COMSOL Exchange

Parallel plate capacitor COMSOL 4.0

Thu, 29 Jul 2010 09:45:46 +0000

This example show the electrostatic potential and electric fields in parallel plate capacitor with air gap.
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Model by Michal Jedrzej Radziwon

Non parallel plate capacitor COMSOL 4.0

Thu, 29 Jul 2010 09:45:30 +0000

This example show the electrostatic potential and electric fields in capacitor which plates are tilted and separated with air gap.
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Model by Michal Jedrzej Radziwon

CoBoGUI - An open source graphical user interface for two dimensional solar cell simulations with Comsol Multiphysics and Matlab

Tue, 22 Jun 2010 18:19:18 +0000

CoBoGUI is a freely available collection of MATLAB scripts for

two dimensional solar cell simulations with COMSOL Multiphysics and MATLAB.

It proviedes a flexible graphical user interface and can be

downloaded from the ISFH-Homepage:

http://www.isfh.de/institut_solarforschung/software.php?dm=1&&_l=1

[SM v3.5a] Rotation constraints in structural module. With complements

Fri, 30 Apr 2010 14:53:05 +0000

There are different boundary constraints in COMSOL structural, but in 2D/3D structural (smpn, smsld ...) there are no angular variables predefined, hence no easy way, as in the Euler beam modules, to enforce angles.

The present model (BeamRotz_4) illustrates 2 ways to constrain the rotation of a gravity loaded beam (by comparing Euler beams and SMPN beam results).

These are either by constrining the angles (which gives very wrong reaction forces) and a cleaner way by applying an external torque until the angle is restrained, through an optimisation approach, as per smeug.pdf p69 v3.5a.

Note:
I use reacf() reaction forces in there for the Torque calculations, so if you need the weak constraints you might get an error message, these reaction forces could be replaced by, albeit supposed to be less accurate, traction forces, or just the lm's.

Further explanations are given in the model properties.

I have added a second "PN" (BeamDispForce_1) and a third "SMPN" (BeamDispForce_smpn_1) example comparing displacement constraints and coupled force & moment load adapted by COMSOL to obtain the same constrained displacement, all on a fixed-free beam in 2D. Further explanations are given in the model properties. THe cntact case is active in the SMPN model. Porting to 3D is almost trivial ;)

Have fun COMSOLing
Ivar

[SM 3.5a] 3D Euler Beam Properties Calculations

Fri, 30 Apr 2010 14:52:43 +0000

3D Euler Beam based FEM models calculate quickly and are very usefull for design otimisation and conctual design phases.

In COMSOL, as most FEM codes, 3D Euler Beams require the input of quite some beam properties data to calculate correctly. But in fact all of them can be solved by COMSOL once the geometry section is correctly sketched in a 2D geometry. In particular "J" the "Torsional Constant", or often called St. Venenat Torsion Constant, can be quite tricky to assess and is often confused wrongly with the polar moment.

Please note that "warping" effects are not explicitely considered herein.

A general procedure and a few COMSOL model examples are given for full and hollow beam sections, on how to use COMSOL to calculate these theoretical torsion constant values.

The pdf presentation is closing with a summary slide, mentioning a few possible improvements for COMSOL to sped up the use of 3D Beam model set-up.

I wish you a pleasant reading,
and pls do not hesitate to report back any errors or possible improvements

A MatLAB-based tool for handling Tessellated Free Shape Objects with a Morphing Mesh Procedure

Mon, 08 Feb 2010 16:59:23 +0000

Description:
This is a fully MatLAB-based tool, called ProMESH, allowing to handle tessellated models (in .STL ASCII file format). Open imported tessellated model may be thickened.
Geometry shape may be modified through a morphing approach.
MatLAB’s GUI allows to pick any control point belonging to the imported geometry and set the relative influence hull, by controlling its sizes and orientation.
The influence hull is assumed as an ellipsoid. The morphed shape may be easily tuned and controlled by modifying any control points of the piece-wise Bezier curve (weight function).
Once the tessellated model is ready, EXPORT button creates the Comsol geometry object (and it is saved into MatLAB workspace), ready to be processed.

Implementation:
ProMESH was developed under MatLAB 2007b and it seems to work well also with MatLAB 2009b.
Comsol Multiphysics must be run with MatLAB.
See [Franciosa, P., Gerbino S., Handling Tessellated Free Shape Objects with a Morphing Mesh Procedure in Comsol Multiphysics®, in Proc. of COMSOL Conference’09, Milano (Italy), October 14-16, 2009].

