Analog rain experiment: plumes of soluble particles

Rain is a critical component of the climate system. A key ingredient of the rain process is the coupling between flow and phase change. We investigate the sedimentation of a suspension of soluble solid particles from a localized point at the top of a water tank, serving as an analog for rain processes. Here, the air in the atmosphere is simulated by water in the tank, and the phase change between rain droplets and water vapor is represented by the dissolution of salt particles in water.



During the experiments, a controlled amount of salt is injected into the water tank to mimic rain, resulting in the formation of a plume due to particle sedimentation. When the tank is filled with non-saturated water, the injected particles dissolve progressively during their descent, significantly influencing the characteristics of the plume.



To quantify these phenomena, we employ light absorption to measure particle concentration and Particle Image Velocimetry (PIV) to analyze velocity fields, enabling us to estimate the entrainment velocity as a function of particle injection rate.



Our findings reveal that the solubility of particles plays a pivotal role in shaping the plume. Furthermore, the entrainment velocity of soluble particles exhibits considerable variation depending on the specific particle properties. These observations hold implications for enhancing our understanding of environmental and climate-related processes impacted by sedimentation and evaporation phenomena.