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Computational Modeling of Sediment Transport Processes
Task Committee of Computational Modeling of SedimentTransport
Processes
Introduction
With the rapid development of mathematical methodologies and
the advances of computational facilities, sophisticated
simulation
tools using highly efficient and user-friendly computers have
be-
come easily accessible to engineers and scientists.
Computational
models to study river morphodynamic processes require the
simu-
lation of flow hydrodynamics, mass transport, deposition and
ero-
sion of sediment, and the advance and retreat of banks. The
gov-
erning equations solved in the models are the
Reynolds-averaged
momentum equations and the continuity equation for the
hydro-
dynamic flow field, the advection equation for mass transport,
and
Exners equation, together with empirical sediment transport
for-mulas for bed change. Numerical techniques vary from the
simple
1D finite-difference method to the complex 2D and 3D finite-
element or finite-volume schemes. Computational models have
advantages over traditional physical models by being
reusable,
cost-effective, user-friendly with built-in pre- and post-
processors, and easily applicable to various proposed design
sce-
narios. However, their accuracy is largely limited by
mathemati-
cal formulation, computational programming, numerical
schemes,
and our knowledge of flow and sediment transport. Therefore,
validation and verification of sediment transport models are
es-
sential for engineers to choose appropriate models for the
desired
accuracy of engineering applications. The ASCE Task
Committee
TC
on Computational Modeling of Sediment Transport Pro-
cesses solicits the aid of engineers and scientists in
assembling
laboratory and field data sets suitable for the verification and
vali-
dation of sediment transport models. The Task Committee also
plans to conduct a state-of-the-art review of sediment
transport
models by evaluating governing equations, numerical schemes,
specific techniques of computing sediment transport,
treatments
of the bed material mixing layer, and methods in calculating
bank
advance/retreat. The focus of this TC is on the numerical
schemes
and algorithms for modeling sediment transport with 1D and
depth-averaged 2D models.
Research Summary
Laboratory experiments have been conducted in various
flumesettings to study sediment transport mechanics. These
experi-
ments are categorized as follows:
1. Experiments in straight channels with nonerodible banks
to
study the fundamental mechanics of sediment transport such
as sediment transport rate, bed forms, the resistance of mo-
bile bed, sorting of nonuniform sediments, and deposition/
erosion of sediments, etc.
2. Experiments in curved or meandering channels with noner-
odible banks to study flow hydrodynamics as well as the
initiation and evolution of point or alternative bars and
pools.
3. Experiments in sand basins with initially straight or
curved
channels of mobile bed and banks to study the migration of
meandering channels resulting from bank erosion.4. Experiments
involving local scour associated with hydraulic
structures to study the complex hydrodynamic flow field
around hydraulic structures such as spur dikes, abutments,
bendway weirs, and bridge piers, etc.
5. Experiments in nondistorted or distorted scaled physical
models to study sediment transport and bed degradation and
aggradation in natural rivers, reservoirs, coastal areas or
es-
tuaries, etc., which are primarily designed for practical
engi-
neering projects.
Sediment transport models should be verified for being ca-
pable of replicating the results of laboratory experiments
in
straight, curved, or meandering channels with erodible or
noner-
odible banks. The measurements of flow and sediment transportin
scaled physical models were obtained in a well-controlled labo-
ratory environment and have better accuracy for model
verifica-
tions than data from the field prototype. The data sets
mentioned
previously are extremely valuable for testing the accuracy
and
feasibility of the developed sediment transport models, and
any
contributions of the original data sets will be highly
appreciated.
Computational modeling of sediment transport processes
should include the modeling of bed load and suspended load,
the
interaction between bed and suspended sediments, the change
of
bed elevation, the update of surface and subsurface material
gra-
dation, and the advance/retreat of banks. The transport rate of
bed
load and suspended load often was calculated by empirical
sedi-
ment transport relations based on laboratory flume experiments
ofequilibrium sediment transport. Nonequilibrium sediment
model-
ing of both suspended- and bed-load transport is often needed
in
sediment transport simulation of degrading or aggrading
chan-
nels. The interaction between suspended sediment and
bed-load
sediment requires the division of the bed material layer into
mul-
tiple strata. Bed elevation change was obtained traditionally
by
solving the sediment continuity equation. The gradations of
bed
surface and subsurface material were calculated by treating
sedi-
ment as a mixture and using fractional bed load and
suspended-
load transport equations. The simulation of bank
retreat/advance
can be accomplished by using a separate bank erosion model
to
account for basal erosion and bank failure. However, methods
such as the quantification of the adaptation length or
recoveringcoefficient for nonequilibrium sediment transport methods
and the
division of the mixing layer, etc., remain as debatable
questions
among sediment modelers. Whether or not computational models
can achieve the accuracy equivalent to scaled physical
models,
whether or not only a complex 3D model is feasible to
simulate
river morphodynamic processes, and what accuracy we can ex-
pect from computational sediment transport models, etc., are
chal-
lenging questions for both model developers and users.
