VIPROM - Virtual Prototyping of Vibro-Acoustic Systems in the Mid-frequency Range
Overview
Background & policy context:
A majority of noise and vibration problems occur in the range between the low and high frequency range (the so-called mid-frequency range), but a general predictive approach is lacking in the mid-frequency range. Deterministic methods such as the Finite and Boundary Element Method (FEM and BEM) are too computationally intensive to be applicable for real-life engineering problems, while statistical methods such as Statistical Energy Analysis (SEA) are not reliable enough. An adequate solution allowing design engineers to virtually prototype in the mid-frequency range by numerical simulation is of crucial importance.
The VIPROM proposal has been initiated after recognizing that the mid-frequency modelling crisis can be overcome by combining deterministic and statistical methods.
Objectives:
The VIPROM training program has coped with predictive modelling of structural-acoustic systems in the mid-frequency range. The objective was to establish, evaluate and validate (from the industrial point of view) coupling mechanisms between deterministic and statistical methods in order to resolve the mid-frequency modelling gap.
The strategy of addressing potential solutions from all possible view-points led to three complementary objectives:
- To extend high frequency techniques towards the mid-frequency range. State-of-the-art methods must be studied, including statistical energy analysis (SEA, both numerical and experimental), Energy flow analysis, and so on.
- To extend low-frequency methods upward to the mid-frequency range. Advancements must be achieved in low-frequency techniques (FEM, BEM) in order to increase their validity up to higher frequencies. This required research into advanced (trim) modelling techniques, parallelisation and efficient solver strategies, component mode synthesis (CMS) for faster design iterations, and so on.
- To tackle dedicated mid-frequency issues such as the effect of uncertainty and variability on the functional performance response, which becomes ever more important with increasing frequency range.
Methodology:
The project started with investigating the first path on coupling FEM and SEA methods. This hybrid method consists of the partitioning of the problem variable (e.g. velocity, pressure, etc) into long-(global) and short- (local) wave length deformations. Though the hybrid SEA/FEM methodology was giving promising results for simple rods, the application to beams revealed several major difficulties when one would further extend the methodology to plates and more complex structures. These difficulties led to the decision to explore promising methodologies from the complementary low-frequency perspective.
Therefore, research continued on extending low-frequency methods upward to the mid-frequency range. In this second phase of the research, targeting breakthrough methodologies from the low- up to medium-frequency perspective, two main approaches have been investigated:
- including uncertainty and variability for allowing more accurate predictions for higher frequencies;
- improving performance (e.g. accuracy, calculation speed) of deterministic techniques such that they can be effectively used for medium-frequency problems. In particular, vibro-acoustic problems were addressed.
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