Flow Characteristics and Novel Applications of Synthetic Jets: A Review

Abstract Synthetic jets, often abbreviated as “SJs” or “Synjets,” are a type of zero net mass flux (ZNMF) jets, which have gained popularity due to their ability to transfer momentum without transferring mass. This property distinguishes SJs from their counterpart traditional continuous jets. Over a stretch of time, SJs have been employed extensively in applications such as active flow control, impingement heat transfer, and miniature electronics cooling. However, researchers are now slowly extending the frontiers of SJ research and making efforts to utilize excellent properties of SJs in novel applications such as autonomous underwater vehicles (AUVs), marine systems, and bio-inspired propulsion systems. This paper strives to identify the gaps in the current research and the areas that have remained unexplored yet. The article begins with a brief discussion of the origin of SJs, i.e., “acoustic streaming.” Resulting segments talk about the formation criteria and the recent works employing various configurations of orifices and cavities. The paper discusses the critical concepts such as jet impact factor, volumetric efficiency, and propulsive efficiency of synthetic jets. It is followed by introduction of novel flow control systems employing SJs such as gurney flaps, bumps, and electro-active synthetic jets. Finally, the most innovative applications of SJs such as AUVs, unmanned air vehicles, and jetting cavities are also brought out. Pulsatile jet flows found in jellyfish, cephalopod, squid, and salp have been discussed in great detail. The exhaustive discussion on future prospects strives to not only provide the reader with the comprehensive insights into SJs, but also to motivate future researchers to overcome the gaps identified in this paper.