- It is similar to the short branch in outward appearance but internally is fitted throughout its whole length with a
cylindrical center tube open at both ends and of 1.25″ diameter, held in position by three longitudinal guide vanes. The advantage is that it gives a more solid jet.
- Theory is that speed of flow of water in hose is greater in the center than at the boundary where there is friction, with the wall of the hose.
- As the cross section area of the central tube does net reduce, the velocity of that part of water which travels through the center tube must be the same at the end as at the beginning.
- The velocity of the slower moving water in contact with the walls of the hose is greatly increased in the branch owing to its tapering shape and on reaching the nozzle, actually travels faster than the water leaving the central tube.
- Thus the jet is composed of a control core held together by faster moving outer sheath water which tends to drag the core along with it giving a solid jet of water.