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Principles and Applications of Plasma Actuators
Published in Ranjan Vepa, Electric Aircraft Dynamics, 2020
Spanwise fences are used on an airfoil surface for trapping vortices. When a fence type device is attached to a wing, part of the bound circulation of the wing is carried over to the fence. Upper surface fences have a favorable effect on longitudinal flow characteristics due to the retardation of spanwise boundary layer flow near the trailing edge, along with a reduction in separation over the outer wing. Wing fences act as barriers to the tipward flow on swept-back wings. They also generate powerful streamwise vortices. This results in a net reduction of the induced drag, due to a reduction in the strength of the tip vortex.
Transonic Flight and Aerofoils
Published in Rose G. Davies, Aerodynamics Principles for Air Transport Pilots, 2020
Wing fences, as shown in Figure 9.14, can be featured on a wing close to the wingtip area to prevent a large wingtip vortex to develop into a “ram horn” vortex, which causes high induced drag and wingtip stall. Wing fences can also interrupt the rear shockwave over a sweepback wing developing widely, and then reduce the turbulent wake separation behind the shockwave.
Investigation of propeller slipstream effects on lateral and directional static stability of transport aircraft
Published in Engineering Applications of Computational Fluid Mechanics, 2022
Shuai Zhao, Jie Li, Youxu Jiang, Ruizhan Qian, Ruifei Xu
The portion of wing immersed in the slipstream will experience a higher dynamic pressure. However, on the downward side of the propeller, the significant decrease in the local angle of attack due to the slipstream swirl counteracts the effect of the increased dynamic pressure on the lift. Hence, when the wing sections (close to the boundary of propeller slipstream, in general) move in or out of the slipstream in a sideslip flow, the lift changes for the sections on the downward side of the propeller are much smaller than the values for the sections on the upward side of the propeller. It should be noted that the reference aircraft has clockwise rotating propellers, which means that the stations of y/R = −3.045 and y/R = −2.823 are located on the upward side of the port propeller. This explains why the maximum decreases in the ΔCl,local caused by the lateral displacement of the propeller slipstream occur at the locations close to the left boundary of the port propeller slipstream region rather than those close to the right boundary of the starboard propeller slipstream region. Accordingly, if a flow control technique, such as a wing fence, is implemented to improve the lateral static stability of the transport aircraft with co-rotating propellers, the portion of wing around the left boundary of the port propeller slipstream region for the configurations with clockwise rotating propellers or around the right boundary of the starboard propeller slipstream region for the configurations with anti-clockwise rotating propellers should be given extraordinary attention.