Trapping Of Wave Energy Research Articles

Acoustofluidic black holes for multifunctional in-droplet particle manipulation.

Acoustic black holes offer superior capabilities for slowing down and trapping acoustic waves for various applications such as metastructures, energy harvesting, and vibration and noise control. However, no studies have considered the linear and nonlinear effects of acoustic black holes on micro/nanoparticles in fluids. This study presents acoustofluidic black holes (AFBHs) that leverage controlled interactions between AFBH-trapped acoustic wave energy and particles in droplets to enable versatile particle manipulation functionalities, such as translation, concentration, and patterning of particles. We investigated the AFBH-enabled wave energy trapping and wavelength shrinking effects, as well as the trapped wave energy-induced acoustic radiation forces on particles and acoustic streaming in droplets. This study not only fills the gap between the emerging fields of acoustofluidics and acoustic black holes but also leads to a class of AFBH-based in-droplet particle manipulation toolsets with great potential for many applications, such as biosensing, point-of-care testing, and drug screening.

A Modeling Study of an Atmospheric Bore Associated With a Nocturnal Convective System Over China

AbstractBores have been shown to play a role in the initiation and maintenance of mesoscale convective systems (MCSs), particularly during the night after the boundary layer stabilizes. To date, the generation, evolution, and structure of bores over China has received little attention. This study utilizes observations and simulations with the WRF‐ARW model to investigate the generation and evolution of an atmospheric bore observed over Yangtze‐Huai Plains of China. The bore was associated with a nocturnal MCS that first formed over elevated terrain. The bore was observed ahead of the MCS with a maximum lateral extension of ~100 km. The feature lasted for over 90 mins and propagated at a speed of ~13 m/s, slightly faster than the MCS. In the simulation, the bore evolved from the separating “head” of the convectively generated gravity current. The bore then continued to propagate ahead of the MCS, even after the dissipation of the feeder current, and took on the appearance of an undular bore. The bore lifted a layer of convectively unstable air above the nocturnal surface inversion, initiating new convection ahead of the MCS to help maintain the MCS. The Scorer parameter ahead of the bore revealed a low‐level wind profile with curvature of the vertical profile of horizontal wind, favoring the trapping of wave energy and the persistence of the bore. These results are generally consistent with the role of bores in the maintenance of nocturnal MCSs and emphasize the need for future studies into the relationship between bores and nocturnal MCSs over China.

Coupling of Integrated Waveguide and Optomechanic Cavity for Microwave Phonon Excitation in Si Nanobeams

The availability of high quality manufacturing for optical micro/nano patterned cavities paves the way to the development of scalable circuits and devices based on optomechanical (OM) interaction of sound and light in extremely small volumes. In this contribution, we propose a new study on OM cavities that can lead to precise control of their coupling with closely integrated waveguides, a necessary condition to enhance mode excitation and wave energy trapping, opening the possibility for many potential applications in wave guiding, filtering, confinement, and sensing. Moreover, in this way the need for bulky experimental setups and/or optical fiber coupling/excitation is avoided. At the same time, quality factors of mechanical and optical modes resonating in the cavity are optimized, together with their OM coupling coefficients: high confinement of both excitations is a prerequisite to enable their acousto-optic (AO) interaction. To this aim, the transversal size of the cavity has been parabolically tapered, with the additional benefit of separating the cavity and the integrated waveguide far from the coupling region. The finite-element method has been used to perform full-wave analysis, and an accurate discussion about the simulation setup needed to properly describe optical scattering and radiation has been provided.

