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The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Fluid Dynamics with Erosion Brandon Lloyd COMP 259 May 2003.

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Presentation on theme: "The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Fluid Dynamics with Erosion Brandon Lloyd COMP 259 May 2003."— Presentation transcript:

1 The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Fluid Dynamics with Erosion Brandon Lloyd COMP 259 May 2003

2 The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Overview Sediment transport in open channels ­Bed-load transport ­Suspensed transport Sediment transport models Model used for this project Implementation issues Future work

3 The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Sediment Transport Bed-load transport: sliding, rolling, saltating Suspended transport: sediment moves through the fluid Sediment Suspension Bed-load Bed

4 The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Bed-load transport Once the forces acting on particles are strong enough to intiate motion… … particles slide, roll, and saltate down the river bed at a steady rate. Figure from Chanson, p. 180 Figure from Chanson, p. 200

5 The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Suspended Transport Suspension occurs here Particles entrained at the bed-load layer Transported by convection, diffusion, and turbulence Figure from Chanson, p. 200

6 The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL 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 The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL 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 The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Implementation Issues Semi-Lagrangian advection causes mass loss in the presence of eddies. What to do at boundaries? zero concentration backward tracing does not see wall  mass loss.

9 The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL 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 The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Results Nice swirls of sediment with erosion and deposition at interactive rates (on a fast machine.)

11 The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL 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 The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL References CHANSON, H The Hydraulics of Open Channel Flow: An Introduction. Arnold. HAUPT, B. J., SEIDOV, D. AND STATTEGGER, K 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 D numerial modeling of flow and sediment transport in open channels. Journal of Hydraulic Engineering, 4-15.


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