Simulation of Guided Waves Propagation in Axial Transmission Measurements in Human Radius

2007 ◽  
Vol 9 ◽  
pp. 127-141
Author(s):  
Łukasz Pieczonka ◽  
Tadeusz Uhl ◽  
Adam Martowicz
Keyword(s):  
Wave Propagation ◽  
Guided Waves ◽  
Three Dimensional ◽  
Low Frequency ◽  
Medical Diagnostics ◽  
Theoretical Background ◽  
Transmission Measurements ◽  
Set Up ◽  
Anatomical Geometry ◽  
Axial Transmission

This paper is a brief review of the axial transmission measurements methodology. Theoretical background and description of the methodology is presented. Simulations made to verify some of the statements found in the scientific literature about the subject matter are described. Simulation performed were meant to be a basis for specifying parameters of the experimental set up to be used in the future. Three dimensional finite difference code was used to simulate wave propagation in human radius. Two models have been prepared to compare the results. One was an idealized geometry of the diaphysis of human radius and second was a reconstructed anatomical geometry from scans acquired with Computed Tomography (CT). Conclusions about the wave propagation character and feasibility of low frequency measurements in medical diagnostics are discussed.

Modeling the impact of soft tissue on axial transmission measurements of ultrasonic guided waves in human radius

2008 ◽  
Vol 124 (4) ◽  
pp. 2364-2373 ◽  
Author(s):  
Petro Moilanen ◽  
Maryline Talmant ◽  
Vantte Kilappa ◽  
Patrick Nicholson ◽  
Sulin Cheng ◽  
...  
Keyword(s):  
Soft Tissue ◽  
Guided Waves ◽  
Ultrasonic Guided Waves ◽  
Transmission Measurements ◽  
The Impact ◽  
Axial Transmission

scholarly journals STUDYING THE EFFECT OF LINEAR REFRACTION ON LOW-FREQUENCY WAVE PROPAGATION (PHYSICAL AND NUMERICAL STUDY)

2012 ◽  
Vol 1 (33) ◽  
pp. 9 ◽  
Author(s):  
Sepehr Eslami Arab ◽  
Ap Van Dongeren ◽  
Peter Wellens
Keyword(s):  
Wave Propagation ◽  
Numerical Study ◽  
Measurement Techniques ◽  
Low Frequency ◽  
The Novel ◽  
Data Set ◽  
Frequency Wave ◽  
Wave Models ◽  
Set Up ◽  
Steep Slopes

This paper describes a laboratorium data set of wave propagation over steep slopes with large angles of incidence, and the model-data comparison with linear and nonlinear wave models (SWAN and TRITON). The reason for this study is that the SWAN model showed an underestimation of the observed low frequency wave energy at nearshore sites in the Eastern Wadden Sea tidal inlet. Van Vledder (2010) showed that potential inaccuracies in modeling refraction over steep slopes of the tidal channel may result in observed discrepancies. The paper addresses the set up of the laboratory experiment, the novel measurement techniques and an analysis of the observed differences between models and data. The results show that there is not one single mechanism that explains the differences, but a combination of mechanisms, and perhaps other phenomena such as reflection play role.

Spontaneous generation of a swirling plume in a stratified ambient

2014 ◽  
Vol 761 ◽  
pp. 443-463 ◽  
Author(s):  
Francisco Marques ◽  
Juan M. Lopez
Keyword(s):  
Temporal Dynamics ◽  
Numerical Study ◽  
Three Dimensional ◽  
Low Frequency ◽  
Spontaneous Generation ◽  
Fixed Temperature ◽  
Very Low Frequency ◽  
External Perturbations ◽  
Spatio Temporal ◽  
Set Up

AbstractThe transition from laminar to complex spatio-temporal dynamics of plumes due to a localized buoyancy source is studied numerically. Several experiments have reported that this transition is sensitive to external perturbations. Therefore, a well-controlled set-up has been chosen for our numerical study, consisting of a localized heat source at the bottom of an enclosed cylinder whose sidewall is maintained at a fixed temperature which varies linearly up the wall. Restricting the dynamics to the axisymmetric subspace, the first instability is to a puffing state. However, for smaller Grashof numbers, the plume becomes unstable to three-dimensional perturbations and a swirling plume spontaneously appears. The next bifurcation, viewed in the rotating frame where the plume is stationary, also exhibits puffing and suggests a connection between the unstable axisymmetric puffing solution and the swirling plume. Further bifurcations result in quasi-periodic states with a very low-frequency modulation, and these eventually become spatio-temporally complex.

