Wave Propagation - Science topic

I'm looking for some analytical results for the wave propagation in 'compressible' hyperelastic cylinders - isotropic / anisotropic, pre-stretched or otherwise. I know several papers on incompressible version of this problem.

The diffraction of light has been referred to as its wave quality since it seemed there was no other solution to describe that phenomenon as its particle quality and subsequently, it exhibited wave-particle duality.

The theme of the diffraction typically refers to a small aperture or obstacle. Here I would like to share a video that I took a few days ago that shows diffraction can be produced by the macroscopic items similarly:

I hope you can explain this phenomenon with wave-particle duality or quantum mechanics. However, I can simply interpret it with my own idea of Inhomogeneously refracted space at:

The shadows of two objects undergo peculiar deformation when they intersect, regardless of the distance between the objects along the optical axis:

In the context of acoustic wave propagation through heterogeneous media, PML is commonly employed technique to impose 'no reflection' boundary condition. I'm interested in knowing whether there exists any other method in which the 'viscous dissipation' is not introduced.

ICMEAAE 2024 provides an enabling platform for Materials Engineering and Applied Mechanics experts to exchange new ideas and present research results. This conference also promotes the establishment of business or research relations among global partners for future collaboration. We hope that this conference could make a significant contribution to the update of knowledge about this latest scientific field.

ICMEAAE 2024 warmly invite you to participate in and look forward to seeing you in Changsha, China.

The topics of interest include, but are not limited to:

1. Materials

- Materials Science and Engineering

- Nanomaterials

- New Energy Materials

......

2. Applied Mechanics

- Vibration Science

- Elasticity

- Particle mechanics

......

All accepted full papers will be published in the conference proceedings and will be submitted to EI Compendex / Scopus for indexing.

Full Paper Submission Date: February 23, 2024

Registration Deadline: March 1, 2024

Final Paper Submission Date: March 8, 2024

Conference Dates: March 15-17, 2024

I want to design an antenna for surface heating not for deep heating of material. So what kind of antennas are suitable for surface heating? Please suggest. Will the use of slow wave structure be beneficial for reducing the velocity of wave propagation or are there some other better options?

Is there a reasonable alternative to the theory of the expanding universe? I believe so -

The idea of an eternal universe is highly speculative and doesn't quite fit with our current understanding of the universe's origins, such as the Big Bang theory. Any idea that has been around for a century cannot be easily dismissed but the James Webb Space Telescope is casting potential doubts on the Big Bang. If this continues, we may well find ourselves in need of another theory explaining cosmic origins.

When we solve (19th-century Scottish physicist James Clerk) Maxwell's equations for light, we find not one but two solutions: a 'retarded' wave, which represents the standard motion of light from one point to another; but also an 'advanced' wave, where the light beam goes backward in time. ("Physics of the Impossible" by Michio Kaku, Penguin Books, p. 276-277) Einstein's equations say gravitational fields carry enough information about electromagnetism to allow Maxwell's equations to be restated in terms of these gravitational fields. This was discovered by the mathematical physicist George Yuri Rainich. (Electrodynamics in the general relativity theory. by G. Y. Rainich. Trans. Amer. Math. Soc. 27 (1925), 106-136 https://www.ams.org/journals/tran/1925-027-01/S0002-9947-1925-1501302-6/)

The farther away a star or galaxy is, the more the advanced part of waves from it will reach into the past, giving us a greater inaccuracy regarding its true distance. This increase is analogous to redshift increasing with distance. We might call it readshift - re(tarded) ad(vanced) shift. Readshift would explain the astronomical results which were interpreted as accelerating expansion of the universe. Surveyed supernovas would appear fainter, therefore apparently farther away than they truly are. Unless advanced waves are considered a possibility, the only rational way to move a supernova from its apparent, distant position to its true nearer location is to conclude the universe has expanded.

