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Design Optimization for Water / Wastewater Treatment and Conveyance Systems using
CFD Modeling
Ferdous Mahmood, P.E. (VA)Malcolm Pirnie / ARCADIS-USDallas, Texas
Computational Fluid Dynamics Modeling
3-D visualization of liquids and gases in motion
Calculates details of flow regime (such as velocity, pressures, flow streamlines, forces, turbulence)
Cost effective evaluation of design and operation• Reduces extensive experimentation and
operational changes • Optimizes design and shortens design cycle• Validates impact of proposed design
Tank Operational (Flow) Analysis
Lower Inflow Rate
Dark blue color implies near zero velocity
Higher Inflow Rate
Lower flow produced poor mixing near the top of tankHigher flow achieves better mixing throughout the tank
Seasonal (Temperature) Analysis
478.0
79.0
80.0
81.0
82.0
83.0
84.0
85.0
86.0
87.0
88.0
Tem
pera
ture
(deg
. F.)
0102030405060708090100110120130140150
Wat
er D
epth
(ft)
-20
0
20
40
60
80
100
120
140
Y
-25025 Z
-20 0 20
X
-20
0
20
40
60
80
100
120
140
Y
-25025 Z
-20 0 20
X
Isothermal Condition
Conc0.80.60.40.20.10.01
Inflow 1 0C Less than Tank Bulk Water
78.0
79.080.0
81.0
82.083.0
84.085.0
86.0
87.088.0
89.0
Tem
pera
ture
(deg
. F.)
0102030405060708090100110120130140150
Wat
er D
epth
(ft)
Time5' below w ater surface 40' below w ater surface 75' below w ater surface140' below w ater surface Tank Level (ft)
Mixed tank
Stratified tank
Design Analysis - Radial Inlet
300
300
300
300
6” dia perforations
Outer sleeve
36” dia inlet pipe
outlet pipe
Velocity Contours
WWTP Clarifier AnalysisVelocity
Contours (m/s)
Velocity Contours
(m/s)
WTP Rapid Mix System Analysis
WTP/ WWTP Filter Flow Distribution Analysis
Dead zone
Lower flow at this filter inlet
Baffle Design and CT Analysis for Rectangular Tanks
9
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0Mas
s Fr
actio
n of
Tra
cer (
Cou
t/Cin
)
Time (hours)
Tracer Curve from CFDVelocity
Contours
Inlet
Outlet
Baffle Walls
Tracer Contours
Clearwell Tracer Movement
1
2
3
4
Tracer Concentration
(0-1 mg/L)
Baffle Design and CT Analysis for Circular Tanks
0
0.5
1
1.5
2
2.5
0 5 10 15 20 25 30 35
Con
c (p
pm)
Time (hours)
Comparisons of Breakthrough Curves
Modeled
Modeled+Cb
Measured
0.02
0.018
0.016
0.014
0.012
0.01
0.008
0.006
0.004
0.002
0
Z
Y
X
X
Close agreement between model results and field data
Clearwell Baffles
Chemical Injection and Mixing Analysis
Chemical Injection
Plates added
72” Pipe
Poor mixing of chemicalChemical only in 2nd pipe branch
Good mixing of chemicalChemical in both branches
Reservoir Short-Circuiting and Water Age Analysis
Water Residence Time
Velocity Vectors
Water Residence Time Distribution
Pump Station Design Evaluation
Velocity Contours
(ft/s)
Pipe Valve Analysis
Velocity Contours
(m/s)
Velocity Contours
(m/s)
Valve location
Large Pipe Connection Evaluation
Velocity Contours
(ft/s)
Velocity Contours
(ft/s)
Junction box
High velocity at pipe intersection corner mitigated by junction box
Dam Spillway and Aqueduct Inlet/Outlet Analysis
Spillway Entrance
AqueductSee attached movie for analysis
