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In a coaxial ultrasonic flow sensor (UFS), wall thickness is a vital parameter of the measurement tube, especially those with small inner diameters. The paper aims to investigate the influence of wall thickness on the transient signal characteristics in an UFS.

First, the problem was researched experimentally using a series of measurement tubes with different wall thicknesses. Second, a finite element method–based model in the time domain was established to validate the experimental results and further discussion. Finally, the plane wave assumption and oblique incident theory were used to analyze the wave propagation in the tube, and an idea of wave packet superposition was proposed to reveal the mechanism of the influence of wall thickness.

Both experimental and simulated results showed that the signal amplitude decreased periodically as the wall thickness increased, and the corresponding waveform varied dramatically. Based on the analysis of wave propagation in the measurement tube, a formula concerning the phase difference between wave packets was derived to characterize the signal variation.

This paper provides a new and explicit explanation of the influence of wall thickness on the transient signal in a co-axial UFS. Both experimental and simulated results were presented, and the mechanism was clearly described.

This paper addresses a significant research gap in the study of Rayleigh surface wave propagation within a piezoelectric medium characterized by piezoelectric properties, thermal effects and voids. Previous research has often overlooked the crucial aspects related to voids. This study aims to provide analytical solutions for Rayleigh waves propagating through a medium consisting of a nonlocal piezo-thermo-elastic material with voids under the Moore–Gibson–Thompson thermo-elasticity theory with memory dependencies.

The analytical solutions are derived using a wave-mode method, and roots are computed from the characteristic equation using the Durand–Kerner method. These roots are then filtered based on the decay condition of surface waves. The analysis pertains to a medium subjected to stress-free and isothermal boundary conditions.

Computational simulations are performed to determine the attenuation coefficient and phase velocity of Rayleigh waves. This investigation goes beyond mere calculations and examines particle motion to gain deeper insights into Rayleigh wave propagation. Furthermore, this investigates how kernel function and nonlocal parameters influence these wave phenomena.

The results of this study reveal several unique cases that significantly contribute to the understanding of Rayleigh wave propagation within this intricate material system, particularly in the presence of voids.

This investigation provides valuable insights into the synergistic dynamics among piezoelectric constituents, void structures and Rayleigh wave propagation, enabling advancements in sensor technology, augmented energy harvesting methodologies and pioneering seismic monitoring approaches.

This study formulates a novel governing equation for a nonlocal piezo-thermo-elastic medium with voids, highlighting the significance of Rayleigh waves and investigating the impact of memory.

Modelling, computation and performance animation of turbomachinery systems has recently enjoyed remarkable attention in CAD research. This is also reflected its application to exhaust machine components such as turbo loaders and the exceptionally novel pressure wave machine (Comprex) in the automobile industry and gas turbines. The necessity for the thermo‐fluidic performance animation of such pressure wave machines results from the fact that the machine geometry must be adapted to the technical and thermo‐fluidic properties of the exhaust flow of the gas turbine or automobile engine. Experimental adaptation or adjustment is costly and should be validated for every application case. Thus the potential to apply accurate animation for such shock‐tube like behaviour of compressible flow is now economically promising with a view to optimizing the design of the pressure wave machine. This paper presents briefly the problem oriented algorithms used and illustrates the performance animation of the pressure wave machine operating under constant speed drive. After introducing the pressure wave machine operation, the principles and summary of the algorithms used to compute the thermodynamic behaviour within the cell, the boundary models and the accuracy of computation. A Comprex cycle operating on an engine exhaust gas with T = 920°K, p = 2bar is illustrated through 3‐dimensional representations for pressure, speed of flow and temperature. The particle path (gas and air) together with time representation of the state variables at different points of the Compex will be shown. The mass balance problem is discussed and the conditions for mass balanced flow for the gas as well as for the air side are given. The results achieved for such materially balanced pressure wave machines indicate a reduction in the costs for subsequent experimental validation and to deliver the sound base for further development towards considering the pre‐balanced transient operation cases as well.

The purpose of this paper is to find the exact solutions of a (3 + 1)-dimensional non-integrable Korteweg-de Vries type (KdV-type) equation, which can be used to describe the stability of soliton in a nonlinear media with weak dispersion.

The authors apply the extended Bell polynomial approach, Hirota’s bilinear method and the homoclinic test technique to find the rogue waves, homoclinic breather waves and soliton waves of the (3 + 1)-dimensional non-integrable KdV-type equation. The used approach formally derives the essential conditions for these solutions to exist.

The results show that the equation exists rogue waves, homoclinic breather waves and soliton waves. To better understand the dynamic behavior of these solutions, the authors analyze the propagation and interaction properties of the these solutions.

These results may help to investigate the local structure and the interaction of waves in KdV-type equations. It is hoped that the results can help enrich the dynamic behavior of such equations.

The purpose of this paper is to compute the phase velocities and attenuation coefficients of coupled longitudinal waves in a generalized thermoporoelastic model and to observe the effect of porosity, frequency and thermal parameters on the phase velocities and attenuation coefficients on these waves graphically.

The linear governing equations of a generalized thermoporoelastic model in the context of Lord and Shulman theory of generalized thermoelasticity are solved with the help of plane harmonic solution method to show the existence of one shear and three kinds of coupled longitudinal waves.

The results obtained show the dependence of phase velocities and attenuation coefficients of coupled longitudinal waves on frequency, porosity, relaxation times and other material parameters.

