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17. High-efficiency broadband absorption/reflection integrated lossy acoustic metasurface via embedded microperforated wall.

Author

He, Jin, Liang, Qingxuan, He, Hailang, Wang, Miao, Li, Dichen, and Chen, Tianning

Subjects
ABSORPTION of sound, SOUND energy, PHASE modulation, FAULT diagnosis, MICROFLUIDICS, ABSORPTION
Abstract

Period phase gradient metasurface plays a great role in promoting the innovation of acoustic application devices. However, harnessing the internal thermal viscosity of the period phase gradient metasurface to realize sound absorption and non-reciprocal transmission faces the narrow working frequency band and uncontrollable efficiency. In this paper, we propose a lossy metasurface by embedded microperforated walls to realize sound redirection and absorption with high efficiency than 90% simultaneously. The phase modulation is realized using an opening channel, which can cover the 2 π phase range in a broadband frequency range by changing the channel depth. The loss introduced by the microperforated walls can achieve efficient sound energy dissipation when negative reflection occurs. The functions can be switched between wave redirection and wave absorption by rotating the metasurface. In addition, this metasurface can redirect the incident wave below −10° and absorb the incident wave above 25° over a wide frequency range from 1500 to 6500 Hz. The simulation and experiment results of our design are in excellent agreement. This research provided a new bridge to integrate wave redirection and absorption with microperforated walls and may have potential applications in acoustic sensing, sound source identification, and mechanical fault diagnosis. [ABSTRACT FROM AUTHOR]

Published
2023
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46. Frequency band-selected one-way topological edge mode via acoustic metamaterials and metasurface.

Author

Song, Xinpei, Chen, Tianning, and Li, Rui

Subjects
*TOPOLOGICAL insulators, *TRANSMISSION of sound, *METAMATERIALS, *EDGES (Geometry), *PHONONIC crystals
Abstract

Single functionality and fixed operating bands maintain the key drawbacks in existing acoustic topological insulators. Here, we report an acoustic system to realize the frequency band-selected one-way topological edge state transmission. The system is combined with a double-layer sonic crystal and a lossy acoustic metasurface. The topological insulators enable the frequency band-selected effect by separating and nesting the two layers of the sonic crystals. The sound one-way transmission effect is ensured by the metasurface. Consequently, the one-way topological edge state transmission is realized, and the operating band of the system can be shifted between two distinct ranges. Our work may have potential in the areas where multiple frequency bands are required, such as sound isolation, acoustic switch, mechanical imaging, acoustic split, and integrated acoustic communications. [ABSTRACT FROM AUTHOR]

Published
2021
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47. Sensitivity of shear wave splitting to fracture connectivity.

Author

He, Yanbin, Rubino, J Germán, Barbosa, Nicolás D, Solazzi, Santiago G, Favino, Marco, Chen, Tianning, Gao, Jinghuai, and Holliger, Klaus

Subjects
SHEAR waves, HYDROCARBON reservoirs, FLUID pressure, EARTHQUAKE prediction, GEOLOGICAL formations, VOLCANIC eruptions
Abstract

Shear wave splitting (SWS) is currently considered to be the most robust seismic attribute to characterize fractures in geological formations. Despite its importance, the influence of fluid pressure communication between connected fractures on SWS remains largely unexplored. Using a 3-D numerical upscaling procedure based on the theory of poroelasticity, we show that fracture connectivity has a significant impact on SWS magnitude and can produce a 90° rotation in the polarization of the fast quasi-shear wave. The simulations also indicate that SWS can become insensitive to the type of fluid located within connected fractures. These effects are due to changes of fracture compliance in response to wave-induced fluid pressure diffusion. Our results improve the understanding of SWS in fractured formations and have important implications for the detection and monitoring of fracture connectivity in hydrocarbon and geothermal reservoirs as well as for the use of SWS as a forecasting tool for earthquakes and volcanic eruptions. [ABSTRACT FROM AUTHOR]

Published
2023
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