Tubercles and Their Applications

The implementation of tubercles on foils has demonstrated significant benefits, with the most evident occurring during post-stall. However, the flow mechanism(s) responsible for these benefits is currently unknown, and several possibilities have been proposed. These include compartmentalization, vortex lift, varying effective angle of attack, and boundary layer momentum exchange. Currently, it is only known that tubercles create pairs of streamwise, counter-rotating vortices. By determining how tubercles work, the effects of their addition to untested foils in untested conditions can be hypothesized. This paper reviews the current status of the field of tubercles, comparing hypotheses with published results. The effects of tubercles on the principal components of drag are conjectured from consideration of similar flow control devices. Current applications of tubercles are detailed, and potential applications are suggested.