5% - eTheses Repository - University of Birmingham

Chapter 3
Figure 1. After Alien (1984). Lee slope landing sites for sediment jetting
over the crest of a sandwave. Sediment is deposited further along the lee
slope with higher values of U/V.
Figure 2. After Alien (1984) . Widthwise dispersion of sediment jetting over
the lee slope of a sandwave.
Figure 3a-j. The plates show the development of a shear layer vortex over a
steep-lee-faced dune at a crest velocity of about 0.Im/s. Had the camera been
slightly further to the left we would see the vortex in plate a) move off
downstream.
Figure 4. The cycloid-like trajectories of two particles entrained into the
shear layer and transported downstream. The crest velocity is about 0.36m/s.
The bedform angle is 30 degrees to the horizontal but appears larger due to
graphical manipulation.
Figure 5. The view field, positioned after the second crest (the rightmost
point of the bedform above) was divided into 24, 0.012m long categories for
gathering of the trajectory data, giving a total view field length of 0.29m
ie 44% of bedform wavelength). Subsequent analysis used groups of three
landing sites denoted by the central value in the range, ie 2,5 etc.
Figure 6. Distribution of particle landing sites of U/V=6. Most of the
particles land on the lee slope within two seconds of leaving the crest.
Figure 7a-g. The seven trajectory modes for jetted particles, a) Ml b)M2 c)
M3 d) M4 e) M5 f) M6 g) M7.
Figure 8. The average vertical velocity (cm/s) of particles landing at each
location downstream of the crest, where X is the horizontal landing position.
The particle quiescent fall speed is 3.4cm/s. It is clear that particles are
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