Wave Research Articles

Effect of the heave plate's diameter on the transitional motions of a straked marine circular cylinder under different marine conditions

This numerical study investigated the influence of the heave plate's diameter on the amplitude of the transitional motions of a marine circular cylinder (MCC) with a low aspect ratio under the marine current and regular waves. Due to the experimental model of the straked MCC, different diameters of the circular heave plate were chosen to be installed at the keel of the 3-straked MCC. In this numerical study, the diameter of the heave plate varied from 1.2 to 1.6 DMCC, while other parameters, such as reduced velocity (VR), Reynolds (Re) number, and Froude number, were kept constant. In this study, the transitional motions, including surge, sway, and heave, were analyzed. The results showed that increasing the heave plate's diameter decreased the amplitude of the transitional motions in both marine current and regular waves. Also, the finding revealed that the heave plate not only reduced the amplitude of the heave motion but also decreased the amplitude of surge and sway motions. Moreover, the outcomes indicated that the heave plate's diameter increased by approximately 20%–40% more than the MCC's diameter. This caused the smaller amplitude of the transitional motions under both marine currents and regular waves.

Evaluation of Robustness of S-Transform Based Phase Velocity Estimation in Viscoelastic Phantoms and Renal Transplants.

Ultrasound shear wave elastography (SWE) methods are being used to differentiate healthy versus diseased tissue on the basis of their viscoelastic mechanical properties. Tissue viscoelasticity is often studied by analyzing shear wave phase velocity dispersion curves, which is the variation of phase velocity with frequency or wavelength. Recently, a unique approach using a generalized Stockwell transformation (GST-SFK) was proposed for the calculation of dispersion curves in viscoelastic media over expanded frequency band. In this work, the method's robustness was evaluated on data from five custom-made viscoelastic tissue-mimicking phantoms and sixty in vivo renal transplants. For each phantom, 15 shear wave motion data acquisitions were taken, while 10-13 acquisitions were acquired for renal transplants measured in the renal cortex. For each data-set mean and standard deviation (SD) of estimated phase velocity dispersion curves were studied. In addition, the viscoelastic parameters of the Zener model were examined, which were preceded by a convergence analysis. For viscoelastic phantoms scanned with a research ultrasound scanner, and for the in vivo renal transplants scanned with a clinical scanner, the decisive advantage of the GST-SFK method over the standard two-dimensional Fourier transform (2D-FT) method was shown. The GST-SFK method provided dispersion curve estimates with lower SD over a wider frequency band in comparison to the 2D-FT method. These advantages are relevant to the analysis of the mechanical properties of tissues in clinical practice to discriminate healthy from diseased tissue.

Analysis of Wave Motion in Micropolar Thermoelastic Medium Based on Moore–Gibson–Thompson Heat Equation Under Non-local and Hyperbolic Two-Temperature

Analysis of Wave Motion in Micropolar Thermoelastic Medium Based on Moore–Gibson–Thompson Heat Equation Under Non-local and Hyperbolic Two-Temperature

Effects of topographical disturbances on flexural wave motion in a viscous fluid

Main causes of ground disturbances are geological events such as earthquakes, underwater gravity mass flows, volcanic eruptions, and bottom explosions. This paper investigates the effects of transitory ground disturbance on the generation of flexural waves in the presence of a thin floating elastic plate. The problem is formulated using the Stokes stream function and wave potential boundary value problems in a viscous fluid. The expression of the plate deflection is obtained as multiple infinite integrals using the Fourier and Laplace transforms, which is further solved by the steepest descent method. Three types of ground disturbances such as H0(x)=e(−x2/2), H0(x)=e−|x|, and H0(x)=δ(x) are considered. The deflection of the floating elastic plate is investigated in connection to ground disturbances, fluid viscosity, and structural parameters such as mass per unit length of the plate and flexural rigidity. The study reveals that with higher viscosity and flexural rigidity, the amplitude of the plate deflection is reduced. Moreover, these two parameters play a great role in the reduction of plate deflection.

