Some phenomenological aspects of jet induced turbulence.

Abstract

Turbulence, induced by transverse and inclined air jets, in an air stream flowing in a four inch square duct at 138-250 feet per second, was studied, Flow patterns were constructed from four hundred velocity profiles measured at various distances from the injector wall and at numerous positions upstream and downstream from the injector under different experimental conditions. The pattern indicates a steady widening of the jet, a curving motion, with the lower portion forming a vortex in the wake. The upper part of the jet widens out, slows down and reaches mainstream velocity farther down the duct. A method for predicting the shape of the upper bounding streamline was developed from two-dimensional potential flow theory and a penetration correlation with exponents deduced from the results in this study. The shape of the lower bounding streamline and the vortex can be predicted by a logarithmic elliptical spiral using constants determined in this investigation. The analogy between the patterns in the wake of a jet and a solid rod was checked in a six inch round duct and found to be of doubtful validity.