COMSOL Exchange

Finite Elements to Computational Engineering Sciences

Thu, 18 Apr 2013 13:34:16 +0000

This site develops discrete implementations of WS theory for diverse variety of problem statements
in the computational engineering sciences. Unique to the FE discrete development, the resulting
algorithms are immediately stated in computable form via a transparent object-oriented programming
syntax. The engineering science problem classes developed herein include.

1. heat conduction
2. structural mechanics
3. mechanical vibrations
4. heat transfer, with convection and radiation
5. fluid mechanics
6. heat/mass convective transport

For more information, please see: www.wiley.com/go/baker/finite

UG Course Projects in Biomedical/Biological Transport Processes

Thu, 28 Mar 2013 21:51:48 +0000

A project-based course (taught since 1996) to help undergraduates think of computer simulation as an important practical tool in design and research projects in the industry as well as academia. Student groups come up with project ideas on their own and go through problem formulation all the way to parametric sensitivity analysis. COMSOL has drastically improved the computation capabilities and ease of use so that we can introduce more realistic physics, multiphysics or complex geometry and spend more time on model validation, written and oral communication, and design. All project reports are at https://courses.cit.cornell.edu/bee4530/pastprojects.html.

A textbook integrates instruction of how to model transport processes (problem formulation, etc.) with COMSOL use (http://www.cambridge.org/us/knowledge/isbn/item2703298/?site_locale=en_US). The newcomer to modeling and/or COMSOL can use the Case Studies in this book to self-learn modeling in biological/biomedical applications.

Plasmaline (microwave SWP)

Tue, 26 Mar 2013 05:31:53 +0000

This is a basic model of a surface wave type microwave Argon plasma. (2D-axisymmetric)(the rest is taken over from the library model)

It is called Plasmaline by its producer.

70 Pa Argon at 500W and 2,45GHz

i have now, something I called a plasmafinger that went to the end of calculation.
but the time step are really small (1e-9 in average), so it took more than 4 days.
(finger-upload.mph)

I have problems in measuring the absorbed power by the plasma?

Any comments?

Thanks

Mie scattering off plasmonic nanoparticles

Tue, 19 Mar 2013 21:22:58 +0000

This is a general model to simulate light scattering off plasmonic or dielectric nano-particles or spherical nano-structures. I computed the total scattering cross-section (SCS), absorption cross-section (ACS), extinction cross-section (ECS), radar cross-section (RCS) and differential scattering cross-section (dSCS) of gold nanoparticles in the near UV, visible and near infrared range. Material properties are taken from peer-reviewed experimental data (P. B. Johnson and R. W. Christy, “Optical Constants of the Noble Metals,” Phys. Rev. B, vol. 6, no. 12, pp. 4370–4379, Dec. 1972). The model can be used as a starting point to compute the absorption and scattering properties of more complicated structures or metamolecules, with broken spherical symmetry and several constituents. This model completes the tutorial file "Optical Scattering off of a gold nano-sphere", by providing efficient ways to compute the total cross-sections. The obtained results match analytical predictions based on Mie theory.

NB : Models compatible with COMSOL 4.3 and 4.3a are available.To visualize the results, you may need to run the file.

Modeling of Binder Removal by Diffusion from Ceramic Green Body

Mon, 14 Jan 2013 20:52:45 +0000

Modeling of Binder Removal by Diffusion from Ceramic Green Bodies
David G. Retzloff and Stephen J. Lombardo, University of Missouri

This presentation delves into the fabrication of ceramic components via powder processing and the removal of the binder that aids in the processing of the ceramic green body. It begins with an introduction to the components involved in the process, and continues with the governing equations used for one-dimensional binder removal, decomposition reaction rate, as well as the relationships between weight fraction, volume fraction, specific volumes V1 and V2, and concentration as pertinent to the binder removal process. The presentation presents a step-by-step guide for how to model this in COMSOL.

David G. Retzloff
Department of Chemical Engineering, University of Missouri
Presently an associate professor in the Chemical Engineering Department at the University of Missouri, David G. Retzloff received his PhD, MS, and BS from the University of Pittsburgh. He has previously worked as a consultant for AT&T and as a research engineer for Exxon. His focus is on analysis of dynamic systems.

Stephen J. Lombardo
Department of Mechanical & Aerospace Engineering, University of Missouri
Currently a professor in the Mechanical and Aerospace Engineering Department at the University of Missouri, Stephen J. Lombardo received his PhD from the University of California-Berkeley, and a BS from Worcester Polytechnic Institute. His industrial experience includes Saint-Gobain Corporation and CeraMem Corporation. He focuses on Ceramic Materials and Ceramic Processing, Electronic Ceramics, and Transport Phenomena and Kinetics.

UG Reserarch Projects with Professor Bruce A. Finlayson

Mon, 14 Jan 2013 18:15:06 +0000

This web site
http://www.chemecomp.com
provides results of studies of microfluidic devices, to determine mixing properties, flow properties, and correlations and design information for laminar flow. The students were Dreyfus Undergraduate Research Scholars, under the Senior Mentor Program awarded to Professor Finlayson by the Camille & Henry Dreyfus Foundation, Inc.

