Quantcast
Channel: Latest Discussions - COMSOL Forums
Viewing all 27024 articles
Browse latest View live
↧

impedance boundary condition in transient pressure acoustic

May 5, 2020, 10:25 am
$
0
0

Hello,

Reviewing the documentation of version 5.5 I found out that, in time domain simulations for pressure acoustic, only resistive (real-valued impedance) can be modeled using user-defined impedance boundary condition; however, in frequency domain simulations the impedance can be any complex-valued number and thus models a surface that is both resistive and reactive. Is there any way to model an imaginary (not complex) impedance boundary which is a function of time in pressure acoustic?

Best, Reza

↧
Search

Modeling Change In Impedance As A Particle Flows Past Electrodes

May 5, 2020, 10:56 am
$
0
0

The below post is related to an archived discussion

I am trying to mix the two example Particle tracing and electrophoretic movement. [https://uk.comsol.com/model/dielectrophoretic-separation-of-platelets-from-red-blood-cells-17013] Impedance change due to particle. [https://www.comsol.com/model/electric-impedance-sensor-7704] Still, I could not able to see any change in impedance due to the particle; irrespective of their size. I guess there is some coupling from partcle tracing to electric field. However, I can see the dieletrophoretic effect, even at 1V. which is quite small electric field for dielectrophoretic effect.

Many Thanks in advance. Vishnu

↧
↧

Modeling Change In Impedance As A Particle Flows Past Electrodes

May 5, 2020, 11:28 am
$
0
0

The below post is related to an archived discussion

I am trying to mix the two example Particle tracing and electrophoretic movement. [https://uk.comsol.com/model/dielectrophoretic-separation-of-platelets-from-red-blood-cells-17013] Impedance change due to particle. [https://www.comsol.com/model/electric-impedance-sensor-7704] Still, I could not able to see any change in impedance due to the particle; irrespective of their size. I guess there is some coupling from partcle tracing to electric field. However, I can see the dieletrophoretic effect, even at 1V. which is quite small electric field for dielectrophoretic effect.

Many Thanks in advance. Vishnu

↧

Phase Change Material modeling

May 5, 2020, 12:07 pm
$
0
0

Hello,

I am trying to use the Phase Change Material domain in the Heat Transfer in Solids physics for 5.5. My material only undergoes its phase change once during heating up and remains in the second phase during/after cooling. What is an easy way to turn the Phase Change Material properties on/off during a time dependent calculation?

Thank you all for your time in advance!

↧

Duplicate parameter/variable name in piezoelectric material

May 5, 2020, 12:16 pm
$
0
0

Hello,

I'm trying to simulate the piezoelectric activity of a disc subject to side forces, in a dynamic problem. My starting point is a 2D simulation adapted from COMSOL library: the transient roling contact. I added piezoelectric physics and changed the ring to a disc.

The solution does not run and gives the above error for the parameter comp1.V

I'm not sure which parts of the model affect it and how to change properly.

Best, Yonatan

↧
↧

out of memory

May 5, 2020, 6:09 pm
$
0
0

Hi All, I am using the COMSOL 5.5, and I think the simulation is able to finish its tasks, unfortunately, the plots are not able to show up, whenever I tried to plot the results, the error will pop up as "out of memory", I also attached the error log file, and any help from anyone will be very thankful.
sincerely, Li

↧

Heterojunction Tunneling

May 5, 2020, 8:29 pm
$
0
0

Hi all. I am trying to model a semiconductor heterojunction tunneling for 8 domains , and i got this error when trying to simulate the model.

"undefined value found in the equation residual vector.there are 2627 degree of freedom giving NaN/Inf in the vector for the variable comp1.Efn_. at coordinate .....".

Can anyone help me with this error. I don't understand and how to fix it.Thank you in advance.

↧

coupling of solid mechanics with heat transfer (moving heat source)

May 6, 2020, 1:01 am
$
0
0

Hello every one, i'm making a model to simulate heat transfer and thermal deformations at welding with a moving heat source through coupling heat transfer and solid mechanics. when i simulate heat transfer and the moving heat soure only, the simulation runs very well but the problem is when i couple it with solid mechanics the moving heat source drifts and doesn't move in a straight forward line (welding direction). also, the moving heat source equation after simulation tells (incosistent unit)

please, can any one tell me where is the problem? what am i missing? or what shoud i do to model this situation

↧
Search

Power from point dipole to port boundary

May 6, 2020, 2:48 am
$
0
0

Hello. I am attempting a simulation to determine the power arriving from a point dipole to ports in a waveguide. This is a 2D simulation using a frequency domain study in the wave optics module.

To do this, I am using an Electric Point Dipole node (with coupling structure) close to a simple rectangular waveguide. The boundaries at the ends of the waveguide are numeric ports, set to "off". After simulating, I can see the electric field (via 2D surface plot) in the waveguide (all the way to the ports), but am strugging to find a way to show the power arriving from the dipole. Or quantify this field in any way, actually.

I notice that when I run a similar simulation with one port set to "on", there are additional plotting options such as transmittance and S-parameters. These are absent when both ports are "off", and I can only plot the mode index and propagation constant, found from the boundary mode analysis.

Can someone point me in the right direction? Am I missing something? I'm happy to provide more details (and an MPH file), if that helps.

Also, I've noticed I cannot animate this field (from the dipole) in the 2D plot. When I do a dynamic data extension, I am left with zero field everywhere. This is at odds with the solution. Again, I am likely missing something.

