Geoscience Reference
In-Depth Information
Fig. 2 Oblique (a) and plan (b) views of seed sand waves generated for a flow of depth-based
Reynolds number
R
¼
169, Froude number
F
¼
0.51, shear velocity ratio
u
*
/
u
*c
¼
1.3, flow
depth
h
¼
0.048 m, and
d
¼
0.28 mm, with flow from
left
to
right
Fig. 3 The development of sand waves for Test 2-600 of
R
441,
F
0.63,
u
*
/
u
*c
3.0,
¼
¼
¼
h
0.068 m, and
d
0.44 mm. Bed profiles have been offset vertically to aid clarity, with
¼
¼
flow from
left
to
right
waves for alluvial flows (e.g. Coleman and Melville
1996
), the laminar-flow bed-
form data suggest that the generation of ripples and dunes in alluvial flows cannot
be attributed to an organised structure of turbulence within the flow. Lajeunesse
et al. (
2010
) provide interesting additional examples of fluvial and submarine
morphodynamics that demonstrate the ability of laminar flow to generate morpho-
dynamic features similar to those generally associated with turbulent flow.
2.2 Fluid-Sediment System Instability and Non-intrusive
Water Tunnel Measurements
Most researchers have attributed the process of fluvial-bedform generation from
plane-bed conditions to instability of the sand-water interface (e.g. Liu
1957
;