The web site also has links to information about Comsol that goes beyond the book, Introduction to Chemical Engineering Computing, 2nd ed., Wiley (2012).

Electromagnetic and hydrodynamic transient coupling

Mon, 17 Dec 2012 14:01:18 +0000

In this model transient electromagnetics and hydrodynamics are coupled
in a so-called strong MHD coupling in a 2D axisymmetric geometry, with
k-epsilon RANS turbulence equations for the fluid flow.

This model focuses on the strong coupling process involved and no
specific checking regarding solver or mesh convergence analysis has been
performed here. Moreover, there is no special treatment of the Hartmann
boundary layer (interaction between the fluid boundary layer and the
transverse magnetic field). Default wall functions available with
k-epsilon model have been used, together with a continuity in the
magnetic vector potential Aphi at the wall. Aphi is in this model not
modified by the turbulent boundary layer.
To be successful, one should take into account that good initial
conditions for the fluid flow must be provided to the time-dependent
solver. This process makes use of 5 stationary steps.
It is possible to use fewer stationary steps, however it may cause more
convergence errors (Tfails and NLfails) or even not converge at all.

Also, one should adjust the time-dependent solver by segregating the
magnetic vector potential Aphi in a separated segregated step. Sometimes
it might be useful also to exclude algebraic degrees of freedom from the
evauation of error in the time-dependent algorithm. This is done in the
advanced options of the solver.

One should note that the conductivity of mercury if significantly
increased in order to better illustrate the physical phenomena that
appears at this moderate magnetic Reynolds number. Highly conducting
flow "takes" magnetic field in the direction of the flow and therefore
it is not symetric as it would be in case of zero velocity (magnetic
Reynods number 0). The full time-dependent solution reveals the
behaviour in time of this kind of strong coupling, which is not
frequently described in the literature.

Many thanks to Eric Favre, from COMSOL France, for his technical support
associated with this case.

Domain decomposition for hyperbolic equations

Mon, 08 Oct 2012 14:23:14 +0000

Domain decomposition for hyperbolic equations
Mikhael Balabane , Université Paris 13
Stephan Savarese, COMSOL France

This model shows how to solve an iterative algorithm using domain decomposition techniques.

Coefficient Form PDE u1 (c4) solves for u1
Coefficient Form PDE u2 (c) solves for u2
Coefficient Form PDE v1 (c2) stores u1 into v1
Coefficient Form PDE v2 (c3) stores u2 into v2
Then compute and iterate as follows:

1. Compute Init U
2. In LOOP > Step1 > Values of Variables not solved for : select Solution : Init U , then Compute
3. In LOOP > Step1 > Values of Variables not solved for : select Solution : LOOP, then Compute as many times as necessary to converge

2D-Cyclic Voltammetry Model: 1 electron 2 speicies dillute diffusion

Mon, 25 Jun 2012 19:30:26 +0000

A simple COMSOL mph cyclic voltammetry (CV) 2D time-dependent model was developed. The model presumes the electrode kinetics are described by a 1 electron transfer process. The transport of a reduced and an oxidized species is described by time-dependent mass transfer principles for diffusion under dilute conditions.

The model is that of a two electrode cell. The reaction at the working electrode is described by concentration dependent Butler-Volmer kinetics. The counter electroded is modeled so that it behaves like an ideal reference electrode.

As in an experimental CV study, the applied cell voltage sets the potential of the working electrode with respect to the reference electrode, in our case also the counter electrode. In the model, the potential of the counter electrode is set to that of the electrolyte at the electrode surface and that potential with respect to ground is set to zero. There is very little potential drop between electrodes in the electrolyte. There is no current flow in the counter electrode. Thus all of the cell's response to an applied potential is the result of changes between the working electrode and the electrolyte next to its active surface, exactly the outcome one looks for in selecting a reference electrode for CV studies.

The model is seen as a tool to help one interpret experimental voltammograms. In this regard, it must also be seen as template for building models with more complex electrochemistry conditions, e.g., multiple electron transfer processes, with chemical reactions and more complex mass transfer conditions. One can then form an hypothesis regarding the interpretation of an experimentally obtained CV, The COMSOL simulations will either bolster ones support for the interpretation or be proof that one needs a better hypothesis.

Another Pandulum (3d truss element)

Wed, 18 Apr 2012 15:00:11 +0000

Pandulum model using 3d truss element.
initial position is from (0,0,0) to (0,2,10).
(0,2,10) end is pinned.
(0,0,0) end has 10kg mass.
gravity is applied in -z direction.

analitical solution is approximated very well:
period =sqrt(Length/gravity)

the model image shows the y displacement vs time.

1D resonant quantum tunneling

Tue, 28 Feb 2012 10:44:03 +0000

The model sets up boundary conditions for the Schrödinger equation
in order to achive tunneling solutions. A resonant barrier potential is created with 1nm separation-width and 0.2nm oxide thickness barriers of 4eV. The result is plotted as the transmission coefficient t^2 vs. the energy (parametric solver). The resosnances are close to to the quantized levels for a particle in a box.