Shear wave propagation in a fiber-laden viscoelastic waveguide under prestress: Inverse modeling challenges

The functional role of skeletal muscle and the hierarchal microstructure and arrangement of fibers within it results in anisotropy and inhomogeneity in both material properties and imposed stresses. Dynamic elastography reconstruction methods for estimating muscle tissue viscoelastic properties that are based on assumptions of homogeneity, isotropy and only bulk wave motion may produce inaccurate estimates. Biases may be introduced in reconstruction by homogenizing muscle with axially aligned fibers and approximating it as transversely isotropic. The significance of these biases, and their interplay with imposed stresses and confounding waveguide effects due to small cross-sectional dimensions, is quantified with a series of numerical finite element and experimental elastography studies on cylindrically-shaped fiber-laden muscle phantoms, with varying fiber dimensions. Specifically, numerical simulations of elastography are conducted on 4-, 60- and 113-fiber models with the aligned fiber cross-sectional area fixed (reduced fiber diameter as fiber count increases) and comprising approximately 40% of the cross-sectional area of the cylindrical phantom that is also undergoing tensile axial pre-loading. Fiber elastic moduli twice that of connective tissue are considered. Experimental studies of the 4-fiber model are used to validate the numerical model. [Funding support: NSF 1852691 and NIH AR071162]

Focused shear wave beam propagation through a 3D printed human rib cage

Transient elastography (TE) is used in clinical screenings for liver fibrosis. TE generates shear wave motion in the liver by vibration of a piston at the skin. The small, flat piston in current devices radiates shear waves that diverge from the liver, resulting in low SNR and high failure rates, especially in obese patients. Our group recently introduced focused shear wave beams for TE [Cormack et al., IEEE TBME (2024)], in which vibration of a concave piston generates shear waves that converge towards the focal region, thereby increasing SNR for liver stiffness estimation. However, because piston sizes needed for efficient shear wave focusing are larger than the typical intercostal space, the rib cage that lies between the skin and the liver may cause shear wave aberration and influence stiffness measurement. Here, we present measurements of broadband focused shear wave propagation in tissue-mimicking gel in which are embedded 3D printed human ribs. Both straight elliptical rods and anatomically realistic 3D printed ribs are used as aberrators. Measurements are compared to 3D simulations of shear wave beam propagation [Archer et al., JASA (2023)]. Effects of shear wave aberration by the rib cage depend on shear wavelength, piston-to-rib distance, and piston radius and curvature.

Teaching concepts of acoustics in air—Part 3, reverberation

This paper has been written to participate in the “Education in Acoustics” session at the 2024 joint conference of the Canadian Acoustical Association and the Acoustical Society of America. It is written to build on Parts 1 and 2 of this series and similarly contains materials extracted from 30 years of teaching to Architects at the University of Waterloo and Dalhousie University in Halifax. Part 1 dealt primarily with sound propagation in air and the concepts of longitudinal wave motion, speed, frequency and wavelength and related effects which relate to what we perceive as pitch. Part 2 expanded on those concepts by discussing superposition and the definition and measurement of sound pressure, decibels and the decibel scale and how to manage decibels, all of which we perceive as loudness. Part 3 deals with reverberation, which is arguably the most important aspect of how sound propagates in indoor spaces. It affects both our ability to communicate and how we experience and perceive the quality of the acoustical environment. Practical demonstrations are provided to enhance learning of the concept of Reverberation. These include “hands on” demonstrations including physical experimentation, an audio demonstration and written materials to advance the concept.

