Turbulent Jet: A DNS Study

TL;DR

This DNS study investigates the boundaries of turbulent jets, emphasizing the importance of defining both the rotational/irrotational and turbulent/non-turbulent interfaces to better understand entrainment and jet behavior.

Contribution

The paper highlights the necessity of defining two distinct boundaries for turbulent jets and discusses their implications for understanding jet entrainment and flow self-similarity.

Findings

Identification of two key jet boundaries: R/IR and T/NT interfaces.

Observation of self-similarity and self-preservation in turbulent jet flow.

Insights into boundary definitions improving entrainment estimation.

Abstract

The entrainment of ambient fluid into a turbulent shear flow has been a topic of wide interest for several decades. To estimate the entrainment of ambient fluid into turbulent jet, it is essential to define the boundary of the jet. The question arises as to what should be the appropriate criterion to determine the edge of the turbulent jet. From the present DNS simulations, we observe that there is a need to define two boundaries for the turbulent jet, namely, the Rotational/Irrotational (R/IR) interface termed here as "Outer boundary" and the Turbulent/Non-Turbulent (T/NT) interface as "Inner boundary". The main aim of the present paper is to identify the need for defining the two boundaries for the jet. We also present some interesting observations of the jet flow, essentially on self similarity and self preservation.