Hydraulic Efficiency of Grate and Curb Inlets - Urban Drainage and ...

Table 3-8: Empirically-derived weir parameters
Slopes
4% and 2%; 4% and 1%; 2% and 2%; 2% and 1%
0.5% and 1%; 0.5% and 2%
V-notch
Weir
Rectangular
Sharp-crested Weir
a = 2.64 a = 15.78
b = 2.50 b = 1.58
R 2 = 0.999 R 2 = 0.999
a = 2.52 a = 13.50
b = 2.45 b = 1.35
R 2 = 0.999 R 2 = 0.999
Flow depth required for each test was measured at the same location roughly 5 prototype
feet upstream of the first inlet. This location was chosen to be free of surface curvature from
flow being drawn into the inlets, free of ripples generated from the upstream approach transition,
and served as a control section to establish the depth and adjust the flow into the model for each
test. Depth of flow was measured using a point gage with ±0.001 ft accuracy, which was
mounted on a data-collection cart designed to slide along the model and perform other watersurface
measurements as well. Figure 3-30 provides a photograph of the data-collection cart. A
camera tripod was mounted on the data-collection cart providing one of the three photograph
points: 1) an elevated oblique view from the data-collection cart, 2) a view laterally opposite
from the inlets, and 3) a plan view from directly above the inlets.
Camera
Tripod
Point
Gage
Tape Measure Used for
Longitudinal Positioning
Figure 3-30: Data-collection cart photograph (looking upstream)
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