Answer:
Both Reynolds and surface roughness
Explanation:
For turbulent flow friction factor is a function of both Reynolds and surface roughness of the pipe.But on the other hand for laminar flow friction factor is a function of only Reynolds number.
Friction factor for turbulent flow:
1. For smooth pipe
[tex]f=0.0032+\dfrac{0.221}{Re^{0.237}}[/tex]
[tex]5\times 10^4<Re<4\times 10^7[/tex]
2. For rough pipe
[tex]\dfrac{1}{\sqrt f}=2\ log_{10}\frac{R}{K}+1.74[/tex]
Where R/K is relative roughness
Friction factor for laminar flow:
[tex]f=\dfrac{64}{Re}[/tex]
