Jet Flow Phenomena

― Fundamentals and Some Applications ―

Abstract

Jet phenomena, in which a fluid with velocity is ejected from a small hole (slit, nozzle) into space, can be seen in nature and in a wide range of industrial fields. Jet phenomena appear to be simple at first glance, but they are essential phenomena in fluid mechanics, including free and wall shear (boundary layer) flows, the generation and rise and fall of large-scale vortex structures associated with them, flow attachment and separation, vibration phenomena, and fluid noise, and it is important from the perspectives of fluid- and thermal-engineering to clarify their characteristics. In this paper, some of these fundamental aspects of jet phenomena will be discussed, namely, the flow patterns and velocity distributions of two-dimensional and three-dimensional circular turbulent free jets, the effect of nozzle shape on the flow characteristics of jets, the generation and rise and fall of vortices in jets, and the attachment phenomenon of jets to adjacent walls (the Coanda effect). Then, some applications of jet phenomena, including boundary layer control, the NOTAR helicopter, and vector control of supersonic jets will be discussed.