A backup to this point of view is presented in the article link at paragraph's end, in which a fresh perspective on the nature of electromagnetism is envisioned. The perspective uses John Wheeler’s geons and confines James Clerk Maxwell’s propagation of electromagnetic waves by oscillating electric and magnetic fields to a quantum-scale role. The confinement restricts the motion of photons – and via George Yuri Rainich, gravitons – to a “bobbing up and down” in the cosmic sea which is perpendicular to the direction of waves’ propagation. The severely limited movements of gravity (space-time) and electromagnetism mean the universe never expands or contracts. (8) (PDF) Measurement of Gravity Leads to Gravitons Decaying Topologically. Available from: https://www.researchgate.net/publication/375758112_Measurement_of_Gravity_Leads_to_Gravitons_Decaying_Topologically [accessed Nov 22 2023].

Surely an alternative to the Big Bang in which there’s no expansion or contraction (no oscillation in either space or time) must be an infinite, eternal cosmos. How is it even possible to think of creating something that has always existed? A model of the cosmos might be built that uses the infinite number pi and imaginary time, and resides in Virtual Reality (artificial, computer-generated simulation). The entanglement (quantum-mechanics style) in the simulated universe is unable to remain separate from the entanglement existing in our perceived reality because computers using so-called "imaginary time" (which is defined by numbers with the property i² = -1) remove all boundaries between the two universes. This enables them to become one Augmented Reality (known now as technology that layers computer-generated enhancements onto an existing reality but seen here as the related layering of virtual reality onto other points in time and space). The poorly named imaginary time of physics and mathematics unites with pi (both are necessary to generate a non-Big-Bang cosmos i.e. an infinite universe which, because space and time can never be separated, is eternal). This manipulation of time, space, and the universe with virtual and augmented reality might possibly be produced by the two-valued binary-digit system used in electronics traversing a wormhole, or shortcut between folds in space and time, designed by humans of the far future. The augmented reality which is layered on “other” points in space-time actually isn’t transmitted to other points. Because of the quantum entanglement of every particle (massive or massless) of everything in spacetime caused by advanced and retarded waves cancelling each other, only one point ever exists. Thus, transmissions to any (apparently other) places or times wouldn’t be restricted to the speed of light but can be made instantaneous by technology of the far future.

It is common that the polarization purity of EM wave will be deteriorated when the propagation environment is to be free space (with obstacles). So, is there any device to preserve the polarization purity of signal at least to a reasonable level (which is supposed to take its propagation in free space).

The fallacy of the aether was that its only function was to propagate light waves. This question goes much further and probes whether space (the vacuum) is an elastic medium that propagates waves at the speed of light. For example, do gravitational waves propagate in the elastic fabric of space? If space is assumed to be an elastic wave propagation medium, then gravitational wave equations imply this medium has enormous impedance of c³/G = 4 x 10³⁵ kg/s.

This is a discussion question, and I am going to take the position that spacetime is an elastic medium with “spacetime foam” properties first proposed by John Wheeler. He determined that the uncertainty principle and vacuum zero-point energy implied space has Planck length oscillations at Planck frequency. This would make spacetime a physical medium that propagates waves at the speed of light with impedance of c³/G. This impedance is so enormous that a rotating wave with Planck length amplitude and an electron’s Compton radius would have an electron’s energy.

I am taking the position that the quantum vacuum is a sonic medium that propagates waves at the speed of light. This medium gives the vacuum its “intrinsic” properties such as vacuum permittivity ε_o, vacuum permeability μ_o, impedance of free space Z_o, virtual particle formation, etc. If spacetime is not a physical medium, why does it have finite values for ε_o, μ_o and Z_o? The following link has more information about my opinion and model. What is your opinion?

We are currently investigating the shock response of materials using molecular dynamics (MD). This project showed us that the preparation of properly equilibrated MD models can be very challenging even for someone with a strong background in molecular modeling. Therefore, we thought of sharing some of our recent MD models with the research community. We would like to share the LAMMPS input and data files required to run MD simulations of shock wave propagation and ballistic impacts. I have provided ~3-minute video overview of the files here: https://youtu.be/hgZXvUdr-Qo

You can download the shock model from here: https://github.com/nuwan-d/MD_model_JAM-21-1174, and the impact model from here: https://github.com/nuwan-d/md_impact_tests

(Added on 2022/01/14): We recently published two more articles, and our MD (LAMMPS) and DFT (VASP) models are freely available.

