How UVP-DUO helps to analyze fine sediment exchanges and shear stress

23 June 2024 by
How UVP-DUO helps to analyze fine sediment exchanges and shear stress
Met-Flow SA

Summary of the experiment

The study focused on understanding the dynamics of fine sediment accumulation and exchange with the riverbed substrate, influenced by shear stress. This research is crucial because the accumulation of fine sediment can reduce vertical water exchanges, negatively affecting river ecosystems. The experiment was conducted in a 6.25-meter-long flume with a width of 15 cm and a substrate layer thickness of 31 cm, composed of a mixture of sand and gravel. The flow conditions were varied, and velocity profiles were measured using a UVP probe to evaluate shear stress at different points along the flume.

UVP-DUO usage

The Met-Flow 4 MHz Ultrasonic Velocity Profiler (UVP) was used to measure flow velocity profiles at 13 locations along the flume. The probe was placed at a 30° angle to the perpendicular of the flume's top slope, measuring points from 5 mm away from the probe with a vertical resolution of 0.64 mm. Each location had 200 velocity profiles measured with 256 repetitions for each profile. The UVP setup allowed for precise determination of shear velocity from the velocity profiles using the logarithmic law of the wall.

Result of the Experiment

The results showed that the velocity profiles measured with the UVP probe could be used to accurately determine shear velocity, which matched well with theoretical values obtained from a backwater curve model. The study found that shear velocity could be well evaluated in areas without significant flow disturbances caused by protruding grains. The UVP measurements helped identify the conditions under which fine sediment deposition occurred, differentiating between surface clogging and inner clogging based on the shear stress.

The UVP-DUO's high-resolution measurements were critical in obtaining detailed velocity profiles, allowing for accurate estimation of shear stress and understanding sediment exchange dynamics. This study demonstrated the effectiveness of UVP in measuring shear stress in flume experiments, providing valuable insights into sediment transport processes and their impact on riverbed clogging.

Read the full paper in our Digital Library here.

Share this post