Numerical Methods
As early as the early 80s, when hardly any procedures for calculating the radiation pattern were commercially available, the FKFS began developing a computation tool based on the boundary element method (BEM) to supplement its measurement engineering competence. In its inverse application, it also allowed calculating surface velocities based on the acoustic pressure measurements around the object.
- BEM calculation of a radiation pattern of a vehicle door
Building on this expertise, the FKFS is currently using software tools that are generally commercially available. With respect to the known computational methods that are employed for problem-solving and development in vehicle acoustics, the following computational tools are available:
- Dynamic finite element methods (NASTRAN)
- Harmonic FEM and BEM (Virtual.Lab)
- Statistical energy analysis, SEA.
- Numerical aeroacoustics (PowerFLOW, OpenFOAM and corresponding post-processing).
For the numerical aeroacoustics, the FKFS performs simulations with state-of-the-art CFD processes based on Navier-Stokes equations as well as the Lattice-Boltzmann method. Depending on the object of investigation, the fluid dynamic simulations are implemented
- as direct simulation (including direct calculation of sound fields),
- with acoustic post-processing (e.g. acoustic analogy of Ffowcs Williams – Hawkings) or
- coupled with a structure code (FEM, BEM, SEA).
- Transient simulation of sunroof buffeting(total pressure, calculated with PowerFLOW®).
The objects of investigation are mainly the known aeroacoustic sources of passenger cars, such as
- the add-on parts (antenna, side view mirror, windshield wiper, etc.),
- the A-pillar vortex,
- the underbody and
- the sunroof and side window buffeting.
Powerful workstations and a cluster with approx. 400 Intel ® Xeon CPUs, for the time being, are available for the simulations.
- SAE model in the scale model wind tunnel of the FKFS for measuring the sunroof buffeting.
The simulations of aeroacoustics are accompanied by verification experiments in the wind tunnels and test benches available at the institute. In particular, the full-scale aeroacoustics wind tunnel and the 1:4 and 1:5 scale model wind tunnel are available for this purpose.
Not only does the FKFS use commercially available CFD codes, but it also tests open source codes and develops new computational methods to optimize conventional methods or to develop new, efficient tools for investigating vehicle acoustic problems.
- Scheme of the simulation of the fluid-structure-interaction.
- Propagation of a pulse in the turbulent flow around a car in order to estimate propagation effects.
© 2011 FKFS – Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart | Impressum | Datenschutz