Flow Loss Coefficient For a Smooth Round Pipe

$ w_0$ - mean flow velocity
$ F_0$ - cross-sectional area
$ D_0$ - internal diameter of pipe
$ \ell$ - length of pipe

Smooth round pipes are the benchmark for fluid flow analysis and are commonly used in laboratory settings, precision manufacturing, and idealized hydraulic modeling. They exhibit fully developed laminar or turbulent flow with minimal surface resistance.

This page provides flow loss coefficients (K-factors) for smooth round pipes based on well-established experimental data. It also includes tools for calculating pressure drop and head loss using dynamic pressure and hydraulic diameter. Smooth pipes serve as a reference point for comparing more complex pipe geometries and surface conditions.

Laminar flow regime ($ \mathrm{Re} \leq 2000 $) - see Hagen-Poiseuille equation:

$$ \lambda = \frac{\Delta p}{(\rho w_0^2 /2)(\ell/D_0)} = \frac{64}{\mathrm{Re}} = f(\mathrm{Re})$$

Transitional flow regime ($ 2000 \leq \mathrm{Re} \leq 4000 $):

$$ \lambda = f(\mathrm{Re}) $$

Turbulent flow regime ($ 4000 \leq \mathrm{Re} \leq 10^5 $) - see Blasius solution for smooth wall channel:

$$ \lambda = \frac{0.3164}{\mathrm{Re}^{0.25}}$$

Turbulent flow regime (any other $ \mathrm{Re} \gt 4000 $):

$$ \lambda = \frac{1}{(1.8 \log_{10}(\mathrm{Re}) - 1.64)^2}$$