Iterative calculations errors

Piotrekdoro

New Member
Joined
Sep 21, 2023
Messages
2
Office Version
  1. 365
  2. 2013
Platform
  1. Windows
Hi, I have a problem with iterating a formula. I need to calculate linear head loss factor (eqution visible on the attached image) but I cant figure out how to do it iteratively using cyclical references (I did remember to turn them on).

I now that the results converge because I've tried to do it manually (for the green Reynolds number), but this is only one of many formulas i need to calculate that way so it would be very tedious. Could someone help me the attached example?

My XL2BB scheet:

IterationTest.xlsx
ABCDEFG
1
2Re - Reynolds numberλ - Linear head loss factor, iterative calculation
37031,364837
431641,14177
547813,28089
673829,33079
793517,15234
8113908,1104
9133595,9319#LICZBA!#LICZBA!<---- How to iterate the formula above
10149064,9346
11165237,0737
12176487,2574
13200393,8979
14229925,6302
15
16Re - Reynolds numberIterationλ - Linear head loss factor, manual calculationNotes
177031,36483710,0636286490,5<---- Initial value
1831641,1417720,0768329650,063628649
1947813,2808930,075461850,076832965
2073829,3307940,0755911860,07546185
2193517,1523450,0755788720,075591186<---- Result converges
22113908,11046
23133595,93197
24149064,93468
25165237,07379
26176487,257410
27200393,897911
28229925,630212
29
Arkusz1
Cell Formulas
RangeFormula
C9C9=(2*LOG10((D9^(1/2))*B9)/2.51)^(-2)
D9D9=C9
D17:D21D17=(2*LOG10((E17^(1/2))*B$23)/2.51)^(-2)
E18:E21E18=D17
 

Attachments

  • Iteration.png
    Iteration.png
    30.5 KB · Views: 3

Excel Facts

Copy formula down without changing references
If you have =SUM(F2:F49) in F50; type Alt+' in F51 to copy =SUM(F2:F49) to F51, leaving the formula in edit mode. Change SUM to COUNT.
This causes a circular reference : C9 refers to D9 and D9 refers to C9
C9C9=(2*LOG10((D9^(1/2))*B9)/2.51)^(-2)
D9D9=C9
 
Upvote 0
This causes a circular reference : C9 refers to D9 and D9 refers to C9
C9C9=(2*LOG10((D9^(1/2))*B9)/2.51)^(-2)
D9D9=C9
I thing I don't understand something fundamental. I thought that's what I'm supposed to do with iterative calculations, one cell should refer to the other. How should I Initialize calculations instead?
 
Upvote 0
Meant to ask previously that iterations was turned on. The error (assuming you have iterations turned on) is that the 1st step tries to do Log10(0) because D9 when it starts = 0
1695621259400.png
 
Upvote 0

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