Accession Number : ADD018052

Title :   A Method for Determining the Approximate Resonance Frequency of a Structure Surrounded by a Compressible Fluid.

Descriptive Note : Patent Application, Filed 15 Apr 96,

Corporate Author : DEPARTMENT OF THE NAVY WASHINGTON DC

Personal Author(s) : McCollum, Michele D ; Siders, Clementina M

PDF Url : ADD018052

Report Date : 15 Apr 1996

Pagination or Media Count : 49

Abstract : A method for determining the approximate resonance frequency of a structure surrounded by a compressible fluid includes the steps of: (1) performing an in-vacuo eigenvalue analysis to determine in-vacuo frequencies and mode shapes of the structure; (2) selecting one of the mode shapes as an in-vacuo mode of interest, (3) computing an influence matrix at the eigenfrequency of the selected mode of interest; (4) combining the computed influence matrix with structural stiffness and mass matrices from a finite element program, and using the modified matrices computing eigenvalues of the structure, including eigenvectors; (5) selecting from the computed eigenvectors a computed mode having substantially the same displaced shape as the in-vacuo mode of interest; (6) determining the eigenfrequency of the selected computed mode; (7) determining any difference between the computed eigenfrequency of the selected computed mode and the in-vacuo eigenfrequency of the selected in-vacuo mode of interest; wherein (8) if the difference is equal to, or less than, a selected tolerance, the computed eigenfrequency of the computed mode is the approximate resonance frequency of the structure; and (9) if the difference is greater than the tolerance, repeating step (3) substituting the computed eigenfrequency of the selected computed mode for the in-vacuo eigenfrequency for the in-vacuo mode of interest, and thereafter, repeating steps (4) - (9), substituting in step (3) a most recent computed eigenfrequency of the selected computed mode for the previously used computed eigenfrequency of the selected computed mode.

Descriptors :   *PATENT APPLICATIONS, *STRUCTURAL ANALYSIS, *RESONANT FREQUENCY, *COMPRESSIBLE FLOW, MATHEMATICAL MODELS, ALGORITHMS, LOAD DISTRIBUTION, WATER FLOW, STRUCTURAL PROPERTIES, MATRICES(MATHEMATICS), FINITE ELEMENT ANALYSIS, STIFFNESS, DISPLACEMENT, DAMPING, EIGENVECTORS, BOUNDARY LAYER, EIGENVALUES, APPROXIMATION(MATHEMATICS), FLEXURAL PROPERTIES, UNDERWATER STRUCTURES, HARMONIC ANALYSIS

Subject Categories : Mechanics
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE