COMSOL 4.2 Tutorial potx

COMSOL 4.2 Tutorial COMSOL Multiphysics (formerly FEMLAB) is a finite element analysis, solver and Simulation software / FEA Software package for various physics and engineering applications, especially coupled phenomena, or multiphysics. COMSOL Multiphysics also offers an extensive interface to MATLAB and its toolboxes for a large variety of programming, preprocessing and postprocessing possibilities. The packages are cross-platform (Windows, Mac, Linux,Unix.) In addition to conventional physics-based user-interfaces, COMSOL Multiphysics also allows for entering coupled systems of partial differential equations (PDEs). How to create a new model in COMSOL 1. Start COMSOL Multiphysics 2. Work through the COMSOL Model Wizard which will require you to select the coordinate system for the model, the relevant physics to the problem, and the type of study you wish to perform (Time dependant or stationary). 3. Define the parameters, equations and variables pertinent to the model (sub directory (Global Definitions). 4. Define the geometry of the model (Geometry). 5. Select the materials you wish to use in your model (Materials). 6. Select the boundary, bulk and initial conditions for your system for each physics you are using (This will be entered separately for each different physics you are using e.g. you will need to enter these for Laminar Flow and again for Heat Transfer if you are using both ). 7. Choose the element size to be used (Mesh). 8. Adjust solver parameters and compute (Study). 10. Display the desired results in the most meaningful way (Results). Not all of these steps are always necessary when building a model. The order is also variable depending on the complexity of the model. Example 1. (Heat transfer) Consider a cylindrical heating rod which is sheathed by a concentric tube of thickness 0.05 m and which starts 0.05 m away from the center. The entire assembly is immersed in a fluid and the system is at steady-state, as shown below. We wish to determine the temperature distribution within the sheath. After thinking about the problem, assume that we arrived at the following approximations (make sure you understand how we arrived at following approximations for your future quiz and test): The temperature of the heater is constant at 400K. The temperature at R1 is the same as the temperature of the heater, 400K. The fluid temperature is constant at 300K and this is the temperature of the surrounding sheath at R2. Given that heat diffusion should be the same at any given θ it is reasonable to define this problem in 2D as follows. Solution using COMSOL: Startup 1. Start COMSOL by clicking the COMSOL Multiphysics 4.2 icon. 2. When COMSOL starts, the Model Wizard will be open automatically. This wizard asks you to define the spatial dimension you’ll be using for the model as well as the applicable physics and the type of study you wish to perform (either time dependant or stationary). For this problem start by selecting 2D, continue by clicking the blue, right pointing arrow at the top right of the Model Wizard screen. 3. Next select the applicable physics for the model. In this case heat transfer in solids will be selected. This can be found under the Heat Transfer module. Click the triangle to the left of the Heat Transfer module to see the drop down menu which contains Heat Transfer in Solids, left click this so that it is highlighted then click the blue, right pointing arrow at the top right of the Model Wizard menu screen. Multiple physics can be added to a single model by left clicking the physics to add and then left clicking the blue + sign at the bottom left of the Model Wizard menu screen. 4. The final step in the Model Wizard is to select the type of study you would like to perform on our model. In our case stationary will be sufficient to find the steady state solution to this problem. As with the physics add the stationary study by left clicking on “Stationary” below the preset studies icon. Click the finish flag at the top right of the Model Wizard to finish startup. Model Builder and Saving Now that we are finished with the Model Wizard we will turn our attention to the Model Builder portion of the program. This is just to the left of where the Model Wizard had been. Before we continue with the Model Builder let us take a second to save our model. This is done by clicking “File” at the top left of the screen and then selecting “Save As” as is the case with most programs. This file will be named “Heat Transfer Example”. By default COMSOL will save all COMSOL files in a folder it creates called COMSOL42 however this folder name will change with the version of COMSOL being used. After giving our file a name and clicking the save button seen in the above image notice that the first icon within the model builder now has the name of our file. From this point on we can essentially just work our way down the Model Builder’s list of options filling in values and conditions where we need them. Geometry Now we are ready to add the geometry of the model. This is very simple because our assumptions have placed the problem into only 2 dimensions. Our geometry consists of only of a rectangle. 1. To create this rectangle first find the geometry icon in the model builder menus and right click it, this will bring up the menu shown at right. 2. Find the “Rectangle” button in this new menu and left click this. 3. At this point the rectangle has been added, however the dimensions of this rectangle need to be changed to fit the dimensions in the problem. We do this by left clicking the white rectangle just to the left of the geometry icon. This will expand the geometry tab to show all the sub tabs contained within geometry. If you added the rectangle correctly you will see the tab called Rectangle 1. This contains all the information regarding this object and to adjust the dimensions and position of this rectangle this is where we do so. Left click the tab labeled Rectangle 1. 4. If you have completed the above steps successfully your screen should resemble the one above. Notice that by default the corner of the rectangle has been placed at the origin (position x= 0, y =0) and given width and height of 1m. For this problem the height needs to be 5 cm (0.05 m) and the width needs to be 30 cm (0.3 m). Enter these values into the designated fields and press the blue building icon at the top right of the rectangle menus. This is the “Build All” button and will add your rectangle to the model. 5. To get the graphical interface of COMSOL to center on the rectangle and adjust the axis bounds click the “Zoom Extents” button Materials To give the rectangle thermal properties such as heat capacity and thermal conductivity we can either add these directly under the “Heat Transfer” tab or by selecting a material to build the rectangle from. In this problem we will make our rectangle out of copper and we will do this using the “Materials” tab. 1. Left click on “Materials” tab and then left click “Materials Browser”. Your screen should look like the screen below. 2. As can be seen above the “Material Browser” has a search bar that allows you to enter the name of the material in question and COMSOL will find any matches within its database. Enter copper into the search bar and click search. 3. Open the “Built-In” tab and then right click “Copper”. Your screen should now look like the one below. Left click “Add Material to Model”. You have now added copper to all domains by default which means the rectangle now has the properties of solid copper. [...]... image to the right We now need to specify a value and a location for our temperature boundary conditions Let’s start with the warm surface Start by left clicking “Temperature 1” The interface region of COMSOL should now look like the image at left We need to do 2 things here The first is to add the surface to which we wish to apply this boundary condition and the second is to give a value to this temperature... right of the “Cut line 2D” screen to have the cut line displayed Your cut line should look like the one below 4 We now need to add a “1D plot group” to the results As you may be beginning to realize COMSOL uses a right click interface for addition of most options So right click “Results” and left click the “1D plot group” 5 We want to add a line graph to our “1D plot group”, so to do this right click... rectangular coordinates To avoid redundancy only the steps that are significantly different from those in example 1 will be explained in detail Startup 1 You will need to start a new model either be restarting COMSOL or by clicking “New” in the “File” menu 2 You will now select “2D Axisymmtric” instead of simply 2D This will take whatever geometry you create and rotate it about an axis and is ideal for problems . reasonable to define this problem in 2D as follows. Solution using COMSOL: Startup 1. Start COMSOL by clicking the COMSOL Multiphysics 4. 2 icon. 2. When COMSOL starts, the Model Wizard will. Transfer Example”. By default COMSOL will save all COMSOL files in a folder it creates called COMSOL4 2 however this folder name will change with the version of COMSOL being used. After giving. COMSOL 4. 2 Tutorial COMSOL Multiphysics (formerly FEMLAB) is a finite element analysis, solver and Simulation