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Instability of wall jet produced by twodimensional inclined jet
Gentaro Takeda,Yu Ito,Kenji Yamashiro,Hideyuki Takahashi,Nao Ninomiya,Yuya Uranaka,Jurai Fujikura 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.1
This paper focuses on a two-dimensional jet that impinges on a sloping wall surface. It investigates the vibration behavior and wall jet development morphology during wall impingement. Flow visualization experiments of jets impinging on a plate arranged vertically and at an angle of 65° were conducted. In the range where the distance between the jet nozzle and the plate is from the near field to the transition region, the vibration form of the impinging jet changes sensitively. The range of the distance between the jet nozzle and the impinged plate where no shear vortex forms on the wall surface is expanded by the inclined impinging jet. On the upward side, where the fluid easily flows due to the inclined impinging jet, an increase in the vibration frequency was also confirmed as the wall jet velocity increased. PIV measurements showed that wall jet separation after inclined impinging was delayed in comparison with vertical impinging, and a stable wall jet was formed.
Gentaro Takeda,Yu Ito,Kenji Yamashiro,Hideyuki Takahashi,Nao Ninomiya,Jurai Fujikura,Shun Akutsu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.11
This paper focuses on the development formation of two-dimensional impinging jets. Since it is known that vibration of a two-dimensional jet injected from a gas wiping nozzle affects the morphology of the coating surface, control of the jet properties is a very important issue. In this paper, jets with different initial velocity distributions were created, depending on the internal shape of the nozzle, and the behavior of the impinging two-dimensional jet in the transition region was evaluated by flow visualization. One nozzle (contoured nozzle) had a curvilinearly contracting shape as the flow approached the nozzle injection port, and the other (straight nozzle) was provided with a parallel part having a length 17 times the width of the nozzle gap in the flow path of the nozzle injection port. The jets ejected from these nozzles differed significantly in the velocity profile and in the vortex formation at the edges of the jet before impingement. There were also differences in the wall jet thickness and jet velocity attenuation of the wall jet. The difference in the wall jet characteristics due to the nozzle type is remarkable in impingement at the beginning of the transition region, but the difference decreases with the impinged wall distance where collapse of the large-scale vortex is seen even in the transition region.