Signal detrending in elastographic wave data with large motion artifacts through a 2D Whittaker smoother

A variety of advanced shear wave elastography techniques require the measurement of frequency-resolved phase velocity to properly characterize wave signals where factors such as tissue viscosity or guided wave effects are present. However, when applying these techniques in a dynamic environment where extrinsic motion cannot be limited, nonlinear and nonstationary trends can be expected in the motion signal used for phase velocity estimation. Because such extrinsic motion signals can contaminate a broad range of frequencies, they can produce significant errors in the phase velocity estimates. In this study, we propose a spatiotemporal detrending approach for elastography wave motion signals built from a 2D Whittaker smoother. This smoother has its origins in nonparametric regression and is well suited for fitting nonlinear curves of arbitrary shape. The resulting detrending filter was applied to Lamb wave signals from clinical ultrasound bladder vibrometry measurements. We found that the proposed detrending filter allowed for phase velocity estimates to be made in acquisitions that are otherwise be too corrupted by large motion. This works was supported by a grant from the NIH (DK131685)

Learning from failure: An analysis of a flawed nonlinear acoustic metamaterial design

Acoustic metamaterials (AMMs) are structured systems designed to exhibit specific, often exotic, effective material properties for acoustic wave motion. Most research on AMMs prioritize linear wave behavior, but a growing body of work has focused on nonlinear phenomena. While the primary approach to enhancing the nonlinear response of a system has been to place highly nonlinear inclusions in the system (such as bubbles, cracks, or buckling beams), an alternative approach is to control the linear material properties to enhance the relative strength of the nonlinearity. For example, one may reduce the shock formation distance of a system by reducing the effective mass density and wave speed even if the coefficient of nonlinearity is left unchanged. However, due to the nature of nonlinear waves, developing a practical design to accomplish this control can be challenging. We recently designed and built an experimental nonlinear AMM and found it to be fundamentally flawed. In this paper we discuss the thought process that led to the flawed design and present the lessons learned from an unsuccessful experiment.

Acoustic Higher-Order Topological Insulators Induced by Orbital-Interactions.

The discovery of higher-order topological insulator metamaterials, in analogy with their condensed-matter counterparts, has enabled various breakthroughs in photonics, mechanics, and acoustics. A common way of inducing higher-order topological wave phenomena is through pseudo-spins, which mimic the electron spins as a symmetry-breaking degree of freedom. Here, this work exploits degenerate orbitals in acoustic resonant cavities to demonstrate versatile, orbital-selective, higher-order topological corner states. Type-II corner states are theoretically investigated and experimentally demonstrated based on tailored orbital interactions, without the need for long-range hoppings that has so far served as a key ingredient for Type-II corner states in single-orbital systems. Due to the orthogonal nature of the degenerate p orbitals, this work also introduces a universal strategy to realize orbital-dependent edge modes, featuring high-Q edge states identified in bulk bands. These findings provide an understanding of the interplay between acoustic orbitals and topology, shedding light on orbital-related topological wave physics, as well as its applications for acoustic sensing and trapping.

Near-field wave interactions with defects and their implications on sub-wavelength acoustic imaging

Acoustic metamaterial concepts, such as metalenses and hyperlenses, have been studied with much interest for super-resolution imaging. However, the physics of wave scattering by sub-wavelength sized defects is still not very well understood. Here, we present studies on acoustic wave interactions with circular defects of sizes varying from over a wavelength to sub-wavelength scale. Near- and far-field scattering patterns of single circular defects are presented, connecting them to analytical frameworks. Scattering field signatures produced by two identical circular defects of different sizes placed side by side are then discussed. The separation distance between the defects is among the parameters varied to understand the effects of geometric features in successful imaging. Experimental results are presented to support the predictions reported in the paper. The insights have important implications for sub-wavelength imaging using acoustic metamaterials.

