Fast Optimization of Tuned Mass-Spring Arrangement for Reduction of Acoustic Power Radiation of Submerged Ribbed Cylinder

Abstract

In this paper, acoustic power radiation of a submerged finite length ribbed cylinder subject to a harmonic point load is minimized by a new fast scheme. For this purpose, two arrangements of non-uniformly distributed sequential point masses and mass springs attached on stiffening ribs of the cylinder are used to optimally reduce the acoustic power radiation. A fully coupled analysis is here carried out based on Finite/Boundary element (FEM/BEM) model. Instead of direct BEM formulation, two beneficial procedures have been proposed for computing BEM matrices in each frequency line. In order to fast solving of equations, the Krylov vectors (produced via Ritz or Arnoldi iterative procedures) and structural mode shapes (modal truncation approach) have been used and validated before performing optimization. As a result, the best strategy for evaluation of response and cost function is using Taylor series expansion for computing BEM matrices and applying Krylov vectors for order reduction. The results show good agreement with previous studies and experiments. The optimization results show noticeable reductions in the acoustic power radiation. In point mass optimization, the most of additional masses has been placed in regions which are near to the excitation point whereas for the absorber design, they are put in the places in opposite side of the excitation point.