Related Experiment Video
Updated: Jul 14, 2026
07:08
Film Control to Study Contributions of Waves to Droplet Impact Dynamics on Thin Flowing Liquid Films
Published on: August 18, 2018
The leading edge of evaporating droplets
G Guéna1, C Poulard, A M Cazabat
1Laboratoire de Physique Statistique de l'Ecole Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France.
Journal of Colloid and Interface Science
|June 6, 2007
Summary
New experiments investigate evaporating drops on smooth surfaces. While models predict drop radius well, contact angle predictions are qualitative, especially for small angles, necessitating further study.
Area of Science:
- Physical Chemistry
- Fluid Dynamics
Background:
- Previous studies examined alkane and water sessile drops, finding theoretical models accurately predict drop radius but only qualitatively predict contact angle.
- Complete wetting conditions on smooth substrates are crucial for understanding evaporation dynamics.
Purpose of the Study:
- To investigate the evaporation dynamics of sessile drops under complete wetting conditions.
- To evaluate the accuracy of existing theoretical models for drop radius and contact angle.
- To explore the influence of fluid properties, such as surface tension, on evaporation.
Main Methods:
- Experiments were conducted on sessile drops of alkanes, water, and polydimethylsiloxane (silicone) oligomers.
- Hanging drop experiments were used to rule out gas-phase convection effects.
- Systematic studies focused on the dynamics of silicone oil drops with varying purity.
Main Results:
- The theoretical model accurately describes the dynamics of the drop radius.
- Contact angle predictions by the model are qualitative, particularly for small angles.
- Experiments with silicone oils, possessing lower surface tensions than alkanes, revealed smaller dynamic contact angles.
- The purity of silicone oils was found to be critical for experimental reproducibility.
Conclusions:
- Existing models require refinement for accurate contact angle prediction, especially at low angles.
- Further theoretical work is needed to fully understand the evaporation dynamics of drops with low surface tension.
- The purity of working fluids is a critical parameter in evaporation studies.
Related Concept Videos
01:18Vaporization
The physical form of a substance changes by changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize (convert into vapor). The process is called vaporization—a surface phenomenon. For vaporization to occur, kinetic energy must be greater than the intermolecular forces that keep molecules bonded. The amount of energy needed to vaporize a quantity of liquid at a given pressure and a constant temperature is called the heat of vaporization. When...
02:39Phase Transitions: Vaporization and Condensation
The physical form of a substance changes on changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize (convert into vapor). The process is called vaporization—a surface phenomenon. Vaporization occurs when the thermal motion of the molecules overcome the intermolecular forces, and the molecules (at the surface) escape into the gaseous state. When a liquid vaporizes in a closed container, gas molecules cannot escape. As these gas phase molecules...
01:24Surface Tension
Surface tension is defined as the force per unit length (γ) acting along the surface of a liquid. It arises due to strong intermolecular forces of attraction. A molecule located inside the bulk of the liquid is surrounded by other molecules and experiences equal forces in all directions. However, a molecule at the surface experiences unbalanced forces because there are more neighboring molecules below than above. This creates a net inward force that pulls surface molecules toward the interior,...
01:01Distillation: Vapor–Liquid Equilibria
Distillation is a separation technique that takes advantage of the boiling point properties of disparate elements in a mixture. To perform distillation, we begin by heating a miscible mixture of two liquids with a significant difference in boiling points (at least 20°C). As the solution heats up and reaches the bubble point of the more volatile component, some molecules of the more volatile component transition into the gas phase and travel upward into the condenser, which is a glass tube with...
01:13Excess Pressure Inside a Drop and a Bubble
The shape of a small drop of liquid can be considered spherical, neglecting the effect of gravity. This drop can further be considered as two equal hemispherical drops put together due to surface tension. The forces acting on the spherical drop are due to the pressure of the liquid inside the drop, the pressure due to air outside the drop, and the force due to the surface tension acting on the two hemispherical drops.
02:34Vapor Pressure
When a liquid vaporizes in a closed container, gas molecules cannot escape. As these gas phase molecules move randomly about, they will occasionally collide with the surface of the condensed phase, and in some cases, these collisions will result in the molecules re-entering the condensed phase. The change from the gas phase to the liquid is called condensation. When the rate of condensation becomes equal to the rate of vaporization, neither the amount of the liquid nor the amount of the vapor...