The problems on coupled heat‐fluid flow in a saturated deformable porous medium are important in various engineering fields, for example, petroleum engineering, chemical engineering, pavement engineering and nuclear waste management. A new generalized thermoporoelastic model is formulated to study the wave phenomena and their dependence on various material parameters.

Since the importance role of ultrasonic tomography (UT) in industry, especially in oil industry, to produce noninvasive and nondestructive plane images, research on UT system with a metal pipe conveyor is investigated. The produced cross-sectional images are used for detecting the concentration of solid and liquid mixture inside the pipe, noninvasively. In practice, due to application of metal pipes as the conveyor of oil mixture so the capability of manufacturing an UT system with a metal pipe is investigated in this paper. The paper aims to discuss these issues.

Finite element software (COMSOL Multiphysics 3.5) for visualizing the structure of pipe with mounted sensors on the periphery of the pipe is used. The manner of ultrasonic wave propagation on different layers on various frequencies and finding the time of flight for transmission mode signal and lamb mode signal are achieved by the means of done simulations. Finding the proper ultrasonic sensor base on its efficiency is the main step of designing an UT system. This is done by estimating the resonance frequency of sensor due to the manner of ultrasonic wave propagation in different frequencies shown in simulation results.

Due to simulation results, lamb wave is a permanent propagation mode of ultrasonic wave which makes interference in measuring process of straight path signal and it is impossible to remove. Relief of the mentioned problem finding an optimum frequency to decrease the affection of lamb wave in detecting point. Optimum frequency of ultrasonic wave to satisfy the objective is 45 kHz which is measured by considering of mathematic of ultrasonic wave propagation in different layers. The reaching time of straight path signal and lamb wave signal in opposite sensor as the receiver are 5.5 and 4.6 μs, respectively.

This investigation is the first step to perform the UT in a noninvasive method to produce the cross-sectional images of metal pipe. Due to the wide application of metal pipes as the conveyor of the liquids/gases, metal pipe for the UT application is studied in this research.

To make wave soldering of SMDs a success, one must realise that not only the process involved is important, but also the board design and SMD mounting aspects play an important role as they may differ considerably from the rules established for reflow soldering. To elucidate this difference is the main issue of this article.

The purpose of this paper is to deal with the propagation of Love waves in inhomogeneous viscoelastic layer overlying a gravitational half-space. It has been observed velocity of Love waves depends on viscosity, gravity, inhomogeneity and initial stress of the layer.

The dispersion relation for the Love wave in closed form is obtained with Whitaker’s function.

The effect of various non-dimensional inhomogeneity factors, gravity factor and internal friction on the non-dimensional Love wave velocity has been shown graphically. The authors observed that the dispersion curve of Love wave increases as the inhomogeneity factor increases. It is seen that increment in gravity, inhomogeneity and internal friction decreases the damping phase velocity of Love waves but it is more prominent in case of internal friction.

Surface plot of Love wave reveals that the velocity ratio increases with the increase of non-dimensional phase velocity and non-dimensional wave number. The above results may attract seismologists and geologists.

This paper aims to develop a wave-transmitting mechanism for a travelling-wave-type omnidirectional mobile robot. Existing omnidirectional mechanisms are prone to movement instability because they establish a small contact area with the ground. The authors have developed a novel omnidirectional mobile robot that achieves stable movement by a large ground-contact area. The proposed robot moves by a wave-transmitting mechanism designed for this purpose.

To achieve stable movement, a spiral-type travelling-wave-propagation mechanism that mimics the locomotion mechanism of a snail was developed. The mechanism was applied to an omnidirectional mobile robot.

The practicality of magnetic attraction was verified in experiments of the wave-transmitting mechanism. Moreover, omnidirectional movement was confirmed in a robot prototype adopting this mechanism.

The proposed robot will eventually be deployed in human spaces such as factories and hospitals. A mechanically improved version of the robot will be evaluated in load-driving experiments and equipped with control systems.

This paper proposes an omnidirectional mobile robot with a large ground contact area that moves by continuous travelling waves. The practicability of this mechanism was experimentally confirmed, and a prototype robot achieved omnidirectional movement.

THE earlier classical treatises on aerodynamics concerned themselves with the properties of incompressible fluids. The theory developed on this basis gave an excellent theoretical background to the aeronautical engineer and made possible a scientific approach to the problems of aircraft flight. With the steady increase of aircraft speed, however, it soon became evident that the theory would have to be extended to take compressibility into account. One important result, brought out by Glauert's analysis, was the modification of the flow pattern with increasing Mach number. A more striking divergence of compressible from incompressible flow, first encountered at near sonic speeds, is the occurrence of shock waves. A shock wave, in the specialized aeronautical sense, is a pressure impulse travelling through the flow causing a sudden transition from supersonic to subsonic speeds (normal to the wave front) with an attendant increase in pressure and temperature. A brief statement of this sort, however, is of little or no value in giving an idea of the physical nature of the phenomenon. A considerable amount of attention is now focused on the repercussions of shock waves on aeroplane design. It is far easier to understand these design trends if one has a good grasp of the fundamentals underlying the problem. This article sets out to give a brief survey of these fundamentals. It is not easy also to give a complete physical picture of a shock wave but at least a discussion of their formation, propagation, etc. goes a long way towards clarifying one's ideas.