| Author | Message | ||
     Ramki raman (greenoaks) New member Username: greenoaks Post Number: 1 Registered: 05-2005 |
I am simulating laser heating and would like to incorporate materials properties that vary with temperature. One such case is when a material has a laser absorption coefficient a1 below temperature T1 and another different one, a2, above T1. How can this be incorporated? Thanks RK | ||
| Robert G. Nelson (rgnelson) Moderator Username: rgnelson Post Number: 370 Registered: 06-2003 |
As you will see from the documentation and examples, material parameters can be defined by any arithmetic expression or cascade of definitions which the mind of man can conceive, including table lookups. You could, for example, define A = if Temp < T1 then A1 else A2 This would NOT be a good idea. FlexPDE controls the timestep by watching the smoothness of the variables in time. Discontinuous parameter values introduce high frequency components into the solution, causing instabilities and slow integration. You should always program a continuous function with a transition width that is reasonable in the context of the current problem. The built-in functions SWAGE and RAMP (see the Help index) allow you to define a "fuzzy IF" that is much better behaved. Other mathematical expressions, like ARCTAN, could be used to achieve the same effect. Alternatively, you could define a table of absorption coefficients that jumps from A1 to A2 over some sensible temperature difference. |