Flow visualization in fluid dynamics is used to make the flow patterns visible, in order to get a qualitative or quantitative information on them.

Flow visualization is the art of making flow patterns visible. Flow visualization can be appreciated on several levels. Most fluids (air, water, etc.) are transparent, thus their flow patterns are invisible to us without some special methods to make them visible.

On another level, we know the governing equations of fluid motion (the Navier-Stokes equations), but they are nonlinear partial differential equations with very few general solutions of practical utility. We can solve them numerically with modern computer methods, but these solutions may not correspond to nature unless verified by experimental results.

On still another level the Navier-Stokes equations are pattern generators, and natural fluid flows display corresponding patterns that can recur on scales differing by many orders of magnitude. Such fluid patterns are familiar to almost everyone: the bathtub vortex and the tornado, the smoke ring and the mushroom cloud, the swinging of wires in the wind and the collapse of a historic bridge due to forced oscillations from aeroelastic flutter.