Error message "This DAE appears to be of index greater than 1."

Hello

I'm getting following error message when solving a 3D parabolic PDE-Problem with solvepde:

"This DAE appears to be of index greater than 1."

I want to solve a thermal Problem, so...

1. I have imported a 8 Layer Geometry prepared in SolidWorks, with each layer stacked on top of each other.

2. I have defined c,f,d by functions, since I have different materials and Power is only generated in the first layer.

3. I have defined the boundaries as Neumann boundaries, only the bottom Face as Dirichlet, since I have a constant temperature there. I have checked the boundaries in my model.

4. Initial condition is defined. In fact, the initial temperature is the same as the Dirichlet boundary condition.

That is roughly my approach. Does anyone have an idea, why I get this error message?

Answer 1

[Baptiste]

Hello

Don't know about thermal problems but: This error mean that your problem involves derivatives a highest order than one (including flux derivative). On my experience, I encountered this issue because my problem was badly scaled. The jacobian of the probem is inverted somewhere in the program and it's rank numerically evaluated: if some parts of the jacobian are too small compared to others there are neglected and that was producing this error despite the index was one.

Regards

[MarionJ]

With badly scaled you mean the meshing?

[Deepa Elizabeth Eapen]

say for example, one variable varies in the order of 10^-3 (say concentration), and another varies in orders of 10^5 (say volume in ml or something). Then the system could be badly scaled.