As for SWATH, the struts resistance has a substantial proportion of total resistance from 35.9% to 76.7%, growing with the augment of submergence depth. At Froude number ranging from 0.36 to 0.72, total resistance, residual resistance and frictional resistance all increase as submergence depth increases. From the resistance standpoint, a small submergence depth may be desired. Besides, it deserves to be considered that the lift force produced by inclined struts while moving in the water can lift the SWATH hull to reduce its submergence depth which has a positive effect on total resistance.
... BM KB KG (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) Where: ...
... L BM --longitudinal metacentric radius KB --height of center of buoyancy to base line KG --Height of the Center of Gravity to the Baseline As it's known: (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) In normal circumstances, the form of main cross section is assumed to be an ellipse, and the vertical direction radius ...
... By Equation (2-13) ~ (2-16), the second moment of the strut waterplane area is: (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) The distance between the buoyant centre of the hull and the first endpoint is cb L : (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) Where S c is the vertical distance of cross section between the hull and the strut (see Figure (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) Thus, by Equation (2)(3)(4)(5)(6)(7)(8) and (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19), B M it can be expressed as: ...
The high-performance ship complies with the trend of the
development of the shipbuilding industry in the world today, for its
outstanding sailing performance, strong carrying capacity, comfort and
economy, it‘s favored by the research institutions around the world.
In this thesis I am making a computational fluid dynamics (CFD)
simulation of a HYSWATH (Hydrofoil Small Waterplane Area Twin Hull)
vessel by using the CFD tool STAR-CCM+. Since I did not have any prior
experience in CFD, a substantial part of the thesis is dedicated to theory in
CFD. This thesis employs Star-CCM+ calculation software to study the
influence of gravity center and demi hull spacing on the resistance
performance of HYSWATH. Using a Hydrofoil Water Area Twin Ship with
the displacement of 1000T as a model, the research studies the influence of
gravity center on the resistance performance at different speeds. The
research is of great importance for improving the resistance performance
of hybrid hull ships. HYSWATH is a new type hybrid vessel with high
speed. It has both advantages of small waterplane area vessel and hybrid
vessel.
In chapter five which studies the resistance property of HYSWATH
by adopting vessel model resistance experiment and compares the data of
model experiment with the result calculated by Computational Fluid
Dynamics Software--Star- CCM+ to validate the accuracy of numerical
computation method and to prepare for future study of effect of vessel
form parameters on vessel resistance is the main part of this thesis.
Based on the model experiment, the chapter carries out the numerical stimulation of viscous flow of HYSWATH by applying Star-CCM+ and
obtains the motion attitude and resistance changing situation of the vessel,
and compares them with experiment data. The result shows that using this
method can accurately calculate the resistance and motion attitude of
HYSWATH.
... The optimization-based approach has also been used by Brizzolara (2004) and more recently reconsidered by Brizzolara and Vernengo (2011a;2011b); in the former study, the geometry of the hull was described by a polynomial function, and this was substituted in the latter study by a more flexible BSpline-based model. Brizzolara and Gaggero (2006) developed an integrated design approach for SWATH passenger ships; this approach includes wave resistance performances and was evaluated using the Mitchell method. ...
The hydrodynamic analysis of a new Semi-SWATH (Small Waterplane Area Twin Hull) design suitable for different applications in the range of medium to high speeds is presented. This may be an attractive crossover configuration resulting from the merging of two more classical shapes, a conventional SWATH and a fast catamaran. The final hull shows a wedge-like waterline shape having the maximum beam at stern and ending with a very narrow entrance angle, a prominent bulbous bow typical of SWATHs vessels and a full stern to arrange waterjets propellers. The aim of the presented analysis is to preliminary assess the hydrodynamic performance of such a complex shape, both in terms of resistance in calm water and seakeeping in regular head waves, in the light of a comparison with those of a conventional SW A TH. The analysis is performed by a Boundary Element Method preliminary validated on a conventional SWATH ship.
... The way we envisage to study these effects is based on global optimization methods using 3D full parametric description of the planing hull surface [23,24] and a medium fidelity CFD tool. This technique initially applied with success to SWATH hull forms [3,4], has been more recently extended to high-speed displacement ships [22] and to fast unconventional multihull hydrodynamic design [36] at the MIT-iShip. ...
