High Performance Computation Codes for Vibroacoustic Simulation in the Automotive Field

In view of the foreseen ISO 362 standard update in a more restrictive way, power-train exterior noise is likely to become a relevant issue in the automotive industry. This will lead to a strong focus on the design of engine shields and other thermo-acoustic trim parts positioned inside the engine bay. The possibility of designing such parts in an efficient and cost-effective way will call for reliable simulation methods to tackle real industrial cases. These methods cannot be easily taken for granted since, to be useful in the design of engine bay components aimed at exterior noise reduction, they have to satisfy quite challenging requirements as being able to: otake into account large frequency ranges (up to 4 or 5 kHz for Pass-by Noise tests) and big model sizes in a reasonable computation time (about 1 day) orepresent very complex domains orepresent design changes affecting sources or acoustic transfer paths. Available deterministic simulation methodologies have been tested during these last years in relation to the above-mentioned problem. The object of the simulations consists in evaluating the exterior Acoustic Transfer Functions (ATFs) of a simplified (but not trivial) vehicle engine bay mockup in the analysis frequency range up to 3.5 kHz. The focus was concentrated on both traditional and more innovative deterministic analysis methods. Boundary Element Method (BEM) and Finite Element Method (FEM) acoustic technologies, and their implementations as Fast Multipole Method (FM BEM) and Automatically Matched Layer (FEM AML) in LMS Virtual.Lab code, have been mainly tested in this benchmarking activity. The computation performance of the very last approach FEM Adaptive Order (FEM AO) has also been evaluated. A comparison with experimental test results is always taken into account as a reference in order to judge on the methods models' accuracy. The capabilities of these methods to well represent both acoustic trim parts effect and apertures positioning around the engine bay was assessed and their computational performance compared.