264
CHAPTER 6. SEDIMENT TRANSPORT MODELS
coastal structures or other bottom-resting weights are being supported by the movable-bed.
f. Nonsimilitude of the relative fall speed scale means that suspended sediment transport will not be properly modeled
by the Lightweight Model.
Kamphuis (1975) provided greater detail and an example to illustrate the
scale effects arising from lightweight materials when used as model sediment. Table 6.2 from Bettess (1990) lists lightweight sediments that have
seen use in coastal engineering model studies.
Table 6.2: Lightweight Modeling Materials (after Bettess 1990).
Specific Gravity (ps/p)
Lightweight Material
1.0 to 1.1
Polystyrene, Sawdust with asphalt
1.1 to 1.2
Nylon, Perspex, PVC, Wood
1.2 to 1.3
ABS * ,
Bakelite, PVC
1.3 to 1.4
Bakelite, Coal, Walnut shells
1.4 to 1.5
Bakelite, Coal, Sand of Loire
1.5 to 1.6
Coal, Sand of Loire
1.6 to 1.7
Lightweight aggregate
Acrylonitrile Butadienne Styrene
As seen from this discussion, the usefulness of the Lightweight Model is
hindered by (1) the difficulty in selecting an appropriate model sediment
to fulfill the criteria, and (2) the inherent scale effects that accompany the
use of lightweight materials. Kamphuis (1985) summed it up when he said,
The seriousness of this limitation of a lightweight coastal movablebed model is now understood by most laboratories, and it has become unusual to see a coastal movable-bed model using lightweight
material, unless the motion of the material is used to give only
qualitative answers away from the surf zone.
CHAPTER 6. SEDIMENT TRANSPORT MODELS
coastal structures or other bottom-resting weights are being supported by the movable-bed.
f. Nonsimilitude of the relative fall speed scale means that suspended sediment transport will not be properly modeled
by the Lightweight Model.
Kamphuis (1975) provided greater detail and an example to illustrate the
scale effects arising from lightweight materials when used as model sediment. Table 6.2 from Bettess (1990) lists lightweight sediments that have
seen use in coastal engineering model studies.
Table 6.2: Lightweight Modeling Materials (after Bettess 1990).
Specific Gravity (ps/p)
Lightweight Material
1.0 to 1.1
Polystyrene, Sawdust with asphalt
1.1 to 1.2
Nylon, Perspex, PVC, Wood
1.2 to 1.3
ABS * ,
Bakelite, PVC
1.3 to 1.4
Bakelite, Coal, Walnut shells
1.4 to 1.5
Bakelite, Coal, Sand of Loire
1.5 to 1.6
Coal, Sand of Loire
1.6 to 1.7
Lightweight aggregate
Acrylonitrile Butadienne Styrene
As seen from this discussion, the usefulness of the Lightweight Model is
hindered by (1) the difficulty in selecting an appropriate model sediment
to fulfill the criteria, and (2) the inherent scale effects that accompany the
use of lightweight materials. Kamphuis (1985) summed it up when he said,
The seriousness of this limitation of a lightweight coastal movablebed model is now understood by most laboratories, and it has become unusual to see a coastal movable-bed model using lightweight
material, unless the motion of the material is used to give only
qualitative answers away from the surf zone.