How to use:
Unzip “Matlab functions.rar” file and run “MainGUI.m”. Model “demofile.stl” may be used just to begin.
A video example, related to the application described in the above paper, is also provided.

Local Drug Delivery by Infusion through a Multi-hole Sprinkler – 3D Model for a Prototype Bioartificial Pancreas Device

Tue, 08 Dec 2009 21:59:51 +0000

This is a fully scaled 3D model built to explore the feasibility of localized drug delivery by infusion through a central sprinkler with multiple, non-axial-symmetric holes into a rodent prototype biohybrid device intended for islet transplantation. It uses a combination of COMSOL’s convection & diffusion and incompressible Navier-Stokes fluid dynamics application modes to obtain an approximate description of drug distribution due to both convective and diffusive fluxes. It served to obtain first estimates of the doses and inflow rates required to achieve and maintain concentrations that are within the expected therapeutic range for most of the volume of the cylindrical device so that localized immunosuppression might be achievable. The model is for a steroid-sized drug (D = 6x10-10 m2/s) delivered at a concentration of 20 microM with a constant influx rate (0.25 microL/h) that can be achieved, for example, with implantable Alzet® osmotic mini-pumps. Details of the model are described in the Proceeding of the COMSOL Conference 2007 Boston as well as in a related paper in Pharmazie 2008, 63, 226. This is a time-dependent model (transient analysis); the stationary solution can be obtained by using the solution from a large enough time (t > 10 h) as starting point.

Square drop oscillation under surface tension – 2D axi-symmetric model

Wed, 18 Nov 2009 16:19:35 +0000

This model is concerned with the simulation of incompressible Newtonian fluid flow problems with surface tension. An initially cubic drop of water is oscillating under surface tension forces. This model is developed for a 2D axi-symmetric transient analysis. The movement and deformation of the computational domain are accounted for by employing the Arbitrary Lagrangian-Eulerian (ALE) description of the fluid kinematics.
The implementation of the model is detailled step by step in the pdf file. To visualize the solution, you need to solve the model (click the solve button).

Deformation of free surface under pressure– 2D model with surface tension

Wed, 18 Nov 2009 11:48:15 +0000

This model is concerned with the simulation of incompressible Newtonian fluid flow problems with surface tension. The fluid is initially at rest in a square tank. A Gaussian pressure is applied on the free surface which deformed the initially flat surface. This model is developed for a 2D transient analysis. The movement and deformation of the computational domain are accounted for by employing the Arbitrary Lagrangian-Eulerian (ALE) description of the fluid kinematics.
To visualize the results, you need to solve the comsol file.

Electrokinetic Motion of a Nonspherical Particle in Microfluidic Channel

Thu, 05 Nov 2009 13:49:01 +0000

This script file follows the motion of a nonspherical particle in a fluid filled microchannel moving under the action of an applied electric field. The channel surfaces and the particle posses a native surface charge (zeta potential), so that the electric field causes both the bulk fluid and the particle to translate along the channel. The transient incompressible Navier-Stokes mode accounts for the fluid motion, while the conductive media DC mode determines the electric field. The ALE moving mesh mode deforms the mesh to allow the particle to translate. Boundary integration coupling variables calculate the forces and torques exerted on the particle, while ODEs are used to calculate the velocities and translations.

A script file was used so that the process of creating new geometry from the deformed mesh and then meshing the new geometry could be automated. The model seeks to track the motion of the particle over a very large displacement, in this case upwards of 50 remeshes were required. The script file can be executed by Comsol Script (versions prior to 3.5), with Matlab+Comsol Multiphysics, or through batch mode of Comsol Multiphysics.

The script file used to model this motion is included, as is a movie file that demonstrates the motion of the particle through the channel (the background in the movie is the electric field strength).

This material is based upon work supported by the National Science Foundation under Grant No. 0348149.

Magnetic Circuits - Two-loop Magnetic Circuit

Fri, 16 Oct 2009 21:26:33 +0000

This simulation calculates the magnetic flux in a two-loop magnetic circuit with an air gap.

Model developed by Dr. Konrad Walus and Carl Tan

http://www.mina.ubc.ca/konradw_comsol_magnetostatics

Magnetic Circuits - Single Loop Circuit

Fri, 16 Oct 2009 21:25:46 +0000

This simulation calculates the magnetic flux in a single loop magnetic circuit with an air gap.

Model developed by Dr. Konrad Walus and Carl Tan

http://www.mina.ubc.ca/konradw_comsol_magnetostatics

Magnetostatic Examples - Parallel Wires Carrying Current in Opposite Direction

Fri, 16 Oct 2009 21:23:37 +0000

This simulation calculates the magnetic field intensity around two parallel wires both carrying current in the opposite direction. Notice that the magnetic field outside the wires is reduced while the magnetic field between the wires is enhanced. As a result, the wires are repelled from each other.

