Flow in a porous media

A porous media can be looked at as a bundle of capillaries having an uneven cross-section. Surface tension plays an important role here. If a capillary is partially immersed in a fluid, the liquid inside the capillary may rise or fall depending upon the contact angle. If contact angle is less than the fluid inside the capillary would rise. In such cases, one might be interested in knowing the time taken for the fluid to rise or the rate of penetration. A few cases are explained in this section.

Horizontal capillary

An understanding of this phenomenon finds applications in the secondary and tertiary oil recovery

Figure 3.7. Horizontal capillary

The driving force behind the flow is the reduction in interfacial energy. This force overcomes the resistance due to friction. Spontaneous penetration occurs for , whereas spontaneous retraction occurs for .