Study on side-jet injection near a duct entry with various injection angles

Turbulent flowfields resulting from an oblique jet injecting from a rectang ular side-inlet duct into a rectangular main duct with an aspect ratio 3.75 without a forced crossflow are presented in terms of laser-Doppler velocim etry measurements. The main focuses are the effects of the side-jet angle ( theta) and side-jet flow rate (Q(s)) on the mass entrainment upstream of si de-jet port and the flowfield in the rectangular duct. The side-inlet angle s investigated were 30, 45, and 60 deg and Reynolds numbers based an the ai r density, rectangular duct height and bulk mean velocity were in the range of 7.1 x 10(3) to 3.6 x 10(4) corresponding to Q(s) values of 1 x 10(3) to 5 x 10(3) L/min. The present study suggests the presence of a critical sid e-injection angle theta(c) (30 less than or equal to theta(c) less than or equal to 45 deg) above which a recirculation zone appears in the rectangula r duct, whereas below which the recirculation zone is absent. For the more tangential angle (theta = 30 deg), almost as much fluid is entrained into t he main duct as was injected from the side jet. The mean flow field in the rectangular duct is found to be a weak function of the Reynolds-number for the range of Q(s) investigated. In addition, a simple linear correlation be tween the mass entrainment upstream of the side-jet port and side-injection angle is obtained Complementary flow visualizations and numerical computat ions with an algebraic Reynolds stress model were also performed. The discr epancies between measured and completed results are documented.