José Albelda

A transversal substructuring modal method for the acoustic analysis of dissipative mufflers with mean flow

This work presents a modal approach to evaluate the transversal modes and wavenumbers for dissipative mufflers with mean flow. The method is based on the division of the transversal section of the muffler into subdomains, for which two simple sets of modes are considered. The first set of modes satisfies the condition of zero pressure at the common boundary between subdomains, while the second fulfils the condition of zero derivative in the direction normal to this boundary. From these sets, a substructuring procedure is applied that provides the final modes of the complete cross section, considering the presence of absorbent material, a perforate and mean flow. The technique avoids iterative schemes associated with the nonlinear characteristic equation found, for instance, in the analytical modelling of perforated dissipative circular mufflers. Once the final transversal modes have been calculated, the mode matching technique is applied at the geometrical discontinuities to completely define the acoustic field inside the muffler. The acoustic attenuation is then predicted by means of the transmission loss. Comparison with finite element calculations and results available in the literature show good agreement. The attenuation of some selected mufflers is analysed, including the effect of the perforate and the mean flow.

Influence of the finite element discretization error over the convergence of structural shape optimization algorithms

This work analyzes the influence of the discretization error contained in the finite element (FE) analyses of each design configuration proposed by structural shape optimization algorithms over the behavior of the algorithm. If the FE analyses are not accurate enough, the final solution will neither be optimal nor satisfy the constraints. The need for the use of adaptive FE analysis techniques in shape optimum design will be shown. The paper also proposes the use of the algorithm described in the previous study conducted in order to reduce the computational cost associated to the adaptive FE analysis of each geometrical configuration when evolutive optimization algorithms are used.

3D Topology Optimization with h-adaptive Refinement Using Cartesian Grids Finite Element Method (cgFEM)

Regarding shape optimization of structural components, topology optimization has become one of the most popular methods to achieve significant reductions in mass and volume, while maintaining stiffness. The basic topology optimization algorithm considered in this paper and a heuristic updating scheme are described in Bendsoe [1].

Efficient implementation of domain decomposition methods using a hierarchical h-adaptive finite element program

A previous contribution[1] showed the hierarchical relationships between parent and child elements that come out if these elements are geometrically similar. Under this similarity condition, the terms involved in the evaluation of element stiffness matrices (ke=∫B t DB∣J∣dV), corresponding to parent and child elements, are related by a constant which is a function of the ratio of the element sizes (scaling factor). These relations were used in the basic implementation of a hierarchical h-adaptive Finite Element program based on element subdivision for the resolution of the 2-D linear elasticity problem. The program makes use of a hierarchical data structure to carry out the h-adaptive process, which significantly reduces the amount of calculations required for the evaluation of the problem stiffness matrix, element stresses, element error estimation,...