sbval

Forum|Forum|3 years ago
July 30, 2022
3 replies
5385 views

Has anyone got an example of successfully getting sbval to work?

I keep getting :

I am playing with a 5th-order non-linear system.

Many thanks in advance!

Calculus_Derivatives

Best answer by rgunwaldsen

I also have been looking for such an example, and SB_10264300 has provided excellent references.

BVP.pdf is the first reference, and BVD_15.xmcd is implementation of it in MathCad 15. BVD_Prime6 is file converted into Prime 6.

S

StuartBruff0

5-Regular Member

https://www.mathcadhelp.com/two-point-boundary-value-problems-12591

https://pages.mtu.edu/~tbco/cm3450/bvp.pdf

G

GeoffD

Author

14-Alexandrite

Thanks for the rapid reply - I had already stumbled on the ww.mathcadhelp page (via Google) and this helped provide confidence that I had not completely messed up decoding the sbval documentation. The mtu.edu reference is very good - it would be great if it could be scooped into Prime documentation to speed things up for future users. I am now happily solving 6th-order highly coupled non-linear differential equations with discontinuous changes in time-dependent coefficients and trying to break things.

Thanks again for the rapid response.

ttokoro

21-Topaz I

t.t.

R

rgunwaldsen

Answer

15-Moonstone

I also have been looking for such an example, and SB_10264300 has provided excellent references.

BVP.pdf is the first reference, and BVD_15.xmcd is implementation of it in MathCad 15. BVD_Prime6 is file converted into Prime 6.

Author

14-Alexandrite

Hi, Many thanks for the references - they helped steer me in the right direction. I tried to break sbval using a really tricky D matrix (no idea what it represents) using:

Remarkably, sbval found the initial conditions to satisfy boundary conditions - see attached terse worksheet. By playing with additional changes I could switch between - "cannot converge" and my original error message - but it was not clear what was causing the switch. But everyone's help showed me that I was at least using sbval correctly and that the problem resided in my D matrix somewhere. I finally got sbval working by non-dimensionalizing the differential equations - which may have cleared up an incipient fault with units that I could not see.

Many thanks for the rapid response from everyone!

1_DrTomCo2.zip

V