MechE PhDProspectus Defense - Reza Ghaffarivardavagh

  • Starts: 2:00 pm on Wednesday, September 19, 2018
  • Ends: 4:00 pm on Wednesday, September 19, 2018
TITLE: TAILORING ACOUSTIC WAVE WITH METAMATERIAL AND METASURFACE COMMITTEE: Prof. Xin Zhang (ME/ECE/MSE/BME) (Advisor) Prof. Stephan Anderson (BUSM/ME) Prof. Thomas Bifano (ME/MSE/BME) Dr. Matthew D. Guild (U. S. Naval Research Laboratory) Prof. R. Glynn Holt (ME) ABSTRACT: Nowadays, metamaterials have found their places in different branches of wave physics ranging from electromagnetics to acoustic wave. Acoustic metamaterials are sub-wavelength structures in which their effective acoustic properties are dominated by their structural shape rather than their constitutive materials. In recent years, acoustic metamaterials have gained increasing interest due to numerous promising applications such as sub-wavelength imaging, perfect absorption, acoustic cloaking and etc. The focus of the work herein is to leverage acoustic metamaterial/metasurface structures to manipulate the acoustic wavefront to pave the road for the future applications of the metamaterials. In the first part of the work, the metamaterial structure is introduced which can be leveraged for better manipulation of the transmitted wave by modulating both phase and amplitude. Initially, a general bound regards to the transmission phase/amplitude space for the case of arbitrary metasurface has been presented and subsequently, the necessary condition for the complete modulation of the transmitted wave is investigated. Next, Horn-like space coiling metamaterial is introduced which satisfies the aforementioned condition and enabled us to simultaneously modulate both the phase and amplitude of the transmitted wave. The performance of the Horn-like space coiling metamaterial presented herein for manipulation of the transmitted acoustic wavefront has been validated both analytically and experimentally. In the second part of this work, a novel metamaterial based methodology is presented for the design of the air permeable acoustic silencer. In this work, the concept of the bilayer- transverse metamaterial is introduced and its functionality for silencing the acoustic wave is demonstrated. Furthermore, it is shown that the methodology presented herein essentially does not limit the ratio of the open area and ultra-open metamaterial silencer may be designed. Eventually, based on the presented methodology the ultra-open metamaterial featuring nearly 60% open area is designed and silencing capacity of about 94% at the targeted frequency is experimentally realized. The proposed metamaterial silencing performance is frequency selective and harmonic in nature, hence it is readily applicable for the fan or engine noise suppression. Ultimately, future works targeting different aspects of acoustic wavefront manipulation using metamaterial and metasurfaces are proposed. This work concentrate on the leveraging of metamaterial and metasurfaces for tailoring acoustic wave.
Room PHO 901, 8 Saint Mary’s Street

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