Fluidvolumens

Fluidvolumens are the local amounts of fluid contained within a defined region of a fluid system, typically represented in simulations as a volumetric quantity denoted V_f. In discrete models, V_f is expressed in cubic meters and can be reported as an absolute volume or as a dimensionless volume fraction by normalizing to the containing cell volume V_cell.

In porous-media contexts, V_f is computed as V_f = φ · V_cell · S_f, where φ is porosity and S_f is the saturation of the fluid within the pore space. In non-porous or single-phase regions, φ may be treated as 1 and V_f reduces to the product of cell volume and the phase fraction. The relation to mass is given by m_f = ρ_f · V_f, where ρ_f is the fluid density.

Dynamics are governed by conservation laws: the change in V_f results from advection of the fluid, compressibility, and any internal sources or sinks. In time-dependent simulations, the evolution of fluidvolumens reflects the balance of volumetric transport and changes in fluid volume due to pressure, temperature, and phase behavior. The concept is often used alongside density and mass conservation to track how much fluid occupies a region over time.

Applications include porous-media flow modeling, reservoir simulations, microfluidics, and swelling soils. While useful in simulations, fluidvolumens depend on grid resolution, porosity estimates, and phase properties, and can be ambiguous when multiple fluids share the same pore space or when phase transitions occur.

See also Porosity, Saturation, Volume fraction, Continuity equation, Multiphase flow.