To provide a pipe for carrying a multiphase flow containing a mixture of oil and gas, and comprising a portion wherein the centerline of the portion follows a substantially helical path, and when fluid flows in such a pipe, the fluid is made to swirl, thereby providing a number of advantages, such as improved in-plane mixing of the fluid, enhanced uniformity of residence time, and so on.

The method of manufacturing a pipe includes: a step of making a flexible pipe portion of a straight linear adjoin another linear flexible part member; a step in which the flexible tube portion of the linear section and the linear flexible part member are twisted to the mutual surroundings: and a step of processing the flexible tube portion so that the flexible tube portion may maintain the configuration.