ENTRANCE REGION OF CIRCULAR PIPES FLOWING PARTLY FULL

This paper presents the results of an experimental study on the characteristics of flow in the entrance region of a circular pipe flowing partly full for slopes of 1,3 and 5%. An analysis of the water surface and velocity profiles in the centerplane indicates the existence of a near-field of the entrance region. At the end of this region, the depth of flow is essentially constant with the velocity in the outer flow (above the boundary layer) having reached a maximum value but the velocity profile is still evolving (in a limited way), associated with the growth of the boundary layer. In this near-field, the flow may be modelled by potential flow with a thin boundary layer of approximately constant thickness. Correlations have been developed for the main characteristics of this near-field.