308
CHAPTER 6. SEDIMENT TRANSPORT MODELS
similarity of the surf similarity parameter and the sediment fall trajectory
were the most important considerations for modeling suspended sediment
transport on beach profiles.
Although both sets of scaling guidance can accommodate a lightweight
sediment, no comparisons have yet been made using beach profiles developed with lightweight model sediment. Note that sediment fall speed is
also a function of p', so the sediment immersed relative density has added
significance in Wang, et al.’s modeling guidance.
An application of the Model B “fall trajectory” guidance was described
by Wang, et al. (1991). A three-dimensional model of Sebastian Inlet was
operated to investigate several structural alternatives aimed at improving
navigation and sand bypassing at the inlet. Model sand finer than the
prototype beach sediment resulted in a geometrically distorted model with
Nx = 60 and Nz = 40 (Q = 1.5).
Tests of Distorted Modeling Criteria. There have been several comparisons made of various proposed scaling relationships for geometrically
distorted movable-bed models of suspended sediment transport.
Sayao and Guimaraes (1984) developed the similarity concept of Valembois (1960) (Eqn. 6.97) to arrive at the same set of scaling relationships as
proposed by Le Méhauté (1970). They undertook 2-d model experiments
to examine this and three other sets of modeling guidance. Sixty-nine regular wave tests, 42 with fine sand and the rest with lightweight sediment,
were performed with a horizontal scale of Nx = 500 and vertical scales
ranging from Nz — 40 to 100. The tests were intended to reproduce prototype beach profiles adjacent to the Sergipe River inlet. Each test was run
until equilibrium was reached, and the best reproduction of beach slope
was obtained for models scaled according to the relationship derived from
Valembois’s expression (or Le Méhauté 1970). The tests using lightweight
model sediment did not provide satisfactory results.
Dette and Uliczka (1986) compared beach profile development observed
in a prototype-scale wave tank with similar tests conducted at 1:10 scale.
The objective of the comparison was to test validity of various scaling relationships and to examine the effects of the initial profile. The model used
the same sand (grain size 0.33 mm) as was used in the prototype. Best comparisons between model and prototype were found when the model profiles
were scaled to prototype using the geometrically distorted model guidance
given by Vellinga (1982); however, the good correspondence was found only
in the surf zone. Offshore, the scaled-up model results were substantially
too shallow. For this case, Froude time scale appeared to govern the transient response, i.e., similar profile development after the same number of
waves.
CHAPTER 6. SEDIMENT TRANSPORT MODELS
similarity of the surf similarity parameter and the sediment fall trajectory
were the most important considerations for modeling suspended sediment
transport on beach profiles.
Although both sets of scaling guidance can accommodate a lightweight
sediment, no comparisons have yet been made using beach profiles developed with lightweight model sediment. Note that sediment fall speed is
also a function of p', so the sediment immersed relative density has added
significance in Wang, et al.’s modeling guidance.
An application of the Model B “fall trajectory” guidance was described
by Wang, et al. (1991). A three-dimensional model of Sebastian Inlet was
operated to investigate several structural alternatives aimed at improving
navigation and sand bypassing at the inlet. Model sand finer than the
prototype beach sediment resulted in a geometrically distorted model with
Nx = 60 and Nz = 40 (Q = 1.5).
Tests of Distorted Modeling Criteria. There have been several comparisons made of various proposed scaling relationships for geometrically
distorted movable-bed models of suspended sediment transport.
Sayao and Guimaraes (1984) developed the similarity concept of Valembois (1960) (Eqn. 6.97) to arrive at the same set of scaling relationships as
proposed by Le Méhauté (1970). They undertook 2-d model experiments
to examine this and three other sets of modeling guidance. Sixty-nine regular wave tests, 42 with fine sand and the rest with lightweight sediment,
were performed with a horizontal scale of Nx = 500 and vertical scales
ranging from Nz — 40 to 100. The tests were intended to reproduce prototype beach profiles adjacent to the Sergipe River inlet. Each test was run
until equilibrium was reached, and the best reproduction of beach slope
was obtained for models scaled according to the relationship derived from
Valembois’s expression (or Le Méhauté 1970). The tests using lightweight
model sediment did not provide satisfactory results.
Dette and Uliczka (1986) compared beach profile development observed
in a prototype-scale wave tank with similar tests conducted at 1:10 scale.
The objective of the comparison was to test validity of various scaling relationships and to examine the effects of the initial profile. The model used
the same sand (grain size 0.33 mm) as was used in the prototype. Best comparisons between model and prototype were found when the model profiles
were scaled to prototype using the geometrically distorted model guidance
given by Vellinga (1982); however, the good correspondence was found only
in the surf zone. Offshore, the scaled-up model results were substantially
too shallow. For this case, Froude time scale appeared to govern the transient response, i.e., similar profile development after the same number of
waves.