Physics at its best brings the world together. Its power is that a single simple framework can describe wildly different systems. But even the greatest descriptive equations reach their limits ...

When a fluid is in motion, it must move in such a way that mass is conserved. To see how mass conservation places restrictions on the velocity field, consider the steady flow of fluid through a duct ...

A new equation for accurate approximation of the Moody friction factor in the general gas-flow equation better approximates a wide range of Reynolds numbers than previously published equations. Other, ...