The first is “Quantum and classical molecular dynamics simulations of shocked polyurea and polyurethane” (https://doi.org/10.1016/j.commatsci.2021.111166). The models are available here: https://github.com/nuwan-d/quantum_md_of_shocked_polymers

The second paper is “Molecular dynamics study on the shock induced spallation of polyethylene”( https://doi.org/10.1063/5.0072249). The models are available here: https://github.com/nuwan-d/shock_response_pe

(Added on 2022/06/08): Our latest MD (LAMMPS) and DFT (VASP) models of phase-separated polyurea are available here: https://github.com/nuwan-d/shock_response_of_polyurea

Good luck with your MD simulations.

Dear all,

I am simulating the blast wave propagation inside a box (just opened in one of the 6 sides) using the coupling method LBE-MMALE. Detonation is loacted outside the box and in the direction of the open side. The box is considered to be rigid.

The entrance of the cubic box have an ambient layer, while all the other 5 faces of the air domain have clamped nodes (all DOFs are constrained). Is this a correct approach? Or should I implement any other BC's in the air domain in order to avoid the physical modelling of the box walls.

Thank you in advance

Hi,

I am currently in my final year at university and for my dissertation I am investigating the propagation of flexural waves in a 2D structure with varying thickness. Currently, I am finding it difficult to find the reflection coefficient using COMSOL. At the moment I am modelling a uniform plate in a frequency domain with a range from 10 Hz to 10,000 kHz with an added excitation point from a point load, I am using a uniform plate so that I can validate a method of finding the reflection coefficient as it should be equal to 1 for a uniform plate.

I have attached the files for the uniform plate, if anybody has any ideas or solutions for my issue I would be hugely grateful.

Thank you

Hi everybody.

I have developed within my research a 3 dimensional numerical wave tank (25 meter long, 10 meter wide and 6 meter water depth) in LS DYNA based on the ICFD method. I have already refined the mesh in the area where the wave acts to increase the accuracy of the wave deflection. At the outlet of the wave tank I have installed a numerical damper to minimize the reflection of the wave.

Now i have evaluated the results at 3 different locations (5m, 10m and 15m) and it is noticeable that energy is lost in the system. The wave deflection decreases at the results at 10m and 15m compared to the results at 5m. Reason for this could be numerical dissipation and numerical dispersion.

My idea now is to either increase the tank length to minimize the influence of the reflecting wave or to adjust the parameters of the linear and quadratic damping terms.

Does anyone of you know about similar problems and has some suggestions for me?

Thanks,

Jonas

The results of our research determined for the first time that for the entire frequency range of acoustic waves, the range of their propagation, measured not in units of measurement of distance, but in cycles, is a constant: the same number of cycles corresponds to the same absorption of acoustic energy. But the presence of correlation in this case is not related to the presence of a cause-and-effect relationship between the frequency of acoustic waves and their propagation distance.

It should be noted that there are signs that the obtained regularity can be extended to transverse waves in water. This is evidenced by the fact that, unlike shorter wind waves, long ocean surface (transverse) waves of spread over a distance of more than 1000 km. Tsunami waves, which have a length greater than the length of "Zibu" waves, spread over a distance of tens of thousands of kilometers. Seismic waves that propagate in the solid shell of the Earth, at lengths close to the length of tsunami waves, also propagate for tens of thousands of kilometers. In the future, different types of waves propagating in different environments can be considered, which does not exclude the possibility of confirming the general (universal) physically justified and understandable regularity of wave attenuation put forward by us.

I modeled Lamb waves propagating in a carbon fiber composite plate by using the semi-analytic finite element method and solved the partial differential equation by using COMSOL PDE module. The Dispersion curve was consistent with that calculated by the "Dispersion Calculator". However, when I got the through thickness profiles obtained by the two methods, they were completely different. I don't know what is the cause of this problem?

Conceptually, as well as source of wave propagation and wave equation

How to calculate the amount of pressure generated by the ultrasonic transducer (single element or multi-phased transducer) after applying a certain voltage to it? I want to use this pressure field as the initial condition for longitudinal wave propagation simulation.

I want complete information about calibration methods of Network Analyzer. I want step-by-step calibration steps.

