Boiling stratified flow: a laboratory analogy for atmospheric moist convection

TL;DR

This study introduces a laboratory experiment using boiling stratified flow as an analogy for atmospheric moist convection, providing insights into the dynamics of cloud formation and lifecycle.

Contribution

The paper develops a novel laboratory model that mimics atmospheric moist convection and derives a theory to predict entrainment rates and boiling regimes.

Findings

The experiment demonstrates transition between intermittent and steady boiling regimes.

A theoretical model accurately predicts entrainment rates and boiling behavior.

Laboratory results suggest similarities with cumulus convection dynamics.

Abstract

We present a novel laboratory experiment, boiling stratified flow, as an analogy for atmospheric moist convection. A layer of diluted syrup is placed below freshwater in a beaker and heated from below. The vertical temperature profile in the experiment is analogous to the vapor mixing ratio in the atmosphere while the vertical profile of freshwater concentration in the experiment is analogous to the potential temperature profile in the atmosphere. Boiling starts when the bottom of the syrup layer reaches the boiling point, producing bubbles and vortex rings that stir the two-layer density interface and bring colder fresh water into the syrup layer. When the syrup layer at the beginning of the experiment is sufficiently thin and diluted, the vortex rings entrain more cold water than needed to remove superheating in the syrup layer, ending the boiling. When the syrup layer is deep and concentrated, the boiling is steady since the entrained colder water instantaneously removes the superheating in the bottom syrup layer. A theory is derived to predict the entrainment rate and the transition between the intermittent and steady boiling regimes, validated by experimental data. We suggest that these dynamics may share similarities with the mixing and lifecycle of cumulus convection.