Wave Disturbances and Their Role in the Maintenance, Structure, and Evolution of a Mesoscale Convection System

AbstractThis study investigates a nocturnal mesoscale convective system (MCS) observed during the Plains Elevated Convection At Night (PECAN) field campaign. A series of wavelike features were observed ahead of this MCS with extensive convective initiation (CI) taking place in the wake of one of these disturbances. Simulations with the WRF-ARW Model were utilized to understand the dynamics of these disturbances and their impact on the MCS. In these simulations, an “elevated bore” formed within an inversion layer aloft in response to the layer being lifted by air flowing up and over the cold pool. As the bore propagated ahead of the MCS, the lifting created an environment more conducive to deep convection allowing the MCS to discretely propagate due to CI in the bore’s wake. The Scorer parameter was somewhat favorable for trapping of this wave energy, although aspects of the environment evolved to be consistent with the expectations for an n = 2 mode deep tropospheric gravity wave. A bore within an inversion layer aloft is reminiscent of disturbances predicted by two-layer hydraulic theory, contrasting with recent studies that suggest bores are frequently initiated by the interaction between the flow within stable nocturnal boundary layer and convectively generated cold pools. Idealized simulations that expand upon this two-layer approach with orography and a well-mixed layer below the inversion suggest that elevated bores provide a possible mechanism for daytime squall lines to remove the capping inversion often found over the Great Plains, particularly in synoptically disturbed environments where vertical shear could create a favorable trapping of wave energy.

An Analytical Solution for Wave Transformation Over Axi-Symmetric Topography

The present study considers wave scattering phenomena around a cylindrical island mounted on a general axi-symmetric topography or a general submerged truncated axi-symmetric shoal based on the mild-slope equation. The method of separation of variables and Taylor series expansion are invoked to find the approximate solution to the variable water depth region which varies proportionally to an arbitrary power of radial distance. Validations against the solutions for the combined wave refraction and diffraction around a cylindrical island mounted on a paraboloidal shoal of Liu et al. in 2004 and the scattering and trapping of wave energy by a submerged truncated paraboloidal shoal of Lin and Liu in 2007 show excellent agreements as the power of radial distance being equal to two. For the solutions of wave refraction and diffraction around a cylindrical island mounted on a shoal with depth proportionally to an arbitrary power of radial distance, good agreements with Zhai et al.’s (2013) solutions are demonstrated. Since the robustness of the assumption of a general axi-symmetric geometry based on an arbitrary power variability of the radial distance, the present solution can be very conveniently employed to investigate the effects of bottom topography on wave scattering and trapping patterns.

Hydrodynamic performance analysis of an integrated wave energy absorption system

The economic competitiveness of the wave energy converter can be improved by adopting a novel approach of integrating a wave energy converter with a vertical porous chambered breakwater. The scope of utilising the wave energy trapped inside a chambered breakwater, using a heaving type wave energy converter model is assessed through experimental and numerical investigations. Three different model cases with different model configurations were tested in a wave tank facility. The reflection characteristics of the chambered breakwater, wave elevations trapped inside the chamber and capability of the wave energy converter model to absorb the trapped wave energy are evaluated and presented in this paper. Adopting a chamber width of the breakwater model that matches the resonant period of the chamber and the incident wave period is found to improve the efficiency of the system to trap more wave energy inside the chamber. The reflection characteristics from the breakwater are found to reduce with the introduction of the wave energy converter model. The average power generation performance of the wave energy converter is found to increase by 20% after integrating it with the chambered breakwater than that of the stand-alone wave energy converter.

Wave Scattering by Twin Surface-Piercing Plates Over A Stepped Bottom: Trapped Wave Energy and Energy Loss

To evaluate the trapped wave energy and energy loss, the problem of wave scattering by twin fixed vertical surfacepiercing plates over a stepped bottom is numerically simulated using the open source package OpenFOAM and the associated toolbox waves2Foam. The volume of fluid (VOF) method was employed to capture the free surface in the time domain. The validation of the present numerical model was performed by comparing with both the analytical and experimental results. The effects of the spacing between two plates and the configuration of stepped bottom on the hydrodynamic characteristics, such as reflection and transmission coefficients, viscous dissipation ratio, and relative wave height between the plates (termed as trapped wave energy), were examined. Moreover, the nonlinear effects of the incident wave height on the hydrodynamic characteristics were addressed as well. The results show that the step configuration can be tuned for efficient-performance of wave damping, and the optimum configurations of the step length B, the step height h1 and the spacing b, separately equaling λ/4, 3h/4, and 0.05h (λ and h are the wavelength and the water depth, respectively), are recommended for the trapping of wave energy.

