Passive flow control of jets

One of the major purposes of fluid mechanics and engineering is to reduce the flow resistance caused by flow friction, flow separation, vortex generation, and other factors. To reduce or eliminate flow resistance, in general, flow control is performed either passively or actively. Passive flow control is performed by changing the flow channel or object shape a little and reducing the total flow resistance. On the contrary, active flow control uses a device requiring power, but it can perform various complex flow controls. In this paper, the passive flow control of jets is examined with flow characteristics, control methods, and some applications because jet flows include the essence of fluid dynamics, such as, boundary layer flow, turbulent flow, shear flow, and flow mixing. In particular, the effects of the nozzle shape, the tab, rib and vortex generator, and the orifice or notched orifice on the flow characteristics of sub- and supersonic jets are examined. Furthermore, the control and suppression of high speed jet noise by a chevron nozzle, some examples of active flow control, and other areas are examined. Globular formation of fine solid particles by flow control, lift control of airplane wings, and the flow control of a NOTAR helicopter without tail rotor are also addressed.