- •Contents
- •Preface
- •1. Main dimensions and main ratios
- •1.3 Depth, draught and freeboard
- •1.7 The design equation
- •1.8 References
- •2. Lines design
- •2.1 Statement of the problem
- •2.2 Shape of sectional area curve
- •2.3 Bow and forward section forms
- •2.4 Bulbous bow
- •2.5 Stern forms
- •2.6 Conventional propeller arrangement
- •2.7 Problems of design in broad, shallow-draught ships
- •2.8 Propeller clearances
- •2.9 The conventional method of lines design
- •2.10 Lines design using distortion of existing forms
- •2.12 References
- •3. Optimization in design
- •3.1 Introduction to methodology of optimization
- •3.2 Scope of application in ship design
- •3.3 Economic basics for optimization
- •3.4 Discussion of some important parameters
- •3.5 Special cases of optimization
- •3.6 Developments of the 1980s and 1990s
- •3.7 References
- •4. Some unconventional propulsion arrangements
- •4.1 Rudder propeller
- •4.2 Overlapping propellers
- •4.3 Contra-rotating propellers
- •4.4 Controllable-pitch propellers
- •4.5 Kort nozzles
- •4.6 Further devices to improve propulsion
- •4.7 References
- •5. Computation of weights and centres of mass
- •5.1 Steel weight
- •5.3 Weight of engine plant
- •5.4 Weight margin
- •5.5 References
- •6. Ship propulsion
- •6.1 Interaction between ship and propeller
- •6.2 Power prognosis using the admiralty formula
- •6.3 Ship resistance under trial conditions
- •6.4 Additional resistance under service conditions
- •6.5 References
- •Appendix
- •A.1 Stability regulations
- •References
- •Nomenclature
- •Index
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