Cheers!

↧
↧

How to induce voltage in a circular coil due to the rotation of circular array of magnets in its premises

May 6, 2020, 8:02 am
$
0
0

Rotor in my model is already rotating, but no voltage induces in the coil. I don't know what I have not defined in it. Can anybody have a look at it for me and guide me?

↧

The walls condition shows the sides to not applicable

May 6, 2020, 8:09 am
$
0
0

Hello everyone, I tried to upload an AUTOCAD drawing into COMSOL in order to simulate the fluid flow. But I am unable to assign the wall BC on the wall inside of the drawing. I have uploaded the mph file below. The left end of the big rectangle is the inlet.

↧

Deformed Geometry/ Moving Mesh Tutorial

May 6, 2020, 9:17 am
$
0
0

Are there any tutorials focussing on Deformed Geometry or Moving Mesh?

↧

Tunneling Current through ATD

May 6, 2020, 10:42 am
$
0
0

I was looking to do some simulation for a tunneling diode I have been designing. It is essentially a silicon dioxide insulator between two polysilicon mediums (of a particular geometry as shown in the picture below). I have added the materials from the available material options (both from semiconductor materials package and other packages like MEMS). I am looking to calculate the tunneling current through the device from the triangular side to the island side. However, when I do the 2D simulation the results does not show a IV curve as it does in many of the online tutorials, which I am not sure why. Also, I had made a 3D model, also shown, which is more specific with regards to boundary conditions and more explicitly describing the actual device. This is what I am more interested in, but also worked with 2D since it is a bit easier.

Help in figuring out how to check for a tunneling current using the 3D model would be greatly appreciated, as I am relatively new to the software. Further information regarding the design can be seen in the .mph of the 3D version provided.

Note: in the image provided the oxide fill (or oxide tunneling medium) is exagerated for display purposes. It is the correct size in the .mph file.

↧
↧

How do you determine the spot of a Gaussian beam defined by "ewfd - Gaussian field - Gaussian beam - plane wave expansion"? Or how do you keep it in a fixed position?

May 6, 2020, 9:04 pm
$
0
0

Hi, everybody, I want to simulate the motion of the microsphere in the optical tweezers system. I used "ewfd - scattering field - gaussian beam - plane wave expansion" to define the incident field, the spot of the Gaussian beam focus at the (0,0,0). But when I use "parametric sweeping" to simulate the position change of microspheres in the incident field, the spot of the Gaussian beam will also change. Why does this happen? It puzzled me. As shown in the multi-section diagram of the microsphere in the attachment, the spot position at (0,0,0), but when the microsphere moves to the position of (0,5,0), the spot focus is also around (0,5,0). Why does this happen? Sincerely, Miao Peng

↧

HOW TO DEFINE THE material of NeFeB

May 6, 2020, 10:56 pm
$
0
0

HOW TO DEFINE THE material of NeFeB ，such as NdFeB

↧
Search

Model shape change over time

May 7, 2020, 1:57 am
$
0
0

Dear all,

I would like to simulate the temperature entry during laser drilling of a microsieve in Comsol. Is it possible that after drilling a hole, the created hole is included in the model form? So that there is no more material at this point.

Best regards Marcel

↧

Impedance in a PCB: a strip line between two ground shields

May 7, 2020, 5:40 am
$
0
0

Hello,

I would like to compute, among other parameters, the impedance in a PCB, for a strip line between two ground shields. An approximation can be use to compute this impedance given by:

where and t are respectively the distance between the strip line and the shields, the strip line width and the line thickness, as shown on Figure_1.png.

I would like, for a given set of parameters, that COMSOL returns the computed impedance of this object. The idea is to compare it with the impedance given by the above formula and then try to optimise the PCB dimensions.

I have implemented this in COMSOL following several tutorials, forum posts and blogs but I never got a satisfying impedance results (imaginary value, NaN, Inf or 0). I was expecting the impedance could be easily computed such as the capacitance that is given by C11.

Implementation: In the strip line a current of 2uA circulates. The two shields are grounded. They are into an insulator with . For other studies, I will work with emw and frequency variation, but to me this impedance computation does not depend on the physics type as it only depends on PCB dimension (maybe I am wrong here). That's why I tried several physics and I woked with a stationnary study. My model is attached below.

What am I doing wrong?

Thanks a lot in advance for your response, help and time.

Cheers, Marina

↧
↧

problem with comsol geometries

May 7, 2020, 8:12 am
$
0
0

I'm trying to simulate a 2D electrostatics IMS however i can't find a beizer polygon (linear one) in the primatives or geometries.

how should i get it ?

Thanks.

↧

heat transfer in solid, pulse

May 7, 2020, 8:22 am
$
0
0

Hi all,

I am simulating pulsed laser material interaction. When th pulse duration is in milisecond range, I would get reasonable resutls. I mean as it would be expected the heat will be dropped down in off time of pulse. However, when I go to nanosecond and microsecond range, the heat won't drop down in off time (see attached figures).

I highly apprecaite if anyone has any suggestion.

↧

How do I implement the continuity equation in COMSOL?

May 7, 2020, 9:34 am
$
0
0

Hi,

Can anyone here guide me in implementing the continuity equation as given below in the comsol? Any example mph files with similar equations implemented would be of much help.

where, porosity, density (from ideal gas law), (Darcy Law) is the velocity, and volumetric generation rate

Thank You

↧
Viewing all 27024 articles
Browse latest View live
Search