Pages 563-678 (December 2020)
1、Erosion rate of sand
and mud mixtures
Chamil Perera, Jarrell
Smith, Weiming Wu, David Perkey, Anthony Priestas
Pages 563-575
2.
Large-eddy
simulation of flash flood propagation and sediment transport in a dry-bed
desert stream
Ali
Khosronejad, Kevin Flora, Zexia Zhang, Seokkoo Kang
Pages
576-586
3、Numerical
modeling of the propagation and morphological changes of turbidity currents
using a cost-saving strategy of solution updating
Peng
Hu, Yue Li
Pages
587-599
4、Influence of
diversion angle on water and sediment flow into diversion channel
Nashwan
Kamalaldeen Alomari, Badronnisa Yusuf, Thamer Ahmad Mohammad, Abdul Halim
Ghazali
Pages
600-608
5、Mass flows and
river response in rapid uplifting regions – A case of lower Yarlung Tsangpo
basin, southeast Tibet, China
Guo-An
Yu, Jianyin Lu, Liqun Lyu, Lujie Han, Zhaoyin Wang
Pages
609-620
6、 Post-analysis
simulation of the collapse of an open sabo dam of steel pipes subjected to
boulder laden debris flow
Toshiyuki
Horiguchi, Vincent Richefeu
Pages
621-635
7、 Circulation
cells topology and their effect on migration pattern of different multi-bend
meandering rivers
Fariba
Sadat Esfahani, Alireza Keshavarzi
Pages
636-650
8 、Comprehensive
evaluation method for sediment allocation effects in the Yellow River
Xujian
Chen, Chunhong Hu, Yuqi An, Zhihao Zhang
Pages
651-658
9、 Quasi-stationary
flow structure in turbidity currents
Shun
Nomura, Giovanni De Cesare, Mikito Furuichi, Yasushi Takeda, Hide Sakaguchi
Pages
659-665
10 、Influence of
surface roughness of dune bedforms on flow and turbulence characteristics
Veysel
Sadan Ozgur Kirca, Seyed Mahdi Saghebian, Kiyoumars Roushangar, Oral Yagci
Pages
666-678
===========================================
1、Erosion rate of sand
and mud mixtures
Chamil Perera, Jarrell
Smith, Weiming Wu, David Perkey, Anthony Priestas
Pages 563-575
https://doi.org/10.1016/j.ijsrc.2020.06.004
https://www.sciencedirect.com/science/article/pii/S1001627920300688
Abstract
Erosion of mixed cohesive and noncohesive sediments is
studied using the erosion test instrument SED Flume. The sediment mixtures are
composed of well-sorted quartz sand (0.25–0.5 mm) and one of the three
used muds: kaolinite, kaolinite-bentonite and Mississippi River muds. The mud
contents cover from 0 to 100%. The measured data of erosion rate and bed shear
stress are used to examine the segmented linear, nonlinear, and exponential
erosion models. The parameters of each erosion model are related to the
physical properties of sediment mixtures, including clay fraction, mud
fraction, mixture dry density, and mud dry density. It is found that the three
models can fit well with the data, and their parameters have strong relations
with the mud fraction and mud dry density, to a less extent with the clay
fraction, but not with the mixture dry density.
Keywords: Cohesive sediments; Noncohesive sediments; Sand
and mud mixtures; Segmented linear model; Nonlinear model; Exponential model
2、Large-eddy
simulation of flash flood propagation and sediment transport in a dry-bed
desert stream
Ali
Khosronejad, Kevin Flora, Zexia Zhang, Seokkoo Kang
Pages
576-586
https://doi.org/10.1016/j.ijsrc.2020.02.002
https://www.sciencedirect.com/science/article/pii/S1001627920300068
Abstract
A
Large-Eddy Simulation (LES) model is used to study flow dynamics of a flash
flood event in a dry-bed, desert wash, the so-called Tex Wash, near the Tex
Wash Bridge on Interstate 10 in the Mojave Desert of California. The evolving
free surface of the flash flood is tracked using the level-set method. A bed
morphodynamics module is coupled to the hydrodynamics model to calculate the
erosion and bed evolution of the mobile bed of the wash under flash flood
conditions. Flash floods in a desert wash can be characterized with a number of
salient features such as the (1) existence of both the dry- and wet-cells on
the bed surface of the wash that correspond to the air and water phases,
respectively; (2) presence of various flow regimes, critical, sub-critical, and
super-critical in the flow domain; and (3) occurrence of a highly transient and
complicated flow field and, subsequently, sediment dynamics throughout the
wash. A numerical modeling effort is presented to study a recorded flash flood
and the corresponding scour processes in the Tex Wash. The flood event occurred
in 2015 and lead to the collapse of the Tex Wash Bridge. The of the current
study is to gain insight into the flood flow and sediment transport mechanisms,
which resulted in the collapse of the bridge. To that end, a study area, which
includes a 0.65 -long
reach of Tex Wash at its intersection with the Tex-Wash Bridge, was selected.
