Design and Simulation of Acoustic Metamaterials for Noise Reduction in Open- Flow Systems
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Applied mechanics (MPAME), MSc
Sound and vibration (MPSOV), MSc
Sound and vibration (MPSOV), MSc
Publicerad
2024
Författare
Ji, Chenya
Reddy, Prajwal Sunil
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The growing demand for larger and more efficient cooling systems in heavy-duty
trucks has led to increased noise levels, particularly from cooling fans, which poses
challenges to both environmental standards and user comfort. Conventional techniques
for sound absorption typically restrict particle motion, which will also impede
flow and increase temperature in a situation when fans are present. Acoustic metamaterial
(AMM) solutions have been explored to address these problems.
A systematic methodology for designing a single metamaterial cell is presented, encompassing
four stages: specification of geometrical parameters, parametrization,
parametric design, and optimization. Noise characterization of a vehicle’s cooling
fan, based on Lu’s study[20], revealed broadband noise and tonal harmonics centred
on the blade passing frequency (BPF).
In response, a double-layer micro-perforated panel (DLMPP) structure was designed
to reduce noise over a broad frequency range; a space-coiling structure was created
to target specific tonal noise. Theoretical calculations show that both structures
have excellent noise absorption performance. Simulations of the space-coiling cell
with a flow field were then conducted. Although the absorption coefficients show
slight deviations from theoretical calculations, the results remain promising for this
study and warrant further investigation. A simulation of an under-cab environment
was also studied by applying the acoustic impedance of DLMPP on target surfaces
under conditions with and without flow. The results demonstrate that the present
AMMs can significantly reduce cooling fan noise while maintaining thermal management
efficiency.
Beskrivning
Ämne/nyckelord
cooling fan noise , acoustic metamaterial design , acoustics metamaterial simulation , broadband noise reduction , tonal noise reduction , computational fluid dynamics , passive noise control , aeroacoustics , micro-perforated panel , space-coiling structure