The AOCF is a state-of-the-art facility for studying smooth- and rough-bed flow hydrodynamics, sediment transport processes, flow-biota interactions and other aspects of fluvial-hydraulics and ecohydraulics. The facility consists of three components; an 18m long and 1.18m wide glass-sided open-channel flume, a four-axis instrumental carriage, and a unique modular robotic Particle Image Velocimetry (PIV) system. The facility was originally completed in 2008, but since then has undergone continual refinement to maintain its world class status.
All aspects of the AOCF, including slope adjustment, flow rate control, manipulation of the tail-water control weir, and operation of the robotic PIV system are computer controlled - permitting a high degree of automation throughout experimental programmes. Such automation allows a level of repeatability and precision that is unobtainable with conventional facilities. Measurement programmes can also be significantly extended to systematically cover a wider range of flow and bed configurations than would be possible with manual operation.
The robotic stereoscopic PIV system is shown here capturing velocity fields in a sequence of cross-flow planes over a rough bed surface. The system can also be configured to measure in the streamwise plane or in a high-resolution near-bed mode. Velocity fields can be captured at up to 200 Hz using a Litron “Plasma” 70mJ diode pumped solid state laser and JAI “Spark” 12 Megapixel cameras. The system can also operate at very low light levels using Andor thermo-electrically cooled “Zyla” sCMOS cameras.
The instrumental carriage is shown here scanning bed surface topography with a laser triangulation sensor. A similar scan can be performed on the flowing water surface using an array of chromatic confocal sensors. Combining the bed and water surface scans allow the flow depth profile to be calculated with very high accuracy.
The AOCF can also be used as a computer numerical control (CNC) milling machine. This video shows the manufacture of a 400x400 mm tile with a computer generated self-affine fractal rough surface. These tiles were then reproduced in epoxy resin to cover the entire bed of the channel.
Automated experiments to measure 'time-to-entrainment' for spherical particles of different density and protrusion. Plastic spheres with a 16 mm diameter are placed on the flume bed one at a time while a light sensitive detector beneath the particle indicates the exact moment the particle becomes entrained by the turbulent flow. Statistical distributions of time-to-entrainment are important for understanding and prediction of sediment transport in rivers.
This sequence shows the measurement of drag force fluctuations on a 3d-printed model of rainbow trout. First, the drag device is zeroed in a bucket of still water, then the flume pumps are started and the flowrate ramped up to a steady operating condition. The drag force time series is then recorded for a 2-hour period. Understanding the forces acting on fish is an important step to designing better fish bypass structures at dams.
This sequence shows performance assessment of 3d-printed horizontal and vertical axis hydrokinetic turbines. The experiments involve torque and drag force measurements across a range of tip-speed-ratios and flow conditions. A computer-controlled stepper motor is used to regulate the turbine speed.