Open channel flow measurements in a moving-bed flume.

The moving bed flume is designed to overcome the length restriction of a traditional laboratory flume. Using a conveyor type belt at the bottom of the flume the bed of the flume can be made to move a predetermined speed. There is no flow in or out of the flume and so the cross sectional mean flow velocity is zero. Measurements of water surface gas transfer, which are normally restricted by flume length, were made and related to bottom shear and water temperature. The moving bed flume is also useful for visualization of coherent structures in the flow, such as secondary currents. Hydrogen bubbles illuminated by a plane of laser light were used to visualize and measure these coherent structures. Flow visualization at the zero velocity point provides a unique view of secondary currents without the interference of the primary flow velocity. (from authors' abstract)