The horseshoe vortex model is a simplified representation of the
vortex
In fluid dynamics, a vortex ( : vortices or vortexes) is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools in t ...
system present in the flow of air around a
wing
A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is exp ...
. This vortex system is modelled by the ''bound vortex'' (bound to the wing) and two ''
trailing vortices'', therefore having a shape vaguely reminiscent of a
horseshoe
A horseshoe is a fabricated product designed to protect a horse hoof from wear. Shoes are attached on the palmar surface (ground side) of the hooves, usually nailed through the insensitive hoof wall that is anatomically akin to the human ...
. A
starting vortex is shed as the wing begins to move through the fluid, which dissipates under the action of
viscosity
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water.
Viscosity quantifies the inte ...
, as do the trailing vortices far behind the aircraft.
The
downwash
In aeronautics, downwash is the change in direction of air deflected by the aerodynamic action of an airfoil, wing, or helicopter rotor blade in motion, as part of the process of producing lift.Crane, Dale: ''Dictionary of Aeronautical Terms, thir ...
is associated with
induced drag
In aerodynamics, lift-induced drag, induced drag, vortex drag, or sometimes drag due to lift, is an aerodynamic drag force that occurs whenever a moving object redirects the airflow coming at it. This drag force occurs in airplanes due to wings or ...
and is a component of the system of trailing vortices.
The horseshoe vortex model is unrealistic in that it implies uniform
circulation
Circulation may refer to:
Science and technology
* Atmospheric circulation, the large-scale movement of air
* Circulation (physics), the path integral of the fluid velocity around a closed curve in a fluid flow field
* Circulatory system, a bio ...
(and hence, according to the