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Method of Acoustic Waveguide UT
Published in Chunguang Xu, Robotic Nondestructive Testing Technology, 2022
Acoustic waveguide is a method of acoustic guide-detection coupling that changes the propagation direction of acoustic wave through the tube bending by using the sound-conducting characteristic of the fluid or solid in the acoustic tube. This method is mainly used for ultrasonic import and export in the ultrasonic testing (UT) of narrow-space cavity-like components. The complex-shaped or special-shaped acoustic tube and the fluid or solid inside it is the core components of the acoustic waveguide detection system. The acoustic propagation path of ultrasound in an irregular acoustic tube is complex, where the ultrasound will encounter the acoustic reflection and transmission from the curved interface. When ultrasound is incident to the reflecting surface, several reflections, refractions, transmissions and wave mode conversions will occur and complex superimposed waves will be formed.
Acoustic Waveguides
Published in J. David, N. Cheeke, Fundamentals and Applications of Ultrasonic Waves, 2017
The slot waveguide is the complementary configuration to the strip. The wave is guided along the bare substrate with strips on either side, as shown in Figure 10.14. The material of the strips is chosen so that it stiffens the Rayleigh velocity of the substrate. As a result, the acoustic wave is trapped in the slot that forms an acoustic waveguide.
Surface elastic waves whispering gallery modes based subwavelength tunable waveguide and cavity modes of the phononic crystals
Published in Mechanics of Advanced Materials and Structures, 2020
C. W. Lim, J. N. Reddy, E. Carrera, Xinsheng Xu, Zhenhuan Zhou
Apart from the Lamb waves, surface wave finds many promising applications in the MEMS [60], photovoltaic and photonic devices [61], sensors and actuators [62], electromagnetic and acoustic waveguide [45, 63, 64], subwavelength wave manipulation [65] and seismic metamaterials in the elastic system [8–10, 66]. In acoustic media, Khelif et al. [43] theoretically studied the propagation of surface acoustic waves in the pillared-based PnC embedded on the surface of semi-infinite substrate. Furthermore, Achaoui et al. [67] experimentally studied the propagation of surface guided waves in the PnC and they reported local resonance and Bragg BGs. Similarly, Benchabane et al. [45] experimentally studied the propagation of surface-guided modes in the holey hypersonic PnCs. A 2-D PnC with the local resonance BGs was recently reported by Li et al. [47]. By analyzing different lattice symmetries, Khelif et al. [46] further investigated the propagation of surface acoustic waves in a pillared-based PnC. In another work, Achaoui et al. [68] studied surface acoustic waves propagation in a random arrangement of pillars placed on the surface of semi-infinite substrate and they demonstrated that local resonance BGs are independent of the system periodicity. In a hypersonic regime, Guo et al. [69] numerically investigated the propagation of surface guided waves by introducing a line defect in the silicon pillar-substrate system.
Effects of Inert and Energetic Nanoparticles on Burning Liquid Ethanol Droplets
Published in Combustion Science and Technology, 2019
Hyung Sub Sim, Miguel A. Plascencia, Andres Vargas, John W. Bennewitz, Owen I. Smith, Ann R. Karagozian
The present droplet combustion experiments were conducted in a closed, atmospheric pressure acoustic waveguide in which the burning fuel droplet was suspended in the center, as indicated in Figure 1(a). The experiments here were conducted in three different ways (see Figure 1(b)): (1) with a burning droplet suspended from a quartz fiber (case I); (2) a droplet suspended from a quartz capillary without continuous fuel delivery during combustion (case II); and (3) a droplet suspended from the capillary with continuous fuel delivery at a volumetric flow rate, Qv via a syringe pump (case III). The quartz capillaries had an average outer diameter of 0.64 mm, and the diameter of the quartz fibers was approximately 0.24 mm, with an average bead diameter of 0.36 mm at the end of the fiber to help suspend the droplet. For case I, a single droplet was deposited on the quartz bead using a small capillary, while for case II, the pump was turned on until a single droplet was formed at the end of the capillary and then the syringe pump was shut off; this is referenced as the “nonfed” capillary case. For case III, the pump ran continuously during combustion, yielding a quasi-steady “fed” combustion process, as described in Sevilla-Esparza et al. (2014) and Bennewitz et al. (2018b) for the study of acoustically coupled fuel droplet combustion. The droplets were ignited using a removable nichrome wire. The fibers and capillaries were cleaned via an ultrasonic bath or manually wiped with a paper towel between experiments and were periodically replaced.
The inverse scattering problem for partially penetrable obstacles
Published in Applicable Analysis, 2018
All the above-mentioned works focus on determining the completely penetrable obstacle. In this paper, we consider a partially penetrable problem (1)–(4), and deal with the IP using the linear sampling method. We remark that Monk and Selgas [14] considered an IP of locating a penetrable obstacle, which is allowed to touch the boundary of the pipe, in an acoustic waveguide from measurements of pressure waves due to point sources inside the waveguide. They adopt the reciprocity gap method to deal with the IP. A kind of interior transmission problem (ITP) associated with the IP is discussed in the above paper [14] (also see [11]). A similar ITP should be investigated in this paper. By using the T-coercivity approach in [15], we can show that the ITP satisfies the conditions of the Fredholm alternative theorem, and the interior transmission eigenvalues form at most a discrete set. Based on this conclusion, in a special solution space, the injectivity and denseness of some related operators are established and then the linear sampling method can be applied to our problem.