Dynamics of Wetting

The wetting dynamics form the foundation to analyze various problems including solid-liquid interfacial behavior, such as dynamics of bubble, droplet or liquid film on a wall. This book introduces some essential concepts of wetting and offers comprehensive treatments to analyze modern engineering topics observed in various industrial fields. In the part of fundamental principle, some basic ideas of interfacial tensions and contact angles are explained mainly from a dynamic viewpoint. The book also introduces some new methods to measure surface tension as well as for advancing and receding contact angles, and briefly touches on the basic principle of controling the wettability of a solid plates. either a or s, not both!
In the part of application, some real-world problems related to wetting phenomena are discussed in detail. Based on the physical mechanism of contact angle hysteresis, sliding of droplets on inclined plates or on a vertical cylinder and detachment of pendant droplet from a curved surface are analyzed from a thermodynamic viewpoint based on the energy minimum principle. In recent progressing industrial techniques such as lab-on-a-tip or microfluidics, it is important to understand the dynamic wetting phenomenon in which contact angles are dependent on the velocity of three-phase contact line. The authors present a wide variety of experimental and MD results for dynamic contact angles appeared in capillary tubes or two-dimensional meniscus on a moving plate. The dynamics of wetting is discussed from theoretical and numerical results with the concept of Navier's slip condition on the wall. The book also introduces some important applicative topics in handling ink jet devices or surfactant solutions, such as a CFD model to appropriately express the force balance on the contact line, the effect of surface viscosity or dynamic surface tension on the stability of surfactant liquid sheet or droplet, and some unique wetting phenomena observed in steel manufacturing process.

This book explores fundamental concepts of interfacial tension and wetting behavior from a dynamic viewpoint. It provides new ideas to discuss the behavior of droplet, capillarity or meniscus actually observed in practical engineering problems.

Surveys fundamental concepts of interfacial tension and wetting behavior from a dynamic viewpoint Provides new ideas to discuss the behavior of droplet, capillarity or meniscus actually observed in practical engineering problems Presents leading-edge topics of the dynamic wetting and some unique wetting phenomena observed in microfluidic device or in high temperature process

Part I: Fundamental Principle (tentative).- 1. Introduction.- 2. Interfacial tensions.- 2.1 Origin of interfacial tensions and surface thermodynamics.- 2.2 Definition of interfacial tension.- 2.3 Scale effect of interfacial tension.- 2.4 Measurement of gas-liquid interfacial tension (Wilhelmy method, Du Noüy ring method, Drop weighing method, ADSA method).- 2.5 Typical phenomena related to interfacial tensions.- (Capillary adhesion, Marangoni convection, Thermo-capillary effect, Ringing of gauge block etc.) .- 3. Profiles of gas-liquid interface.- 3.1 Laplace equation.- 3.2 Profile of liquid meniscus.- 3.3 Droplet and bubble.- 4. Principles of wetting.- 4.1 Complete wetting and partial wetting.- 4.2 Work of spreading, work of adhesion and work of immersion.- 4.3 Equilibrium contact angle and Young-Dupret's equation.- 4.4 Wettability (Zisman's law, estimation from polarizability).- 4.5 Contact angles on practical solid surface (Wenzel and Cassie's contact angle).- 4.6 Measuring method of contact angle.- 4.7 Basic principles of hydrophobic and hydrophilic surface.- Part II Application (tentative).- Sliding of droplet on inclined plates, Detachment of droplet from curved surface.- Hysteresis phenomenon of contact angle.- Dynamic wetting, Behavior of three-phase contact line,Numerical simulation of dynamic wetting.- Stability of surfactant liquid film (soap film), Surface viscosity, Dynamic surface tension.- Instability of liquid sheet and cylindrical liquid jet (ink jet).- Microfluidics (Manipulation of droplet or bubble, Electro wetting etc.).- Topics in thermal process.