A 3-D numerical investigation on the heaving performance of a wave floater

A 3-D mathematical model of regular wave flume is conducted to investigate the heaving performance of a cylindrical floater. The results show that the transverse velocities near the floater distribute symmetrically at the wave crest and trough times, its symmetry axis is the longitudinal straight line across the floater center, and 4 extreme regions distribute near the floater. With the increase of relative width of wave flume, the trapped wave energy and the relative response amplitude increase firstly. Then, they decreases and appear to be stable for the relative width of wave flume higher than 10. The trapped wave energy and the relative response amplitude increase with the increase of incident wave height, respectively. With the increase of wave period, the trapped wave energy decreases, however, the relative response amplitude increases.

The role of Alfvén wave heating in solar prominences

Observations have shown that magnetohydrodynamic waves over a large frequency range are ubiquitous in solar prominences. The waves are probably driven by photospheric motions and may transport energy up to prominences suspended in the corona. Dissipation of wave energy can lead to heating of the cool prominence plasma, so contributing to the local energy balance within the prominence. Here we discuss the role of Alfv\'en wave dissipation as a heating mechanism for the prominence plasma. We consider a slab-like quiescent prominence model with a transverse magnetic field embedded in the solar corona. The prominence medium is modelled as a partially ionized plasma composed of a charged ion-electron single fluid and two separate neutral fluids corresponding to neutral hydrogen and neutral helium. Friction between the three fluids acts as a dissipative mechanism for the waves. The heating caused by externally-driven Alfv\'en waves incident on the prominence slab is analytically explored. We find that the dense prominence slab acts as a resonant cavity for the waves. The fraction of incident wave energy that is channelled into the slab strongly depends upon the wave period, $P$. Using typical prominence conditions, we obtain that wave energy trapping and associated heating are negligible when $P \gtrsim 100$ s, so that it is unlikely that those waves have a relevant influence on prominence energetics. When $1$ s $\lesssim P \lesssim 100$ s the energy absorption into the slab shows several sharp and narrow peaks, that can reach up to 100%, when the incident wave frequency matches a cavity resonance of the slab. Wave heating is enhanced at those resonant frequencies. Conversely, when $P \lesssim 1$ s cavity resonances are absent, but the waves are heavily damped by the strong dissipation. We estimate that wave heating may compensate for about 10% of radiative losses of the prominence plasma.

Wave-Induced Boundary Layer Separation in the Lee of the Medicine Bow Mountains. Part II: Numerical Modeling

Abstract Mountain waves and rotors in the lee of the Medicine Bow Mountains in southeastern Wyoming are investigated in a two-part paper. Part I by French et al. delivers a detailed observational account of two rotor events: one displays characteristics of a hydraulic jump and the other displays characteristics of a classic lee-wave rotor. In Part II, presented here, results of high-resolution numerical simulations are conveyed and physical processes involved in the formation and dynamical evolution of these two rotor events are examined. The simulation results reveal that the origin of the observed rotors lies in boundary layer separation, induced by wave perturbations whose amplitudes reach maxima at or near the mountain top. An undular hydraulic jump that gave rise to a rotor in one of these events was found to be triggered by midtropospheric wave breaking and an ensuing strong downslope windstorm. Lee waves spawning rotors developed under conditions favoring wave energy trapping at low levels in different phases of these two events. The upstream shift of the boundary layer separation zone, documented to occur over a relatively short period of time in both events, is shown to be the manifestation of a transition in flow regimes, from downslope windstorms to trapped lee waves, in response to a rapid change in the upstream environment, related to the passage of a short-wave synoptic disturbance aloft. The model results also suggest that the secondary obstacles surrounding the Medicine Bow Mountains play a role in the dynamics of wave and rotor events by promoting lee-wave resonance in the complex terrain of southeastern Wyoming.

