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Three-Dimensional CFD Modeling for Optimization of Invert Trap
Configuration to Be Used in Sewer Solids Management
Article in Particulate Science And Technology · September 2008
DOI: 10.1080/02726350802367951
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Particulate Science and Technology, 26: 507–519, 2008
Copyright # Taylor & Francis Group, LLC
ISSN: 0272-6351 print/1548-0046 online
DOI: 10.1080/02726350802367951
Three-Dimensional CFD Modeling for Optimization
of Invert Trap Configuration to Be Used in Sewer
Solids Management
T. THINGLAS AND D. R. KAUSHAL
Civil Engineering Department, IIT Delhi, New Delhi, India
Flow field prediction and optimization of invert trap configuration have been carried
Downloaded By: [Indian Institute of Technology] At: 09:54 2 June 2010
out by using three-dimensional computational fluid dynamics (CFD) modeling with
the help of FLUENT software using renormalization group (RNG) k-e along with
the discrete phase model (DPM). A hexagonal=tetrahedral shape and map-type
nonuniform grid were chosen to discretize the entire computational domain, and a
control volume finite difference method was used to solve the governing equations.
In the present study, five different invert trap configurations (rectangular with
and without lid on both sides, trapezoidal, trapezoidal with rectangular base, and
rectangular with trapezoidal base with lid on both sides) have been simulated for
the flow of three different inert sediment types (sand, styrocell, and plastic beads)
at six flow rates (0.35, 0.70, 1.05, 1.35, 4.55, and 9.95 Lps) for each trap. The dis-
charges selected in the present study cover the entire range of discharge expected in
channels during dry weather flow and monsoon. The simulation results are capable
of showing particle trajectories and the effect of flow rate and trap geometry on
the flow patterns developed within the trap. Based on 3-D CFD modeling and
experimental measurements, it has been concluded that the invert trap having a
rectangular shape with trapezoidal base with lids on both sides is the most efficient
trap configuration with highest sediment retention ratio.
Keywords 3-D CFD modeling, invert trap, sediment trapping, urban drainage
Introduction
Liquid-solid two-phase flow through pipelines, rectangular ducts, and open channels
is widely employed in the chemical and mining industries and is encountered in slurry
transport, sewer lines, irrigation channels, and natural phenomena such as river
mechanics. In any practical situation, the transported solids are multisized and their
size may span three orders of magnitude. The flow of sediments in rivers and sewers
is very complex. Once sediment has been entrained into the flow, it travels suspended
or as bed load. Finer, lighter material tends to travel in suspension and is primarily
influenced by turbulence fluctuations in flow, which in turn is influenced by bed
shear. It is advected at mean flow velocity. Heavier material travels by rolling, slid-
ing, or saltating along the pipe invert (or deposited bed) as bed load. This type of
movement is affected by the local velocity, and advection velocities in this mode
are considerably lower than the mean flow velocity.
Address correspondence to D. R. Kaushal, Civil Engineering Department, IIT Delhi,
Hauz Khas, New Delhi-110016, India. E-mail: kaushal@civil.iitd.ac.in
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