Cyclic fluid-fluid displacements in disordered media feature hysteresis, multivaluedness, and memory properties in the pressure-saturation relationship. Quantitative understanding of the underlying pore-scale mechanisms and their extrapolation across scales constitutes a major challenge. Here we find that the capillary action of a single constriction in the fluid passage contains the key features of hysteresis. This insight forms the building block for an ab initio model that provides the quantitative link between the microscopic capillary physics, spatially-extended collective events (Haines jumps) and large-scale hysteresis. The mechanisms identified here apply to a broad range of problems in hydrology, geophysics and engineering.

无序介质中的循环流体-流体位移具有滞后性，多值性和压力-饱和关系中的记忆特性。对潜在的孔尺度机制及其跨尺度外推的定量理解构成了一项重大挑战。在这里，我们发现流体通道中单个收缩的毛细作用包含滞后的关键特征。这种见解构成了从头算模型的基础，该模型从微观毛细管物理学，空间扩展的集体事件（Haines跳跃）和大规模磁滞现象之间提供了定量联系。此处确定的机制适用于水文学，地球物理学和工程学中的广泛问题。