The bathymetry of the wash was obtained using light-detection-and-ranging
(LiDAR) technology and used to construct the computational domain of the wash
and bridge foundations. The transient flow of the flash flood, in both air and
water phases, and the evolving morphology of the wash are numerically
simulated. The site-specific numerical simulation revealed the formation of
deep scour regions adjacent to the right abutment of the upstream bridge, where
significant erosion caused the collapse of the bridge. Moreover, the results
show that most of the scour processes take place during the steady phase of the
flash flood when the desert stream is filled with water. However, the transient
phase of the flash flood is rather short and contributes to a very limited
amount of erosion within the stream.
Graphical abstract
Large-eddy simulation (LES) model is used to study flow
dynamics of a flash flood event in a dry-bed desert wash, the so-called Tex
Wash, near the Tex Wash Bridge on Interstate 10 in the Mojave Desert of
California. Our results show that most of the scour processes takes place
during the steady phase of the flash flood when the stream is filled with the
flood water. Figure 1: Computed instantaneous flow field of the flash
flood in the Tex wash at the water surface. (A) shows the contour of the velocity
magnitude (V) and the bed elevation (zb) of the wash. The zoomed-in
view of (B) shows the contour of velocity magnitude around the bridge piers
“P1” and “P2” within the narrow channel. In the zoomed-in window of (C), the
contours of velocity magnitude is presented. Near the upper part of this
window, one can see the hydraulic jump. The zoomed-in window of (D) shows the
Fr number distribution in the wash. The flash flood flows from bottom to top.
Keywords: Flash flood; Dry-bed stream; Large eddy
simulation; Sediment transport
3、Numerical
modeling of the propagation and morphological changes of turbidity currents
using a cost-saving strategy of solution updating
Peng
Hu, Yue Li
Pages
587-599
https://doi.org/10.1016/j.ijsrc.2020.05.003
https://www.sciencedirect.com/science/article/pii/S1001627920300548
Abstract
Existing layer-averaged numerical models for turbidity
currents have mostly adopted the global minimum time step (GMiTS) for solution
updating, which confines their computational efficiency and limits their
attractiveness for field applications. This paper presents a highly efficient
layer-averaged numerical model for turbidity currents by implementing the
combined approach of the local graded-time-step (LGTS) and the global
maximum-time-step (GMaTS). The governing equations are solved for unstructured
triangular meshes by the shock-capturing finite volume method along with a set
of well-balanced evaluations of the numerical flux and geometrical slope source
terms. The quantitative accuracy of the model, given reasonably estimated
empirical and model parameters (e.g., bed friction, water entrainment, sediment
deposition and erosion coefficients), is demonstrated by comparing the
numerical solutions against laboratory data of the current front positions and
deposition profiles, as well as field data of the current front positions. The
improved computational efficiency is demonstrated by comparing the
computational cost of the present model against that of a traditional model
that uses a GMiTS. For the present simulated cases, the maximum reduction of
the computational cost is approximately 80% (e.g., a simulation that cost
1 h before will only require 12 min with the new model).
Keywords:
Turbidity
currents; Numerical modeling; Computational efficiency; Time step
4、Influence of
diversion angle on water and sediment flow into diversion channel
Nashwan
Kamalaldeen Alomari, Badronnisa Yusuf, Thamer Ahmad Mohammad, Abdul Halim
Ghazali
Pages
600-608
https://doi.org/10.1016/j.ijsrc.2020.06.006
https://www.sciencedirect.com/science/article/pii/S1001627920300706
Abstract
Accumulation of the sediment in the stream of the
diversion channels adversely affects its operational systems. Diversion
channels are often constructed perpendicular to the main river. In this study,
the water flow and sediment transport in the diversion channel with different
angles were investigated in an attempt to maximize water discharge and minimize
sediment discharge. A physical model with movable bed was used to simulate
water and sediment flow with five diversion angles (θ) between (30°–90°).
