A RATIONAL STRIP THEORY OF SHIP MOTIONS: PART I

The exact ideal-fluid boundary-value problem is formulated for a ship forced to heave and pitch sinusoidally in otherwise calm water. This problem is then simplified by applying three restrictions: 1) the body must be slender; 2) the motions must be small in amplitude compared with ship beam or draft; 3) the frequency of oscillation, must be high, based on the slenderness parameter. The hydrodynamic problem is then recast as a singular perturbation problem which is solved by the method of matched asymptotic expansions. Formulas are derived for the hydrodynamic heave force and pitch moment, from which added-mass and damping coefficients can be easily obtained. The latter are similar but not identical to those used in several other versions of "strip theory;" in particular, the forward-speed effects have the symmetry required by the theorem of Timman and Newman, A result which has not been realized in previous versions of strip theory. In order to calculate the coefficients by the formulas derived, it is necessary to solve numerically a set of boundary-value problems in two dimensions, namely, the problem of a cylinder oscillating vertically in the free surface, At least two practical procedures are available to this purpose.

Corporate Authors:
University of Michigan, Ann Arbor

Department of Naval Architects and Marine Engineers
Ann Arbor, MI United States 48109
Authors:
- Ogilvie, T F
- Tuck, E O
Publication Date: 1969-3-1

Media Info

Features: Appendices; References;
Pagination: 101 p.

Subject/Index Terms

TRT Terms: Coefficients; Mass; Oscillation; Ship motion; Ships; Thinness
Old TRIS Terms: Added mass; Oscillating bodies; Slender bodies; Thin ship theory
Subject Areas: Marine Transportation; Vehicles and Equipment;

Filing Info

Accession Number: 00072742
Record Type: Publication
Source Agency: University of Michigan, Ann Arbor
Report/Paper Numbers: No. 013 Intrm Rpt
Contract Numbers: N00014-67A-0181-0016
Files: TRIS
Created Date: Dec 31 1974 12:00AM