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awaughtal1-Visitor
1-Visitor
February 21, 2013
Solved

Solver unable to find solution

  • February 21, 2013
  • 4 replies
  • 2107 views

Hello,

I am new to Mathcad and am trying to solve a set of linear equations. (Context: given environment and pipe pressure conditions, need to find minimum wall thickness)

I have tried many arrangements and tutorials, but am still not able to reach a solution. It's gotten to the point where I am literally out of ideas (I also tried to use range variables and matricies)

I doubt it is the equations, since I am referencing them directly from an industry standard.

File and reference material attached.

Any help would be very (GREATLY) appreciated,

Amy

Reference1.JPG

Best answer by RichardJ

The problem is that the two sides of your equation evaluate to very large numbers: about 10^17 Pa^3, but you have your convergence tolerance, CTOL, set to the default 10^-3. Set CTOL to 1000 and it works.

4 replies

RichardJ19-TanzaniteAnswer
19-Tanzanite
February 21, 2013

The problem is that the two sides of your equation evaluate to very large numbers: about 10^17 Pa^3, but you have your convergence tolerance, CTOL, set to the default 10^-3. Set CTOL to 1000 and it works.

awaughtal1-VisitorAuthor
1-Visitor
February 21, 2013

Thank you so much, I had been trying to change CTOL in the Worksheet Options menu and it obviously wasn't working.

Do you mind looking at the second method on the sheet? And maybe explaining why that one isn't working as well? I forsee more Mathcad solving in my future, so additional insight would be good.

RichardJ19-Tanzanite
19-Tanzanite
February 21, 2013

It's s numeric solve block, and will therefore not do symbolic substitution of one expression into another. It looks at your first equation, determines that b is an undefined variable, and quits with an error.

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