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This model provides a three-dimensional space of the various states of a fictitious substance with water-like properties. [2] This plot has coordinates volume (x), entropy (y), and energy (z). It was based on the American scientist Josiah Willard Gibbs’ graphical thermodynamics papers of 1873.
The discontinuity in , and other properties, e.g. internal energy, , and entropy,, of the substance, is called a first order phase transition. [12] [13] In order to specify the unique experimentally observed pressure, (), at which it occurs another thermodynamic condition is required, for from Fig.1 it could clearly occur for any pressure in the range .
A century later Gibbs [3] proposed a modification to Young's equation to account for the volumetric dependence of the contact angle. Gibbs postulated the existence of a line tension, which acts at the three-phase boundary and accounts for the excess energy at the confluence of the solid-liquid-gas phase interface, and is given as:
Bridge scour – Erosion of sediment near bridge foundations by water; Isosurface – Surface representing points of constant value within a volume; Keulegan–Carpenter number – Dimensionless quantity used in fluid dynamics; Entrance length (fluid dynamics) – Distance a flow travels after entering a pipe before fully developed
The technique is closely related to using gas adsorption to measure pore sizes, but uses the Gibbs–Thomson equation rather than the Kelvin equation.They are both particular cases of the Gibbs Equations of Josiah Willard Gibbs: the Kelvin equation is the constant temperature case, and the Gibbs–Thomson equation is the constant pressure case. [1]
When perfectly pure, the interface between fluids usually displays only surface tension. [1] The stress within a fluid interface can be affected by the adsorption of surfactants in several ways: Change in the surface concentration of surfactants when the in-plane flow tends to alter the surface area of the interface (Gibbs' elasticity). [2]
Wulff construction. The surface free energy is shown in red, with in black normals to lines from the origin to .The inner envelope is the Wulff shape, shown in blue. The Wulff construction is a method to determine the equilibrium shape of a droplet or crystal of fixed volume inside a separate phase (usually its saturated solution or vapor).
The definition of the Gibbs function is = + where H is the enthalpy defined by: = +. Taking differentials of each definition to find dH and dG, then using the fundamental thermodynamic relation (always true for reversible or irreversible processes): = where S is the entropy, V is volume, (minus sign due to reversibility, in which dU = 0: work other than pressure-volume may be done and is equal ...