Papers by Keyword: Wave Propagation

Abstract: This paper describes the analysis of the propagation of regular and irregular waves in a flume by using Fluent® model, which is based on the Navier-Stokes (NS) equations and employs the finite volume method and the Volume of Fluid (VoF) technique to deal with two-phase flows (air and water). At the end of the flume, a numerical beach is used to suppress wave reflections. The methodology consists of adding a damping sink term to the momentum equation. In this study, this term is calibrated for three cases of regular incident waves (H = 1 m, T = 5, 7.5, and 12 s) by varying the linear and quadratic damping coefficients of the formulation. In general, while lower values of damping coefficients cause residuals on the free surface elevation due to wave interactions with the outlet boundary, reflection occurs on the numerical beach when higher values are used. A range of optimal damping coefficients are found considering one of them null. In one of these cases, temporal series of free surface elevation are compared with theoretical ones and very good agreement is reached. Afterwards, an irregular wave propagation, characterized by a JONSWAP spectrum, is investigated. Several gauges along the flume are evaluated and good agreement between the spectrum obtained numerically and the ones imposed at beginning of the flume is verified. This study shows the capacity of NS models, such as Fluent®, to simulate adequately regular and irregular wave propagations in a flume with numerical beach to avoid reflections.

Abstract: s The longitudinal impact between rigid body and variable cross-section elastic rod with fixed boundary condition was studied, the velocity and stress distribution law during 1st impact wave period was derived for the variable cross-section rod, the influence of cross-section change rate on rod response was discussed. Some examples calculations were carried on, It is shown that the cross-section change rate is a significant influencing factor for the velocity and stress distribution in the rod during impact.

Abstract: Wave propagation is introduced to analyze out-of-plane vibration problem of a rotating ring. Harmonic wave solutions are found for the coupled equations of the axial and torsional motion. Wavenumber spectra and phase velocity map are obtained, and the ratio of axial displacement to torsional displacement and the cut-off frequencies are determined. Examples for the free vibration of the uniform rotating thin ring are given to illustrate the validity of the wave propagation. This research will be valuable in the application of a solid cage in high speed roller bearing.

Abstract: The resonant column method is established as a standard laboratory method for the study of the elastic properties of soils. The study presents low-amplitude resonant column test results on volcanic sands with intra-particle voids. The experiments were performed on dry samples prepared at variable relative densities and tested in torsional mode of vibration. In the first part of the article, the important factors that control the elastic stiffness of uncemented sands are described shortly and recent findings on granular soils dynamic properties are presented briefly. The second part describes the basic features of the resonant column used in the investigation and the materials of the study and in the third part representative results of an extensive experimental testing program on volcanic granular soils are presented and discussed with a focus on comparisons between the elastic stiffness of volcanic and quartz granular soils. The importance of the effect of the presence of intra-particle voids within the particle mass of the volcanic soils is emphasized, which in turn affects markedly the global void ratio of the samples.

Abstract: The use of advanced materials in automotive, aerospace and communication technologies has called for re-assessment of classical models of many structural elements. The primary objective of this study relates to the use of a higher-order continuum model for discerning the contribution of certain geometric and material properties on wave propagation behavior of a spinning appendage of an aircraft appendage. The spinning appendage is characterized by a through-thickness functional material gradation and subjected to an axial dead load. The foundation of the present model rests on the trio of the mechanics of functionally graded solid structures, the extended Hamilton’s principle and the thin beam theory. Numerical results from the wave mechanics analyses reveal the noticeable influence of axial dead load and attendant wave splitting effect caused by the gyroscopic moment of the system. The wave mechanics result paves the way for the non-destructive damage testing of the element.

Abstract: We characterize the elastic response of Apricena marble by using advanced ultrasonic nondestructive techniques. An innovative experimental device for ultrasonic immersion tests is employed for the determination of ultrasonic velocities of waves travelling into the sample for any angle of propagation. The interpretation of the experimental results within the theoretical framework of wave propagation in elastic materials allows for both the classification of the anisotropy and the determination of the elastic moduli.

Abstract: In the recent years a big focus is subjected to the response of structures subjected to out-of-plane loading such as blasts, impact, etc. not only to homogenous materials, but also to heterogeneous materials, such as composites. Such form of loading can cause considerable damage to the structure. In the case of layered composite materials the damage can have several forms, starting from damage in layers up to delamination and full damage of the construction. This paper describes the investigation of shockwave propagation in composite structures caused by impact loading. The composite consists of carbon fibers in a polymer matrix, in which the fibers are much stiffer then the matrix. Finite element simulations were carried out for a “bird” strike impact on a composite wing leading edge. Results show a good impact resistance and good damping abilities of shockwaves.

Abstract: Considering the energy variation, cylindrical P-wave propagation across a linear elastic rock joint is analyzed. Then parametric studies are carried out to investigate the effects of the wave source distance,the joint stiffness and the incident waveforms on wave propagation across a jointed rock mass.

Abstract: Theory of elastic waves layered homogeneous medium or even medium for the study can not meet the actual demand for seismic exploration, especially for fine rock to construct reservoirs for the study, had to consider small-scale heterogeneity of seismic wave propagation effects. In this thesis, multi-scale model of a complex medium, in ensuring the premise to further improve simulation accuracy simulation efficiency issue, the introduction of a variable grid numerical simulation techniques, and were analyzed for different types of grid difference, establish a different media model simulation results verify the validity of simulation and analyzes its efficiency and accuracy problems.

Abstract: According to the displacement discontinuity method and the conservation of momentum at the wave fronts, analysis for cylindrical P-wave propagation across a linear elastic rock joint is carried out. Considering the energy variation for wave propagation in one medium, the wave propagation equation was derived and expressed in an iterative form. The transmission and reflection coefficients are then obtained from the equation. By verification, the results agree very well with those from the existing results.