Is it better to measure waveguide components SOLT or TRL ??

What is the difference between SOLT and TRL?

Hi,

I am working on numerical simulation of ultrasonic wave propagation through an elastic medium without any defect. I calculated the velocity of wave by using time and distance relationship. But when i used model with void or crack, i got less time to detect the first wave, while it should be longer as there is hole in model and wave propagation through it should be more. Can anyone help me out this problem i.e. how wave velocity is calculated in the model with defect.

Hello to all

Two questions

1. Does the use of metals with high magnetic permeability, such as iron alloy in the waveguide, cause insertion losses?

2- What about chrome or copper plating?

If you know the article in this field, please introduce it. Thank you

Dear all,

I want to apply the "periodic" boundary condition to the existing boundaries along wave propagation direction in a curved cell unit (attached image); However, this boundary condition does not appear to be applicable to curved surfaces, and some changes to the coordinate system used are required.

Unfortunately, I do not know what coordinate system to use and how to use it in "orientation of source".

I would be grateful if someone would help me.

Any help would be extremely appreciated.

When we need to conduct a FE simulation of guided wave propagation, small element size and time step must be used to capture the waves, especially for high-frequency cases. Millions of elements would be normal for a model with a small size, say a plate with a dimension of 200mm*200mm*1mm. Is there any shortcut to avoid this type of difficulty or software that is more suitable for this work than ABAQUS or ANSYS, .etc?

Hello .

I want to design and build a waveguide load in X Band.

1- How to design that the VSWR is maximum 1.1? (What should I use inside the waveguide, what material? With what dimensions?)

2-How to test it with Network Analyzer after making it?

I was wondering if surface electromagnetic waves can propagate at interface between two dielectrics, both isotropic and homogeneous, but having different relative permittivities.

The literature shows that their characteristics must be different.

Consider a fluid-elastic structure interaction problem. We know that the density and shear module affect the elastic wave propagation velocity. Let's begin a discussion on the effect of density on the deformation intensity and recovering the shape.

Hi

I wanna solve partial differential equation in terms of x and t (spatial and time), As I know one of the most useful way for solving pde is variable separation. well explained examples about mentioned way are wave equation, heat equation, diffusion....

wave equation is Utt=C^2 .Uxx

in other word; derivatives of displacement to time, equals to derivatives of displacement to spatial multiplied by constant or vice versa.

however my equation is not like that and derivatives are multiplied to each other.for example : Uxx=(1+Ux)*Utt

Im wondering how to solve this equation.

I will be thankful to hear any idea.

I have heard that SWAN software is free software. But I am unclear whether SWAN software independtly exists or is it used in conjunction with Delft3d software.

Also, if there are any other software, please suggest.

I want to apply a pulse-echo methodology (by using one single transducer as both transmitter and receiver). Do you know how to connect the transducer to the wave generator and oscilloscope to detect both transmitted pulse and echoes?

I have been trying to use the burst feature in manual mode by pressing the trigger button in the wave generator. However, when I do that, the oscilloscope is only capable of reading the wave generated instead of receiving as well the back-wall echo.

I am also using these types of transducers from Stemininc: Piezo Ceramic Plate 20x15x2.1mm 1 MHz, Piezo Ceramic Plate 7x7x0.2mm 250 KHz, and Piezo Ceramic Plate 20x15x3mm 710 KHz. Thus, I'm not sure if they are indicated to use this pulse-echo methodology.

I have two alligator cables connected to the oscillator and to the transducer: 1 to work as the transmitter and one to work as the receiver; and they are both connected in the same wires of the transducer. However, so far, it seems that these alligator cables connected to the same transducer are giving me the same wave. 

Do you know if this equipment as it is is capable of doing these readings:

I am using a manually triggered pulse sine wave of amplitudes of either 10Vpp or 24Vpp, but the outcome is always identical. Should I be using a higher amplitude to make sure I receive the echoes?

Any help would be much appreciated.

Recently, I got a revision on one of my papers in which the reflection and transmission phenomenon of waves has been studied in a piezoelectric medium with the consideration of a flexoelectric effect.

In the said article I used the classical method for finding the amplitude ratios of the waves.

