In the aviation

Aviation

Aviation is the design, development, production, operation, and use of aircraft, especially heavier-than-air aircraft. Aviation is derived from avis, the Latin word for bird.-History:...

 field, the term tuft refers to a strip of yarn or string of varying length (typically ~6" long) attached to an aircraft surface in a grid pattern and imaged during flight. The motion of these tufts during flight can be observed and recorded in order to locate flow features such as boundary layer separation and reattachment. Tufting can be considered a technique for flow visualization

Flow visualization

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

, used in aeronautics

Aeronautics

Aeronautics is the science involved with the study, design, and manufacturing of airflight-capable machines, or the techniques of operating aircraft and rocketry within the atmosphere...

 flight testing to study air flow direction, strength, and boundary layer

Boundary layer

In physics and fluid mechanics, a boundary layer is that layer of fluid in the immediate vicinity of a bounding surface where effects of viscosity of the fluid are considered in detail. In the Earth's atmosphere, the planetary boundary layer is the air layer near the ground affected by diurnal...

properties.

The world's largest bed of tufts (61 feet by 61 feet) was created at NASA Ames Research Center to study air flow fields involving a helicopter's rotor disk.