FAST OPTIMIZATION OF TUNED MASS-SPRING ARRANGEMENT FOR REDUCTION OF ACOUSTIC POWER RADIATION OF SUBMERGED RIBBED CYLINDER

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MEHDY DADKHAH
SAEED ZIAEI-RAD
ABDULREZA KABIRI ATAABADI

Abstract

IN THIS PAPER, ACOUSTIC POWER RADIATION OF A SUBMERGED RIBBED CYLIN-DER SUBJECT TO A HARMONIC POINT LOAD IS MINIMIZED BY A NEW FAST SCHEME. FOR THIS PURPOSE, TWO ARRANGEMENTS OF NON-UNIFORMLY DIS-TRIBUTED SEQUENTIAL POINT MASSES AND MASS SPRINGS ATTACHED ON STIFF-ENING RIBS OF THE CYLINDER ARE USED TO OPTIMALLY REDUCE THE ACOUSTIC POWER RADIATION. IN ORDER TO CONSIDER THE EFFECT OF DENSE FLUID, A FULLY COUPLED ANALYSIS IS HERE CARRIED OUT BASED ON FINITE/BOUNDARY ELE-MENT (FEM/BEM) MODEL WHICH ARE UPDATED BY ADDED MASS MATRICES OF FLUID AND DYNAMIC ABSORBER AGENTS. TRUNCATED MODAL MATRIX AND KRYLOV VECTORS ARE USED TO REDUCE THE SYSTEM DIMENSION AND THE CALCULATION TIME. AS A RESULT, FOR THE SPECIAL CASE STUDY THE BEST STRATEGY FOR EVALUATION OF COST FUNCTION IS APPLYING RITZ VECTORS FOR ORDER REDUCTION AND APPLYING TAYLOR SERIES EXPANSION FOR COMPUTING BEM MATRICES IN EACH FREQUENCY LOOP. THE RESULTS SHOW GOOD AGREEMENT WITH PREVIOUS STUDIES AND EXPERIMENTS. IN ADDITION, THE OPTIMIZATION RESULTS SHOW 11 DB AND 20.7 DB REDUCTIONS IN THE ACOUSTIC POWER RADIATION RESPECTIVELY FOR POINT MASS AND DYNAMIC ABSORBERS. 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.

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