On 5/27/19 11:01 AM, Muhammad Mashhood wrote: > I am working with deal.ii step-26 to implement temperature > dependent thermal diffusivity. Currently for thermal diffusivity values > > order of 1e-2 the results are quit satisfactory but if I use the low thermal > diffusivity values like the order of 1e-6 to 1e-3, I get temperature > oscillations (temperature going to -ve value even with all positive > temperature initial and boundary conditions in domain and at boundaries). > If anyone has faced the same issue in thermal conduction simulations or knows > the criteria to keep simulation stable in terms of thermal diffusivity, time > step and mesh size then kindly suggest and share the opinion. Thank you in > advance!
In the limit of no thermal diffusivity, your equation ends up as an ordinary differential equation and that means that you lose stability in the H^1 norm -- in other words, you will get oscillations. That's just part of the nature of the equation. What is the situation you are trying to model that leads to such a small diffusivity? Best W. -- ------------------------------------------------------------------------ Wolfgang Bangerth email: [email protected] www: http://www.math.colostate.edu/~bangerth/ -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/84cc645b-9b75-79ec-8c3b-53d428ab8fc8%40colostate.edu. For more options, visit https://groups.google.com/d/optout.
