how can solve for ' f ' in 1/sqrt(f) = -2*log(((e​/d)/3.7)+(​2.51/Re*sq​rt(f))) . Re = 1000, d=0.0254, e0.03

how can solve for ' f ' in 1/sqrt(f) = -2*log(((e/d)/3.7)+(2.51/Re*sqrt(f))) . Re = 1000, d=0.0254, e=0.03

Answer 1

[Azzi Abdelmalek]

Re = 1000, d=0.0254, e=0.03
syms f
solve(1/sqrt(f) == -2*log(((e/d)/3.7)+(2.51/Re*sqrt(f))))

[apukayilatavida sasikumar]

hey m getting an emty set as my answer. Is this really works ?

[Azzi Abdelmalek]

ans =

73166.235272205724820291017624331

Answer 2

[Star Strider]

You can use fzero. I plotted it and found two real roots (necessary because fzero hs its limitations):

Re = 1000; d=0.0254; e=0.03;
Eqn = @(f) 1./sqrt(f) + 2*log(((e/d)/3.7)+(2.51/Re*sqrt(f)));
f1 = fzero(Eqn, 1)
f2 = fzero(Eqn, 1E5)

produces:

f1 =

     192.8954e-003

f2 =

      73.1662e+003