PROGRAMM - DAGA 2012

Programm DAGA 2012 181Mi. 15:40 vanadium 2.03 Numerische Akustik 2Genetic Algorithm Applied to Geometry Design for Planar BeamformingW.D. Fonseca a , J.P. Ristow a und S.N.Y. Gerges ba Federal University of Santa Catarina (Brazil); b UFSC, Florianopolis(Brazil)Beamforming is an acoustic image technique able to estimate the sounddistribution generated by sources of noise using a microphone array.A suitable design of the array is fundamental to obtain satisfactory resultsusing this technique. Among the main characteristics to determinetheir effectiveness, the shape of the array, i.e. the geometry composedby the microphones, is a point to be focused. There are several standardgeometries (e.g. spiral, square) and these are successfully used,however, they can be improved to suit particular needs. Aiming this improvement,this work uses the concept of genetic algorithm to optimizearrays’ geometries - with restricted features - in order to maximize thedynamic range of a focal point. The modeling of the problem is describedwith the definition of the chromosomes, the fitness function, theevolution method and the operators of crossover and mutation. Parameterslike the size of the population and the mutation rate are also definedand his influences in the evolution of the response along the generationsare analyzed. Simulations were done with the classical delay-and-sumalgorithm to validate responses. The results are discussed, offering theadvantages and disadvantages of the solutions obtained and of the useof the technique.Mi. 16:30 vanadium 2.03 Numerische Akustik 2Aeroacoustic Sound Computation of a Generic Side Mirror usingSpectral Finite ElementsA. Hüppe a , M. Kaltenbacher a und A. Reppenhagen ba Alps-Adriatic University of Klagenfurt; b Kompetenzzentrum - Das VirtuelleFahrzeug, GrazThe driving noise of current automobiles at higher speeds is dominatedby sound generating vortices in the flow field which arise e.g. behindmounting parts such as side mirrors or antennas. Schemes for computationalaeroacoustics (CAA) which can predict this effect are importantfor a better understanding of the generation mechanisms and can helpto minimize this unwanted noise. One established finite element schemefor CAA is based on the second order wave equation with source termscomputed by Lighthills acoustic analogy. Even though this approach givesgood results in the far field, the predicted sound close and inside theflow region seems to be inaccurate. Therefore, we apply the acousticperturbation equations (APE), which use the Lamb vector as a sourceterm and consider convective effects on the sound propagation. As thestandard finite element method (FEM) is not applicable to APE, we presentand utilize a penalized mixed FEM to obtain stable and accurate