Experimental study of the Reynolds stress distribution and its self-similarity in a semi-confined impinging jet

Abstract

This paper investigates the Reynolds stress distribution and its self-similarity of a semi-confined impinging jet using the two-dimensional particle image velocimetry (2D-PIV) technology. The confinement is achieved by placing a plate parallel to the impinging plate at the nozzle exit. Nine sets of measurements are conducted at three impingement distances (4, 5, and 6 times the nozzle diameter) and three Reynolds numbers (5084, 8179, and 13,926). The spatial distribution and the self-similarity of Reynolds stresses are obtained. The results indicate that high turbulence occurs mainly in the free jet shear layer and the wall jet shear layer. The variation of Reynolds stresses with impingement distances and Reynolds numbers are determined. The Reynolds stresses in the radial wall jet region do not exhibit self-similarity in the outer-scaled coordinates. Scaling parameters based on Reynolds stresses are proposed, and the Reynolds stress velocity scales decay by a power-law function in the self-similar region, while the Reynolds stress length scales increase linearly. The Reynolds stresses in the radial wall jet region show extremely strong self-similarity using the Reynolds stress scaling parameters normalization. Finally, the corresponding scaling laws for Reynolds stresses are obtained.