Porousmedia

Porous media are materials containing a solid framework with interconnected voids or pores through which fluids can move. The pore space stores and transfers fluids. Porosity is the fraction of volume occupied by pores. It can be total porosity, measured by all voids, or effective porosity, representing the portion connected to the flow network. Permeability, a property of the solid matrix, quantifies the ease with which fluid can move through the pore network and depends on pore size, shape, connectivity, and tortuosity.

Transport in porous media combines advection with diffusion and, for multiphase systems, capillary and interfacial effects. For laminar single-phase flow, Darcy's law governs the relation between Darcy velocity q and pressure gradient ∇P: q = - (k/μ) ∇P, where k is intrinsic permeability and μ is fluid viscosity. For high velocities or complex flows, Forchheimer or other nonlinear terms are used. In multiphase flow, relative permeabilities and capillary pressure curves describe how each phase shares the pore space.

Pore structure is characterized by porosity, permeability, pore-size distribution, specific surface area, and tortuosity. Measurements include gravimetric porosimetry, gas adsorption, mercury intrusion porosimetry, and imaging techniques such as computed tomography. Natural porous media include soils, sandstones, and clays; engineered porous media include ceramics, foams, and porous polymers. Porous materials can be homogeneous or heterogeneous and may deform under fluid pressure, a field described by poroelasticity and Biot theory.

Applications span groundwater hydrology, petroleum reservoir engineering, filtration and separation, catalysis, energy storage (batteries and supercapacitors), and environmental remediation. Porous media science integrates geology, physics, chemistry, and engineering to model and optimize fluid transport, storage, and reactions in complex pore networks.