Journal of Computational Acoustics

Whilst most people in developed societies would celebrate the route from innovation to impact, particularly in the context of engineering and biomedicine, it is not often acknowledged that the definitions of the start, mid-points and even end-points of that route vary between groups in society. Since that route requires funding, this variety of opinion leaves regions of the route vulnerable to underfunding, particularly in times of recession. This paper explores how this can lead to failure to foresee problems and underpin solutions on the 10–50 year timescale. Furthermore, policies designed to support the route from innovation to impact can have the opposite effect. The route is illustrated with examples from the author's research.

We present physical/mathematical models base on partial differential equations (PDEs) and efficient numerical simulation schemes based on the Finite Element (FE) method for multi-field problems, where the acoustic field is the field of main interest. Acoustics, the theory of sound, is an emerging scientific field including disciplines from physics over engineering to medical science. We concentrate on the following three topics: vibro-acoustics, aero-acoustics and high intensity focused ultrasound. For each topic, we discuss the physical/mathematical modeling, efficient numerical schemes and provide practical applications.

Often, acoustic simulation techniques suffer from errors of the computational model and its parameters. Quantification of the boundary condition is a crucial point for simulations. In particular, the boundary admittance is often unknown and hard to quantify. This article demonstrates how to reduce a fluid-structure interaction model to a pure fluid model with local or nonlocal admittance boundary conditions. Starting point is a BEM formulation for the fluid and a FEM formulation for the structure. An admittance matrix is derived from this formulation. Then, the multidimensional BEM–FEM formulation is adjusted to a one-dimensional example, a duct with structural elements at both ends. Two configurations are investigated, one with local admittance boundary conditions and one with nonlocal admittance boundary conditions which result in a diagonal and in a fully populated admittance matrix, respectively.

This paper applies a parallel algorithm for a coupled Finite Element/Scaled Boundary Element (FEM/SBFEM)-approach to study soil-structure-interaction problems. The application code is designed to run on clusters of computers, and it enables the analysis of large-scale problems. A crucial point of the approach is that the SBFEM fulfills the radiation condition. Hence, the hybrid numerical approach is well suited for such problems where wave propagation to infinity in an unbounded domain must be considered. The main focus of the paper is to show the applicability of the numerical implementation on large scale problems. First the coupled FEM/SBFEM approach is validated by comparing the numerical results with a semi-analytical solution for a settlement problem. Then the implemented algorithm is applied to study the dynamical behavior of founded wind energy plants under time dependent loading.

In this article we present an algorithm for the three-dimensional numerical simulation of the sound spectrum and the propagation of acoustic radiation inside and around long slender hollow objects. The fluid inside and close to the object is meshed by Lagrangian tetrahedral finite elements. To obtain results in the far field of the object, complex conjugated Astley-Leis infinite elements are used. To apply these infinite elements the finite element domain is meshed either in a spherical or an ellipsoidal shape. Advantages and disadvantages of both shapes regarding the form of the object are discussed in this article. The formulation leads to a quadratic eigenvalue problem with real, large and nonsymmetric matrices. An eigenvalue search algorithm is implemented to concentrate on the computation of the interior eigenmodes. This algorithm is based on a linearization of the quadratic problem in a state space formulation. The search algorithm uses a complex shift to efficiently extract the relevant eigenvalues only.