RII Track-4: Exploiting Thermoacoustic Assonance to Enrich Multifunctional Meta-Structures

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Airborne noise mitigation is a significant challenge in several engineering applications, particularly in the aerospace realm where it diminishes efficiency, hampers stealth, contributes to environmental pollution and curtails commercial viability. Conventional technologies have reached practical limits in addressing airborne noise, especially for low-frequency (~1000 Hz) spectra. In partnership with NASA’s Langley Research Center, Thermo-Acoustic Meta-Structures (TAMS), a new class of multifunctional structures will be explored with a focus on mitigating aircraft turbofan engine’s core-noise. A confluence of innovative multi-physical mechanisms within a novel design framework termed ‘assonance’ will be investigated to enrich broadband, low-frequency performance for TAMS. It is expected that new insights will be gained into underlying phenomena enabling the development of modeling tools to create prototype TAMS for evaluation in NASA’s facilities. Successful completion of this project will deliver a new technology for airborne noise mitigation, enhancing critical mission capabilities in several military and commercial engineering applications. This project has substantial congruence with the economic vision and strengths of the regional industrial and educational ecosystem of the State of Oklahoma while also contributing to national aerospace and defense interests and directly enabling technological solutions for sustainable global aviation.The overarching goal of this project is to educe new insights into scaling laws and structure-performance relationships for Thermo-Acoustic Meta-Structures (TAMS) aiding the development of impactful solutions for multifunctional applications, especially in the aerospace realm. Specifically, opportunities to address the aircraft turbofan engine core-noise mitigation priorities of NASA will be explored. Core-noise has significant low-frequency (~1000 Hz) components, as yet unaddressed using conventional acoustic liners. Utilizing available thermal gradients across the engine’s core-wall, a confluence of innovative designs for structural materials and interactive multiphysical mechanisms thereof will be employed to embed thermoacoustic elements into liner meta-structures. A new, computationally-efficient modeling tool based on a mulitphysical model for TAMS embedding the Rott’s model for thermoacoustics in conjunction with vibroacoustic elements within NASA’s Zwikker-Kosten Transmission Line (ZKTL) model for acoustic liners is proposed to be developed. An emergent metamaterials-inspired design framework termed ‘assonance’ will be explored to enrich broadband performance for TAMS. In partnership with NASA, state-of-the-art structural material configurations and fabrication processes will be utilized to construct prototypical test articles for evaluation using NASA’s experimental facilities. Generation of extensive data sets under varying acoustic conditions will help validate the model, extract scaling laws for power-to-volume ratio, influence of radiation impedance and frequency-thermal gradient dependencies and establish new insights into structure-performance relationships for assonant meta-structures. Successful completion of this project will deliver a new technology for airborne noise mitigation, enhancing critical mission capabilities in several military and commercial engineering applications and directly contributing to sustainable global aviation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.