ELI5: Explain Like I'm 5

Navier-Stokes equations

Navier-Stokes equations are like a set of instructions that tell us how water and other liquids move. They tell us the speed and direction of a liquid and how it changes if something else changes. For example, if we want to know how fast water will flow through a pipe, we can use the Navier-Stokes equations to figure out the answer.