Communications on Hydraulic and Geotechnical Engineering: Measurements of theFlow Field in a Rotating Annular Flume

摘要

Annular flumes are used for studying erosion and/or deposition of cohesivesediments in the laboratory. These flumes have advantages over straight recirculating flumes in that effects of inflow and outflow conditions are avoided and that there are no pumps which break down the suspended flocculated sediment. A disadvantage of annular flumes is that, because of the curvature secondary flow, velocities are generated in the flowing water, yielding a complex three dimensional flow field that is not well known up to now. The present report describes experiments in a rotating annular flume, i.e. an annular flume in which not only the top lid rotates but the flume itself as well. The investigation is aimed at the accurate optimization of the ratio of rotational speeds of top lid and flume. Two different optimizing criteria were considered. The first criterion (criterion I) is the minimal intensity of secondary flow (especially in the lower part of the flume) and the second criterion (criterion II) a uniform distribution of tangential velocity and of near bottom shear stress over the flume width. A simplified analysis of the flow in carousels is given. This analysis provides a method to obtain several relations for carousel flow.