Harnessing fluid-structure interactions to design self-regulating acoustic metamaterials

Abstract

The design of phononic crystals and acoustic metamaterials with tunable and adaptive wave properties remains one of the outstanding challenges for the development of next generation acoustic devices. We report on the numerical and experimental demonstration of a locally resonant acoustic metamaterial with dispersion characteristics which autonomously adapt in response to changes of an incident aerodynamic flow. The metamaterial consists of a slender beam featuring a periodic array or airfoil-shaped masses supported by a linear and torsional springs. The resonance characteristics of the airfoils lead to strong attenuation at frequencies defined by the properties of the airfoils and the speed on the incident fluid. The proposed concept expands the ability of existing acoustic bandgap materials to autonomously adapt their dispersion properties through fluid-structure interactions, and has the potential to dramatically impact a variety of applications, such as robotics, civil infrastructures, and defense systems.

Dynamic Simulation of a Metamaterial Beam Consisting of Tunable Shape Memory Material Absorbers

“…The performance of this class of design was verified experimentally by Zhu et al [22]. In addition, Casadei et al [23] proposed a metamaterial consisting of a slender beam featuring a periodic array of airfoil-shaped masses supported by linear and torsional springs. The resonance characteristics of the airfoils lead to strong attenuation at frequencies defined by the properties of the airfoils and the speed on the incident fluid.…”

“…In other words, the mass ratio of the absorber changed the bandwidth of the stopband, while the natural frequency of the absorber shifted the frequency of the stopband without alteration of its frequency ratio. The simulation of changing the natural frequency of the absorber was conducted to examine the possible influence of switching SMA from martensite to austenite, which generates a change in the Young's modulus of three folds [23]. the absorber shifted the frequency of the stopband without alteration of its frequency ratio.…”

“…the absorber shifted the frequency of the stopband without alteration of its frequency ratio. The simulation of changing the natural frequency of the absorber was conducted to examine the possible influence of switching SMA from martensite to austenite, which generates a change in the Young's modulus of three folds [23].…”

Experimental and Theoretical Investigation of Lowering the Band Gaps of Phononic Crystal Beams through Fluid-Solid Coupling

“…Although fluid-solid PCs have been one of the research focuses in the past years, in most literature fluid only serves as a constituent or a medium through which acoustic waves propagate [7][8][9][10][11]. Conventionally, accelerometers (e.g., [8,12] for flexural waves) or ultrasonic immersion transmission technique (e.g., [9,11] for longitudinal waves) are used to detect the transmission spectra of phononic crystals.The fluid-structure interaction (FSI) on tuning the band-gap or transmission properties of the PCs are seldom addressed. As a promising method for the PCs to adapt to different operation conditions, tuning band gaps through solid-fluid coupling is currently receiving attention.…”

“…To actively control the localized modes for guiding or filtering waves, Jin et al theoretically investigated the dynamics of a phononic crystal plate with hollow and liquid-filled pillars [7]. Casadei and Bertoldi realized self-regulation of dispersion properties by coupling incident aerodynamic flow to a slender beam carrying a periodic array of local resonators [12]. In fact, in addition to band gap tuning, knowledge about the influence of fluids coupled to PC beams or plates on elastic band-gap and transmission properties is fundamental to a variety of potential applications for the PCs, from environmental or liquid sensing to structural design or vibration control in the marine environment.…”