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

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Constants in Equation 2-8 are associated with specific grates listed in Table 2-4. Table 2-4: Splash-over velocity constants for inlet grates (UDFCD, 2008) Type of Grate α β γ η Bar P-1-7/8 2.22 4.03 0.65 0.06 Bar P-1-1/8 1.76 3.12 0.45 0.03 Vane Grate 0.30 4.85 1.31 0.15 45º Bar 0.99 2.64 0.36 0.03 Bar P-1-7/8-4 0.74 2.44 0.27 0.02 30º Bar 0.51 2.34 0.20 0.01 Reticuline 0.28 2.28 0.18 0.01 The ratio of side flow captured to total side flow approaching the grate can be determined using Equation 2-9: R s = 1 1.8 0.15V Equation 2-9 1+ 2.3 S L x where: R s = ratio of side flow captured to total side flow; S x = side slope; L = length of grate (ft); and V = velocity of flow in the gutter (ft/s). Capture efficiency of a grate inlet may be determined using Equation 2-10, which uses the parameters determined previously: ⎛ Qw ⎞ ⎛ Qs ⎞ E = R f ⎜ ⎟ + Rs ⎜ ⎟ Equation 2-10 ⎝ Q ⎠ ⎝ Q ⎠ where: E = grate inlet efficiency; R s = ratio of side flow captured to total side flow; R f = ratio of frontal flow captured to total frontal flow; Q = volumetric flow rate (cfs); Q w = flow rate in the depressed section of the gutter (cfs); and Q s = flow rate in the section above the depressed section (cfs). Efficiency for combination inlets is typically determined by only considering the grate when the curb opening and grate are of equal length (UDFCD, 2008), and Equation 2-10 is used. 12
2.2.3 Curb Opening Inlets Curb opening inlets can be located in either depressed or not depressed gutters. Depressed gutters are defined as a configuration in which the invert of the curb inlet is lower than the bottom of the gutter flow line. Various curb inlet types used by the UDFCD are shown in Figure 2-3. Type R curb inlets are used alone; the curb inlet used with the combination inlet typically has a grate component (UDFCD, 2008). Calculations presented in this section apply to the Type R curb inlet only, because the grate portion of a combination inlet typically diverts flow away from the curb inlet. (a) horizontal throat (b) inclined throat (c) vertical throat Figure 2-3: Curb inlet openings types (UDFCD, 2008) Efficiency (E) of curb inlets is primarily a function of the curb opening length. Equation 2-11 is used for determining the efficiency of the Type R curb inlets: [ 1− ( L L )] 1. 8 E = Equation 2-11 1− T where: L = curb opening length in the direction of flow (ft); and L T = curb opening length required to capture 100% of gutter flow. Equation 2-11 is valid for a curb opening length (L) less than the length required for 100% flow capture (L T ), otherwise the efficiency (E) is equal to one. The parameter L T is a 13
Page 1: HYDRAULIC EFFICIENCY OF GRATE AND C
Page 5 and 6: TABLE OF CONTENTS LIST OF FIGURES .
Page 7 and 8: LIST OF FIGURES Figure 1-1: Map of
Page 9 and 10: Figure 5-7: Predicted vs. observed
Page 11 and 12: LIST OF TABLES Table 2-1: Summary o
Page 13 and 14: LIST OF SYMBOLS, UNITS OF MEASURE,
Page 15 and 16: S c , Sc, cross slope cross (or lat
Page 17 and 18: ID mag meter No. QC ® R5 R9 R12 R1
Page 19 and 20: 1 INTRODUCTION A research program w
Page 21 and 22: 1-1 often require use of these thre
Page 23 and 24: 2 LITERATURE REVIEW Urban storm dra
Page 25 and 26: • All grates showed patterns of i
Page 27 and 28: Q = Q w + Q s Equation 2-1 where: 2
Page 29: Inlet Name Bar P-1-7/8 Bar P-1-7/8-
Page 33 and 34: 2.3 Manning’s Equation Uniform fl
Page 35 and 36: where: q 1 = dependent parameter; q
Page 37: Q ⎛ L L Qw ⎞ = f ⎜ , ⎟ Equa
Page 40 and 41: Headbox Pipe Network Inlets Street
Page 42 and 43: capacity. A similar study performed
Page 44 and 45: Table 3-3: Test matrix for 0.33-ft
Page 46 and 47: Table 3-5: Test matrix for 1-ft pro
Page 48 and 49: Solid Plexiglas ® was milled to pr
Page 50 and 51: Figure 3-10: Triple No. 13 combinat
Page 52 and 53: Figure 3-16: Single No. 16 combinat
Page 54 and 55: Figure 3-22: Single No. 16 combinat
Page 56 and 57: Note Safety Bar Figure 3-28: R5 wit
Page 58 and 59: Flow entering and exiting the model
Page 60 and 61: Following a standardized testing pr
Page 63 and 64: 4 DATA AND OBSERVATIONS Testing res
Page 65 and 66: Figure 4-2: Type 16 combination-inl
Page 67 and 68: 45 40 35 Captured flow (cfs) 30 25
Page 69 and 70: 5 ANALYSIS AND RESULTS Data selecte
Page 71 and 72: likely due to the nature of the ori
Page 73 and 74: 1 Observed 0.9 0.8 0.7 0.6 0.5 0.4
Page 75 and 76: Total flow (Q) is known from the ob
Page 77 and 78: Observed 1 0.9 0.8 0.7 0.6 0.5 0.4
Page 79 and 80: 1 0.9 Observed 0.8 0.7 0.6 0.5 0.4
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The second Pi group is the square o
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Table 5-2: Empirical equations for
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Agreement is best at the smallest f
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Efficiency/base efficiency 2.2 2 1.
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were typically seen at higher flow
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Average difference in calculated ef
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Depth (ft) Table 5-3: Efficiency er
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test data for typical design depths
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Observed efficiency 1 0.9 0.8 0.7 0
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7 REFERENCES Bos, M. G. (1989). Dis
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(P-1-7/8 grate does not have the 10
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Figure A-3: Curved vane grate (UDFC
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Figure A-5: 30º-tilt bar grate (UD
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APPENDIX B ON-GRADE TEST DATA 93
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Test ID Number Configuration Table
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Table B-3: 2% and 1% on-grade test
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Test ID Number Configuration Longit
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Test ID Number Configuration Table
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Table B-7: Additional debris tests
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106
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For the additional sump tests, only
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110
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(a) (b) Figure D-2: Type 16 inlet s
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(a) (b) (c) Figure D-4: Type R curb
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116
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Extent of Flow Station (x) Position
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120
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Test ID Number depth (ft) Tw (ft) A
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Table F-2: Additional parameters fo
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130
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132
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Plot of rstudent*pred. Legend: A =
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The REG Procedure Model: MODEL1 Dep
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Plot of logE*pred. Legend: A = 1 ob
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Plot of rstudent*pred. Legend: A =
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142
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144
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Test ID Number Depth (ft) Grates Fl
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Test ID Number Depth (ft) Grates Fl
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Test ID Number Depth Length Flow Ef
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