Effect of Coflow Turbulence on the Dynamics and Mixing of a Nonbuoyant Turbulent Jet

Abstract

The effect of a turbulent coflow on a turbulent round jet is investigated experimentally. The primary objective of this work is to study the evolution of the turbulent jet as the level of the coflow turbulence is varied. Velocity measurements of the jet were conducted at three Reynolds numbers, with the jet issuing into two different levels of coflow turbulence. It is observed that the decay rate of the centerline mean velocity, spreading rate, and mass flow rate of the jet increase as the level of the coflow turbulence increases. Similarly, both the inward mean radial velocity close to the edges of the jet, which can be related to the entrainment velocity, and the velocity variances increase when the turbulence level of coflow increases. Given the increased spreading rate, mass flow rate, and inward mean radial velocities, it can be inferred that the entrainment into the jet also increases as the coflow turbulence intensifies. Lastly, for the range of parameters studied, self-similarity of mean velocity profiles occurs at a downstream position for which the ratio of the coflow to jet integral lengthscales is of order one.