Effect of initial velocity distribution and Reynolds number on two-dimensional wall jet of transition region impinging

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.