Lecture 3 Sediment transport. Processes of transport (And a few examples)
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Transcript of Lecture 3 Sediment transport. Processes of transport (And a few examples)
Transport in fluids
• By settling: Stokes Law
U = r2g/18
U = settling velocity
r = radius of particle
g = gravitational acceleration
difference in density
viscosity
Transport in fluids
• By settling: Stokes Law
U = r2g/18
What will fall faster?
Boulders or sand grains?
Transport in fluids
• By settling: Stokes Law
U = r2g/18
What will fall faster?
Heavier grains or lighter grains?
Transport in fluids
• By settling: Stokes Law
U = r2g/18
What will fall faster?
Grains in clear water or grains in turbid water?
Transport in fluids
• By settling: Stokes Law
U = r2g/18
What will fall faster?
Clasts on Earth or clasts on Mars?
The effect of turbulence
Multiple grains also slow settling, because they increase the effective viscosity
…density, mass, shape, size, flow velocity, and turbulence.
Consider, for example, the influence of flow velocity
Shear of the fluid near the bed produces lift.
If the lift forces are greater than the gravitational forces on the grain, the grain moves off the bed.
Transport environments
• Gravity-dominated– Rock falls, taluses
• Water-dominated– Rivers, lakes, oceans, estuaries
Transport environments
• Gravity-dominated– Rock falls, taluses
• Water-dominated
• Ice-dominated
• Atmosphere-dominated