[gumby79]

Originally Posted by Piotrsko

Anything above or below a wing is called a fence generically. Flaps are hinged things that deploy to alter airflow.

Sorry, Wikipedia disagrees , wing fences are perpendicular to Gurney flaps , and developed for use on swept-wing aircraft that suffer from full span stall. Basically a full cord Vortex Generator.
Gurney flaps sole purpose is to give a simple basic flatish/concave shape a more complex convex curved air flow/ boundry layer pattern without the complexity

Gurney flap

The Gurney flap (or wickerbill) is a small tab projecting from the trailing edge of a wing. Typically it is set at a right angle to the pressure-side surface of the airfoil[1] and projects 1% to 2% of the wing chord.[2] This trailing edge device can improve the performance of a simple airfoil to nearly the same level as a complex high-performance design.[3]


A Gurney flap shown on the underside of a Newman airfoil (from NASA Technical Memorandum 4071).
The device operates by increasing pressure on the pressure side, decreasing pressure on the suction side, and helping the boundary layer flow stay attached all the way to the trailing edge on the suction side of the airfoil.[4] Common applications occur in auto racing, helicopter horizontal stabilizers, and aircraft where high lift is essential, such as banner-towing airplanes.[5]

It is named for its inventor and developer, American race car driver Dan Gurney.[6][7]

Wing fence =

Wing fences, also known as boundary layer fences and potential fences are fixed aerodynamic devices attached to aircraft wings. Often seen on swept-wing aircraft, wing fences are flat plates fixed to the upper surfaces parallel to the wing chord and in line with the free stream airflow, typically wrapping around the leading edge