Moreover, three bed width ratios (Br) (the relation between
diversion to main channel bed width) between 30% and 50% and five total
discharges between (7.25 L/s to 12.25 L/s) were considered for each
case of (θ). The results showed, up to 10%, increasing in proportion discharge
ratios for 30 and 45 diversion angles compared with 90° diversion angle. The
results also showed that the lowest diversion sediment concentration was
provided by the (θ) of 30°. Across all scenarios, the average proportion
concentration reduction was 64%, compared with 90° diversion angle. Closer observation
of the diversion system mechanism confirmed that decreased (θ) result in
decreased sediment concentrations in the diversion channels. In conclusion, the
diversion channel water and sediment discharge could be effectively managed by
changing the (θ) to 30° or 45° instead of 90°.
Keywords
Diversion
channel; Diversion angle; Lowest diversion sediment concentration; Bed width
ratio; Sediment concentration
5、Mass flows and river
response in rapid uplifting regions – A case of lower Yarlung Tsangpo basin,
southeast Tibet, China
Guo-An
Yu, Jianyin Lu, Liqun Lyu, Lujie Han, Zhaoyin Wang
Pages
609-620
https://doi.org/10.1016/j.ijsrc.2020.05.006
https://www.sciencedirect.com/science/article/pii/S1001627920300573
Abstract
The fluvial geomorphology in tectonically active
(particularly rapid uplift) regions often undergoes continuous change. The
rapid uplift is coincident with high erosion rates; consequently, incised
valleys are formed. Mass flows (for example, avalanches, landslides, and debris
flows) in incised valleys can markedly influence fluvial processes and even
reshape valley geomorphology. However, these processes and long-term evolution
corresponding to mass flows require further clarification. Field campaigns were
carried out in the region near the Yigong Tsangpo and Palong Tsangpo Rivers
(hereafter the Yigong and Palong Rivers), the two largest tributaries of the
lower Yarlung Tsangpo River, to examine the feedback between fluvial processes
and mass flows. Remote sensing images from recent decades were used to compare
the channel morphology before and after typical mass flows (particularly
catastrophic ones). The morphology of the lower Yigong River has evidently been
impacted by landslides, while that of the Palong River has mainly been shaped
by glacial processes and debris flows. At present, the morphology of the latter
consists of alternating sections of gorges and wide valleys, with a
staircase-like longitudinal profile. The gorge sections exhibit single and
deeply incised channels with a high-gradient channel bed and terraces. In
contrast, the wide valley sections consist of lakes, braided or anabranching
channels, gentle bed gradients, and thick alluvial deposits. Debris flows occur
more frequently in gullies in the reaches of the gorge sections and rarely in
gullies along the wide valley sections. The occurrence of mass flow events has
resulted in an imbalance of the previous (quasi-)equilibrium in the river
morphology; however, this has triggered negative feedback that is driving the
transient river morphology to a new state of (quasi-)equilibrium.
Keywords：Mass
flow; Debris flow; Glacial erosion; Fluvial processes; Negative feedback
6、 Post-analysis
simulation of the collapse of an open sabo dam of steel pipes subjected to
boulder laden debris flow
Toshiyuki
Horiguchi, Vincent Richefeu
Pages
621-635
https://doi.org/10.1016/j.ijsrc.2020.05.002
https://www.sciencedirect.com/science/article/pii/S1001627920300536
Abstract
The objective of the proposed method
is to utilize a site investigation of a debris flow disaster and verify a real
scale analysis to evaluate the impulsive load on an open sabo dam. The Nagiso
debris flow disaster which occurred in Nagano in 2014, where damage caused by
Typhoon Neogri was studied. The verification result of the site investigation
demonstrated the weak components of the open Sabo dam experienced damage owing
to the debris flow. A discrete element method is normally applied to a solid
body to calculate an interaction function force with respect to the contact
point between boulders and the dam. The numerical method initially concatenates
elements that model the open Sabo dam. Moreover, the stiffness coefficient of
flanges and coupling joints between pipes was expressed to utilize the
sectional partition method to determine the structural characteristics. The
method was improved to separate from the connecting elements beyond the
boundary conditions. The debris flow model uses a water flow distribution
model, and the debris flow flowed from 200 m upstream of the open sabo
dam. Accordingly, the proposed method was examined to verify the primary cause
of damage to the open sabo dam and used to reproduce the circumstances that
evaluated the impulsive load occurrence mechanism in the case of a real
disaster. In addition, the coupling joints between the hollow steel pipes
utilized a ‘reproduction analysis’ for a real sabo dam and a ‘reinforced
analysis’ for a reinforced sabo dam were applied to assess the weak point of
the dam.
