The Math Forum

Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Math Forum » Discussions » Software » comp.soft-sys.matlab

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

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

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]

Posts: 1,717
Registered: 11/8/10
Re: ODE stiffness problems
Posted: Mar 15, 2013 4:54 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

"Matthew" wrote in message <khtlea$ba3$>...
> 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

Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© The Math Forum at NCTM 1994-2018. All Rights Reserved.