×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Given Find Minerr problems

Given Find Minerr problems

Given Find Minerr problems

(OP)
I currently have problems with finding solutions using the solve block, “Given   ____   Find.”  The problem is when I have equations in the solve block that very far apart in their solutions.  Example: a solve block used to calculate flow would have variables with solutions of 10^7 for one variable and other variables with solutions in the order of 10^-6.  The existing solve block will not solve these types of equations together in a solve block.  The solve block can handle any single equation by it self; however, not when combined into a single block.  To be more specific the equations are Reynolds number, Colebrook equation, General Flow Equation for compressible fluids, Velocity, and minor friction losses.  I have tried to change TOL, CTOL, and initial guesses with no success.  There is only one solution for the set of equations, and I have been manually iterating for the solution of dP or Flow depending on the problem.  Just seems a shame that I either do not know how to use the tools of the program or the program will not work as advertised.   When I try “Given ____ Minerr”, the program give an incorrect solution.   


I was in hopes of not having to write a program to do what a solve block is supposed to do.   Do you have any suggestions?  I contacted the folks at MathCad and ask if there were any improvements from 2001i to the current version that might help, and they said no.  

RE: Given Find Minerr problems

There is something you can try before writing your own program.  Right-click on "Find", go up to non-linear, then select Levenberg-Marquardt for the solution method.  The other solving routines often do not work well even for remarkably simple problems.  There is no guarantee that L-M will work either, but it is usually more reliable than the others.

Peter

RE: Given Find Minerr problems

Sometimes, you can get the equations to solve if the variables are moved around.  I've had cases where moving something from the denominator on one side to the numerator on the other side allows the solution to proceed.

TTFN



Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login



News


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close