👉 A foreign fluid, also known as an external or interfacial fluid, refers to a substance that is introduced into a system where it interacts with both the bulk fluid and the solid or other components of that system, but does not mix completely with them. This can include gases dissolved in liquids or vapors in liquids, or even liquid droplets dispersed in a gas. These fluids behave differently from the primary fluids due to their unique interactions at the interface, often exhibiting properties like surface tension and interfacial tension. In many cases, foreign fluids can significantly affect the thermodynamic and transport properties of the system, making their study crucial in fields like chemical engineering, environmental science, and materials science.
