Dynamics of a buoyant plume in a linearly stratified environment using simultaneous PIV-PLIF measurements

TL;DR

This study investigates the dynamics of a buoyant plume in a linearly stratified environment by simultaneously measuring velocity and density, revealing how stratification influences plume behavior and mixing processes.

Contribution

It provides detailed measurements of velocity, turbulence, and buoyancy flux in a stratified plume using simultaneous PIV-PLIF techniques, which is a novel approach.

Findings

Centerline velocity decreases with height.

Unstable layer identified through Reynolds stress and buoyancy flux profiles.

Stratification significantly affects plume mixing dynamics.

Abstract

The presence of stratified layer in atmosphere and ocean leads to buoyant vertical motions, commonly referred to as plumes. It is important to study the mixing dynamics of a plume at a local scale in order to model their evolution and growth. Such a characterization requires measuring the velocity and density of the mixing fluids simultaneously. Here, we present the results of a buoyant plume propagating in a linearly stratified medium with a density difference of 0.5%, thus yielding a buoyancy frequency of N=0.15 s^{-1}. To understand the plume behaviour, statistics such as centerline and axial velocities along varying downstream locations, turbulent kinetic energy, Reynolds stress, and buoyancy flux were measured. The centerline velocity was found to decrease with increase in height. The Reynolds stress and buoyancy flux profiles showed the presence of a unstable layer and the mixing associated within that layer.