Rotating Annular Flume

The Rotating Annular Flume (or Carousel) is a ring-shaped flume imitating a flow channel with no beginning and no end. A special adaptation largely neutralizes the secondary flow due to the curvature. Consequently a never ending straight flow channel is simulated. The facility consists of a circular channel with a mean diameter of 2.1 m and a width of 0.2 m. The water depth is variable with a maximum of 0.3 m. A circular lid at the surface of the water layer drives the flow. In order to minimise the effect of secondary currents near the bottom, the flume itself rotates in the opposite direction. The optimal ratio of the angular velocities of upper lid and flume is a function of the water depth and the surface properties of the sediment in the flume. The sampling of sediments as well as the rotational speeds of the lid and the flume is computer controlled. Data are transmitted between the rotating flume and the personal computer with the aid of a wireless network transmitter and receiver.

The Rotating Annular Flume is situated in a climate-controlled room. The temperature can be kept at any level between 4 and 30 °C. The relative humidity can be controlled at any level between 70% and 100%. This makes the flume also suitable for research concerning biological impact on material properties. The Rotating Annular Flume is a closed system, without sources or sinks, which makes it also suitable for studying biochemical processes at the sediment surface.

Application Areas

The Rotating Annular Flume can be used for all kinds of researches in civil engineering like coastal, river, harbour and sewer engineering. The dedication of the experiments varies form fundamental process research to verification and validation of theories, concepts and technologies, either autonomous natural dynamical processes to human operations. A wide range of measurements is. The set-up of the flume has a good optical accessibility and can be modified also to match difficult requirements. As a standard water temperature, pH and oxygen-content are monitored during an experiment. The oxygen content can be controlled according to specification. An optical measurement system for the online monitoring of the particle concentration in the water column is available. The mean shear stress on the bed can be measured. The bed topography can be measured with laser light at a resolution of about a millimetre in all three dimensions. On-line bedding development can be monitored from the inside the flume. On-line water sampling is possible.

Projects

The carousel is applicable for various measurements on a wide range of materials. Measurements have been done on fundamental physical, chemical and biological processes and mutual interactions.

• erosion properties of several types of mud
• accretion and erosion of sewage sludge
• impact of chemical / biological processes on the erodability of sediment
• segregation processes in dynamic sediment layers
• saltating transport phenomena
• turbidity currents
• gelled bedding transport phenomena
• biological activities in water beds.

Technical specifications

• Flume channel
  Mean diameter: 2.1 m
  Width: 0.2 m
  Depth: variable to a maximum of 0.3 m.
  Rotational velocity: 2.1 rad/s
• Circular lid
  Rotational velocity: 2.6 rad/s
• On-line computer controlled water and sediment sampling
• Wireless data transfer
• Rotating video cameras
• Climate-controlled room
  Temperature: any level between 4 and 30 °C.
  Relative humidity: any level between 70% and 100%