6.2. MOVABLE-BED SCALING REQUIREMENTS
245
sediment transport, solid structures, and model boundaries. Scaling relationships can be derived for more specific versions of the generalized model
where some aspects are neglected, but it is unlikely that any scale relationship will be able to model all interactions simultaneously. “In fact, coastal
(movable-bed) models have shown that most interactions are modeled incorrectly” (Kamphuis 1985).
A multitude of scaling relationships for modeling coastal sedimentary
processes has been proposed over the years (see Hudson et al. 1979; Kamphuis 1982; Yalin 1971; Fan and Le Méhauté 1969 for overviews and lists of
references) . Earlier development of movable-bed scaling criteria for river
applications has provided some of the initial direction for coastal scaling
criteria3; and the proposed relationships vary from completely empirical
to completely theoretical, each with its own advantages, assumptions, and
constraints. In fact, there are so many candidate scaling laws for coastal
movable-bed models that selection of an appropriate set for a given model
application is sometimes difficult (Hudson, et al. 1979).
3See Le Méhauté (1970) for a comparison between river and coastal movable-bed
models.
Le Méhauté (1976) defended the “art” of movable-bed modeling in the
face of conflicting scaling criteria by saying,
The more we know of the laws of sediment transport (and we
still have a lot to learn), the more the scientists of the profession
become convinced that similitude is impossible. However, engineers do not appear to care that specialists in sediment transport
have declared that the movable-bed scale models are wrong; so,
just like the bumblebee who goes on flying even though it has
been declared aerodynamically impossible for him to do so, engineers keep using the movable-bed scale model, and most of the
time with great success.
Researchers throughout the world continue to gather knowledge and experience by working with movable-bed models, and this will ultimately lead
to greater understanding of the inherent model scale effects. Nevertheless,
model validation remains the key ingredient for a successful model.
6.2.1 Sediment Transport Dimensional Analysis
There are two approaches to determining important parameters (and resulting scaling relationships) for the coastal sediment transport model:
a. Assume that the sediment process is reacting primarily to a
unidirectional flow situation with waves added.
245
sediment transport, solid structures, and model boundaries. Scaling relationships can be derived for more specific versions of the generalized model
where some aspects are neglected, but it is unlikely that any scale relationship will be able to model all interactions simultaneously. “In fact, coastal
(movable-bed) models have shown that most interactions are modeled incorrectly” (Kamphuis 1985).
A multitude of scaling relationships for modeling coastal sedimentary
processes has been proposed over the years (see Hudson et al. 1979; Kamphuis 1982; Yalin 1971; Fan and Le Méhauté 1969 for overviews and lists of
references) . Earlier development of movable-bed scaling criteria for river
applications has provided some of the initial direction for coastal scaling
criteria3; and the proposed relationships vary from completely empirical
to completely theoretical, each with its own advantages, assumptions, and
constraints. In fact, there are so many candidate scaling laws for coastal
movable-bed models that selection of an appropriate set for a given model
application is sometimes difficult (Hudson, et al. 1979).
3See Le Méhauté (1970) for a comparison between river and coastal movable-bed
models.
Le Méhauté (1976) defended the “art” of movable-bed modeling in the
face of conflicting scaling criteria by saying,
The more we know of the laws of sediment transport (and we
still have a lot to learn), the more the scientists of the profession
become convinced that similitude is impossible. However, engineers do not appear to care that specialists in sediment transport
have declared that the movable-bed scale models are wrong; so,
just like the bumblebee who goes on flying even though it has
been declared aerodynamically impossible for him to do so, engineers keep using the movable-bed scale model, and most of the
time with great success.
Researchers throughout the world continue to gather knowledge and experience by working with movable-bed models, and this will ultimately lead
to greater understanding of the inherent model scale effects. Nevertheless,
model validation remains the key ingredient for a successful model.
6.2.1 Sediment Transport Dimensional Analysis
There are two approaches to determining important parameters (and resulting scaling relationships) for the coastal sediment transport model:
a. Assume that the sediment process is reacting primarily to a
unidirectional flow situation with waves added.