4. Two-phase flow in long pipes

4.1 Notion of two-phase flow

In many industrial processes, the flow in a pipe is not that of a homogeneous fluid, compressible or not, but of a mixture of two fluids (including at least one liquid) or of a fluid and solid particles. This is known as two-phase flow. Numerous examples can be found in the oil industry, in the hydraulic transport of excavated material or fuels, in the pneumatic transport of many powdered materials, in the flow of steam and water in steam generators, in emulsion pumps, and so on.

4.2 Difficulties...