Aerodynamic performance increase over an A320 morphing wing in transonic regime by numerical simulation at high Reynolds number

PurposeThis study aims to investigate the morphing concepts able to manipulate the dynamics of the downstream unsteadiness in the separated shear layers and, in the wake, be able to modify the upstream shock–boundary layer interaction (SBLI) around an A320 morphing prototype to control these instabilities, with emphasis to the attenuation or even suppression of the transonic buffet. The modification of the aerodynamic performances according to a large parametric study carried out at Reynolds number of 4.5 × 106, Mach number of 0.78 and various angles of attack in the range of (0, 2.4)° according to two morphing concepts (travelling waves and trailing edge vibration) are discussed, and the final benefits in aerodynamic performance increase are evaluated.Design/methodology/approachThis article examines through high fidelity (Hi-Fi) numerical simulation the effects of the trailing edge (TE) actuation and of travelling waves along a specific area of the suction side starting from practically the most downstream position of the shock wave motion according to the buffet and extending up to nearly the TE. The present paper studies through spectral analysis the coherent structures development in the near wake and the comparison of the aerodynamic forces to the non-actuated case. Thus, the physical mechanisms of the morphing leading to the increase of the lift-to-drag ratio and the drag and noise sources reduction are identified.FindingsThis study investigates the influence of shear-layer and near-wake vortices on the SBLI around an A320 aerofoil and attenuation of the related instabilities thanks to novel morphing: travelling waves generated along the suction side and trailing-edge vibration. A drag reduction of 14% and a lift-to-drag increase in the order of 8% are obtained. The morphing has shown a lift increase in the range of (1.8, 2.5)% for angle of attack of 1.8° and 2.4°, where a significant lift increase of 7.7% is obtained for the angle of incidence of 0° with a drag reduction of 3.66% yielding an aerodynamic efficiency of 11.8%.Originality/valueThis paper presents results of morphing A320 aerofoil, with a chord of 70cm and subjected to two actuation kinds, original in the state of the art at M = 0.78 and Re = 4.5 million. These Hi-Fi simulations are rather rare; a majority of existing ones concern smaller dimensions. This study showed for the first time a modified buffet mode, displaying periodic high-lift “plateaus” interspersed by shorter lift-decrease intervals. Through trailing-edge vibration, this pattern is modified towards a sinusoidal-like buffet, with a considerable amplitude decrease. Lock-in of buffet frequency to the actuation is obtained, leading to this amplitude reduction and a drastic aerodynamic performance increase.

Locomotion control of a rigid-soft coupled snake robot in multiple environments

The versatile motion capability of snake robots offers themselves robust adaptability in varieties of challenging environments where traditional robots may be incapacitated. This study reports a novel flexible snake robot featuring a rigid–flexible coupling structure and multiple motion gaits. To better understand the robot’s behavior, a bending model for the soft actuator is established. Furthermore, a dynamic model is developed to map the relationship between the input air pressure and joint torque, which is the model base for controlling the robot effectively. Based on the wave motion generated by the joint coupling direction function in different planes, multiple motion gait planning methods of the snake-like robot are proposed. In order to evaluate the adaptability and maneuverability of the developed snake robot, extensive experiments were conducted in complex environments. The results demonstrate the robot’s effectiveness in navigating through intricate settings, underscoring its potential for applications in various fields.

Laboratory and non-hydrostatic modelling of focused wave group evolution over fringing reef

This paper presents physical experiments and numerical simulations to study the propagation of focused waves group across hypothetical fringing reef profiles. A wave flume is 69 m long and 1.0 m deep, and the reef cross section is made up of a reef face, a reef flat and a vertical wall. A reef crest of 0.085 m is optionally constructed on the outside to replicate the reef crown. By focusing wave trains of the JONSWAP or constant wave amplitude spectrum, the transient wave group is generated on the reef slope. Free surface elevations and flow velocity are measured over time along the flume's centreline. The focused wave process and the development of higher harmonics as a result of the nonlinear interaction over the reef face are clearly visible in the wavelet and FFT analyses of the observed free surface elevation. Low frequency wave is increasing on the reef flat while these short-period wave motions are primarily absorbed by rapid breaking on reef edge and crest. On the flat, it is discovered that reef crest has the effect of reducing short-period wave motion and increasing long-period wave motion. A numerical multi-layer non-hydrostatic wave model is employed and its ability to describe the propagation of focused wave groups over fringing reef profiles is assessed.

