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Topic: ODE stiffness problems
Replies: 3   Last Post: Apr 22, 2013 9:49 PM

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Torsten

Posts: 1,458
Registered: 11/8/10
Re: ODE stiffness problems
Posted: Mar 15, 2013 4:54 AM
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"Matthew" wrote in message <khtlea$ba3$1@newscl01ah.mathworks.com>...
> I removed the abs and signs by putting a constant low flow rate just to see if it would work. However it doesn't make any change it still stops at the same point.


I solved your problem with another software and it worked without problems.

The problem with ODE15s seems to be the abrupt change of the variables
in the time span from t=0.95 to t=1. This is caused by the parameter Av.

A remedy (I also used within my ODE integrator) is to call ODE15s seperately for
the time span from t=0 to t=0.05, then from t=0.05 to t=0.95 and then from t=0.95 to t=1.
Do it in a loop and set the inital conditions of the variables for a new time span to the final values of the variables from the preceeding time span.

Best wishes
Torsten.



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