Model developed by Dr. Konrad Walus and Carl Tan

http://www.mina.ubc.ca/konradw_comsol_magnetostatics

Magnetostatic Examples - Parallel Wires Carrying Current in Same Direction

Fri, 16 Oct 2009 21:22:43 +0000

This simulation calculates the magnetic field intensity around two parallel wires both carrying current in the same direction. Notice that the magnetic field outside the wires adds up while the magnetic field between the wires cancels. The force acting upon the wires can be found using Lorentz force, which predicts that the wires will be attracted to each other.

Model developed by Dr. Konrad Walus and Carl Tan

http://www.mina.ubc.ca/konradw_comsol_magnetostatics

Faraday's Cage Examples - External Field

Fri, 16 Oct 2009 21:19:37 +0000

In 1836 Michael Faraday observed that the charge on a charged conductor resided only on its exterior and had no influence on anything enclosed within it. Since in a perfect conductor, no electric field can exist within the conductor, charges are redistributed at the surface of the conductor such that the location of a charge within the cage has no influence on the distribution of field on the outside of the cage. Note that the total surface charge on the outside of the cage is equal to the total charge within the cage.

The image is Faraday's cage with an electric field outside of the cage.

Model developed by Dr. Konrad Walus and Carl Tan

http://www.mina.ubc.ca/konradw_comsol_electrostatics

Faraday's Cage Examples - Corner Charge

Fri, 16 Oct 2009 21:16:47 +0000

In 1836 Michael Faraday observed that the charge on a charged conductor resided only on its exterior and had no influence on anything enclosed within it. Since in a perfect conductor, no electric field can exist within the conductor, charges are redistributed at the surface of the conductor such that the location of a charge within the cage has no influence on the distribution of field on the outside of the cage. Note that the total surface charge on the outside of the cage is equal to the total charge within the cage.
Central Charge

Model developed by Dr. Konrad Walus and Carl Tan

http://www.mina.ubc.ca/konradw_comsol_electrostatics

Faraday's Cage Examples - Central Charge

Fri, 16 Oct 2009 21:15:46 +0000

In 1836 Michael Faraday observed that the charge on a charged conductor resided only on its exterior and had no influence on anything enclosed within it. Since in a perfect conductor, no electric field can exist within the conductor, charges are redistributed at the surface of the conductor such that the location of a charge within the cage has no influence on the distribution of field on the outside of the cage. Note that the total surface charge on the outside of the cage is equal to the total charge within the cage.

Model developed by Dr. Konrad Walus and Carl Tan

http://www.mina.ubc.ca/konradw_comsol_electrostatics

Capacitor Examples - Microstrip

Fri, 16 Oct 2009 21:13:58 +0000

A Microstrip is a thin electrical conductor separated from a ground plane by a dielectric layer. Microstrips are used in printed circuit boards. The calculated capacitance of this capacitor is 2.14*10^-10F/m. Using an analytic formula for microstrips, the result is 2.1766*10^-10F/m, an error of 2%.

Model developed by Dr. Konrad Walus and Carl Tan

http://www.mina.ubc.ca/konradw_comsol_electrostatics

Capacitor Examples - Capacitor with Non-Parallel Plates

Fri, 16 Oct 2009 21:12:53 +0000

In this example, two conductors are rotated by an angle phi. The calculated capacitance using COMSOL of this capacitor is 9.9528*10^-11F/m. If we assume that there is no fringing we can manually calculate the capacitance to be 9.758*10^-11F/m, an error of 3%.

Model developed by Dr. Konrad Walus and Carl Tan

http://www.mina.ubc.ca/konradw_comsol_electrostatics

Capacitor Examples - Capacitor with Non-Uniform Dielectric

Fri, 16 Oct 2009 21:11:26 +0000

In this example, the electrostatic potential, electric field, and capacitance of a parallel plate capacitor with non-uniform dielectric is calculated. This capacitor is modeled with 2 conductors and 6 sub-domains of dielectric material. 3 of the sub-domains have a dielectric constant of 12 (Silicon), while the other 3 have a dielectric constant of 1 (vacuum). Notice the changes in electric field within the dielectric that result from the different dielectric constants. The capacitance of this capacitor was calculated to be 5.1677*10^-11F/m.

Model developed by Dr. Konrad Walus and Carl Tan

http://www.mina.ubc.ca/konradw_comsol_electrostatics