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JR_917519110-Marble
10-Marble
January 14, 2024
Solved

"This value must be a scalar or a vector"

After fixing an issue with an earlier solve block I am now finding this,

JR_9175191_0-1705210386849.png

Please advise and thank you!

 

    Werner_E
    Werner_EAnswer
    25-Diamond I
    January 14, 2024

    Main problem is that variable Ws is not defined - not as a variable or vector (its defined as a function!).

    But what do you mean by   L = |Zb| ?
    Actually a vector L can't equal the scalar |Zb| but Prime would interpret this constraint that each element in vector L should equal the scalar on the right hand side.
    Did you possibly mean |L|=|Zb| ?

    Werner_E_0-1705212637366.png

     

    Was Ws meant to be uses as the function (of Q) you defined on top of the sheet?

    Werner_E_1-1705213299102.png

     

     

     

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    3 replies

    Werner_E
    Werner_E25-Diamond IAnswer
    25-Diamond I
    January 14, 2024

    Main problem is that variable Ws is not defined - not as a variable or vector (its defined as a function!).

    But what do you mean by   L = |Zb| ?
    Actually a vector L can't equal the scalar |Zb| but Prime would interpret this constraint that each element in vector L should equal the scalar on the right hand side.
    Did you possibly mean |L|=|Zb| ?

    Werner_E_0-1705212637366.png

     

    Was Ws meant to be uses as the function (of Q) you defined on top of the sheet?

    Werner_E_1-1705213299102.png

     

     

     

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      JR_917519110-MarbleAuthor
      10-Marble
      January 14, 2024

      First equation is NPSHA = NPSHR

      Then the relationship between the pipe length L and the elevation Zb. From my understanding they are supposed to be the same as they represent the NPSHA (available). But I will verify this with my professor, the solution you gave me of |L| would give me individual values for each diameter which if needed is a quick change.

       

      Had to replace Ws with Wp which I had changed earlier on another post.

       

      JR_9175191_0-1705239461333.png

       

      Thank you Werner

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      Werner_E
      Werner_E25-Diamond I
      25-Diamond I
      January 14, 2024

      Looks like Wp is the very same as Ws(Q)  which I suggested 🙂

      Werner_E_2-1705249324361.png

       

      I have no expertise at all in the field you are working in, but if that constraint in question would be OK and both values in L are supposed to be the same as |Zb|, then there would be no need to define L as a vector of values!
      Actually it would not be necessary to use L at all in the solve block - you could as well replace Li by Zb in the first equation, solve for Pb and Zb only and then set all values of L to the absolute value of Zb:

      Werner_E_1-1705249212228.png

       

      I can't imagine that this really would be what its supposed to be, though.

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