Zernike Polynomial extraction of deformed optical surface

Tue, 28 Feb 2012 07:43:00 +0000

You will find hereby a COMSOL Multiphysics v4.2a Solid + Optimisation model extracting the first dozen Zernike polynomials from a deformed circular surface, expressed in RMS values.

In optics, the expressions of the deformations of an optical surface, such as a mirror under gravity or pressure loads, are often decomposed in Zernike orthogonal polynomial coefficients.

Unfortunately, there are several normalisation of these polynomials, the different optical programmes uses each there own normalisation, so the results should be carefully benchmarked against each particular softeware you use. And pls be aware of the loong formulas, these might still contain typos ;)

The present normalisation is the one from J.C.Wyant, 2003, "ZernikePolonymialsForTheWeb" that can be found under www.mpia.de /AO/...

Have fun COMSOLING

Pyramidal Horn Antenna

Thu, 09 Feb 2012 02:48:32 +0000

We provide a convenient 3D RF model of a generic pyramidal microwave horn, with a simple user-adjustable (parameterized) geometry. The model was prepared with Comsol Multiphysics v4.2a with the RF module. The user may specify the input waveguide size (width and height), horn flare length, horn aperture dimensions, and some other useful settings, all as global definitions. Computational region, meshes, and frequency range are then defined automatically (but can also be modified by the user). Two symmetry planes are employed to speed up the computation. The model computes the gain, VSWR, and E-plane and H-plane far-field beam patterns.

2D transient pressure field from a boundary

Tue, 17 Jan 2012 11:13:07 +0000

This very simple 2D transient model uses the Acoustic Module to show how a pressure wave propagates in time.

The scenario is a simple 2D rectangle with one boundary acting as the source of the pressure field and the other 3 are given wave radiation boundaries so that there is minimum reflection.

The model is made up so that you can define:

1) The frequency of the pulse
2) How many pulses you wish to simulate

The model is handy as it shows you how to create a boundary condition which varies in time.

Also, the model has been made so that the mesh (which is frequency dependant) is generated automatically. I think its quite nice and should help with some basic models of acoustics.

This model is similar to the Gauss explosion model.

Also, please note that the time stepping has been defined in the global definitions> parameters along with other values.

Thanks goes to Glenston Miranda for the function.

Rob

ps, Check Pressure 1 for the function which defines the BC.

Loudspeaker Driver Electromagnetic v4.1

Fri, 27 May 2011 11:59:31 +0000

This model is the electromagnetic part of the Loudspeaker Driver model (http://www.comsol.com/showroom/gallery/1369/). The acoustic module is NOT required to open this model.

Low Reynold's k-epsilon model for Comsol v3.5

Thu, 31 Mar 2011 00:56:52 +0000

This implemented Low-Re k-epsilon Comsol model is based on the Launder-Sharma damping functions as described in Wilcox's Turbulence modeling for CFD book. Model implementation was in 2D under steady state situation but it can be extended to 3D with relative ease.

The variables solved in the model are U,V,P,k, and epsilt (epsilon tilde) using equation based modelling in general form.

The model also includes a k-e model from the chemical engineering module for comparison.

Hints: go to options-> expressions -> scaler or subdomain expressions to learn more about its implementation.

CoBoGUI - An open source graphical user interface for two dimensional solar cell simulations with Comsol Multiphysics v3.5 and Matlab

Sun, 13 Mar 2011 21:27:34 +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-website:

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

It can also be seen as a multi purpose batch GUI, since it can be used to batch any feasible Matlab function.

If you want to cite the CoBoGUI, please use following publication:
http://www.isfh.de/institut_solarforschung/files/25eupvsec_eidelloth.pdf

The CoBoGUI was created for Comsol v3.5a.

Edit: There is a new version for Comsol v4.1 available (in alpha state).

SPICE RCL-circuit with initial conditions

Tue, 05 Oct 2010 19:39:04 +0000

This model shows how to set up a SPICE model of a RCL-circuit in COMSOL4.0a with other initial conditions than default.

The SPICE (Electric Circuit, "cir") in COMSOL does not allow you to specify initial voltage of a capacitor or an initial current through an inductor.

This is a way of walking around this problem, using sub-circuits (External IvsU and UvsI) in combination with the equations of state for C and L in an "ODEs and DAEs"-node in COMSOL.

The tricky part is to find out what the variable name for the voltage across the inductor (mod1.cir.UvsI1_v) and the current through the capacitor (mod1.cir.X1_i) are, as these enters in the ODE's. One could find out these from the plot-menu: Results->1D Plot Group 1->Global 1->Expressions->(+)->Electrical Circuit->Voltage across device UvsI1 (mod1.cir.UvsI1_v).

Parallel plate capacitor COMSOL 4.0

Thu, 29 Jul 2010 15:45:46 +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 15:45:30 +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