ABSTRACT
This chapter introduces the student into the physical principles on which some representative visualization techniques rely. Perhaps the most popular flow visualization technique consists in continuously releasing smoke at a point upstream the region where one desires to visualize the flow. A more quantitative technique that exploits the variations of the shear stress found in different flow regions is that of the oil-film interferometry. One of the most common applications of flow visualization techniques is to make apparent to the sight the main features of the fluid flow around an aerodynamic body, including the direction of the fluid velocity at different points. Besides the streamlines, experimental aerodynamicists are usually interested in finding regions of flow separation, recirculation bubbles, and vortical structures. A more quantitative way of using smoke tracers consists in analyzing the deformation of a tracer line to obtain the velocity profile as its fluid particles are advected downstream.