Investigation of elastic wave transmission in a metaconcrete slab

A new type of modified concrete, termed metaconcrete, has been shown to exhibit trapping of wave energy and a reduction in mortar stress when subjected to dynamic loading. Metaconcrete replaces the standard stone and gravel aggregates of regular concrete with spherical inclusions consisting of a heavy core coated with a compliant outer layer. These new layered aggregates resonate at designed frequencies by allowing for relative motion between the heavy core and the mortar matrix, which causes the aggregate to absorb energy and therefore reduce stress within the mortar phase of the composite material. The transmission of wave energy through a metaconcrete slab can be used to visualize the effect of resonant behavior within the metaconcrete aggregates. To quantify this behavior we compute a transmission coefficient, which is a method of measuring the absorption of wave energy as an applied forcing of known frequency travels through the material. The transmission coefficient is plotted against forcing frequency for four different aggregate material and geometry configurations. A reduction in transmission ratio is observed at or near the computed natural modes of the aggregate, indicating the activation of resonance within the inclusions. This behavior is consistent with observations from studies on sonic metamaterials containing resonant inclusions with a similar layered structure. The frequency location and width of the dip in transmission coefficient will aid in the design of metaconcrete aggregates for specific forcing applications.

An Analysis of Internal Gravity Wave Tunnelling in a Stratified Region Along with Rotation

The internal gravity wave tunnelling in presence of earth’s rotation is studiedfor different density barriers. An exponential approximation used revealsthe existence of evanescence in the barrier region which signifies the trappingof wave energy in the tunnelling region. The Transmission coefficients arecomputed for different density barriers and the comparative study shows thatacross the locally mixed region the transmission is enhanced. The asymptoticanalysis of the transmission co-efficient using the rotational parameter revealsthe convergence and the graphs shows that the transmission decreases continuouslyand leads to the non-rotating case. The results are compared with thenon-rotations case and we observe that the evanescence caused by the rotationmakes the waves travel more along the horizontal direction than in the verticaldirection.

Edge waves propagating in a two-layer fluid along a periodic coastline

We investigate the trapping of wave energy along periodic coastlines in a two-layer fluid. We derive conditions on the nearshore slope which, if satisfied, guarantee the existence of edge waves. These conditions are easy to check, and they show that many simple coast profiles such as shelf and cliff coasts and sloping beaches support edge waves.

Wave energy trapping and localization in a plate with a delamination

The research aims at an experimental approval of the trapping mode effect theoretically predicted for an elastic plate-like structure with a horizontal crack. The effect is featured by a sharp capture of incident wave energy at certain resonance frequencies with its localization between the crack and plate surfaces in the form of energy vortices yielding long-enduring standing waves. The trapping modes are eigensolutions of the related diffraction problem associated with nearly real complex points of its discrete frequency spectrum. To detect such resonance motion, a laser vibrometer based system has been employed for the acquisition and appropriate visualization of piezoelectrically actuated out-of-plane surface motion of a two-layer aluminum plate with an artificial strip-like delamination. The measurements at resonance and off-resonance frequencies have revealed a time-harmonic oscillation of good quality above the delamination in the resonance case. It lasts for a long time after the scattered waves have left that area. The measured frequency of the trapped standing-wave oscillation is in a good agreement with that predicted using the integral equation based mathematical model.

Tsunami Propagation and Inundation Due to Tsunamigenic Earthquakes in the Sumatra-Andaman Subduction Zone: Impact at Visakhapatnam

The Sumatra-Andaman arc is an active subduction zone that has generated several destructive tsunamis. The December 26, 2004, Sumatra-Andaman earthquake of magnitude Mw∼9.3 generated the most destructive tsunami known to man. The sustained high water level in several regions on the east coast of India due to tsunamis in the Bay of Bengal can be attributed to the reflection of direct tsunami waves and trapping of wave energy. In this paper we have simulated two scenarios of tsunamigenic earthquakes, the 2004 Sumatra earthquake and a possible great earthquake in the Andaman region. Tsunami wave propagation and inundation at Visakhapatnam due to these two earthquakes have been modeled. We find that the tsunami run-up heights for the 2004 Sumatra earthquake were about 1.5 m. For the other possible scenario, we observed that the run-up is about 3–4.6 m. The inundated distances have been estimated and are 1–2 km.

