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ptc-66825971-Visitor
1-Visitor
October 8, 2014
Question

Bernoulli Modelling

  • October 8, 2014
  • 1 reply
  • 1482 views

Hi

Unsure where to go with this now. I am modelling a system where the diameters of the pipes are different and have 13 equations with 13 unknowns

I am modifying an example from a textbook to suit my requirements. (Cengel and Cimbala's Fluid Mechanics Fundamentals and Applications 2nd ed. Page 375) but It's been a while since I have used MathCAD and I'm not an expert in getting it to work. Any help is appreciated.

1 reply

W
Werner_E25-Diamond I
25-Diamond I
October 8, 2014

You have to replace the matrix/vector indices you have user by literal indices (the ones you get by typing the period). You cannot use the comma in a variable name.

Then assign a guess value to every variable you are going to search for.

After that type the word "Given" in a math region

Follow this by all your equations (at first glance it looks to me that you are short of one equation).

Finish that solve block by typing "find(variable1, variable2,......)="

According to one of your equation you have h.L=h.L1=h.L2, so I suggest you just use h.L and when you have solved you may define h.L1:=h.L.

A.1 and A.2 can be directly calculated above the solve block and you should do so (by using the :=)

V.dot, W.elect and h.pump can be simply calculated and defined after the solve block - no need to make the solve block to search for them, too.

You can also set equal the two expressions for h.L1 and h.L2 and that way have not h.L or hL1, h.L2 in your seolve block - you can also calculate the, afterwards.

After doing all of that you still have just 7 equations for 8 unknowns (V, V.dot, Re and f; all with index 1 and 2)

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