Subsonic round and plane macrojets and microjets in a transverse acoustic field

26 In comparison with microjets, the investigation of free macrojets has attracted greater attention because of their wide use in various fields of science and engi� neering. However, interest in studying free microjets has recently increased considerably (1) because of, in particular, the development of MEMS technologies. The possibility of the potential use of microjets in var� ious processes appeared, for example, in microcool� ing, jet burning, nanopowder manufacture, etc. Spe� cial attention is given to the investigation of the acous� ticfield action on the microjet (2-5), which is of importance both for understanding the physics of the process and for the possibility of practical use of the phenomenon, for example, in aviation, astronautics, and the chemical industry. The purpose of these investigations consists in experimental study of the mechanism of developing round and plane macroand microjets under the acousticfield action and comparison of the obtained results with the results of recent works in this direction. In this study, we discussed the results of the experi� mental investigations of the mechanism of developing jet flows with small Reynolds numbers in a transverse acoustic field. We investigated the round macrojet (Re d = 5300, d = 20 mm) and microjet (Red = 20-60, d = 200-600 μm) and the plane macrojet (Reh = 3600, h = 14.5 mm) and microjet (Reh = 75, h = 200- 700 μm) depending on the velocity profile at the noz� zle end (from the shock one with the narrow velocity� gradient region and gradientfree jet core to the para� bolic one). Thermoanemometric measurements and the smoke visualization of flows were carried out. The patterns as a result of the smoke visualization of flows were obtained with the help of laser illumination of the jet synchronized with the acousticaction frequency, which enabled us to obtain new data on the mecha� nism of the development of jets.