However, the reviewer suggests that

" It would have been better if the solution methodology was based on Lame displacement potentials where the dilatational and the distortional character of the waves are more easily distinguished."

But as far I know this methodology, the Lame potentials are best suited for the isotropic media.

So,

Is the Lame displacement potential method can be used for transversally isotropic media?

I want to establish the influence of prestress on the propagation characteristics of guided waves, and analyze which guided waves in which modes or frequencies are most sensitive to stress changes

While going through different Rayleigh wave propagation papers. I have seen sometimes author is using Helmotz decomposition and sometimes not. What is rule? When should we use it? Any suggestions will be helpful.

Dear R^G members:

Screenshot from:

Vonsovskii, S. V. and Svirskii, M. S. 1961. About the spin of phonons. Soviet Physics of the Solid State. 3:2160. In Russian.

Do you know any article/book which uses explicit expressions containing Anisotropic Elastic Langragians L( C_ij )?

For instance: cubic, hexagonal, or tetragonal ones? Other symmetries are also welcome.

L can be written in the 4^th index range - _ijkl or Voig - _ij notations, but the math expressions must contain explicitly the elastic stiffness components C_ij or compliances S_ij (if S^-1 C ~ 1) according to the point symmetry group.

For example: in the isotropy case: 2, in the cubic case 3, in the hexagonal case 6 and so on.

A lagrangian is defined as L(C_ij) = K( ρ v² ) - U( C_ij ), therefore the potential term U(C_ij) does have to include an expression invariant to the point group symmetry considered.

I did an intensive search on the web, so far only two papers with two expressions (isotropic and cubic cases) both papers from the '60s.

Thank you all so much for the interest.

Hello everyone,

I'm trying to implement a material with non-diagonal conductivity in my FDTD code. By the way, I'm using Dr. Elsherbeni's code for my purpose. Although I managed to implement diagonal anisotropy in my code, my code seems to be unstable for non-diagonal matrices. Through research, I've found out that my updating equations are not correct. Since it is necessary to interpolate the fields in irrelevant positions, it seems the updating equations also have to be organized differently than the isotropic case.

I attach the equations in a PDF below. the first equation on every page represents the equations in half-steps and the second one represents the updating equations implemented in the code.

Any help or hint would be appreciated.

I also have to point out that the source for the equations is the paper in the link below:

I am doing simulation in Abaqus. My topic is damage detection by using lamb wave propagation.

I am giving input data as sine sweep(48 sec). For that what is the time step and how much increment should use to get the output result and what is the approximate mesh size should be used. And what are the inputs we have to include in f-output and history output.

I am currently modelling an acoustic planar wave, generated by a speaker, travelling through an expanding cross sectional area duct/horn system. When plotting a graph of transmission coefficient against frequency, the model suggests the transmission coefficient is between 0.5 and 1 for all frequencies. Should transmission coefficient, defined as the ratio of output to input amplitude, have a transmission coefficient above one, or do my results seem feasible?

Note, the medium through which the wave propagates is constant (air).

Talking to Dr. Jörn Schliewe inspired me to raise this illustrated question and how you may call these barriers in the experiment of diffraction? Would you call it n-slits or n-obstacles?

Staggered grid finite-difference (FD) methods are widely used for elastic wave equation modelling because of their high computational efficiency, smaller memory requirement and easy implementation. I am looking for the mathematical foundation for higher order (8th) of finite difference staggered-grid method on 2D P-SV elastic wave propagation.

If water waves are disturbance of the water medium , the light is electromagnetic waves, and the gravity is space-time waves, then what is the medium in which the quantum waves propagate?

I am using transient solution type in HFSSv15, and two same UWB Antennas are in far field of each other. One antenna is transmitting and other antenna is receiving antenna.

I have read numerous research papers on various mechanisms of excitation of surface plasma wave. But why do we need to excite a wave? Is it necessary? Can't the wave propagate without being excited?

I need information concerning the penetration and reflection capacity of ultraviolet and infrared radiation wavelengths on different most common materials.

Edit.

Can somebody recommend a book to learn about? I'm especially interested in spectrogroscopy with a city environment materials and albedo.

