Accession Number : AD0692507

Title :   A RATIONAL STRIP THEORY OF SHIP MOTIONS: PART I.

Descriptive Note : Interim technical rept. 1 Nov 68-28 Feb 69,

Corporate Author : MICHIGAN UNIV ANN ARBOR DEPT OF NAVAL ARCHITECTURE AND MARINE ENGINEERING

Personal Author(s) : Ogilvie,T. Francis ; Tuck,Ernest O.

Report Date : 01 MAR 1969

Pagination or Media Count : 105

Abstract : 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. 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 for this purpose. (Author)

Descriptors :   (*SHIPS, *HYDRODYNAMICS), EQUATIONS OF MOTION, THEORY, BOUNDARY VALUE PROBLEMS, PITCH(MOTION), OSCILLATION, MOMENTS

Subject Categories : Marine Engineering
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE