Accession Number : ADA307891

Title :   Improved Boundary Element Methods for Predicting Sectional Hydrodynamic Coefficients for Strip Theory Ship Motion Programs.

Descriptive Note : Technical memo.,

Corporate Author : DEFENCE RESEARCH ESTABLISHMENT ATLANTIC DARTMOUTH (NOVA SCOTIA)

Personal Author(s) : McTaggart, Kevin A.

PDF Url : ADA307891

Report Date : MAR 1996

Pagination or Media Count : 69

Abstract : This technical memorandum presents two improved boundary element methods for predicting hydrodynamic coefficients of two dimensional sections. The first method is a source distribution method, while the second is a direct method for determining velocity potential. A major objective of these improved methods is to eliminate errors due to irregular frequencies, which currently exist in the close-fit method used by the strip theory program SHIPMO. Both new methods successfully eliminate problems caused by horizontal and vertical line segments with the close-fit method. To eliminate irregular frequencies of surface-piercing sections, the source distribution method employs additional sources on a deck lid at the waterline. The introduction of a deck lid eliminates some irregular frequencies but introduces new irregular frequencies. Alternatively, a modified direct method effectively eliminates all irregular frequencies. Future strip theory implementations should incorporate this modified direct method. This technical memorandum also reviews low and high frequency limits of hydrodynamic coefficients.

Descriptors :   *SHIP MOTION, *HYDRODYNAMICS, VELOCITY, COMPUTER PROGRAM DOCUMENTATION, MATHEMATICAL MODELS, LOAD DISTRIBUTION, PITCH(MOTION), MATRICES(MATHEMATICS), CANADA, DAMPING, BOUNDARY LAYER, COMPUTATIONAL FLUID DYNAMICS, FORTRAN, MATHEMATICAL PREDICTION, APPROXIMATION(MATHEMATICS), NUMERICAL INTEGRATION, BOUNDARY VALUE PROBLEMS, PARTIAL DIFFERENTIAL EQUATIONS, HYDRODYNAMIC CODES, TWO DIMENSIONAL FLOW, SUBROUTINES, GREENS FUNCTIONS, ERROR CORRECTION CODES, SHIP DECKS, SHIP BOWS, LAPLACE TRANSFORMATION, NUMERICAL QUADRATURE.

Subject Categories : Marine Engineering
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE