5% - eTheses Repository - University of Birmingham

stoss slope suspension studies of chapter 4 are difficult to
overcome. One plausible approach would involve attaching a layer
of particles to the bedforms providing a rough surface for
retention of a second layer of free particles. Should this prove
insufficient to solve the problem then magnetics may provide the
answer. Each particle could conceivably be coated with, say,
iron powder and held to the bedform during flow development with
an electromagnet either beneath the flume or built into the
bedform.
3.2 Numerical modelling techniques
The fixed core modelling of chapter 5 should be extended to
encompass more starting conditions and different vorticity
distributions such as the Gaussian core. Essentially, the
criterion C(X,Y,VX ,VY ) should be found for all relevant values of
the initial position (X,Y) of the particle at initial velocities
(VX ,VY ) . For the sandwave problem (X,Y) should be considered
from (-20,-20) to (20,20) at (VX ,VY ) from (0,-VT ) to (U,0) where
U is the maximum mean stream speed, about say 2m/s for dunes.
This comprehensive set would be too large to be of use directly,
but would allow rules to be defined concerning particle capture
and ejection which should be of more general use to modellers.
The growing vortex model of the shear layer should be extended
to include different growth laws ie adapted to account for shear
layers that do not have constant velocity difference. This is
needed because the shear layer over sandwaves cannot sensibly
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