Problem Setup Guidelines

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Problem Setup Guidelines

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In posing any problem for FlexPDE, there are some guidelines that should be followed.

Start with a fundamental statement of the physical system.  Descriptions of basic conservation principles usually work better than the heavily massaged pseudo-analytic "simplifications" which frequently appear in textbooks.


Start with a simple model, preferably one for which you know the answer.  This allows you both to validate your presentation of the problem, and to increase your confidence in the reliability of FlexPDE.  (One useful technique is to assume an analytic answer and plug it into the PDE to generate the source terms necessary to produce that solution.  Be sure to take into account the appropriate boundary conditions.)


Use simple material parameters at first. Don't worry about the exact form of nonlinear coefficients or material properties at first.  Try to get a simple problem to work, and add the complexities later.


Map out the domain.  Draw the outer boundary first, placing boundary conditions as you go.  Then overlay the other material regions.  Later regions will overlay and replace anything under them, so you don't have to replicate a lot of complicated interfaces.


Use MONITORS of anything that might help you see what is happening in the solution.  Don't just plot the final value you want to see and then wonder why it's wrong.  Get feedback!  That's what the MONITORS section is there for.


Annotate your script with frequent comments. Later you will want to know just what it was you were thinking when you wrote the script.  Include references to sources of the equations or notes on the derivation.


Save your work.  FlexPDE will write the script to disk whenever you click "Domain Review" or "Run Script".  But if you are doing a lot of typing, use "Save" or "Save_as" to protect your work from unforeseen interruptions.