fluidphase

Fluidphase is a term used to describe a phase of matter in which the substance can flow and deform under applied stresses. It encompasses liquids and gases, including vapors and supercritical fluids that do not fit neatly into the standard categories of liquid or gas. A fluid phase is defined by molecular mobility and the absence of long-range crystalline order typical of solids.

In a pressure–temperature diagram, the fluid region comprises the liquid and gaseous states. Fluid phases are separated from solids by phase boundaries such as melting and vaporization lines; the liquid–gas boundary ends at the critical point. At the triple point, solid, liquid, and gas phases can coexist, illustrating the broader context of phase behavior.

Key properties of fluid phases include the ability to flow, form interfaces, and respond to pressure and temperature changes. Viscosity, density, compressibility, diffusion, and surface tension distinguish diverse fluids. Fluids exhibit laminar or turbulent flow described by fluid mechanics and can demonstrate complex multiphase behavior when more than one fluid phase is present in a system.

Applications span engineering, science, and natural processes. Fluid phases are central to water and air transport, chemical processing, and energy extraction. In geology, subsurface fluids such as brines or hydrocarbons undergo phase changes under varying conditions. In industry, modeling multiphase flow helps design pipelines, reactors, and environmental remediation strategies.

Thermodynamic treatment relies on equilibria, equations of state, and chemical potentials to predict when and how phases coexist. Experimental methods include calorimetry and spectroscopy, while simulations use computational fluid dynamics and related models to study fluid-phase behavior in complex systems.