S20  Vibroac˙stica
 
 Title:
NUMERICAL PROBLEMS IN THE CALCULATION OF ACOUSTIC SCATTERING WITH THE SOURCE SIMULATION TECHNIQUE
 
Summary :
IN THIS WORK THE SOURCE SIMULATION TECHNIQUE WAS USED TO CALCULATE THE SCATTERING OF A PLANE WAVE BY A CIRCULAR CYLINDER WITH RADIAL OR ELLIPTICAL TRANSVERSE SECTION. THE EXTENT TO WHICH THE SIMULATED FIELD REPRODUCES THE ORIGINAL FIELD DEPENDS ON THE DEGREE OF CORRESPONDENCE BETWEEN THE SIMULATED AND THE GIVEN BOUNDARY CONDITIONS. NUMERICAL SIMULATIONS HAVE SHOWN THAT: 1) THE SHAPE OF THE AUXILIARY SURFACE, 2) THE NUMBER OF SOURCES, AND 3) THE WAY THE SOURCES ARE DISTRIBUTED ARE THE MOST RELEVANT PARAMETERS TO ENSURE AN ACCURATE SOLUTION FOR THE PROBLEM. IN THE CASE OF THE SINGLE-LAYER METHOD, SOURCES, SHOULD NOT BE POSITIONED CLOSE TO THE SURFACE OR TO THE CENTER OF THE BODY, BECAUSE THE PROBLEM BECOMES ILL-CONDITIONED. THE AUXILIARY SURFACE AND THE SCATTERER SHOULD BE AS SIMILAR AS POSSIBLE IN ORDER TO MINIMIZE THE BOUNDARY ERROR. WITH RESPECT TO THE NUMBER OF SOURCES (N), THERE ARE TWO OPPOSITE EFFECTS: 1) IF (N) IS TOO SMALL, THE SOUND FILED IS NOT REPRODUCED ACCURATELY; 2) IF (N) IS TOO LAGE, COMUTING TIMEINCREAES AND SOLUTION ACCURACY DECREASES. THE METHOD BREAKS DOWN WHEN EXCITATION FREQUENCY COINCIDES WITH THE EIGENFREQUENCIES OF THE SPACE FORMED BY THE AUXILIARY SURFACE. KEYWORDS: SCATTERING, EIGENFREQUENCIES, AUXILIARY SURFACE.  
 
Author :
Zannin, Paulo Henrique Trombetta
 
 
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