6.4. SUSPENSION-DOMINATED MODELS
293
Nx =
1.62 Nz _ 1.62 (16)
or a modest geometric distortion of
O
_ N* _ 18-3 _ . ..
' “Hallermeier —
— 1-14
However, testing the movable-bed model at different wave periods requires recalculation of the length scale.
Epilogue. At this point of the study, all the new software upgrades arrived, and the
team dissolved for several months to load the new programs onto their PC's and to
convert all the old computer files to the (surprise) new file format.
6.4.2 Scale Criteria Dependent on Fall Speed
An alternate approach to theoretical arguments in developing movablebed model guidance is to identify important dimensionless parameters or
physical features that appear to be related to the sedimentary processes,
and than assure that these parameters or features are held constant between
prototype and model.
One of the most relevant requirements for modeling sediment transport
dynamics in energetic nearshore regions is to attain similarity of the equilibrium beach profile between prototype and model, particularly in the surf
zone. Parameters that appear to correspond to features of the equilibrium
profile are similarity candidates for developing scaling criteria. Many investigators have expressed opinions regarding the important physical parameters to be considered in formulating guidance in these turbulence-dominated
nearshore regions.
Early Developments Incorporating Sediment Fall Speed. Valembois (1960) appears to have been among the first to propose a “condition of
similitude” for beach profile modeling that included sediment fall speed. He
stated that similarity of equilibrium beach profiles being formed by wave
breaking and sediment suspension requires the ratio
fall speed/depth
g?)
mass transport velocity/horizontal distance
to be the same in the movable-bed model as in the prototype. The numerator can be interpreted as the inverse of the “vertical fall time, and
the denominator is the inverse of the “horizontal particle excursion time,
293
Nx =
1.62 Nz _ 1.62 (16)
or a modest geometric distortion of
O
_ N* _ 18-3 _ . ..
' “Hallermeier —
— 1-14
However, testing the movable-bed model at different wave periods requires recalculation of the length scale.
Epilogue. At this point of the study, all the new software upgrades arrived, and the
team dissolved for several months to load the new programs onto their PC's and to
convert all the old computer files to the (surprise) new file format.
6.4.2 Scale Criteria Dependent on Fall Speed
An alternate approach to theoretical arguments in developing movablebed model guidance is to identify important dimensionless parameters or
physical features that appear to be related to the sedimentary processes,
and than assure that these parameters or features are held constant between
prototype and model.
One of the most relevant requirements for modeling sediment transport
dynamics in energetic nearshore regions is to attain similarity of the equilibrium beach profile between prototype and model, particularly in the surf
zone. Parameters that appear to correspond to features of the equilibrium
profile are similarity candidates for developing scaling criteria. Many investigators have expressed opinions regarding the important physical parameters to be considered in formulating guidance in these turbulence-dominated
nearshore regions.
Early Developments Incorporating Sediment Fall Speed. Valembois (1960) appears to have been among the first to propose a “condition of
similitude” for beach profile modeling that included sediment fall speed. He
stated that similarity of equilibrium beach profiles being formed by wave
breaking and sediment suspension requires the ratio
fall speed/depth
g?)
mass transport velocity/horizontal distance
to be the same in the movable-bed model as in the prototype. The numerator can be interpreted as the inverse of the “vertical fall time, and
the denominator is the inverse of the “horizontal particle excursion time,