Can someone provide the wave propagation assumption that applies to the transfer function-based square impedance tube method. How it differs from a cylindrical impedance tube?

If we consider a marine communication scenario, what are the factors affecting the propagation of radio waves other than reflection, refraction, diffraction, scattering, and antenna height?

As part of my research, I need to couple a loaded, custom-sized, rectangular, waveguide (in which a hybrid mode propagates at 8.5GHz) to either a) a coaxial transmission line or b) to a standard X-band waveguide.

I need to understand the design and optimization processes for both including impedance matching and/or mode conversion as required.

What is the best, most efficient way of approaching such a task?

Any useful resources on the topic would also be very much appreciated.

Kind Regards

Simon

Hi,

I am looking for a good summary of advances done in the field of multiscale modeling. Would appreciate it if people working in this domain could link me to relevant publications/ articles.

Thanks,

Pranoy Nair

I wish to apply Floquet boundary condition at left-right ends and up-down ends, and the wish to find out the dispersion relation for the unit cell.

But I fail to find any option of Periodic condition in the list. If I make this an area-type geometry or a volume-type geometry, I can find the option, but not for the geometry provided (see attached image).

Please help me on how to do it. Thanks in advance.

Hi, I am trying to create a computation model of acoustic plane wave propagation through multiple layers of fluid. What should be the appropriate boundary conditions in my fluid-fluid interface? Thank you.

I have the following scenario.

In a marine environment, an object X moves below the surface of water from point A to point B. As it moves it displaces water around it which creates ripples (or increases detectable pressure levels) in the surroundings. We have sensors Si installed underwater at distance di with known geographic positions. I want to know the following.

1. How do we measure the intensity I of the ripples (generated by the object) at any sensor Si located di meters away from the object?

2. How do we measure the time required for the propagation of the ripple from its origin to sensor Si such that sensor Si can detect intensity I.

Thanks

I am in a urgent need for material explaining the basics of wave propagation in soils. I came across lot of advanced material, which deals with specific conditions. Kindly suggest a good book or article about this.

I did an experiment on a glass composite thin plate and generated Lamb wave. I increased the stiffness of the plate by forming a sandwich structure. I could find Ao mode with very attenuated amplitude but So is very diminishing. Confused, as per my understanding, I should get both modes frequencies even if the amplitude is small. But only Ao I could obtain its frequency but So not.

I used the waveguide port to excite the momopole antenna and get appropriate results and now i want to alter the type of port to discrete port but I got different results with discrete the port.

Any one have experienc to help?

Hello,

I am working on the finite element modeling of the ultrasound wave propagation. I want to check the wave transmission from water (impedance 1.5 *10^6 kg/(m^2.s)) to two different materials:

#1: Density=1050 kg/m^3 wave speed=2297.2 m/s acoustic impedance=2.41 (*10^6 kg/(m^2.s))

#2: Density=2000 kg/m^3 wave speed=1664.5 m/s acoustic impedance=3.33 (*10^6 kg/(m^2.s))

Based on my model, the reflection from water to material 1 is higher than 2. What is the reason for it? Material 2 has higher impedance, therefore should lead to higher reflection!

The wave speed in material 2 is really close to the wave speed in the water (1500 m/s). Does this cause less reflection at the boundary?

Thanks,

Hamed

Hello,

I am working on the lamb waves based on the semi-analytical finite element method (SAFEM) in the laminate structures.

When drawing dispersion curves, a number of additional curves are created in the system. I wanted to know what caused these curves to form and how can I eliminate them.

You can see the diagram in the attached files.

Thanks a lot for comments and answers

I have submitted a paper in a journal where a primary radiator is surrounded by 36 periodic symmetrical structures similar to what is shown in the attached picture.

I have named it a metsurface patch antenna. The reviewer thinks it is it is a "CP patch antenna coupled with parasitic elements" NOT a metsurface patch antenna.

I want to know how we can differentiate between parasitic elements and metsurface?

I am simulating wave propagation in a plate. In that process, I need to apply nodal displacement in the radial direction at the actuator position. I entered the wave excitation signal in the amplitude module. But when I am trying to select the displacement direction, I am not finding any option to apply radial displacement. I have attached the image of what I want to achieve. If anyone can help me out, I will be grateful.