A Benchmark Study of Modeling Lamb Wave Scattering by a Through Hole Using a Time-Domain Spectral Element Method

2018 ◽  
Vol 1 (2) ◽  
Author(s):  
Menglong Liu ◽  
David Schmicker ◽  
Zhongqing Su ◽  
Fangsen Cui
Keyword(s):  
Numerical Simulation ◽  
Wave Propagation ◽  
Time Domain ◽  
Lamb Wave ◽  
Spectral Element Method ◽  
Guided Waves ◽  
Three Dimensional ◽  
Spectral Element ◽  
Benchmark Study ◽  
Through Hole

Ultrasonic guided waves (GWs) are being extensively investigated and applied to nondestructive evaluation and structural health monitoring. Guided waves are, under most circumstances, excited in a frequency range up to several hundred kilohertz or megahertz for detecting defect/damage effectively. In this regard, numerical simulation using finite element analysis (FEA) offers a powerful tool to study the interaction between wave and defect/damage. Nevertheless, the simulation, based on linear/quadratic interpolation, may be inaccurate to depict the complex wave mode shape. Moreover, the mass lumping technique used in FEA for diagonalizing mass matrix in the explicit time integration may also undermine the calculation accuracy. In recognition of this, a time domain spectral element method (SEM)—a high-order FEA with Gauss–Lobatto–Legendre (GLL) node distribution and Lobatto quadrature algorithm—is studied to accurately model wave propagation. To start with, a simplified two-dimensional (2D) plane strain model of Lamb wave propagation is developed using SEM. The group velocity of the fundamental antisymmetric mode (A0) is extracted as indicator of accuracy, where SEM exhibits a trend of quick convergence rate and high calculation accuracy (0.03% error). A benchmark study of calculation accuracy and efficiency using SEM is accomplished. To further extend SEM-based simulation to interpret wave propagation in structures of complex geometry, a three-dimensional (3D) SEM model with arbitrary in-plane geometry is developed. Three-dimensional numerical simulation is conducted in which the scattering of A0 mode by a through hole is interrogated, showing a good match with experimental and analytical results.

scholarly journals Vibration characteristics of triple-gear-rotor system in compressed air energy storage under variable torque load

2021 ◽  
Vol 104 (1) ◽  
pp. 003685042098705
Author(s):  
Xinran Wang ◽  
Yangli Zhu ◽  
Wen Li ◽  
Dongxu Hu ◽  
Xuehui Zhang ◽  
...  
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Element Model ◽  
Rotor System ◽  
Dynamic Responses ◽  
System Response ◽  
Rotating Speed ◽  
Torque Load ◽  
Set Up ◽  
Two Stages

This paper focuses on the effects of the off-design operation of CAES on the dynamic characteristics of the triple-gear-rotor system. A finite element model of the system is set up with unbalanced excitations, torque load excitations, and backlash which lead to variations of tooth contact status. An experiment is carried out to verify the accuracy of the mathematical model. The results show that when the system is subjected to large-scale torque load lifting at a high rotating speed, it has two stages of relatively strong periodicity when the torque load is light, and of chaotic when the torque load is heavy, with the transition between the two states being relatively quick and violent. The analysis of the three-dimensional acceleration spectrum and the meshing force shows that the variation in the meshing state and the fluctuation of the meshing force is the basic reasons for the variation in the system response with the torque load. In addition, the three rotors in the triple-gear-rotor system studied show a strong similarity in the meshing states and meshing force fluctuations, which result in the similarity in the dynamic responses of the three rotors.

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