PROGRAMM - DAGA 2012

92 DAGA 2012 Programm∂ np + δ∂ 2 τ p =0,where δ =(1+ı) √ η/(2ωρ 0) is related to the boundary layer thicknessand ∂ 2 τ is the second tangential derivative. With this approach the solutionfor far field takes into account absorption inside the boundary layerand gives highly accurate description of the pressure or velocity in thedomain outside a small layer close to the boundary.The boundary conditions have been derived up to second order for curvedboundaries by a multiscale analysis, which separate velocity andpressure into far field and correcting near field. The boundary conditionsare stable and asymptotically exact, which is justified by a completemathematical analysis.Dienstag (bis Mi. 12:00)Numerische Akustik (Poster)A new preconditioner for the iterative solution of the systems describingthe vibro-acoustics of multi-layered panelsP. Rong und O. von EstorffTU Hamburg-Harburg, Inst. f. Modellierung und BerechnungIn this work an efficient solution algorithm to investigate the vibroacousticsof multi-layered panels is presented. The panels can be composedof air gaps, elastic, and porous materials. Each layer is individuallyformulated and coupled to each other. In a standard finite elementanalysis, such a system is often badly conditioned, i.e. it can be hardlysolved by iterative methods. In order to improve the condition of thesystem matrix, a new preconditioner is developed by following the divideand-conquerprinciple. It takes advantage of the fact that each layer ofthe panel is only coupled with its direct neighbors. Using a strategy similarto an iterative coupling scheme, the system matrix is progressivelydecomposed into the triangular forms by means of the Schur complement.The suggested approach offers not only the acceleration of thedecomposition of the global system but also the flexibility to individuallydecompose the subsystem of each layer with the methodology that suitsbest.Dienstag (bis Mi. 12:00)Numerische Akustik (Poster)Modeling boundaries in acoustic TLM - local reflection coefficientsvs. locally reacting impedancesM. Kaletta and M. BlauInst. für Hörtechnik und Audiologie, Jade Hochschule OldenburgThe transmission line matrix (TLM) model is a method to simulate thepropagation of waves in a medium by discretizing the wave equation.Lambda is a software, developed at IHA Oldenburg, that makes use ofthis method to simulate the propagation of sound in a two-dimensionalmedium. One major problem common to all numerical methods in acousticsis the realization of boundary conditions. In Lambda, boundariesare modeled by local reflection coefficients that can be either constant