Development and Validation of an Instrument for Wave Height Measurement with Encoder Sensors and Accelerometer

Ocean waves play a significant role in coastal dynamics and the management of coastal development activities. However, there are limited instruments to measure the wave height, particularly in developing countries. This study introduces a novel instrument design for simple and cost-effective wave height measurement. The proposed instrument combines a Hall-effect sensor and an accelerometer to capture the rise and fall of a buoy in response to wave movements. The Hall-effect sensor as a rotary encoder detects the rotation of the buoy while the accelerometer measures the tilt of the instrument caused by ocean waves. The instrument is constructed using PVC pipes and incorporates long-range (LoRa) communication technology for real-time monitoring. Experimental tests were conducted at a study site in Banyuwangi Regency, Indonesia, where the performance of the instrument was compared with an ultrasonic sensor-based instrument. The results validate the effectiveness of the proposed instrument design for wave height measurement. The collected data were transmitted via the LoRa communication system, enabling convenient monitoring and analysis of sea-level changes. The valuable contribution of the instrument to the field stems from its precision in measuring the wave height, adaptability to diverse conditions, and potential applicability in shallow waters.

PERBANDINGAN HASIL BELAJAR FISIKA SISWA MATERI POKOK GELOMBANG DENGAN MENGGUNAKAN METODE RESTASI DAN METODE DISKUSI DI KELAS VIII SMP NEGERI 3 PADANGSIDIMPUAN

This study aims to look at the picture of the results of learning subject matter wave physics using a method in a class recitation SMP Negeri 3 Padangsidimpuan , to describe the learning outcomes of the subject matter wave physics using a method in a class discussion SMP Negeri 3 Padangsidimpuan , and to see whether there differences in learning outcomes physics subject matter waves using the method of recitation and discussion in class VIII SMP Negeri 3 Padangsidimpuan . This research was carried out by using the experimental method to see the difference of implementation measures . The population in this study were all students of Class VIII SMP Negeri 3 Padangsidimpuan which consists of 8 classes totaling 304 people . The sampling technique used was cluster random sampling technique , so that the sample obtained in class VIII1 = 38 and = 38 VIII2 class numbered 76 people .
 The data collected was analyzed in two ways : first descriptive analysis to see the general description of the two variables , and then to determine whether there is a difference between the two variables we used t - tests to test Sudjana . Meanwhile, to capture the necessary data is done with the test . In order to obtain data on the outcomes of learning subject matter wave physics using recitation methods and discussion methods. Learning outcomes of the research subject matter wave physics using the recitation obtained an average of 76.33 in the category of " Good " . If consultation with the criteria in Table 4 Chapter III . While the value of the subject matter wave physics learning using discussion method obtained an average of 72.89 in the category of " Good " . If consulted in Table 4 Chapter III .
 Based on calculations performed obtained values ​​" of t " at 2.11 , while the 5 % significance level and df = n1 + n2 - 2 = 38 + 38-2 = 74 . Ttable value at 5 % significance level of 74 is 1.66 . Based on the calculation above it can be concluded that of t greater than ttable ( tcount > ttable = 2.11 > 1.66 ) . Means hypothesis upheld in this study can be accepted or approved . That is There a Difference Physics Learning Outcomes Topic Wave Method using recitation and Methods Discussion in class VIII SMP Negeri 3 Padangsidimpuan.

