Dear all,
I developed a VBA function for evaluating Colebrook White's equation that might be helpfull to someone. Please, find the code bellow.
Best regards.
'VBA function by Ricardo Carvalho (Lisbon, Portugal)
'February, 2003, E-mail:
goldmundo@clix.pt
'Colebrook-White formula
Function J(U, D, k, v As Double) As Double
J = 0.0055 * U ^ 2 / (2 * 9.81 * D) * (1 + (2000 * k / D + 1000000# / (U * D / v)) ^ (1 / 3))
dJ = 100: delta = 0.0000000001
While Not Abs(dJ / J) < delta
f1 = J - U ^ 2 / (8 * 9.81 * D) / Application.Log(k / (3.7 * D) + (2.51 * v) / (D * (2 * 9.81 * D * J) ^ 0.5)) ^ 2
f2 = (J + delta) - U ^ 2 / (8 * 9.81 * D) / Application.Log(k / (3.7 * D) + (2.51 * v) / (D * (2 * 9.81 * D * (J + delta)) ^ 0.5)) ^ 2
dJ = f1 * delta / (f2 - f1)
J = J - dJ
Wend
End Function