Improved Surface Drainage of Pavements Final Report (1998) / Chapter Skim
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Appendix B Review of Models
Appendix B Review of Models
Pages 173-182
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From page 173... ...
Several types of models are available for predicting the depth of sheet flow: One-d~mensional models: Two~uneDsional models; Depth of flow over porous pavements Porous media flow models; and Other models. These models were discussed in the main body of this report, and additional information regarding these models is presented here.
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From page 174... ...
m,n - Empirically determined exponents S = Slope of the flow path (m/m) The values of K, m, and n were determined from data collected on a rolled asphalt pavement with chipp~ngs and on a brushed concrete pavement.
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From page 175... ...
Although the relationships developed by these authors were not used In this study, their work does represent a significant contribution to the literature, and their data were used to verify the models developed during this study.
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From page 176... ...
The equations were one-~mensional, inasmuch as they were developed from data collected from surfaces with slopes in a single principal direction. The equations, based on a regression analysis, used plane length, rainfall intensity, texture depth, and pavement slope to predict water depth.
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From page 177... ...
On impervious surfaces, such as Portland cement concrete, the infiltration rate is zero, and the term f in equations 4 and 5 is dropped from the right-hand side of the equation. Thus, if infiltration is zero, the equation representing the conservation of momentum is: bu ah i u fix g fix h Ox fx The kinematic approximation assumes that the velocity terms In equation B-5 are negligible (i.e., gradually varied flow)
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From page 178... ...
Further development results in equations 6 through ~ as discussed in the body of this report. Two-D'mensional Flow Models Flow on highway pavements is a two~,mensional phenomenon.
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From page 179... ...
v = Spatially averaged velocities (y - direction) i = Rainfall intensity over the domain f TnfiItration rate ~Incoming rainfall minus Infiltration into subsurface Conservation of momentum In the Erection leads to: (B-9)
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From page 180... ...
In most two~mensional models the remaking terms are retained, and the partial differential terms are approximated using either a finite difference or finite element scheme. In general, the system of nonlinear, partial differential equations has no analytical solution and must be solved by numerical methods.
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From page 181... ...
developed a two~unensional, free-surface model to analyze flows affecting roadway structures, such as culverts, embankments, and bridges. It has the capacity to analyze unsteady, nonuniform flows but is limited to situations where flow enters or leaves the flow domain at the boundaries and cannot account for infiltration or flows due to a spatially distributed source, such as rainfall, on a pavement surface.
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