# Tag Info

If you pump gas along a pipe then pressure drop per unit length of the pipe depends on the diameter of the pipe. The smaller the pipe the harder it is to pump the gas through it. The pressure drop is given by the Darcy-Weisbach equation: $$\Delta P = f_D \frac{\rho v^2}{2} \frac{\ell}{d}$$ though with the complication that the density of the gas depends ...