4-hydraulic modeling the black art

8/10/2019 4-Hydraulic Modeling the Black Art

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Hydraulic Modeling:The Black Art


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Hydraulic Modeling: The Black Art

Part I

What Is Hydraulic Modeling?

Part IIThe Process


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Who is Vinnie Bergl?

Graduated from Marquette University B.S. in Civil and Environmental Engineering

Class of 2006

P.E. in Illinois and Wisconsin

Started working at RJN in 2005

Various SSES and sewer design projects

Specialize in hydraulic modeling of sewer

systems


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What is hydraulic modeling?


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Hydraulic modeling is a pseudoscientificpowerful signaling device engineering tool


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using math nobody in the industry

understands hydrodynamic and hydrologicalprinciples


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understands hydrodynamic and hydrologicalprinciples to create a fictionalization simulation

of a hydraulic network


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of a hydraulic network that can be used to

affirm preconceptions evaluate current

conditions,


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conditions, rationalize recommend

improvements,


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improvements, and predict outcomes under

various hypothetical scenarios


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improvements, and predict outcomes under

various hypothetical scenarios that will never

actually happen.


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Hydrology, Hydraulics, and

Hydrodynamics (for Sewers) Hydrology methodology to predict how

rainfall becomes flowin a hydraulic network

Hydraulics principles that govern the behaviorof waterunder a given set of conditions

Hydrodynamics computations that dictate themovement of flow from place to placethrough a hydraulic network


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Sewer Hydraulics

Bernoulli Equation

(energy balance)

Mannings Formula

(open-channel flow)


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Sewer Model Hydrodynamics

Continuity Equation

(conservation of flow)

Momentum Equation

(conservation of momentum)

St. Venant Equations relationships fundamental

to dynamic modelingmethods

Engines / Solvers computerized algorithms that

iteratively solvethe hydrodynamic equations


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Continuity Equation

(conservation of flow)

Momentum Equation

(conservation of momentum)

time step time interval at which the solvercalculates changing conditions in the model

short time step = more accurate

long time step = faster simulation


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time step time interval between calculatedconditions in the model

less accurate more accurate


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Sewer Models

model methods and computations used tosimulate a sewershed for given parameters

hydrological model generates runoff, loads

it into the hydraulic network hydraulic model simulates the movement of

flow through the network

water quality model simulates pollutantloads as flow moves through the network

platform software; may support multiplemodels, engines, and hydrological methods


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Software Platforms

Platform SoftwareDeveloper SupportedModels Strengths/Applications

Bentley Bentley,

SWMM

sewer systems

XP Software SWMM stormwater and 2Dmodels

Innovyze Wallingford sanitary systems

Innovyze SWMM stormwater and 2D

models

URBANDanish Hydraulic

Institute (DHI)MOUSE,

SWMM

integrated urban

sewershed models

SWMM5EPA (freeware) SWMM sewer systems


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Requisite Car Analogies

SWMM : Wallingford :: Cadillac : Jaguar

(different models)

Explicit : Implicit :: diesel : gasoline(different engines)

InfoSWMM : EPA SWMM5 ::

Lexus ES350 with voice recognition and moon roof :

Toyota Camry with manual locks and no AC

(same model, different features)


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Sanitary vs. Storm

Sanitary Stormwater

Model Network Underground (pipes) Underground and overland

Main Concern Backups / Overflows Flooding

Conditions Dry and wet weather Wet weather only

Overflow Gone from system Goes to overland network

*combined sewer models a bit of

both


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The Process

Stage 1: Building the Physical Model

Stage 2: Flow Monitoring Data Analysis

Stage 3: Flow Input and Distribution Stage 4: Model Calibration

Stage 5: Analysis of Existing Conditions

Stage 6: Development of Alternatives Stage 7: Analysis of Alternatives


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Building the Physical Model

beautiful infrastructurefunction l

bstr ction


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Defining the Network

Full model All sewers in

study area modeled

Skeletal model Only

trunk and limbs modeled

Diameter threshold

Tributary area


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Venous? Arterial?

Like:

Not like:


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Physical Features

node any junction or storage location manholes / inlets

wet wells

tanks

link path along which flow moves between nodes

gravity mains

force mains

overland channels

catchment hydrological boundary; turns rain into runoff

meter [sub-]basin

drainage area


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Data Import

collected sourcesGIStablemodel


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Data Import

geodatabase fields

model softwaresbuilt-in fields


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Lift Stations

Pumps

Design points

Pump curves

Discharge piping

Wet wells Dimensions

Operating ranges


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Control Structures

Diversion chambers

Control valves

Weirs Gates

Dams

Orifices


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Outfall Conditions


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Flow Data Analysis

Sanitary Combined Stormwater

Dry-WeatherAnalysis X X

RTK

Analysis X

CalibrationEvents X X X

How does meter data feed the

model?


