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

Report Date:

1996-04-15

Pagination or Media Count:

49.0

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.

Subject Categories:

  • Mechanics
  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE