Measurements of steady turbulent flow through a rigid simulated collapsed tube

Axial and transverse components of liquid velocity are measured by laser Do ppler anemometer in a perspex tube that has been deformed at one point to r esemble the shape of the throat of a partially collapsed flexible tube, con veying fluid while being compressed externally. The Reynolds number is 5900 . The flow downstream of the throat consists of two side-jets with reverse flow extending all across the cross-section between them. The jets spread o ut around the central retrograde-flow zone, initially forming crescents of high-speed forward flow and then, at three diameters downstream, an almost complete annulus of forward flow around a central zone of lower-speed but n ow forward flow. Comparison is made between the features of this turbulent flow and those of a previously investigated laminar flow through the same g eometry. In both, retrograde flow ceases between two and three diameters do wnstream of the centre of the throat. However, the laminar flow is annular at three diameters downstream, whereas here the jets remain influential at that station. The maximum normalised turbulence intensity exceeds 1.35.