A new numerical approach based on the Vortex Lattice Method (VLM) for the solution of the hydrodynamic performances of cambered hulls in steady planing is formulated and validated. Due to its fully 3D formulation, the method can be applied to both cambered and un-cambered dihedral planing surfaces of any shape without any further approximation. The exact three-dimensional wetted surface of the hull is where the body boundary condition is fulfilled. The sprays region detaching both in front of the stagnation root line and from the wet portion of the chine are modeled in the numerical scheme by means of additional vortex lattice regions. The dynamic boundary condition at the stern of the hull is non-linear with respect to the perturbation potential. Results show the dynamic pressure consistently accounts for the 3D features of the flow especially in the case of cambered planing surfaces. The numerical method is verified by a systematic analysis against semi-empirical methods and it is finally validated with experimental results on prismatic as well as cambered dihedral planing surfaces. Excellent correlations are found for both types of planing surfaces that range in the same confidence interval of higher fidelity numerical models, such as RANSE solvers.
... This form of the objective function allows for a linear compensation of the small tolerance considered for the given displacement constraint. A low order Boundary Element Method (BEM) is used for the wave resistance computation; this numerical method was been extensively validated on different types of fast mono and multihulls [11], and other unconventional types of fast multihulls, such as fast SWATHs [8] [12] and semi-SWATH [13]. A tolerance of 5% has been used to allow a relative difference on the volume with respect to its reference (initial) value while for the Longitudinal Centre of Buoyancy, LCB, the variation relative to its reference value has been allowed within the 3%. ...
Hydrodynamic performance optimization of ship hulls by CFD methods is becoming popular in modern naval architecture. From local or partial parametric shape optimization, the current frontline of the research is to solve the global hull shape optimization by automatic computational procedures. Key of these procedures is in the parametric hull form modification. Two different techniques are considered in this study: Full parametric hull form definition as opposed to the Free Form Deformation technique. After a general definition, pro and contra of both approached are discussed on the basis of the results obtain in a real hydrodynamic hull optimization example: A high speed round bilge monohulls optimized by means of a panel method for the minimum wave resistance at design speed.
... In the proposed simulator, the USV might have kinetic and not kinetic capabilities, while in this scenario the AUV don't have kinetic weapons, but could produce jamming and other notkinetic actions; the UAV carry multi sensors and weapons. In comparison with electric drones, the AUV was modeled with capability to communicate in RF in surface and through acoustic modems underwater; vice versa the USV used for this scenario was inspired to SWATH (Small Waterplane Area Twin Hulls) USV characterized by Superior Operability over wide spectrum of sea states and able to provide support AUV (Brizzolara, Curtin, Bovio, Vernengo 2011;Brizzolara and Vernengo 2011). ...
Conference code: 104545, Cited By :1, Export Date: 20 August 2016, References: Andronov, A., Merkuryev, Y., Optimization of statistical sample sizes in simulation (2000) Journal of Statistical Planning and Inference, 85, pp. 93-102;
This scoping review assesses the current use of simulation-based design optimization (SBDO) in marine engineering, focusing on identifying research trends, methodologies, and application areas. Analyzing 277 studies from Scopus and Web of Science, the review finds that SBDO is predominantly applied to optimizing marine vessel hulls, including both surface and underwater types, and extends to key components like bows, sterns, propellers, and fins. It also covers marine structures and renewable energy systems. A notable trend is the preference for deterministic single-objective optimization methods, indicating potential growth areas in multi-objective and stochastic approaches. The review points out the necessity of integrating more comprehensive multidisciplinary optimization methods to address the complex challenges in marine environments. Despite the extensive application of SBDO in marine engineering, there remains a need for enhancing the methodologies’ efficiency and robustness. This review offers a critical overview of SBDO’s role in marine engineering and highlights opportunities for future research to advance the field.
The seakeeping characteristics of a Small Waterplane Area Twin Hull (SWATH) vehicle equipped with fixed stabilizing fins was investigated by experimental and numerical methods The calculation methods range from viscous CFD simulation based on an unsteady RANS approach to Boundary Element Method (BEM) based on Three Dimensional Translating-pulsating Source Green Function (3DTP). Responses of ship motions in head regular waves and nonlinear effects on motion responses with increasing wave amplitude were analyzed. Numerical simulations have been validated by comparisons with experimental tests. The results indicate that the heave and pitch transfer functions depict two peaks with the increase of wave length. Comparisons amongst experimental data and different numerical calculations illustrate that the RANS method predicts ship motions with higher accuracy and allows the detection of nonlinear effects. The heave and pitch transfer functions see a downward trend with the increasing wave amplitude in the resonant zone at low speed.
