Quantification of turbulent structures in and around the boundary region of a turbulent round jet released into counter-flow

This experimental study reports the turbulent flow structure of the interaction of turbulent round jet issued into a counter turbulent flow for improved understanding of the turbulent mixing characteristics including pollutant dispersal at the estuarine region for tidal river flows. A high-frequency data acquisition system (Acoustic Doppler velocimeter) was employed to quantify the turbulent flow structures within the mixing region of the turbulent jet. It was found that the cross-sectional mean axial jet velocity decayed faster in counter turbulence compared to a quiescent background. A reduced occurrence of engulfment and nibbling processes were evident which signified that the entrainment rate of the moving fluid reduced owing to the jet released into the counter flow. Further, the intermittency and diffusion depth of eddies decreased for jets issued against the current. The kinetic energy budget revealed that the pressure diffusion term of the turbulent kinetic energy budget equation supplied energy to the jet from the mean background flow at the self-similar region of the jet.

Automated summary

The study found that the axial jet velocity decays faster in counter turbulence, leading to a reduced entrainment rate of the moving fluid. Eddy intermittency and diffusion depth decreased for jets issued against the current. The kinetic energy budget analysis showed that the pressure diffusion term supplied energy to the jet from the mean background flow.