I am trying to run a coupled model (HD and SW MIKE 21), for a one year period (8760 time steps; 3600 time step interval). However, after approx 200 time steps there is an Abnormal Run error, 'Blow-Up wave height too large'. What are some reasons that would cause this, and some solutions?

I want to model 2D wave propagation in a different medium and its reflex from the boundary with different shapes like rectangular or circle. Is any software or Matlab script that can do this?

thanks a lot for your helping

Hello! I apologize for the long question, but I’m a bit lost so I’ll try to be as precise as I can.

I am trying to implement a time-domain PML formulation for wave propagation, which can be found in this work

Here, the author has developed a set of equations to deal with the wave propagation in fluid and solid medium (please refer to eq. 5.9 of the work as I can't copy-paste them here). They are valid throughout the whole domain (PML and the physical domain), and within the physical domain the equations simplify to the general wave equation.

I'm using FEniCS as the Finite Element solver, and I need to provide the weak form of the PDE I'm willing to solve. Fortunately the weak form is in the work too (please see eqs. 5.10a-d).

I'm concerned only with the wave propagation in the fluid region, so I consider only eqs. 5.10a and 5.10c. Moreover, in eq. 5.10a, I believe the term with the integral over gamma vanishes as there is no fluid-solid interface.

The problem is I need to provide the Weak Form in only one equation. I'm confused with the term d phi/dx_j and I'm not sure how to rewrite eqs. 5.10a and 5.10c in the form a=L.

Can someone help me with this?

Many thanks!

I established a simple model in ABAQUS to simulate the stress wave propagating in a plane.

I set up the Infinite element CINPE4 on the border of the plane in .inp file. it more or less had some effects, but the boundary reflected wave can not be completely absorbed on the boundary.

Does anyone have the similar problem? How to deal with it? Thank you!

Dear all. Sensors are often used to detect specific physical phenomena (displacement, magnetic fields, temperature, etc.). The acquired signal is generally in the form current, voltage, etc. The signal waveform reflects the physical behavior of the phenomena to be inspected, but in no case the physical phenomena. Does the particle wave duality represent two ways of observing particle behavior ? Thank you for your comments.

We are all familiar with the presentation of the light-ray as a sequence of photons/energy-packets just like the figure shown.

What is the relation among "wave-length λ", the length between the black lines (name?), and the length between the red lines (name?) in the figure shown?

Does the overall amplitude (of black modes or red modes) have any relation to the amplitude of the sinoid-wave of monochromatic light?

4/5/2020

Tools in Matlab for modelling ultrasonic wave propagation in composite material

Hello everyone!

I wonder way EM wave propagates in vacuum space unlike sound waves. As we know EM waves are generated by charges in motion. Similar question for Light propagation from the distant stars to earth. Is there any alternative physical interpretation of propagation phenomena ?

The propagation velocity of EM waves depends on quality of wave guide and thier physical properties (for example, it depends on the permeability and permitivity of medium, etc.) and less than light C velocity. This may be mean that EM magnetic propagation need to "medium" to propagate" with physical properties. In the other hand, some cosmic particles have speed more than light speed.

Thank you for your comments!

https://earthsky.org/space/jan-14-2019-gamma-ray-burst-brightest-so-far

In a structural dynamic wave propagation problem, is the displacement at a point a continuous function of time or is it a continuous function of time only after the wave reaches the point?

Hi guys,

I hope you are in the best of your health.

I am working on Lamb wave propagation in anisotropic composite laminates. I want to apply the non-reflection boundary conditions in the simulation model. I am expecting to avoid the reflections from the plate edge by using non-reflection edges. Any idea how it can be done in ABAQUS? Or any other way to avoid these unwanted reflections?

Thank you!

Saqib

I know that for isotropic materials, a rule for the maximum element size L_max is:

L_max < lambda_min / 10

where lambda_min is the min. wavelength, defined as:

lambda_min = c_T / f

where f is the excitation frequency and c_T the transverse wave speed:

c_T = sqrt(G/rho)

Now I wonder:

- Can I take the same approach for an orthotropic material?

- If so, how can I calculate or obtain the transverse wave speed?