Evaporation versus imbibition in a porous medium

Area of Science:

• Fluid dynamics
• Porous media physics
• Interfacial phenomena

Background:

• Controlling liquid movement in porous materials is vital for applications like groundwater flow, oil recovery, and material processing.
• Existing models often simplify or neglect the interplay between capillary forces, gravity, and evaporation.
• A comprehensive understanding of these combined effects is needed for accurate prediction and control.

Purpose of the Study:

• To derive a general analytical solution for flat liquid front dynamics in porous media.
• To investigate the influence of capillary imbibition, gravity, and evaporation on liquid front movement.
• To classify and analyze the different types of liquid front dynamics based on key dimensionless numbers.

Main Methods:

• Derivation of a general analytical solution incorporating capillary, gravitational, and evaporative forces.
• Introduction and analysis of two dimensionless numbers: gravity-capillary number (G) and evaporation-capillary number (E).
• Comprehensive analysis of liquid front dynamics as a function of G and E, including limiting cases.

Main Results:

• The liquid front dynamics are governed by the gravity-capillary number (G) and evaporation-capillary number (E).
• Seven distinct types of liquid front dynamics, categorized into three main behaviors, were identified.
• Simplified expressions for the general solution were derived for each limiting case.

Conclusions:

• The derived analytical solution provides a unified framework for understanding liquid front dynamics in porous media.
• The study reveals a rich variety of dynamic behaviors influenced by fluid properties, porous medium characteristics, and environmental conditions.
• Estimated G and E values highlight common regimes and dynamics encountered in practical applications, aiding in prediction and control.