Simplified data input
The end-user defines a set of materials and domains. The geometry is defined easily by straight segments or simple objects (polygons, circles), representing domain boundaries. Criteria for minimum mesh density per wavelength and minimum number of elements are then applied at each frequency to generate the mesh. Besides, input of a complex geometrical object (such as a tunnel) can be achieved by defining the point coordinates of closed contour from an image file.
Optimization of computation time
BEM and FEM meshes are generated automatically at each frequency. FEM domains are condensed on nodes coupled with BEM domains and FEM meshes are organized to reduce height of matrices columns.
Method modularity depending on domains
The user can choose which domains are modelled sing FEM or BEM. Infinite and homogeneous domains such as ground layers can easily be taken into account thanks to BEM. On the other hand, complex domains with multiple heterogeneities (such as track rails and slabs, or building foundations) are modelled more easily using FEM.
2D calculation is available but is not recommended, except as a preliminary step and in order to compare situations.
2.5D calculation is on the other hand well-adapted to many situations, especially train vibration problems. Indeed, this type of calculation assumes that the geometry remains the same in one direction, which approximates well a railway track on the ground or in a tunnel underground. 2.5D formalism is implemented both for BEM and FEM methods. At each frequency, 2.5D approach is based on a set of calculations for different wavenumbers.
Possibility to model multilayer ground and tunnels
Complex stratifications profiles are defined with straight segments with are automatically extended at each frequency. Tunnels are defined using their inside and outside contours and they can intersect a boundary between two layers (MEFISSTO can handle multiple tractions at a junction).
Module for estimation of structure-borne noise in building rooms using a hybrid approach
Apart from 2.5D calculation, which is used to predict vibration levels in the ground and in structures, MEFISSTO offers the possibility to define 3D volumes in which the acoustic radiation of walls is used to predict structure-borne noise inside the rooms. This approach has been validated against full 3D calculations.
MEFISSTO therefore provides a complete simulation kit to deal with structure-borne noise, from the vibrations induced by the pass-by of a nearby train to the acoustic emission from building walls and floors.
Did you know ?
MEFISSTO outputs have been validated against in situ measurement of tunnel mobility as part of preliminary studies of Grand Paris lines. It is also the reference tool for all vibration impact studies for the whole project.