312
CHAPTER 6. SEDIMENT TRANSPORT MODELS
by stating, “More extensive data are required to establish further the degree
of validity of the proposed modeling criteria.”
The scaling criteria advocated by Dean (1985) are given in terms of
scale ratios by combining the undistorted Froude hydrodynamic criterion
Nt —
(6.153)
with the fall speed parameter scaling requirement given by Eqn. 6.108, i.e.,
Nl = N^Nt
(6.154)
(where Nl has replaced Nz)- Substituting for Nt in Eqn. 6.154 and rearranging gives the fall speed scale relationship
N„ = y/NgNL
(6.155)
Equation 6.155 is essentially the same as the relative fall speed criterion
given by Eqn. 6.76.
The scaling recommendations of Dean (1985) were specifically tested
in undistorted, erosive movable-bed models by Kriebel, Dally, and Dean
(1986) and by Vellinga (1986). Both studies documented success in reproducing prototype-scale profile development. Sayao and Nairn (1988)
advocated geometrically undistorted models in which the model fall speed
parameter is the same as the prototype, but they stated that scale effects
will still be present due to nonsimilitude of the relative grain size parameter and an empirical parameter relating grain size to beach slope. Sayao
(1991) elaborated further on these scale effects in reference to the design of
“pocket beaches” using movable-bed physical models. Other acceptance of
the scaling criteria is discussed in Hughes and Fowler (1990a).
More recently, Fowler and Hughes (1989) and Hughes and Fowler (1990a,
1990b) used a l-to-7.5 scale (midscale) movable-bed physical model to validate the criteria suggested by Dean. Two-dimensional flume tests successfully reproduced profile evolution observed in prototype-scale wave flume
tests conducted in at the GoBer Wellenkanal in Germany under both regular and irregular wave conditions. For the case of regular waves, a sloping
concrete revetment was exposed, thus validating the scaling guidance for
use in studying scour at coastal structures. Comparisons between regular
wave and irregular wave profile evolution indicated that best correspondence for these tests was achieved when the significant wave height equaled
the monochromatic wave height. Other researchers have indicated that
using root-mean-squared wave height or even mean wave height provided
better correspondence to regular wave profile development. Hughes and
CHAPTER 6. SEDIMENT TRANSPORT MODELS
by stating, “More extensive data are required to establish further the degree
of validity of the proposed modeling criteria.”
The scaling criteria advocated by Dean (1985) are given in terms of
scale ratios by combining the undistorted Froude hydrodynamic criterion
Nt —
(6.153)
with the fall speed parameter scaling requirement given by Eqn. 6.108, i.e.,
Nl = N^Nt
(6.154)
(where Nl has replaced Nz)- Substituting for Nt in Eqn. 6.154 and rearranging gives the fall speed scale relationship
N„ = y/NgNL
(6.155)
Equation 6.155 is essentially the same as the relative fall speed criterion
given by Eqn. 6.76.
The scaling recommendations of Dean (1985) were specifically tested
in undistorted, erosive movable-bed models by Kriebel, Dally, and Dean
(1986) and by Vellinga (1986). Both studies documented success in reproducing prototype-scale profile development. Sayao and Nairn (1988)
advocated geometrically undistorted models in which the model fall speed
parameter is the same as the prototype, but they stated that scale effects
will still be present due to nonsimilitude of the relative grain size parameter and an empirical parameter relating grain size to beach slope. Sayao
(1991) elaborated further on these scale effects in reference to the design of
“pocket beaches” using movable-bed physical models. Other acceptance of
the scaling criteria is discussed in Hughes and Fowler (1990a).
More recently, Fowler and Hughes (1989) and Hughes and Fowler (1990a,
1990b) used a l-to-7.5 scale (midscale) movable-bed physical model to validate the criteria suggested by Dean. Two-dimensional flume tests successfully reproduced profile evolution observed in prototype-scale wave flume
tests conducted in at the GoBer Wellenkanal in Germany under both regular and irregular wave conditions. For the case of regular waves, a sloping
concrete revetment was exposed, thus validating the scaling guidance for
use in studying scour at coastal structures. Comparisons between regular
wave and irregular wave profile evolution indicated that best correspondence for these tests was achieved when the significant wave height equaled
the monochromatic wave height. Other researchers have indicated that
using root-mean-squared wave height or even mean wave height provided
better correspondence to regular wave profile development. Hughes and