HEC-22 Inlets in INFOSWMM and H2OMAP SWMM...

HEC-22 Inlets in INFOSWMM

and H2OMAP SWMM v12

Table of Contents

How the Inlet and Overland Junctions are Defined 3

Why Would You Use the HEC-22 Inlets Option? 4

Types of Inlets 5

Nodes in InfoSWMM and H2OMAP SWMM 6

Major and Minor System 7

Continuous Grate 8

Continuous Grate Parameters 9

Continuous Curb-Opening 10

Continuous Curb-Opening Parameters 11

Sag Grate 12

Sag Grate 13

Sag Grate 14

Sag Curb-Opening 15

Sag Curb-Opening Parameters 16

Flow Equations for a Sag Curb Opening Inlet 17

Sag Combination 18

Sag Combination Inlet Parameters 19

Sag Combination is a Combination of the Weir and Orifice Equation 20

New Report and Graph Option for HEC-22 Inlets 21

Efficiency of a Continuous Grate Inlet 22

Efficiency (E) of Inlets 23

Front Flow Interception, Rf 24

Side Flow Interception, Rs 25

Ratio of frontal flow to total gutter flow, Eo26

Engineering Technical Services Page -2

How the Inlet and Overland Junctions are

Defined

The Inlet is Defined at the Inlet Node and the Inlet Flow comes

from the Overland Junction. Flow travels down the open

channel streets to the Inlet and then the HEC-22 Inlet Equations

are used to estimate the Captured Flow and Bypass Flow


Why Would You Use the HEC-22 Inlets

Option?

What can happen at a node in InfoSWMM when It floods:

1. Excess Flow is lost out the top of the Manhole

2. Excess Flow is ponded at the top of the Manhole in an

artificial storage

3. Excess Flow is Surcharged at the top of the Manhole if the

links are Force Mains

4. Excess Flow leaves the node in a SWMM 5 Outlet which

connects the Major and Minor Networks

5. Excess Flow leaves the node to a 1D Overland Network via

a HEC-22 Inlet

6. Excess Flow leaves the node to a 2D Mesh


Types of Inlets

HEC-22

Inlets

Continuous Grate

Continuous Curb-

Opening

Sag Continuous

Grate

Sag Continuous

Curb-Opening

Sag Combination


Nodes in InfoSWMM and H2OMAP SWMM

@Elevation at Surcharged Depth

+ Rim Elevation

Pressure Node or Flooded Node

Above Rim Elevation

Unsurcharged Node

above Invert Elevation

@Rim Elevation, Node Floods,

Connects to Inlet or

Connects to 2D Mesh

Surcharged Node above

Crown of Pipe


Major and Minor System


Continuous Grate


Continuous Grate Parameters

Cross slope (Sx) or the road cross slope

Width of grate (W) in feet or meters

Length of grate (L) in feet or meters

Velocity where splash-over first occurs (V0) in feet/second or meters/second


Continuous Curb-Opening


Continuous Curb-Opening Parameters

Cross slope (Sx) or road cross slope,

Length of curb opening (L) in feet or meters,

Height of curb opening (h) in feet or meters,

Gutter depression (a) in feet or meters

Lateral width of gutter depression (Wd) in feet or meters


Sag Grate


Sag Grate

Cross slope (Sx) or the road cross slope

Width of grate (W) in feet or meters,

Length of grate (L) in feet or meters,

Clear opening area of grate (Ag)

Depth up to which gate behaves as weir or the Threshold Depth in feet or meters,


Sag Grate

Orifice Flow

Weir Flow Until

Threshold Depth

The flow is calculated as weir flow up until the Threshold depth

and then an Orifice equation is used.

0.5[2 ( 0.5 )]i o g xQ C A g d WS

1.5( 0.5 )i w xQ C P d WS


Sag Curb-Opening


Sag Curb-Opening Parameters

8/11/2012

Length of curb opening (L) in feet or meters,

Lateral width of gutter depression (Wd) in feet or meters,


Depth up to which gate behaves as weir as the Threshold depth in feet or meters


Flow Equations for a Sag Curb

Opening Inlet

Orifice Flow

Weir Flow Until Threshold Depth

for Depressed Inlet

Weir Flow Until Threshold Depth for Undepressed

Inlet

1.5( 1.8 )i w dQ C L W d

1.5

i wQ C Ld

0.5[2 ( 0.5 ]i oQ C hL g d h


depending on whether the inlet is depressed or undepressed and

then an Orifice equation is used.


Sag Combination


Sag Combination Inlet Parameters

Cross slope (Sx) or road cross slope

Width of grate (W) in feet or meters,

Length of grate (L) in feet or meters,

Clear opening area of grate(Ag)


Length of curb opening (l) in feet or meters,

Depth up to which gate behaves as weir or Threshold Depth in feet or meters.


Orifice Flow

Weir Flow Until

Threshold Depth

Sag Combination is a Combination

of the Weir and Orifice Equation

0.5 0.5[2 ( ] (2 )o g o oQorifice C A g d C hl gd

1.5( 0.5 )w xQweir C P d WS


and then an Orifice equation is used.


New Report and Graph Option for

HEC-22 Inlets The Inlet

Flow to the

node along

with the Total

and Lateral

Inflow can be

plotted in

Output

Report

Manager.


Efficiency of a Continuous Grate Inlet

Captured

Flow

Bypassed

Flow Gutter Flow Street Flow

Gutter

Flow

Street

Flow

Gutter

Flow

Street

Flow


Efficiency (E) of Inlets


0 0(1 )f sE R E R E

Rf = ratio of frontal flow intercepted to total frontal flow

Rs = ratio of side flow intercepted to total side flow

E0 = ratio of frontal flow to total gutter flow

Front Flow Interception, Rf


Ku = 0.295 (0.09 English units)

V = velocity of flow in gutter, m/s (ft/s) (V is either DS velocity or US velocity in the overland link

V0 = gutter velocity where splash-over first occurs (m/s)

01 ( )f uR K V V

Side Flow Interception, Rs


Ku = 0.0828 (0.15 English units)

V = velocity of flow in gutter, m/s (ft/s)

Sx = road cross slope, m/m (ft/ft)

L = length of the grate, m (ft)

1.8

2.31/ (1 )u

s

x

K VR

S L

Ratio of frontal flow to total gutter flow, Eo


W = width of the grate, m (ft)

T = total spread of water and is calculated from:

d = T*Sx

d = Upstream node head - min(Ground level, upstream node invert), m (ft)

Sx = road cross slope, m/m (ft/ft)

2.67

0 1 1W

ET

HEC-22 Inlets in INFOSWMM and H2OMAP SWMM...

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