Latest Discussions - COMSOL Forums

Script to add many point loads to geometry?

Wed, 01 Sep 2021 00:57:17 +0000

Hi - I'm new to Comsol, and coming from ANSYS where this problem would be easy. I have a very complex load defined at 10^6 points. Wondering if I can write a script to define points in the geomety and then apply forces at those points. Alternatively I could apply forces at nearest nodes if I knew how to find them. Or, I could spread the point loads into areas and define pressures, but I don't know how to define the areas for those loads either.

I can easily write a program to create a script, but not sure what it should say. Web serches haven't turned up anything. Thanks for any help.

2D array of spring mass system

Tue, 31 Aug 2021 16:15:46 +0000

Hello all,

I am trying to model a two dimensional spring mass system in COMSOL 5.6 using the Lumped Mechanical System module. However, there is no option to do so. I know how to model a one dimensional spring-mass system. The LMS users' guide also provides no information.

Kindly help in this regard.

The model looks like this.

EM energy harvester modelling

Tue, 31 Aug 2021 05:59:00 +0000

please help me in modelling

Thrust and Torque Calculation in COMSOL

Tue, 31 Aug 2021 04:22:37 +0000

Hi,

I am currently simulationg a rotating propeller with transient study. I have ran one case at a constant RPM speed, but COMSOL does not have any output file calculations to determine forces such as Thurst and Torque acting on the propeller surface. How can one go about calculating these parameters in COMSOL post-processing?

Thanks in advance.

Electromagnetic emission

Tue, 31 Aug 2021 01:15:39 +0000

Hello everyone, I want to make a simulation of electromagnetic railgun launch, but I don't know how to realize it. Do you have any suggestions？

Oscillating flow conditions

Mon, 30 Aug 2021 19:44:32 +0000

Hi I am doing a sample problem of a oscillating fluid flow in a channel (emulating fluidic diodes / tesla valves) and wanted to understand boundary conditions. I've tried searching the forum and did not find the exact answer. So, in the figure attached "left side" is assigned an inflow velocity profile with a sinosoidal form so that it reverses after sometime. The "right side" is assigned an outlet condition with 0 static pressure. I am interested in looking at the difference in pressure b/w the "left" & "right" sides during the postive part of the sine cycle vs the negative part when the flow reverses (ratio of this pressure difference is referred to as diodicity for tesla valves).

Question Even though the flow reverses, since my metric is the pressure difference, does the following pressure profile look reasonable? First plot uses 0 static pressure for the outlet and 2nd plot uses 0 total pressure. Not sure why they are different (which really impacts velocity performance) and should there be a different condition so that the plot is symmetric during the +ve and -ve parts of the sinosoidal cycle?

Info of Eliminated stiffness matrix

Mon, 30 Aug 2021 18:34:49 +0000

The below post is related to an archived discussion

Hi,

The reply from Remi Magnard perfectly answered how to extract the imformation of the assembled matrice, such as stiffness matrix "K" or mass matrix "E".

But now my question is how to extract the imformation of the eliminated matrice, such as "Kc" and "Ec". Are those informations also in the "mphxmeshinfo"? For reference, we are using those matrics to calculate the natural frequency and eigen values.

Thank you very much,

Yan

Determining Thermal Conductivity

Mon, 30 Aug 2021 17:56:25 +0000

Hi, i am new to the comsol and the group. I am trying to find thermal conductivity of rock sample. I have thermal camera which i can use to determine the temperature of surface. I was thinking heating the rock for few minutes and record the temperature and perform some transient heat transfer simulation to find the thermal conductivity. Somebody told me i can input the range of thermal conductivity in the simulation in COMSOL. Has anyone give me insight. Thank you all in advance

when you can‘t install COMSOL it may because your Windows username is Chinese

Mon, 30 Aug 2021 14:30:06 +0000

When i want to install COMSOL , i have meet a situation that the COMSOL only come out a popup of "Setup is loading installation components. This may take a minute or two" and the popup disappeared without the installation window comes out. i have try a lot of way to deal with it, finally i was inspired with what i have done when installing latex , i have meet a problem cause by Window's username in Chinese, which lead to the situation that the installation program can't recognize the Temp System environment variable. So i edit my Temp System environment variable as '%SystemRoot%\TEMP' , which have a english location, and by this way, iinstall it successfully.

Band Structure of SAW Phononic crystal

Mon, 30 Aug 2021 13:18:48 +0000

Hi,

1) I would like to reproduce the results from the paper https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.10.064019 regarding the simulation of Surface Acoustic wave band gap of a phononic crystals. I would like to know is there any general way to span over arbitrary brillouin zone to obtain the desired band structure i.e, how to plot for the BZ shown in the paper? I have knowledge for square lattice but how to extend it further for triangualar lattice and desired brillouin zone

2) Also how to plot the radiation modes in band spectrum and the transmission spectrum?