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Dry-Weather Flow Patterns


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Dry-Weather Flow Patterns

Each meter basin has unique DWF


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What does RTK do again?

DeconstructsRDII into an elemental unit


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What does RTK do again?

Model reassembles RDII response usingRTK UH as building block; rain as catalyst


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More tortured analogies

Observed RDII

Response

RTK Unit

Hydrograph

Model RDII

Response


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Why RTK?

Prevailing method for sanitary models

Scales well

Consistent with RDII narrative


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The Process



Stage 3: Flow Input and Distribution Stage 4: Model Calibration


Stage 6: Development of Alternatives

Stage 7: Analysis of Alternatives


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Dry-Weather Flow (DWF) Input

1. Large point flows are input to nearestnode


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Dry-Weather Flow (DWF) Input

2. Remaining flow apportioned by area orpopulation


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Wet-Weather Flow Distribution

1. Delineate catchments

2. Define hydrology

3. Apply rain

4. Run model


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Sanitary WWF Distribution

Meter basins subdivided

catchment = sub-basin

RTK hydrology


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Sub-Basin Delineation


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Wet-Weather Flow (WWF) Input

catchment areaXrain intensityXUH =WWF

X X


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Stormwater Runoff

Part of storm and combinedsewer models

catchment = drainage area

Hydrology

SWMM runoff

NRCS method

Rational method


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Catchment Properties

Area

Ground slope

Imperviousness


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Sanitary vs. Stormwater Hydrology

Sanitary Stormwater

Catchments Sub-basins (polygons) Drainage areas (blobs)

Delineation property boundaries contours

Basis Flow monitoring data Physical catchment properties

Methods RTK NRCS, SWMM, Rational, others

Scaling Factor % rainfall capture Imperviousness (CN, C value,etc.)


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Model Calibration

Process of validating model results bycomparing against observed data


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Dry-Weather Calibration

REPLICATION

D-V-Q

Volume

Timing


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Whats good enough?

WASTEWATER PLANNING USERS GROUP (WaPUG) CODE OFPRACTICE FOR THE HYDRAULIC MODELLING OF SEWER SYSTEMS

WaPUG =


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Wet-Weather Calibration

Simulation of observed

(metered) rain events

Used to test and refine

hydrological inputs


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WaPUG (UDG) says


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WaPUG (UDG) says

+20 to -4


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WaPUG (UDG) says

Flow Flow

Depth- Depth

REPLICATION.


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Village of Deerfield


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plateaus


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clean

peaks


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replicationclean

peaks


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Continuity and Stability

Qin= Qout

Is itstable?


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The Process



Stage 3: Flow Input and Distribution

Stage 4: Model Calibration




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Dry-Weather Flow

Will it scour?

slow flowsiltingcapacity loss

2 fps


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Sustainable Peaking Factor (SPF)

Simple measure ofexcess flow capacity

< 3.0 = undersized

SPF = avg. capacity ADWF


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Sustainable Peaking Factor (SPF)


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Design Storm Analysis

Typically 24-hr. events

SCSType II storm

IDF from Bulletin 70

Recurrence intervals of

2 months to 100 years


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SCS Type II Distribution


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10-yr, 60-min. storm


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10-yr, 12-hr. storm


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10-yr, 24-hr. storm

L l f P i A l i


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Level of Protection Analysis

How protected is the system against

L l f P t ti A l i


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surcharging

L l f P t ti A l i


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overflows / overland flooding


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Surcharging and Overflows

L l f P t ti A l i


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CSO events

L l f P t ti A l i


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basement backups

P t ti l B k


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Potential Backups

Th P


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The Process







D l t f Alt ti


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Development of Alternatives

Where are the problem areas?

What are the options? Increase capacity?

Reduce flow?

Both?

And how do we assess the impact?


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Hydraulic Grade Line (HGL) Profiles


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with relief sewers



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with relief sewers and I/I reduction

Level of Protection (LOP)


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existing condition



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with relief and storage



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Okay, so it would work.

But is it optimal?

The Process


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The Process







But first


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But first

Some real life context

A lunch break (at some point)

2:00 Wet-Weather Freakonomics


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Questions?

Comments?

4-hydraulic modeling the black art

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