Exa Corporation, a global innovator of simulation software for product engineering, today revealed its patent-pending FIND (Flow-Induced Noise Detection) capability within Exa PowerACOUSTICS. This integrated solution represents a critical advancement for Exa’s existing aeroacoustic computational fluid dynamics (CFD) simulations by clearly pinpointing the origins of airflow-induced noise. Exa PowerFLOW has long been the established leader in aeroacoustic simulations, but engineers have been challenged to unravel the complex turbulent flows in order to understand how to acoustically improve their designs by reducing the noise sources. Now the FIND software can analyze the fluid flow of a design and rank the different noise sources in order of importance, providing engineers with the insight they need. The noise generated can also be listened to before and after design modifications, so that the impact of any proposed improvements can be aurally assessed. Exa’s solutions empower engineers to understand issues early in the development process. Product designs can then be improved in a digital environment, long before costly physical prototypes that provide no insight have been built.
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A video animation of the FIND module within Exa PowerACOUSTICS can be seen here: https://youtu.be/Ahvu9EP9hnY
For the automotive industry, the FIND module within Exa PowerACOUSTICS predicts the flow-induced noise sources for areas such as greenhouse or underbody wind noise, HVAC and blower noise, or noise from within exhaust systems. Using a patent-pending method, it analyzes the airflow simulated with Exa’s PowerFLOW, the market leader in ground vehicle aeroacoustics and the fastest and most accurate solution available. As always with PowerFLOW, the simulation reproduces the transient nature of real fluid flow, resulting in accurate modeling of turbulence. Flow-induced noise sources, even those normally masked by turbulent airflow, are then pinpointed in space by the FIND model and their intensity quantified, enabling a precise localization and ranking of noise problems. Thanks to other Exa products, the results can be visualized in 3D: quickly, clearly and simultaneously with the underlying design geometry. This makes it easy to convey the findings to engineers and managers, and easy to decide how to improve the design.
“Exa PowerFLOW accurately predicts aeroacoustic noise levels and PowerACOUSTICS FIND provides an unprecedented insight to identify noise sources. This allows engineers to make design changes that will reduce the generated noise levels,” remarked Dr. Franck Perot, Sr. Director of Acoustic Applications for Exa. “This capability applies to all aeroacoustics applications across multiple industries, such as wind noise and HVAC systems noise in automotive, landing-gear noise in aerospace, or applications in the rail industry. FIND provides significant additional value to our clients through these breakthrough capabilities that were not available anywhere, until now.”
Collaboration with BMW
The noise produced by the HVAC system is one of the top complaints for automotive passengers. In close collaboration with Exa, BMW Group has already used the new tool to perform aeroacoustic evaluations of complete HVAC systems. BMW had previously found that analysis of the flow through standalone components such as ducts or blowers gave incomplete information on the acoustic performance of the whole system. Worse still, it had been found that it could be misleading to decide on which sub-system to improve, based solely on the sounds it generated.
“We initially used PowerFLOW and PowerACOUSTICS FIND for the BMW 7 Series and Rolls-Royce Phantom,” said BMW ‘s Group Leader for Overall Vehicle Development, Dr.-Ing. Michael Spickenreuther. “We were so impressed with the noise sourcing capability that we have now implemented FIND across all our platforms. FIND is enabling us to deliver quieter cars.”
By using PowerFLOW’s transient simulation as the basis for an analysis of the complete HVAC system, BMW engineers were able to see how the sound was not only generated, but propagated through the system, from the initial source to the passenger’s ear. The new FIND model provided enhanced insight by localizing, quantifying and ranking the generated acoustic power, providing a more complex and accurate view on where noise reduction improvements could be made within the system. Overall, BMW found that the tool enabled efficient optimization of HVAC aeroacoustics in the earliest stages of vehicle development. BMW published this work in a paper, Acoustic Source Detection for Climate Systems via Computational Fluid Dynamics for Improved Cabin Comfort, and presented it at the 3rd International ATZ Conference, held in Zurich, Switzerland.