Trans RINA, Vol 154, Part C1, Intl J Marine Design, Jan - Jun 2012


ON DESIGN-SPACE EXPLORATION AND DESIGN REFINEMENT BY NUMERICAL SIMULATION


P Couser, Formation Design Systems Pty Ltd, Fremantle, Australia S Harries, Friendship Systems GmbH - A GL Company, Potsdam, Germany F Tillig, SSPA Sweden AB, Göteborg, Sweden. (DOI No: 10.3940/rina.ijmd.2012.c1.10)


SUMMARY


Naval architects draw inspiration from previous designs, literature reviews, statistical regression models and systematic series. In this paper, a complementary approach, using simulation-driven design, is presented: exploration of the multi- dimensional design-space using first-principles methods. Here the vessel is modelled parametrically with the free- variables that define the design-space. The design-space is then populated by systematic variation of these variables using “design of experiments” approach to explore the design-space in an efficient manner. A multi-dimensional Kriging technique is used to “fit” a meta-model to the simulation-calculated performance measures of each of the design variants. The subsequent meta-model can be used for


three key functions: visualisation of the design-space by


interpolation of iso-parametric surfaces; answering “what if … ?” style questions (e.g. “what if the length is increased by 0.5m?”); providing performance data, in an extremely efficient manner, for simulation-driven formal optimisation. The key benefit of the proposed method is that it allows the design team to quickly explore the design-space and build up a knowledge base ahead of an anticipated project. This then allows quick interrogation of the numerical model series to substantiate design decisions during the bidding and tendering process as well as provide the data necessary for formal design optimisation.


The proposed method is elaborated using an example of a fast luxury motor-yacht of approximately 70m in length. The vessel’s calm water hydrodynamics are studied for speeds up to 20kn by means of SHIPFLOW (FLOWTECH); sea- keeping performance is determined using Seakeeper (FormSys); intact stability is assessed with Hydromax (FormSys). The parametric model is realized within the FRIENDSHIP-Framework (FRIENDSHIP SYSTEMS) which also serves as the integration platform for the analysis software.


NOMENCLATURE ABT


AM BDWL 1.


Bulb cross-section area [m2] Midship cross-section area [m2] Beam on design waterline [m]


Cfull(Bulb) Fullness coefficient of bulbous bow Cfull(DWL) Fullness coefficient of DWL CM


Midship area coefficient CPF


DWL fBT iE


LAX LPP


VCG


Prismatic coefficient of fore part of hull Design Waterline [m]


Bulb area to Midship area ratio: ABT / AM Half angle of entrance of DWL [deg]


Longitudinal position of section with maximum cross-section area [m] Length between perpendiculars [m] Vertical Centre of Gravity [m]


ABBREVIATIONS CFD


DoE FFW HM


INTRODUCTION


Prior knowledge of the relevant design-space for a ship design project enables the design team to achieve a sensible compromise that meets the customer’s requirements. The design team will be at an advantage if they have gained an understanding of the design-space in which the solution will lie and have ascertained the (un)feasibility of the requirements.


There are many resources to which a designer may turn to when contemplating a new ship design. These are well known and include reviews of existing vessels (that the designer may, or may not have been directly involved with); regression models based on systematic series data; etc. This paper describes an additional tool which may be added to the designer's toolbox:


Computational Fluid Dynamics Design of Experiments


FRIENDSHIP-Framework (Software) Hydromax (Software)


MSI Motion Sickness Incidence RSM SK


Response Surface Model Seakeeper (Software)


Design-space


exploration by means of numerical simulation. In essence the design-space is explored in an automated manner using numerical simulation to calculate the performance measures of interest for the design variants; the results of these simulations are captured and may be used at a later stage of the design process.


This design-space knowledge helps the design team to:  gain an insight into the design-space early in the project;


 enable rapid prototyping of ideas for novel design solutions;


©2012: The Royal Institution of Naval Architects C-17


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