Constraints on contact angles for multiple phases in thermodynamic equilibrium

For three or more fluid phases in thermodynamic equilibrium and in contact with a solid surface, the Young equation can be used to find relations between the contact angles for different pairs of fluids. For an n-fluid-phase system, n(n - 1)/2 contact angles can be defined, but there are (n - 1)(n - 2)/2 constraints between them, leaving only n - 1 independent values of the contact angle. These constraints are very powerful in limiting and determining possible types of wetting behavior. The consequences are discussed for three- and four-phase Row. They have important applications for the understanding of gas injection processes in petroleum reservoirs. (C) 2001 Academic Press.