More points on each streamline

Sun, 29 Aug 2021 22:03:38 +0000

I am studying Electrostatics on my geometry. When I create a streamline plot of the field with each streamline comprised of roughly 350 points (that I see when exporting the plot). is there a way to make each streamline to be made of more points? My mesh is already extra fine.

Convergence plot saved in results

Sun, 29 Aug 2021 06:21:51 +0000

I need to have Convergence plot saved in results. I red that it should be possible using Probe. What probe and what probe expression should I use?

Multiple Loads With Different Frequencies In Frequency Domain Study

Sat, 28 Aug 2021 11:25:17 +0000

Hi, I'm trying to evaluate the Transmission Loss on a glass panel when subjected to two different loads at the same time. In particular one is a boundary load representing an incident acoustic wave and has to be swept in frequency from 35 Hz to 4000 Hz; the other one is an edge load with a fixed frequency of 100 kHz that causes the propagation of a plane wave on the surface of the panel. I have to evaluate the Transmission Loss as a function of frequency (in the range 35-4000 Hz) considering both loads. To do so I have to perform a frequency domain study but the problem is that I want to vary the frequency of the boundary load only (from 35 Hz to 4000 Hz), while I want to keep the frequency of the edge load fixed at 100 kHz and consider both their contributions. Does anyone know a way to do it?

Thank you in advance, Tommaso

Handling multi-core simulations

Fri, 27 Aug 2021 14:41:16 +0000

Hi, I have a 32 core computer (2 processors with 16 cores each). I read on the help page that we can specify the number of cores to be used for a given simulation.

My question is : If I start 2 simulations simultaneously that I specify to utilize 16 cores each, how I do I prevent them from sharing a few common cores? Each simulation ideally should be able to run on its independent core. Is that something COMSOL does automatically?

Thanks

0.2 micron silver was coated with a 3 micron thick aluminum oxide film and tested for reflectivity absorptivity at 0.3 to 4 microns

Fri, 27 Aug 2021 09:07:01 +0000

According to the general understanding, this structure is equivalent to a mirror, at 0.3 to 4 microns should have a high reflectivity, this result is clearly wrong, can not find the fault! Hope someone can help, thank you very much, wish you a happy life

How does COMSOL deal with the partial derivative of the complex variable to the dependent variable to form the Jacobian matrix ?

Fri, 27 Aug 2021 03:35:59 +0000

When we need some user-defined variables in the physical model, such as principal stress and principal strain, they are the eigenvalues of the stress tensor and strain tensor, respectively. When obtaining the Jacobian matrix of the system, the partial derivative of the residual to the dependent variable is usually required. Will COMSOL perform the derivative of principal stress and principal strain with respect to the displacement field variables? Because this may be difficult to achieve mathematically, or how does COMSOL handle the complex variables like principal stress and principal strain in the Jacobian matrix?

Emission from a point dipole source

Thu, 26 Aug 2021 15:38:31 +0000

I want to simulate a dielectric dimer having a small gap. The source is a point electric dipole that will emit EM radiation. The source will be placed in the middle of the gap. This will be a 3D problem. I found that point electric dipole can be placed in the Physics interface. However I do not understand how to put a background incident field/power for the source. Also I want to know what does it mean by dipole moment direction and magnitude. How they are linked to incident field/power?

Fluid Velocity due to Structural Movement of Walls

Thu, 26 Aug 2021 10:03:50 +0000

Hi Everyone, I would like to perfom a one way FSI to find the velocity of fluid inside a 2D domain (say rectangular slot).I am using a FSI, fixed geometry interface. I want to apply a sinusoidal loading to the material at its boundary (say top wall) in a time dependent study. Structural boundary conditions include fixing the left vertical end.

How should I apply the loading on the boundaries. I tried applying a prescribed displacement of the form : A*sin(2*pi*3*t) where A is the amplitude. Also only the boundaries of the slot are a solid material while the enclosed domain is a stationary fluid. How do I assign only the boundaires to be solved within a solid mechanics module.

Particularly I want to know how to setup the laminar flow module i.e pressure is not important here. What should be the boundary conditions or is there any additional physics setup that I must use.

My main intention is to find the velocity of fluid due to motion of walls and then use that velocity in an other interface. Will be happy to receive inputs.

Thank You.

Contact Pairs

Wed, 25 Aug 2021 16:21:21 +0000

Hello All,

I am attempting to use a contact pair between two stacked blocks. I want to allow a vertical force to transmit from one block to another but not a horizontal force, thus I am looking at roller boundary conditions between the two blocks.

How do roller contact pairs differ from regular roller boundaries?

Thanks

export single streamline data with the corresponding field in it

Wed, 25 Aug 2021 16:17:29 +0000

Hi all, I am looking for a way to export the electric field along a single chosen streamline (and preferably to get both on the the same file). I can generate a single streamline on its own and the electric field map (for the entire geometry) on its own but didn't see anyway to get them both together. Even just getting the field data for that streamline on its own will be a huge help.