Questions related to Wave Propagation
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
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
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?
Modeling multi-phase flow propagation using Ansys Fluent, OpenFOAM, Flow-3D, etc., how the force, such as Drag force and Surface Tension, apply to each of the phases?
What about other forces? Do the forces such as, Added Mass, and Basset Force apply in the all phases? How?
Is there any concise reference or instruction for the modeling of multicomponent fluids?
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.
In an absorbing medium, the reflective index becomes a complex number: 𝑛̃ = 𝑛 ′ + 𝑖𝑛 ′′. Assume that a plane wave 𝐸⃗ (𝑥,𝑡) = 𝐸⃗ 0𝑒 −𝑖(𝜔𝑡−𝑘𝑥) is incident on this medium. (a) Starting from the plane wave dispersion in a medium (ω = 𝑐 𝑛 𝑘), show that the field intensity (|𝐸| 2 ) decreases exponentially over distance (i.e. |𝐸| 2 ∝ e −𝛼𝑥). (b) Express the absorption coefficient α in terms of other parameters.
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:
- reading of the transmitted and received waves (of amplitude vs. time), separately, by using this setup as is (when using two different cables), or
- reading of the transmitted and received waves combined in the same curve: maximum peak sent and resultant received echoes (back-end wall or cracks, for example)?
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.
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
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:
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.
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).
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.
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.
Can somebody recommend a book to learn about? I'm especially interested in spectrogroscopy with a city environment materials and albedo.
I performed some experiements with a FMCW Radar Instrument emitting waves of 3.8mm. I can see some "movements" when I am looking on the relative displacements (+/- 0.15mm) over multiple stable points (corner reflectors). I assume part of this "displacements" is caused by temperature, humidity and pressure variation over the time of measurement (outdoor experiment). However, when applying Rüeger (2002, Refractive Index Formulae for Radio Waves) formula then the values are about a factor of 10x too small. There does not seem to be an error of units. The paper mentions resonance lines at about 67GHz and I am wondering if this could have an influence on the measurements with 79.5GHz and is there a publication specifically for the frequencies around 80 GHz?
Would anyone have a suggestion what else could cause this "movements". The radar and the targets are mounted on a concrete pillar and I assume that there is no relative displacements due to the similar setup.
Thank you very much and best regards,
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.
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.
To draw fragility surface based on the peak ground acceleration (PGA) and wave propagation velocity (PV), it is necessary to make accelerogram with different values of the PGA and PV.
Is it possible to change the wave propagation velocity in earthquake accelerogram? Or can I produce accelerograms with different wave propagation velocity?
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.
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 am conducting a project where underground blasting effects are analysed on soil and structures above the soil. I've currently only have a very basic Abaqus model of a soil block with an implicit dynamic step. A time history amplitude was induced on this basic block model of soil. It shows the stress wave propagations. It has parameters for the Mohr-Coloumb plasticity. I am looking for books or any literature to further understand how the vibration of the blast will effect the soil layer, and possibly different layers of soil (rocks, clay, silty, soil etc). Any help or advice is appreciated!
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.
As we know,the pulse propagates in wave form and the velocity of wave propagation depends on the propagation medium features. So,Is it possible to use the measurment of velocity of pulse propagation in the body to diagnose cardiovascular problems such as hypertension and hypotension?
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?
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?
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?
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/dxj 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?
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!
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!
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?
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?
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?
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?
I want to find an analytical model for the wave propagation of acoustic sound from a vibrating area (for example circular piston) without any baffle around it. I read many acoustic reference books, but i'm confused about this problem. The analytical models don't match with the F.E.A results!!
I'm appreciate if any body can guide me about 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.
In Balanis pp.67. he refers to fact that we should modify CP phase difference in the wave propagates in +Z direction. it not clear for me how to modifying these two relations.
can any one help with this ?
We want to establish a metamaterial laboratory at mechanical faculty. What equipments do we need to have? our focus will be on vibration and wave propagation.
It is said that light passing through a single slit forms a diffraction pattern. However, I couldn't find any research to say whether where this phenomenon starts? Before? Inside? Or after the single slit? At the inlet edges? Or at the outlet edges?
Please let me know if there is any reference for it.
After getting the view of guided waves propagating in Honeycomb sandwich structure, I am unable to view the Deformed Shape of the simulation results in ABAQUS....Any ideas would be appreciated gratefully.
How to distinguish between travelling wave solutions and solitary wave solutions of nonlinear dispersive equation like KdV-Burgers' equation? While analysing the wave propagation of solution figue, how actually one identifies it as soliton?
Thanks in advance
Recently, I have got familiar with metamaterials which exhibit no wave propagation in some frequency intervals. The unit cell contains 2D sketch that form a lattice structure with periodic boundary condition. Secondarily, I need to know how to define parameters such as basis vectors, wave vectors (k), and etc to have a completely user-defined evaluation of my unit cell. I would appreciate if anyone could help me.
I am interestet in simulating the distribution of energy from sea waves onto a shore line.
Ex. Helmholz would do the job I think as we can approximate sea waves with ordinary wave equation for shallow water, but this is to slow for the purpose.
I have built three 2D plane strain model in Abaqus, each model was applied dynamic concentrated forces (1 MHz, last 10 microsecond), which are equivalent, at point A as shown in the figure named 'resultant decomposed force', and the results were the displacement of Rayleigh wave in the far field (at point B) on the free surface.
Except for the forces are different, everything else for the three models are the same, the results should be the same since the forces are equivalent. However, the results are not the same, results of force 2 and 3 are the same, results of force 1 is different.
The results for force 1, 2, 3 can be found in the attached pictures. I have no idea why the results are not the same. Does the synthesis and decomposition of forces not apply to dynamics?
Would you please help me, thank you a lot.
I am working on lamb waves propagation in isotropic and in anisotropic plates.
I am interested in plotting dispersion curves based on SAFE method. I have tried to program the SAFE method in Matlab, but I did not get the right dispersion curves for 2D Aluminium plate. You find in the attached files my program. So I would like to ask you if it is possible to guide me more to get the right curves.
Hi, I built a 2D plain strain model, put a concentrated time-harmonic force below the free surface, and detected Rayleigh wave on the free surface, I found that the amplitude of Rayleigh wave decay with the distances increasing. The material is aluminum, I just set density, Young modulus, no damping. I have no idea why the amplitude of Rayleigh wave would decay with distance.