PGK

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11 years, 183 days

MaplePrimes Activity


These are replies submitted by PGK

Hi Jacques, Indeed, I am now certain that that is the cause of the problem. There is no expectation that DAE will be able to tackle the system of equations in its present form. There is a solution that my colleges and I worked out late last night that will allow us to express the problem differently in terms of 27 linear constraints and 27 functions. That is a great improvement on the system I have been working with so far. I will be silent for a week or so while I work out the new details of the problem. But I will return with some updates. Thank you for taking the time to give me help. Best wishes, PGK
Being new here, I didn't post my replies to you correctly. Sorry about that. I have added two new comments in reply to your helpful posts. Thank you, PGK
Being new here, I didn't post my replies to you correctly. Sorry about that. I have added two new comments in reply to your helpful posts. Thank you, PGK
I believe my system of equations can be solved; but to do that, I need to use the appropriate algorythm. Today, I received a copy of what promises to be a very helpful book, _Numerical Solution of Initial-Value Problems in Differential-Algebraic Equatins_, by K. E. Brenan, S. L. Campbell, and L. R. Petzold. The book explains many of the important ideas such as the meaning of "index" as well as providing insight into various numerical methods and their applications. Thanks, PGK

Hi Jacques,

Thank you for that clarification.  Fortunately, all of the variables that appear in the set of constraint equations are linear.  If I understand the procedure for converting the constraints into ODEs correctly, then the index would be one.

Unfortunately, the there are 30 constraint equations in only 27 functions, therefore, I believe Maple is having some trouble.

Thanks,

PGK

 

Hi Jacques,

Thank you for your reply, and for suggesting an alternative DAETS package.  It might be necessary to use it as the project matures.

If by index you mean the order of the derivatives used, then I can tell you that they are all first order, and in fact the system is actually fairly simple.  Unfortunately, I cannot post the code at this point because of non-disclosure agreements. 

There is one change I need to make to the worksheet which might actually improve the prospects of the system being solved.  I will report back a little later.

Thanks for you help,

PGK

 

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