COMSOL Intro


An important thing to remember about COMOSL 4.0 is that this interface employs the use of right clicks as shortcuts. One of the big changes from the old COMSOL gui to the new one is the suppressed menus; the upshot is a simpler looking interface… though sometimes finding stuff can be difficult. That said just don’t forget to look for menus by right clicking.

Start Up

COMSOL Multiphysics 4.0a (Classkit License) is the specific breed of software we will be using. After entering the program there should be a screen like this:

There’s a couple of things to get used to here but mainly just focus on the left hand menu bar… we are going to select a geometry there. The example problem we have is the handout given on Tuesday. If you don’t have it, just keep reading.

Model Selection

We are going to start off with a 2D model with three domains (regions). Here are the steps:

  1. COMSOL Multiphysics 4.0a (Classkit License) startup
  2. Left hand column, under Model Wizard, go ahead and Select Space Dimension (click on 2D and press the advance arrow at the top of the Model Wizard bar)
  3. Left hand column, under Model Wizard, let’s pick a physics… under Chemical Species Transport select Transport of Diluted Species. Select the type and then click the advance arrow.
  4. Left hand column, under Model Wizard, if you will Select Study Type… that’d be stationary. Try to suppress the urge to select time dependent, we can be men later. Click the flag to finish your model selection.
  5. Now left hand column, select the Model Builder tab. You’re done!

Here’s your screen if you have followed the steps:

Geometry

The subject I kicked my big brother’s butt in. Anyway let the first thing that you notice on your screen (or the second) be that along the top bar there are a good number of icons for building a certain type of geometry. You can use those, but the old COMSOL used to have an interface where you could input your dimensions of the geometry by points and side lengths, radii… basically a less visual but often more precise method. That still exists in COMSOL but it’s under the right click menus. Try this out:

  1. Left hand column, under Model Builder, left click once on Geometry then right click on Geometry to bring up the right click menu.
  2. Select rectangle and aha! there is that menu that let us build stuff.
  3. Put in values for your rectangle: height = .8 and width = .2.
  4. Press enter and… nothing happens. You need to Build All, it’s under that left hand column near the top… it looks like a building.

Boundary Conditions

Let’s have a short talk about this stuff… like what was said before, the right click menus are important here. We’ll do a sample and then suppose that the rest are similar. Check it out:

  1. Left hand column, under Model Builder, left click Transport of Diluted Species (chds) then right click the highlighted selection and a list of BCs come up.
  2. Try Concentration and check the Species C checkbox. Enter the concentration the desired concentration.
  3. Go into your Graphics window and select a boundary, then click the + button. If you have done it correctly your boundary number shows up in your list.

Here is where you can set certain physical properties like bulk density, porosity… etc. Just try to find the appropriate condition where you would find your value and it’s likely there. Do not forget to press the + or your changes will not take place.

Solution

Let’s mesh:

  1. Left hand column, under Model Builder, let’s right click the Mesh category
  2. Select your mesh
  3. Top right corner of the left hand column, Build All… it’s the building… haha.

Now your meshed. Let’s solve this puppy:

  1. Left hand column, under Model Builder, right click the category for Study.
  2. Compute

That’s it… I think there’s a COMSOL help manual somewhere crying tears of blood and shaking it’s head at me right now. Toododoloose.

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About pavlovsr

I'm a college student, just here to get some stuff out. Hope this helps. View all posts by pavlovsr

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