Discussion Forum

Hi Greg,
Just like before, you can enter for your Initial Value an expression that is spatially dependent and/or you can also have several Initial Value nodes for different domains.
Do I misunderstand your question?
Best,
Jeff

Hi Jeff,
Actually, I need to be able input discrete initial values (i.e., I have no spatially dependent expression) within a domain. The reason is that I am approximating the heating of a food being rotated on a turntable in a microwave oven by discrete rotation steps. One step involves rotating the food a small angle, recalculating the microwave field, then allow heating to occur for a small time interval. The "initial" temperature for one step is the final temperature distribution of the previous step.

I was going to implement this using Livelink for Matlab, so that Matlab will handle the data manipulation between steps and set up the new step (new food position, initial values) in Comsol.

This has been done with other FEM packages, but it seems always with two different packages, one handling the actual FEM heat transfer modeling and the other handling the electromagnetic field setup. I'd like to be able to do this with Comsol alone, but I am stuck at how to transfer the output from the previous step (discrete temperatures within the food domain at one position) to the input of the next step (discrete initial values within the food domain at a slightly rotated position).

I thought of another way of doing this, but not sure if it would work. Instead of rotating the food within the oven, I thought it would be easier rotating the oven around the food. This would fix the food in space and eliminate the need to remap temperatures from the food's previous position onto the new position for the next heating step. But again, I'd have to make Comsol understand to retain the temperatures from the previous step for the next one.
Greg

I am no EM expert so there may be some fundamental reason not to do this that I don't know about, but my first instinct would be to perform a single time-dependent analysis with a moving geometry. Then the temperature distribution at the end of a particular time interval would automatically be the initial temperature distribution for the next time interval.
Jeff

I think I made this more complicated than it needed to be. At the very basic level, independent of any physics involved, if I have a table of coordinates within a domain and the associated temperatures at each of those coordinates, is there a way to input those to Comsol as an initial condition?

Yes, by using an interpolation function. See Reference Manual, version 4.4, page 245 for the details.
Jeff