Experimental investigation on flow characteristics of vertical and oblique circular impinging jet

Abstract

The present study experimentally investigates the flow characteristics of a fully developed circular water jet (vertical and oblique) over a wide range of Reynolds numbers, impinging heights, and impinging angles using particle image velocity technique. This study focuses on the velocity distribution along the jet centerline and the flow structure in the uphill and downhill regions. The results revealed that the velocity profiles of the impinging jet maintain self-similarity before impingement on the bottom plate (at y/H ≤ 0.979). Depending on the impinging height, the development of the jet centerline velocity can exhibit two, three, or four distinct regions. A semi-empirical equation has been developed for the jet centerline velocity based on the obtained experimental data and theoretical analysis. For the oblique impinging jet, the position of stagnation point highly depends on the jet height and impinging angle, but it is insensitive to the Reynolds number. There exists a recirculation zone in the uphill direction induced by pressure gradients and shear forces, whose size and position depend on the impinging height, impinging angle, and Reynolds number. Different flow states are observed for relatively small impinging heights near the geometric center in the downhill region. The flow patterns for various Reynolds numbers and impinging heights are self-similar in the downhill region at a/d ≥ 6.