An example of the application of a "dimpled" surface is a surface of a golf ball that is covered by the pattern of spherical dimples. Early studies of the sphere aerodynamics of golf balls Bearman and Harvey (1976) indicated that they flew further and straighter when scored or marked. As shown in Figure 1, the drag force curve for the dimpled golf ball in the critical/supercritical flow regime differs remarkably from the corresponding curves for smooth and sand-roughened spheres; this results in a much further range than the smooth ball for the same initial conditions.

A wide range of studies have confirmed that flowing a gaseous medium over surfaces covered by spherical dimples can generate extremely stable vortices which provide very intensive mass and heat transfer between the dimpled surface and surrounding medium as illustrated in Figure 2a. The enhancement of heat transfer by this means will be referred to below as Vortex Heat Transfer Enhancement (VHTE).

In visualization experiments with the flat "dimpled" surfaces it was observed that columnar vortices generated by individual dimples at appropriate conditions are sucking the flow from the vicinity of the dimple and evacuating it in the core of the main flow stream. Moreover, those vortices actively interact with each other and create an oscillating flow pattern as shown in Figure 2b.

Figure 1 Variation of golf ball and sphere drag Bearman and Harvey (1976)

Figure 2 Basic mechanism of vortex formation in a dimple Afanasiev et al. (1993) and visualization of the flow over a dimpled surface Kiknadze et al. (2005) confirming the existence of the vortex