Defect-Embedded Phononic Crystals for Passive Turbulent Flow Control
Date:
Abstract: Phononic crystals (PnCs) are a class of architected materials that leverage material or geometric periodicity and the resulting Bragg scattering phenomenon to control the wave propagation characteristics in the material bulk. Initial PnC studies primarily focused on engineering the phononic pass bands for applications, e.g., mechanical wave guiding, cloaking, and computing. However, subsequent studies exploring wave dynamics in phononic band gaps, e.g., topological edge and bulk modes, and truncation resonances, have revealed the additional advantages of engineering localized responses in PnCs for modern applications in energy harvesting, fluid-metamaterial interaction, and passive flow control. The single/multi-point interaction and response of PnCs to state-dependent acoustic loads and fluid flow in these modern applications presents a key modeling and design challenge, compared to traditional PnC applications, where PnCs primarily respond to single-point interactions with prescribed external loads. Therefore, motivated to study this relatively unexplored domain of PnC dynamics, we present a defect-embedded PnC featuring an engineered BG resonance (i.e., defect mode) that can be leveraged for passive turbulent flow control.
In this presentation, we analytically formulate the dependence of three critical behavioral characteristics, i.e., the frequency, mode shape, and velocity amplitude envelope of the resonant defect mode, on the material properties of the PnC. Subsequently, we deploy these defect-embedded PnCs as subsurfaces in turbulent channel flow and numerically study the resulting fluid-structure interaction. Given the broadband and stochastic nature of turbulent flow pressure, defect-embedded PnCs are chosen for their beneficial responses, e.g., narrow-band response centered at the defect frequency, high energy localization, stable pressure-deformation phase. The PnC behavioral characteristics, i.e., defect mode frequency and velocity amplitude envelopes, and spatial periodicity of multiple PnCs, are correlated with the relevant fluid characteristics, i.e., statistically dominant fluid frequency, pressure intensity, and dominant fluid wavelengths, respectively, conducive for drag reduction, to inform the PnC designs. A weakly-coupled turbulent flow-PnC interaction study is then conducted to quantify the change in turbulent drag as a function of the above behavioral parameters. Preliminary results indicate a nominal drag reduction in certain frequency-amplitude regimes, motivating further investigations to improve the effectiveness of PnCs for passive turbulent flow control. In addition, our PnC design approach provides a template to systematically explore other types of phononic materials with relevant behavioral characteristics for flow control in various flow conditions.
Citation: V. Ramakrishnan, C. T. Lin, A. J. Goza, K. H. Matlack, H. J. Bae, “Defect-Embedded Phononic Crystals for Passive Turbulent Flow Control”, SES 2025, Atlanta, GA, October 12 - 15, 2025’