Timeline for NDSolve DAE with Constraints
Current License: CC BY-SA 4.0
11 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jun 3, 2018 at 18:53 | comment | added | 407PZ | It appears that I have to accept 5 10^-2, although the accuracy in the real problem might be not very satisfying. It's really pity to see that NDSolve has difficulty to deal with some DAEs (especially in my case). | |
| Jun 3, 2018 at 12:34 | comment | added | bbgodfrey | @407Peezy With respect to your second comment here, running the second block of code in my answer on the complete tae does not give me an NDSolveValue:: mconly error. Instead , it gives me an NDSolveValue::ndsz error, indicating stiffness. The IDA algorithm as implemented in Mathematica does not appear to have am option for dealing with this problem. Instead, all three answers that stay with your original DAE system increase the lower bound of Clip to circumvent it. The question is, can you live with a lower bound of, say, 5 10^-2? | |
| Jun 3, 2018 at 11:52 | comment | added | bbgodfrey | @407Peezy Twelve seems like a manageable number, especially if the algebraic variables are single-valued functions of the other variables. If not, then care will be needed to follow the correct branches of the algebraic variables, especially if they cross. But, that could be true in the original differential-algebraic system too. | |
| Jun 3, 2018 at 10:48 | comment | added | 407PZ | There are 12 differential equations and 12 algebraic ones | |
| Jun 3, 2018 at 4:27 | comment | added | bbgodfrey | @407Peezy Don't be too quick to dismiss using functions to eliminate algebraic equations. How many differential equations and how many algebraic equations are included in your complete problem? | |
| Jun 3, 2018 at 1:17 | history | edited | bbgodfrey | CC BY-SA 4.0 | added final sentence |
| Jun 3, 2018 at 0:55 | history | edited | bbgodfrey | CC BY-SA 4.0 | added Addendum; corrected a line of code |
| Jun 3, 2018 at 0:05 | comment | added | 407PZ | However, I have to admit, it seems that the ODE solver is really more stable than the DAE solver. | |
| Jun 3, 2018 at 0:03 | comment | added | 407PZ | And the to 2nd part. Although it runs to the end with 3 10^-3 in the simplified version, it still fails to run to completion for the full interpolated function tae[tau]. mconly still appears. | |
| Jun 3, 2018 at 0:01 | comment | added | 407PZ | Thanks for your answer. However, like already mentioned, the real problem cannot be easily rewritten into pure ODE system. Thus, it would be better, if it doesn't require to transform the DAE system into ODE system. | |
| Jun 2, 2018 at 23:47 | history | answered | bbgodfrey | CC BY-SA 4.0 |