gravitationstömning

Gravitationstömning refers to gravity-driven drainage of liquids through a porous medium. In this sense, it denotes the process by which fluid moves downward under the influence of gravity, especially when capillary forces are insufficient to retain the liquid in the pores. The term is used in Swedish-language hydrology, soil physics, and geotechnical engineering to describe the vertical drainage that follows infiltration or irrigation, as well as the natural drying of soils after a wet period.

Physically, gravitationstömning is governed by gravity potential and hydraulic conductivity. In saturated conditions the flow is described by Darcy's law, with a downward flux proportional to the hydraulic gradient including the gravity term. In unsaturated media, the Richards equation models how water content evolves under gravity and capillarity, with the gravity component driving downward movement while capillary suction resists drainage. The rate depends on soil structure, porosity, permeability, and moisture retention characteristics, and it often exhibits non-linear, hysteretic behavior as the soil dries and becomes less permeable to further drainage.

Contexts and relevance include agriculture and civil engineering, where predicting drainage, irrigation efficiency, and slope stability is important; hydrogeology, for understanding recharge and groundwater-surface water interactions; and petroleum engineering, where gravity drainage can influence reservoir depletion and fluid distribution. Gravitationstömning interacts with evaporation, transpiration, and lateral drainage to determine overall moisture distribution in landscapes and engineered systems.

Terminology and notes: gravitationstömning is sometimes translated as gravitational drainage or gravity-driven drainage. While gravity plays a central role, capillarity and pore-scale structure often dominate at finer scales, so the term emphasizes the downward movement caused by gravity rather than purely capillary effects.