Geoscience Reference
In-Depth Information
a
0.8
1000
0.8
1000
800
800
0.6
600
0.6
600
400
400
0.4
200
0.4
200
0
0
0.2
−
200
0.2
−
200
−
400
−
400
0
−
600
0
−
600
0
0.2
0.4
0.6
0.8
1
1.2
0
0.2
0.4
0.6
0.8
1
1.2
x/D
(
−
)
x/D
(
−
)
b
1
1
1000
1000
800
800
0.8
0.8
600
600
400
400
0.6
0.6
200
200
0.4
0.4
0
0
−
200
−
200
0.2
0.2
−
400
−
400
0
0
−
600
−
600
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
x/D
(
−
)
x/D
(
−
)
c
0.8
0.8
300
0.7
200
0.7
200
0.6
0.6
100
100
0.5
0.5
0
0
0.4
0.4
−
100
−
100
0.3
0.3
−
200
−
200
0.2
0.2
−
300
−
300
0.1
0.1
−
400
−
400
0
0
0
0.1 0.2
0.3
0.4
0.5 0.6
0.7
0.8
0.9
1
1.1
1.2
0
0.1 0.2
0.3
0.4
0.5 0.6
0.7
0.8
0.9
1
1.1
1.2
x/D
(
−
)
x/D
(
−
)
Fig. 43 Instantaneous vorticity maps. (a) the vertical plane of symmetry (with streamlines), (b)
vertical plane at 30
from the symmetry axis (with streamlines), and (c) the scour hole, at a vertical
plane 45
from the symmetry axis (with velocity vectors). Vorticity in s
1
a jet along the wall of the cylinder that, by reaching the flow bed, undergoes
separation digging the hole (zone 1) and surrounding the cylinder near the bottom
(see Fig.
44
). Due to this process, the displaced sediments are mostly transported
downward, by the downstream flow. A small part is transported, inside the scour
hole, to higher topography levels by the downward-flow which incorporates the
horseshoe vortex. It was seen that the horseshoe vortex moves frequently towards
the cylinder, interacting strongly with the downflow.
