Iterative calculations errors

[Piotrekdoro]

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
	A	B	C	D	E	F	G
1
2		Re - Reynolds number	λ - Linear head loss factor, iterative calculation
3		7031,364837
4		31641,14177
5		47813,28089
6		73829,33079
7		93517,15234
8		113908,1104
9		133595,9319	#LICZBA!	#LICZBA!	<---- How to iterate the formula above
10		149064,9346
11		165237,0737
12		176487,2574
13		200393,8979
14		229925,6302
15
16		Re - Reynolds number	Iteration	λ - Linear head loss factor, manual calculation		Notes
17		7031,364837	1	0,063628649	0,5	<---- Initial value
18		31641,14177	2	0,076832965	0,063628649
19		47813,28089	3	0,07546185	0,076832965
20		73829,33079	4	0,075591186	0,07546185
21		93517,15234	5	0,075578872	0,075591186	<---- Result converges
22		113908,1104	6
23		133595,9319	7
24		149064,9346	8
25		165237,0737	9
26		176487,2574	10
27		200393,8979	11
28		229925,6302	12
29
Arkusz1

Cell Formulas
Range	Formula
C9	C9	=(2*LOG10((D9^(1/2))*B9)/2.51)^(-2)
D9	D9	=C9
D17:D21	D17	=(2*LOG10((E17^(1/2))*B$23)/2.51)^(-2)
E18:E21	E18	=D17

 

[nemmi69]

This causes a circular reference : C9 refers to D9 and D9 refers to C9

C9	C9	=(2*LOG10((D9^(1/2))*B9)/2.51)^(-2)
D9	D9	=C9

 

[Piotrekdoro]

This causes a circular reference : C9 refers to D9 and D9 refers to C9

C9	C9	=(2*LOG10((D9^(1/2))*B9)/2.51)^(-2)
D9	D9	=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?

 

[nemmi69]

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

 

[nemmi69]

Try