As a byproduct of lift generation, higher pressure below the wing induces the flow to curl about the wingtip from the low-pressure region onto the upper surface. The process forms a flow of helical structure known as a wingtip vortex that entrains the wing wake and propagates downstream, as shown in Figure 1. A vortex flow is typically considered a region in a fluid in which the gradient or curl of the velocity components provides vorticity magnitudes and directions, indicating a spiral flow [1,2,3]. Wingtip vortices have an impact on the flight operations of aircraft because of the development of induced drag and turbulence [4]. It is well known that wingtip vortices impact the pressure field near the wing tip where the lifting surface terminates in the fluid [5]. In other words, when the wing generates lift, a net circulation around the wing and in the downstream flow is essentially inevitable [6,7,8].

Wingtip vortices alter the trajectory of the fluid flow in the wake [10,11,12]. The dynamic behavior of the wingtip not only affects the induced drag forces on the wing [13,14,15] but also creates an undesirable flow structure in the wake of the wing. Researchers have studied this phenomenon with a view to reducing its adverse effects on aircraft safety, fuel consumption, and the structural integrity of aircraft wings. The effects of wingtip vortices on aerodynamic performance are well known in many applications, such as in aeronautical, marine, agricultural, industrial, and environmental science [16,17]. The resultant wingtip vortices, for instance, prolong the durations of take-off, flying, and landing. Moreover, they cause a non-uniform, inhomogeneous flow pattern in the downstream flow when agricultural spraying is performed using an airplane [18]. In marine engineering, wingtip vortices initiate cavitation on the surface of the blades and cause detrimental vibrations [17]. Similarly, vortices are also generated from the finite structures [19,20,21]. The noise generation and energy losses are other demerits of wingtip vortices [22,23,24]. Engineers and scientists have, for many years, been dedicated to discovering methods to alleviate the detrimental impacts of these vortices across a broad spectrum of applications. In the natural world, creatures like owls alter their wingtip feathers in a manner that effectively suppresses wingtip vortices and the accompanying noise [25,26,27,28].

The phenomenon of wingtip vortices has captivated researchers for many decades in their attempts to minimize their harmful effects. Researchers have made extensive experimental and theoretical studies [29,30,31,32,33,34,35] as well as numerical investigations [29,35,36,37,38,39,40,41] to understand the characteristics of wingtip vortices. To mitigate the adverse effect of wingtip vorticities, many wingtip devices have been proposed over the years with varying degrees of success. Some of the claimed benefits of these devices are summed up in the following points:

• Reduced fuel consumption [42];
• Increased flight range [43,44];
• Reduced take-off field length [44];
• Increased cruise speed and altitude [45];
• Reduced take-off noise [46,47];
• Increased aircraft stability [48];
• Improved runway throughput by mitigating wake turbulence and allowing for closer aircraft spacing [49].

4. History of Wingtip Devices and Some Commercial Applications