Hydraulic Efficiency of Grate and Curb Inlets - Urban Drainage and ...
Hydraulic Efficiency of Grate and Curb Inlets - Urban Drainage and ...
Hydraulic Efficiency of Grate and Curb Inlets - Urban Drainage and ...
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<strong>Efficiency</strong>/base efficiency<br />
2<br />
1.8<br />
1.6<br />
1.4<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
0<br />
velocity<br />
depth<br />
length<br />
cross slope<br />
0 0.5 1 1.5 2<br />
Parameter/base value<br />
Figure 5-16: Type R curb inlet regression parameter sensitivity<br />
5.4 Combination-inlet <strong>Efficiency</strong> Compared to <strong>Grate</strong> <strong>and</strong> <strong>Curb</strong> Inlet<br />
<strong>Efficiency</strong><br />
The difference in efficiency between a combination inlet, a grate-only inlet utilizing the<br />
same grate as the combination inlet, <strong>and</strong> a curb-only inlet utilizing the same curb opening as the<br />
combination inlet is illustrated in this section. Of the 318 tests performed, twelve test<br />
configurations were performed with the combination inlet <strong>and</strong> then repeated with the grate only<br />
<strong>and</strong> the curb opening only. These tests were performed with single Type 13 <strong>and</strong> 16 grates.<br />
Graphical comparisons were developed in which the efficiency for each configuration (grate<br />
only, curb only, <strong>and</strong> their sum) was plotted against the combination-inlet efficiency, <strong>and</strong> are<br />
presented in Figure 5-17 <strong>and</strong> Figure 5-18. An efficiency difference is read in these figures from<br />
the combination-inlet line to the desired inlet configuration line. Differences in efficiency can be<br />
determined from these figures when, for instance, the combination-inlet efficiency is known but<br />
the grate-only efficiency is desired. Similar comparisons can be made between the combinationinlet<br />
efficiency <strong>and</strong> the sum <strong>of</strong> the grate-only <strong>and</strong> curb-only efficiencies. An average difference<br />
<strong>of</strong> 3% efficiency was observed when the combination <strong>and</strong> the grate-only inlets were compared,<br />
<strong>and</strong> an average difference <strong>of</strong> 12% efficiency was observed when the combination <strong>and</strong> curb-only<br />
inlets were compared. When the curb-only <strong>and</strong> grate-only efficiencies are summed, they overpredict<br />
combination-inlet efficiency by an average <strong>of</strong> 7%. The largest differences in efficiency<br />
70
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