Highly Sensitive Detection of Defects in Piping Using Multireflecting Guided Wave Energy Trapping Method

A multireflecting guided wave energy trapping (MGET) method has been developed for the highly sensitive detection of defects in a pipe using a guided wave. The MGET method enhances the amplitude of a defect signal using two wave reflectors. In the MGET method, the two reflectors are set at both ends of a region of piping to be inspected, and a guided wave is generated, which propagates in the region of inspection. With this setup, multireflection can be observed between the two reflectors. If a defect exists in the region, the amplitude of the defect signal increases owing to the increase in the number of reflections at the reflectors because n combinations of multiple propagation paths having the same path length exist in the defect signal after n reflections. Details of the principle of the MGET method and its experimental verification are reported. The sensitivity of the MGET method is about 10 times higher than that of the conventional guided wave method. The efficiency of the method is quantitatively discussed by considering a simple mathematical model together with the experimental results.

1J2-6 Efficient nondestructive evaluation of pipes by Multireflecting Guided wave Energy Trapping (MGET) method(Measurement techniques, Imaging, Nondestructive evaluation II)

1J2-6 Efficient nondestructive evaluation of pipes by Multireflecting Guided wave Energy Trapping (MGET) method(Measurement techniques, Imaging, Nondestructive evaluation II)

J0406-4-6 ガイド波多重反射エネルギー閉じ込め法による欠陥検出性能向上の検討(超音波計測・解析法の新展開(4))

J0406-4-6 ガイド波多重反射エネルギー閉じ込め法による欠陥検出性能向上の検討(超音波計測・解析法の新展開(4))

Scattering and Trapping of Wave Energy by a Submerged Truncated Paraboloidal Shoal

In this paper, we study the scattering and trapping of wave energy by a submerged truncated paraboloidal shoal. The analytical approach of Liu et al. in 2004 for solving wave amplification around a circular island mounted on a shoal is extended in this study to investigate waves above a submerged shoal. In this approach, the mild-slope equation is first transformed into an explicit equation by using Hunt's 1979 Pade approximation to the wave dispersion equation. It is then solved analytically in terms of combined Fourier series and Taylor series. For incident waves varying from short to long waves, wave amplifications in the vicinity of the shoal are calculated using the newly derived analytical model and they agree excellently with the finite difference solutions of Lin in 2004. It is found that, for the particular shoal studied in this paper, there exists an energy focal point where the wave amplitude is the maximum. This point is the result of combined wave refraction, diffraction, and reflection. The point is always located along the x-axis and it is behind the shoal center for very short waves. As the increase of wave period, it moves upstream and it can come in front of the shoal center for very long waves when wave reflection is significant. For a particular incident wave, wave amplification increases and the focal point moves toward the shoal center with the reduction of the water depth above the shoal center. The maximum wave amplitude increases exponentially as the decrease of local water depth. It is also found that there exists the so-called calm areas for shallowly submerged shoal, which are located behind the focal point and the local amplitude can be as small as nearly zero.

Observations of shear-coupledPLwaves from shallow earthquakes in the Sumatra and Java subduction zones

SUMMARY S phases generated by shallow earthquakes in the Sumatra subduction zone and recorded at the Geoscope station PAF on the Kerguelen Isles in the southern Indian Ocean, are often followed by a long and particularly large wave train on the longitudinal component. The wave train has a dominant period of 25‐30 s and lasts usually for more than 100 s. It shows slight normal dispersion, and has a prograde elliptical motion in the vertical propagation plane. These characteristics suggest that the observed waves are shear-coupled PL (SPL) waves. Similar wave trains are not observed for events at comparable distances in other source regions. A computational scheme, based on the reflectivity method and allowing for different crust and upper mantle structures beneath source and receiver, has been used to model the SPL waveforms for six of the events located beneath the accretionary domain and outer high of the Sumatra subduction zone. For the source area, a model representing the structure seaward of the trench has been used, comprising a 5.5 km water layer and 600 m of sediments. By placing the sources in the sedimentary layer, the SPL wave train on the longitudinal component is reproduced quite well. These findings suggest that wave energy is guided into the water and sedimentary layers seaward of the trench, where P and S wave reverberations are generated and leak as SV waves into the mantle. The guidance can be explained by trapping of wave energy within the wedge shaped accretionary domain and outer high, or in oceanic sediments which are subducted with the oceanic plate.