Navier–Stokes equations
The Navier–Stokes equations dictate not position but rather velocity (how fast the fluid is going and where it is going). A solution of the Navier–Stokes equations is called a velocity field or flow field, which is a description of the velocity of the fluid at a given point in space and time. Once the velocity field is solved for, other quantities of interest (such as flow rate or drag force) may be found. This is different from what one normally sees in classical mechanics, where solutions are typically paths of a particle over time. Studying velocity instead of position makes more sense for a fluid, but for visualization purposes one also can compute various paths that a particle could flow along.