There are about 6 different equations. Mode 2.51 is… 1/sqrt(f)=-2*Log(Rr/3.7+2.51/(Re*sqrt(f))) Mode 1.74 is… 1/sqrt(f)=1.74-2*Log(2*Rr+18.7/(Re*sqrt(f))) Mode 1.14 is… 1/sqrt(f)=1.14+2*Log(1/Rr)-2*Log(1+(9.3/(Re*Rr*sqrt(f))) Mode 9.35 is… 1/sqrt(f)=1.14-2*Log(Rr+9.35/(Re*sqrt(f))) Mode 3.71 is… 1/sqrt(f)=-2*Log(Rr/3.71+2.51/(Re*sqrt(f))) Mode 3.72 is… 1/sqrt(f)=-2*Log(Rr/3.72+2.51/(Re*sqrt(f)))

Since the equation starts with "1/sqrt(f)=" and have a another thing of the right like "sqrt(f)". But the equations have not been solved since 1930. May folks have made "approximations", and some are close and some are not right. But I have learned a easy and true solution for different equations.

My solutions are easy and true in Excel.

For the Colebrook-White equations change to f=1/(______)^2 where the ______ is the made right equations.

Rr= 0.02722 (Rr number is at cell B1)

Re= 66,391 (Re number is at cell B2)

Equation 1/sqrt(f)=-2*Log(Rr/3.7+2.51/(Re*sqrt(f))) (Cells A6 to A25 is 1 to 20)

Solution =1/(-2*LOG($B$1/3.7+2.51/($B$2*SQRT(B4))))^2 (This will be at cell B6)

Guess f= 1 (Guess number at cell B5)

1 0.0550474813204902 FALSE (Enter at C6 is "=B5=B6)

2 0.0554204850782122 FALSE (Copy cell B6 and C6 down to places)

3 0.0554188475042326 FALSE

4 0.0554188546575135 FALSE

5 0.0554188546262658 FALSE

6 0.0554188546264023 FALSE

7 0.0554188546264016 FALSE

8 0.0554188546264016 TRUE

9 0.0554188546264016 TRUE

10 0.0554188546264016 TRUE

11 0.0554188546264016 TRUE

12 0.0554188546264016 TRUE

13 0.0554188546264016 TRUE

14 0.0554188546264016 TRUE

15 0.0554188546264016 TRUE

16 0.0554188546264016 TRUE

17 0.0554188546264016 TRUE

18 0.0554188546264016 TRUE

19 0.0554188546264016 TRUE

20 0.0554188546264016 TRUE

Do you have a comparison of these 6 correlations? I have used the first for 30 years. It worked in the beginning, so I never changed. Should I?

Bobby