An alternate development of a non-orthogonal coordinate system that is useful in studying fluid flow in helical tubes in the limit of large pitch is presented. It is based on a rotating Cartesian system of coordinates. An analytical solution is developed for the creeping flow limit in such tubes. Also the complete equations of motion are solved numerically for a set of parameter values (viz. pitch, radius of coil and aspect ratio) that yield an approximate square in the direction along the central helix. The ratio of the friction factor of a square helical tube to that of a square straight tube has been correlated through the use of the flow helical number.
- Curved tube
- Finite pitch