Fluid Dynamics with Erosion

1
Fluid Dynamics with Erosion

• Brandon Lloyd
• COMP 259
• May 2003

2
Overview

• Sediment transport in open channels
• Bed-load transport
• Suspensed transport
• Sediment transport models
• Model used for this project
• Implementation issues
• Future work

3
Sediment Transport

• Bed-load transport sliding, rolling, saltating
• Suspended transport sediment moves through the
  fluid

Suspension
Sediment
Bed-load
Bed
4
Bed-load transport
Once the forces acting on particles are
strong enough to intiate motion
Figure from Chanson, p. 200
particles slide, roll, and saltate down the
river bed at a steady rate.
Figure from Chanson, p. 180
5
Suspended Transport

• Particles entrained at the bed-load layer
• Transported by convection, diffusion, and
  turbulence

Suspension occurs here
Figure from Chanson, p. 200
6
Sediment Transport Models

• Difficult problem most models are empirical.
• Usually make simplifying assumptions about flow.
• Many different formulas exist.

Table from Chanson, p. 198
7
My Model

• Simplified version of model used in Haupt et al.
  1999
• Transport occurs above critical velocity.
• Fluid has a transport capacity related to
  velocity.
• Concentration of sediment relative to capacity
  determines change in terrain

8
Implementation Issues
zero concentration

• Semi-Lagrangian advection causes mass loss in the
  presence of eddies.
• What to do at boundaries?

backward tracing does not see wall ? mass loss.
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Implementation Issues

• Semi-Lagrangian advection causes mass loss in the
  presence of eddies.
• What to do at boundaries?

Recycle concentration(limits the time-step)
10
Results

• Nice swirls of sediment with erosion and
  deposition at interactive rates (on a fast
  machine ?.)

11
Future Work

• Add bed-load transport
• Add instability based on slope
• Add variable material properties
• Fix spikes and improve robustness
• Better handling of velocities near heightfield.
• Experiment with and compare different
  fluid/advection models
• Add a free surface
• Implement on GPU

12
References

• CHANSON, H. 1999. The Hydraulics of Open Channel
  Flow An Introduction. Arnold.
• HAUPT, B. J., SEIDOV, D. AND STATTEGGER, K. 1999.
  SEDLOB and PATLOB Two numerical tools for
  modeling climatically forced sediment and water
  volume transport in large ocean basins. In
  Computerized Modeling of Sedimentary Systems.
  Springer-Verlag, Berlin.
• WU, W., RODI, W. AND THOMAS, W. 2000. 3D numerial
  modeling of flow and sediment transport in open
  channels. Journal of Hydraulic Engineering, 4-15.