110 Ship Design for Efficiency and Economy

C weight of steel hull following SCHNEEKLUTH, 1985 REAL B, BMST, CBD, C1, D, LPP, T, VOLU VOLU=LPP*B*D*CBD C1=BMST*(1.+0.2E-5*(LPP-120.)**2) STARUM=VOLU*C1

&*(1.+0.057*(MAX(10.,LPP/D)-12.))

&*SQRT(30./(D+14.))

&*(1.+0.1*(B/D-2.1)**2)

&*(1.+0.2*(0.85-T/D))

&*(0.92+(1.-CBD)**2)

END

The example shows that the actual formulation of the problem is relatively easy, especially since it can be based on existing Fortran procedures (steel weight in this example).

Even an optimization shell is not foolproof and errors occur frequently when beginners start using the shell. Not the least of the problems is that users formulate problems which allow no solution as improper constraints are imposed.

Another problem is that, in reality, many design problems are not so clearly defined. While there are, in principle, techniques to include uncertainty in the optimization (other than through sensitivity analyses) (e.g. Schmidt, 1996), extended functionality always comes at the price of added complexity for the user, which in our experience at present prevents acceptance.

Optimization shells of the future should try to extend functionality without sacrificing user-friendliness. Perhaps further incorporation of knowledge-based techniques, namely in formulating and interpreting results, could be the path to a solution. But even the most `intelligent' system will not relieve the designer of the task to think and to decide.

3.7 References

BENFORD, H. (1965). Fundamentals of ship design economics. Department of Naval Architects and Marine Engineers, Lecture Notes, University of Michigan

BUXTON, I. L. (1976). Engineering economics and ship design. British Ship Research Association report, 2nd edn

EAMES, M. C. and DRUMMOND, T. G. (1977). Concept explorationÐan approach to small warship design. Trans. RINA 119, p. 29

ERIKSTAD, S. O. (1994). Improving concept exploration in the early stages of the ship design process. 5th International Marine Design Conference, Delft, p. 491

ERIKSTAD, S. O. (1996). A Decision Support Model for Preliminary Ship Design. Ph.D. thesis, University of Trondheim

GEORGESCU, C., VERBAAS, F. and BOONSTRA, H. (1990). Concept exploration models for merchant ships. CFD and CAD in Ship Design, Elsevier Science Publishers, p. 49

GUDENSCHWAGER, H. (1988). Optimierungscompiler und Formberechnungsverfahren: Entwicklung und Anwendung im Vorentwurf von RO/RO-Schiffen. IfS-Report 482, University of Hamburg HEES, M. VAN (1992). Quaestor: A knowledge-based system for computations in preliminary ship

design. PRADS' 92, NewCastle, p. 21284

JANSON, C. E. (1997). Potential Flow Panel Methods for the Calculation of Free-surface Flows with Lift. Ph.D. thesis, Gothenborg

KAEDING, P. (1997). Ein Ansatz zum Abgleich von Fertigungsund Widerstandsaspekten beim Formentwurf. Jahrbuch Schiffbautechn. Gesellschaft

KEANE, A. J., PRICE, W. G. and SCHACHTER, R. D. (1991). Optimization techniques in ship concept design. Trans. RINA 133, p. 123

¨

KERLEN, H. (1985). Uber den Einfluß der V olligkeit¨ auf die Rumpfstahlkosten von Frachtschiffen. IfS Rep. 456, University of Hamburg

Optimization in design 111

LIU, D., HUGHES, O. and MAHOWALD, J. (1981). Applications of a computer-aided, optimal preliminary ship structural design method. Trans. SNAME 89, p. 275

MALONE, J. A., LITTLE, D. E. and ALLMAN, M. (1980). Effects of hull foulants and cleaning/coating practices on ship performance and economics. Trans. SNAME 88, p. 75

MALZAHN, H., SCHNEEKLUTH, H. and KERLEN, H. (1978). OPTIMA, Ein EDV-Programm fur¨ Probleme des Vorentwurfs von Frachtschiffen. Report 81, Forschungszentrum des Deutschen Schiffbaus, Hamburg

NETHERCOTE, W. C. E., ENG, P. and SCHMITKE, R. T. (1981). A concept exploration model for SWATH ships. The Naval Architect, p. 113

PAPANIKOLAOU, A. and KARIAMBAS, E. (1994). Optimization of the preliminary design and cost evaluation of fishing vessel. Schiffstechnik 41, p. 46

RAY, T. and SHA, O .P. (1994). Multicriteria optimization model for containership design. Marine Technology 31/4, p. 258

SCHMIDT, D. (1996). Programm-Generatoren fur¨ Optimierung unter Berucksichtigung¨ von Unsicherheiten in schiffstechnischen Berechnungen. IfS Rep. 567, University of Hamburg SCHNEEKLUTH, H. (1957). Die wirtschaftliche Lange¨ von Seefrachtschiffen und ihre Einfluß

faktoren, Schiffstechnik 13, p. 576

SCHNEEKLUTH, H. (1967). Die Bestimmung von Schiffslange¨ und Blockkoeffizienten nach Kostengesichtspunkten, Hansa, p. 367

SEN, P. (1992). Marine design: The multiple criteria approach. Trans. RINA, p. 261

¨ , . (1977). Ship design and construction programs (2). New Ships 22/8, p. 272

SODING H

TOWNSIN, R. L., BYRNE, D., SVENSEN, T. E. and MILNE, A. (1981). Estimating the technical and economic penalties of hull and propeller roughness. Trans. SNAME 89, p. 295

WIJNHOLST, N. (1995). Design Innovation in Shipping. Delft University Press

WINKLE, I. E. and BAIRD, D. (1985). Towards more effective structural design through synthesis and optimisation of relative fabrication costs. Naval Architect, p. 313; also in Trans. RINA (1986), p. 313