CAS Sediment Transport Demonstration Channel

5. We can examine the structure of turbulence in the flow using dye injection, interesting for the dune bedform configuration and clearly demonstrates separation on the lee face.

Fixed, smooth bed flow:

The channel may be used without sediment on the bed to demonstrate several flow phenomena and equations:

6. Rapid, super critical flow dominance of intertial over gravity forces, shock waves from flow obstructions.
7. Turbulence.
8. Governing equations of open channel flow Reynold’s number, Froude number, continuity, Bernoulli’s equation, weir equations.
9. Tranquil, sub critical flow movement of surface waves upstream against flow.
10. Hydraulic jump transition from super to sub critical flow, air entrainment, mixing.
11. Flow measurement using sharp crested weirs.

Bedform hysteresis:

12. If the discharge in the channel changes quickly, there is no sufficient time for bedforms to adjust to the new flow regime. Hence, if a flood hydrograph is simulated by increasing and then decreasing the discharge, different depths will occur for the same discharge on the rising and falling limbs.

Data collection and numerical evaluation (computational work):

13. In addition to illustrating flow and sediment phenomena, we can use the channel for basic data collection and numerical evaluation of the following:
• Flow resistance.
• Manning, Chezy and Darcy-Weisbach fricion factors for several bedform configuration.
• Bedform prediction.
• Velocity Hjulstrom diagram.
• Suspended load movement by suspension.
• Shields parameter Bogardi diagram.
• Stream power Simons and Richarson charts.
• Boundary shear stress Leeder chart.
• Initiation of motion.
• Shields diagram.
• Hjulstrom’s curve.

Mechanics of sediment transport:

14. We can observe the movement of grains, starting from a plane bed with no motion, on the following:
• Initiation of motion.
• Trajectory of initial motion.
• Movement by rolling and sliding (contact load).
• Movement by hopping (saltation load).
• Movement by suspension.

Depositionary features and facies:

15. We can observe the deposition of sediment load and the resulting patterns of grains within the sand body may be identified.

Local scour:

16. Scour under boils and vortices in the flow is observed under both the lower and upper regime bedforms. Obstructions may be introduced to represent bridge piers, sills, revetments, etc, and the resulting pattern of scour examined.