Jean-Louis Migeot

Numerical integration in the vicinity of a logarithmic singularity

Abstract This paper presents a study of the numerical integration of the (1n r ) function in the vicinity of the singularity. This problem occurs for instance in the solution of field problems by the boundary element method. Two methods are considered, the Gauss-Legendre method and the analytical one. As a first step, the computing time of both methods are compared and an upper limit of the number of economic Gauss points is found. We then compute the error for various observation points and plot the iso-ϵ curves from which we derive a rule giving the number of Gauss points necessary to obtain a given precision as a function of the relative distance to the mid-point of the element. More surprising is the occurrence of lines of vanishing error. This last point is of great importance, in the boundary integral equation method for instance, as it allows important time economy in the integration.

Use of the student edition of ACTRAN in acoustics education

The power of computation has changed the way problems are solved in acoustics, and students should be trained to have an adequate background in modern techniques and software packages to simulate noise and vibration. Universities often cannot provide industrial-grade packages for their students due to the cost limitations. But recently a student version of a modern acoustics computation package was released, Student Edition of ACTRAN. This tool lets students solve a wide variety of problems using finite elements and infinite elements. This talk will describe the software and how it was used in a graduate level course in computational acoustics. Two examples that will be shown include finding the modes of an irregularly shaped room and computing the acoustic radiation from a gearbox. But it is clear that this software can be used in many different ways, for both undergraduate and graduate acoustics education. Instructors can demonstrate acoustical phenomena for students not adept at using the software them...

A new finite/infinite scheme to model acoustic trim under realistic working conditions

The paper presents a finite‐element scheme modeling all aspects of the behavior of acoustic trim: insulation, absorption, and damping. The models can combine different materials (viscoelastic, poroelastic, incompressible), acoustic fluid, and include complex effects like visco‐thermal dissipation in thin air layers. Unbounded acoustic regions are modeled using stabilized conjugated infinite elements that present exceptional convergence properties. The structure can be subjected to a number of different excitations: kinematical (fixed motion), dynamical (discrete or distributed forces) or acoustical. An incident diffuse sound field or distributed pressure fluctuations corresponding to aerodynamic boundary layers can also excite the structure. The presentation will be organized as follows: (1) a brief review of the techniques involved: finite‐element method for the structure and the acoustic near field, infinite elements for the acoustic far field; (2) material models considered: viscoelastic, poroelastic, ...