Page 18: of Maritime Reporter Magazine (November 1980)

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SNAME 88th Annual

Meeting — Preview (continued from page 17) suggest the minimum number of investigations necessary for mak- ing the designer qualified to take the first decisions in the evalua- tion process without assistance from vibration experts. Costly and time-consuming calculations are recommended only when serious vibration problems may occur.

Paper No. 12—"Hydroelasticity and Vibrations of Internal Steel- work of Tanks" by Guy C. Volcy,

Michele M. Baudin, Michel D.

Bereau and Francois G. Besnier.

SYNOPSIS — Theoretical studies aimed at solving the problem of vibrations revealed the lack of a rational method for taking into account an important parameter, the apparent supplementary mass (called virtual added mass of fluid). It was necessary to estab- blish a program including fluid finite elements and coupling ele-

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Write 115 on Reader Service Card c Anixter Bros., Inc. 1980 ments with solid elements used by F.E.M. calculations, enabling the designer to proceed with such calculations and correctly treat the concerned vibratory problems.

The paper presents the results of these theoretical studies concern- ing F.E.M. modelization of the steelwork and calculations of free vibrations in air and in fluid of the assembly of a transverse ring of a tanker, calling for lumped masses and fluid finite-element methods. The correlation with measurements also is presented.

Paper No. 13 — "Notes on

Thrusters for Ship Maneuvering and Dynamic Positioning" by

Ralph A. Norrby and Donald E.


SYNOPSIS—This paper presents the historical development of thrusters as maneuvering aids, as well as current thruster types and their applications. Various aspects of mechanical design are dis- cussed including gears, bearings and seals. Hydrodynamic consid- erations based on model testing are explored, and a merit coeffi- cient based on the work of Bende- mann is proposed for use. In addition, thruster controls and sources of vibration and noise are addressed.

Paper No. 14—"Early Design-

Stage Approach to Reducing Hull

Surface Forces Due to Propeller

Cavitation" by Kjell Olav Holden,

Odd Fagerjord and Ragnar Frost- ad.

SYNOPSIS — The authors have based their paper on regression analysis of data from model wake field measurements and full-scale investigations. Recommendations on selection of afterbody lines to reduce the wake peak are given for both slender V-shaped and full-form ships. Presented are cri- teria for acceptable pressure fluc- tuations on the hull which should give satisfactory local vibration level in the afterbody structure as well as global vibration levels in the accommodation area. As a basis for further investigations, more specific guidelines are pre- sented on selecting main propeller parameters and clearances, and a proposal on using the developed methods in a complete procedure is made.

Discussions of the papers, both written and oral, will be given after each paper to the extent that time permits.

Special Events

Business Session—The Annual

Business Session will immediately follow the presentation and dis- cussion of Paper No. 5 in the

Trianon Ballroom at 4:00 p.m. on Thursday, November 13. The agenda for this meeting will in- clude the election of the president of the Society, consideration of proposed amendments to the By- laws, a report of the elections which occurred at the Council

Meeting on Wednesday, and such (continued on page 20) 18 Maritime Reporter/Engineering News

Maritime Reporter

First published in 1881 Maritime Reporter is the world's largest audited circulation publication serving the global maritime industry.