function f=fanning2(ed,Re)
if Re<=2100
    f=16/Re;
else
    f0=4e-3;c=1;tol=1e-5;
    while c>tol
        f=(-4*log10(ed/3.7+1.255/Re/sqrt(f0)))^(-2);c=abs(f-f0);f0=f;
    end
end
end