Upconversion Photonic Doppler Velocimetry Based on Stimulated Brillouin Scattering

Optical up-conversion photonic Doppler velocimetry (PDV) based on stimulated Brillouin Scattering (SBS) with an all-fiber link structure is proposed in this article. Because SBS limits the laser power transmitted by a fiber over long distances, the probe does not have enough outgoing light to reach the measured surface and cannot receive the signal light. Traditionally, SBS is avoided, but it is a phase-conjugated light and shifts down relative to the source light, so it can be used as a reference light in the laser interference structure to achieve up-conversion heterodyne velocimetry. Compared with general homodyne velocimetry (DPS), SBS-PDV naturally upconverts and has more interference fringes and higher resolution at low-speed measurement. In the gas multiple reflection impact compression experiment, the velocity measurement results of SBS-PDV and dual-laser heterodyne Velocimetry (DLHV) are basically consistent, and the accuracy is better than 0.8%. Due to its coaxial heterodyne optical path, this kind of photonic Doppler velocimetry is suitable for low-velocity and long-distance practical applications in the field of shock wave physics.

Numerical Solution of the Korteweg-De Vries Equation Using Finite Difference Method

The Korteweg-de Vries (KdV) equation is a nonlinear partial differential equation that has a key role in wave physics and many other disciplines. In this article, we develop numerical solutions of the KdV equation using the finite difference method with the Crank-Nicolson scheme. We explain the basic theory behind the KdV equation and the finite difference method, and outline the implementation of the Crank-Nicolson scheme in this context. We also give an overview of the space and time discretization and initial conditions used in the simulation. The results of these simulations are presented through graphical visualizations, which allow us to understand how the KdV solution evolves over time. Through analysis of the results, we explore the behavior of the solutions and perform comparisons with exact solutions in certain cases. Our conclusion summarizes our findings and discusses the advantages and limitations of the method used. We also provide suggestions for future research in this area.

The effects of gravitational and magnetic fields on the propagation of cylindrical strong shock waves in a van der Waals gas

The present study aims to investigate the effects of non-idealness parameter, gravitation and magnetic fields behind the flow of motion for cylindrical hydro-magnetic strong shock waves travelling through a tube of variable cross-section in a self-gravitating van der Waals gas. The analytical expressions of the flow variables for one-dimensional adiabatic flow behind the hydro-magnetic strong shock waves are obtained using Chester-Chisnell-Whitham’s (CCW) Method. The initial density distribution of the medium is assumed to be ρ0=ρ'r−w where ρ' is the density at the axis of symmetry, w is a constant and r is the distance from the axis of symmetry. The magnetic field, on the other hand, is assumed to have only constant axial and variable azimuthal components. Due to the presence of magnetic and gravitational fields, the uniform density distribution of the medium becomes non-uniform and this becomes an interesting fact to study. It is found that, all flow variables except the pressure rises with the shock propagation distance. It is also demonstrated that the gravitational and magnetic fields cause the numerical values of the flow variables to increase behind the shock wave. Further, research shows that even a small increase in the gravitational field increases the pressure behind the shock wave, whereas a small increase in the magnetic field has a little effect on it. Furthermore, it is found that the flow variables get strengthened behind the shock wave in comparison with ahead of the shock. The trends of the current findings are in good agreement with the existing experimental observations and results.

Three-wave lump solutions and their dynamic behaviors for the (3+1)-dimensional constant-coefficient and variable-coeffcient differential equations

In this paper, we propose two theorems to illustrate the types of equations that can be solved using the quadratic function method to derive the lump solutions localized in the whole plane, which are called three-wave lump solutions, and provide two constant-coefficient equations to illustrate. We further extend the quadratic function method to the variable-coefficient differential equations and obtain the three-wave lump solutions for two (3+1)-dimensional variable-coefficient equations. Moreover, the amplitudes of these lump waves and the distances between the two valleys of each lump are also obtained. Meanwhile, the motion trails, displacements and the velocities of these lump waves are analyzed in detail by virtue of numerical simulation. The study can be used to describe the motion of nonlinear waves in shallow water under the influence of time, and the results can enrich the types of solutions for the KdV-type equations. In addition, the 3d plots and corresponding density plots of the lump waves are displayed to show their spatial structures.