Abstract: An internal formation for a conduit. The formation has a longitudinally extending member adapted to extend along an inside surface of at least a portion of the length of the conduit. The longitudinally extending member has an asymmetric profile in a direction transverse of the longitudinal axis of the member.

Abstract: A tubular conduit (1) is disclosed. The tubular conduit comprises a tubular portion made from a flexible material and an axially extending external helical formation (16) located around the outside of the tubular portion. The external helical formation (16) is for supporting the tubular portion. Optionally the tubular portion also comprises an axially extending internal helical protrusion (15), which imparts a helical flow to a fluid passing through the tubular portion. It is preferred that the tubular conduit (1) is a vascular graft.

Abstract: A Method of Determining the Helix Angle of a Helical Formation for a Conduit. A method of determining the helix angle of a helical formation (4) within a conduit (1). The method includes specifying the internal dimensions of the conduit (1) and an intended fluid mass flow through the conduit (1). The helix angle is determined from the pressure drop and the turbulent kinetic energy for a conduit (1) having the specified internal dimensions and intended fluid mass flow.

Abstract: A method of assessing the effect of a conduit section (11) on flow characteristics of a first fluid in a first conduit system (1). A first fluid is caused to flow through the first conduit system (1). A transverse flow parameter of the first fluid in the first conduit system (1) downstream of the conduit section (11) is detected. At least one transverse flow characteristic of the first fluid is determined from the detected transverse flow parameter. The effect of the conduit section (11) is then assessed from the determined flow characteristics.