What is the difference in pressure between two phases in equilibrium at the same depth called?

What is the difference in pressure between two phases in equilibrium at the same depth called?

• A. Differential Pressure
• B. Capillary Pressure
• C. Hydrostatic Pressure
• D. Phase-pressure Difference

Answer: (B)

Capillary pressure is the pressure difference between two immiscible fluids occupying the same location in a porous medium. This difference arises from the interfacial tension and the curvature of the fluid–fluid interface. At a given depth, the hydrostatic pressures of the two fluids would reflect their densities, but the actual pressure difference that matters at the interface is the capillary pressure, defined as the pressure in the non-wetting phase minus the pressure in the wetting phase. This concept explains why two phases in contact don’t share the same pressure even though they sit at the same depth, and it governs how fluids distribute in porous rocks during drainage and imbibition. Other terms like differential pressure describe a general pressure difference, hydrostatic pressure refers to the weight of a single fluid column, and a nonstandard term isn’t used in this context.

Capillary pressure is the pressure difference between two immiscible fluids occupying the same location in a porous medium. This difference arises from the interfacial tension and the curvature of the fluid–fluid interface. At a given depth, the hydrostatic pressures of the two fluids would reflect their densities, but the actual pressure difference that matters at the interface is the capillary pressure, defined as the pressure in the non-wetting phase minus the pressure in the wetting phase. This concept explains why two phases in contact don’t share the same pressure even though they sit at the same depth, and it governs how fluids distribute in porous rocks during drainage and imbibition. Other terms like differential pressure describe a general pressure difference, hydrostatic pressure refers to the weight of a single fluid column, and a nonstandard term isn’t used in this context.