However,
this committee will start with a focus on collecting data sets
for
sediment model verification and prepare a state-of-the-art
review
of 2D sediment transport models. Literature review will be
based
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J. Hydraul. Eng. 2004.130:597-598.
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on publicly available documentation e.g., user manuals and
tech-nical manuals of available commercial models and other
models
published in papers.
Committee Activity
The Task Committee first met during the 2003 Water Resources
Conference in Philadelphia on June 21, 2003. To enable
state-of-
the-art research, the immediate tasks of this TC are to sponsor
two
sessions at the 2004 ASCE-EWRI Conference in Salt Lake Cityand a
panel discussion at the 2005 ASCE-EWRI Conference. The
first session will be devoted to Data sets for Verification
and
Validation of Sediment Transport Models. This session will
gather papers of laboratory and field experimental data sets
of
sediment transport processes. Laboratory experiments
conducted
in recirculating straight flumes, sine-generated meandering
chan-
nels, and scaled physical models will be welcome. Field
measure-
ments on natural alluvial channels, river meandering reaches,
res-
ervoirs, and around river-training structures are also
expected.
Other data sets that reflect the effect of bank erosion to
sediment
transport processes will be included. These data sets will
poten-
tially be used as the data sets for verifications and
validations of
sediment transport models. The second session will examine
Numerical Modeling of Sediment Transport Processes. Thissession
will consist of papers presenting sediment transport mod-
els developed in academic institutions, federal agencies, and
the
private sector. Applications of commercially available
sediment
transport models for solving engineering problems are
sought.
This session aims to foster exchanges of information and
experi-
ence regarding recent advances in modeling sediment
transport
and its applications to engineering projects. The title of the
pro-
posed panel discussion is The Future of Sediment Transport
Models and will combine invited papers with a short
discussion.
The invited papers will synthesize the state-of-the-art in
simulat-
ing sedimentation processes in watersheds, alluvial channels,
and
modified natural channels. Panelists representing academic
insti-
tutions, federal R&D agencies, and private entities will be
invited
by the TC and approved by the Computational Hydraulics Tech-
nical Committee of the Hydraulics and Waterway Council.
The objective of this forum is to call for your participation
in
the technical activities of this TC, to obtain submissions of
papers
to sessions and panel discussions, and to get your
recommenda-
tions. We would also highly appreciate your efforts if you
would
like to contribute experimental, field, or other pertinent data
sets
to share with colleagues.
We hope to receive your critiques and recommendations. You
may send your comments to [email protected]; they will be for-
warded to all committee members. If you would like to reach
an
individual committee member, our contact information is as
fol-
lows:
Brian D. Barkdoll, PhD, P.E., Associate Professor, Environ-
mental and Water Resources Engineering, Michigan Technologi-
cal Univ., Houghton, Mich. E-mail: [email protected]
Jennifer G. Duan, PhD, P.E., Chair of TC, Assistant Research
Professor, Desert Research Institute, Univ. and Community
Col-
lege System of Nevada, Las Vegas, Nev. E-mail: [email protected]
Shou-shan Fan, PhD, Adjunct Research Professor, Dept. of
Civil Engineering, Clarkson Univ., Potsdam, N.Y. E-mail:
[email protected]
Cassie C. Klumpp, P.E., Hydraulic Engineer, Sedimentation
and River Hydraulics Group D8540, U.S. Bureau of
Reclamation,
Denver Service Center, Denver. E-mail: [email protected]
Bill McAnnally, PhD, P.E., Research Professor, Dept. of
Civil
and Environmental Engineering, Mississippi State Univ.,
Miss.
E-mail: [email protected]
Thanos Papanicolaou, PhD, Associate Professor, Dept. of
Civil
and Environmental Engineering, the Univ. of Iowa, Iowa City,
Iowa. E-mail: [email protected]
Steve Scott, PhD, P.E., Research Hydraulic Engineer, Coastal
and Hydraulics Laboratory, Waterways Experiment Station,
Engineering Research and Development Center, U.S. Army
Corps of Engineers, Vicksburg, Miss. E-mail: Steve.H.Scott@
erdc.usace.army.mil
Sam S. Y. Wang, PhD, P.E., Director and Professor, National
Center for Computational Hydrosciences and Engineering, the
Univ. of Mississippi, Miss. E-mail: [email protected]
Weiming Wu, PhD, Vice Chair of TC, Assistant Research
Professor, National Center for Computational Hydrosciences
and
Engineering, the Univ. of Mississippi, Miss.
E-mail:[email protected]
Xinya Ying, PhD, Research Scientist, National Center for
Computational Hydrosciences and Engineering, the Univ. of
Mis-
sissippi, Miss. E-mail: [email protected]
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J. Hydraul. Eng. 2004.130:597-598.