Keywords: Open sabo dam; Site investigation; Damage
verification; Discrete element method
7 、Circulation
cells topology and their effect on migration pattern of different multi-bend
meandering rivers
Fariba
Sadat Esfahani, Alireza Keshavarzi
Pages
636-650
https://doi.org/10.1016/j.ijsrc.2020.04.004
https://www.sciencedirect.com/science/article/pii/S1001627920300500
Abstract
In meandering rivers, a cross-stream flow, referred to as
a secondary current, has important effects on broad spectra of
hydraulic/environmental characteristics, running the gamut from river
hydrodynamics and geomorphology to stream ecology. The transport equation for
vorticity and kinetic energy transfer should be analyzed to specify terms
involved in generation of secondary currents. However, there is limited
research on scrutinizing these terms in meandering rivers. On the other hand,
while rivers are mostly multi-bend, previous studies have been limited to
single bends. In the current paper, three physical multi-bend channels
representing a strongly curved bend, a mild bend and an elongated symmetrical
meander loop are designed in order to unravel mechanisms responsible for
forming circulation cells in cross sections. Experiments are carried out in the
middle bend of these models. Cross-stream turbulence anisotropy considerably
strengthens almost all near bank cells. Moreover, contrary to single sharp
bends, multi bend effects hinder the transfer of the kinetic energy in both
directions in the entrance section of the strongly curved bend.
Keywords: Circulation cells; Multi bend channels; Vorticity
equation; Kinetic energy transfer
8、Comprehensive
evaluation method for sediment allocation effects in the Yellow River
Xujian
Chen, Chunhong Hu, Yuqi An, Zhihao Zhang
Pages
651-658
https://doi.org/10.1016/j.ijsrc.2020.04.002
https://www.sciencedirect.com/science/article/pii/S1001627920300482
Abstract
Scientific evaluation of the sediment allocation effects
in the Yellow River plays an important role in the comprehensive harnessing of
the Yellow River. A new evaluation index system for sediment allocation has
been established using the Analytic Hierarchy Process, and six main evaluation
indexes have been selected for this study. The calculation methods and
evaluation criteria of each evaluation index are proposed. The evaluation
criterion of bankfull discharge in the upper reach is 2,000 m3/s,
that of Tongguan elevation in the middle reach is 325.7 m, and that of
bankfull discharge in the lower reach is 4,000 m3/s. The evaluation
criteria of water volume and sediment volume into the Yellow River are 25
billion m3/a and 300 million t/a, respectively, and that of sediment volume
into the sea to maintain stability of the estuary is 130–260 million t/a. The
comprehensive evaluation method and grade index are proposed, and the effect of
sediment allocation in the Yellow River from 1960 to 2015 is evaluated. The
comprehensive evaluation grades in different periods are determined. The
evaluation results objectively reflect the situation of sediment allocation in
the Yellow River, and the new comprehensive evaluation method can be applied to
evaluate the sediment allocation scheme of the Yellow River in the future.
Keywords:Yellow River; Sediment allocation; Evaluation
index; Evaluation method; Evaluation grade
9、Quasi-stationary
flow structure in turbidity currents
Shun
Nomura, Giovanni De Cesare, Mikito Furuichi, Yasushi Takeda, Hide Sakaguchi
Pages
659-665
https://doi.org/10.1016/j.ijsrc.2020.04.003
https://www.sciencedirect.com/science/article/pii/S1001627920300494
Abstract
A turbidity current is a particle-laden current driven by
density differences due to suspended sediment particles. Turbidity currents can
transport large amounts of sediment down slopes over great distances, and play
a significant role in fluvial, lake and submarine systems. To better understand
the sediment transport process, the flow system of an experimentally produced
turbidity current in an inclined flume was investigated using video processing.
We observed that the current progresses with constant frontal velocity and
maintains an unchanged global interface geometry. In addition, the
spatio-temporal profiles of the inner mean and turbulence velocity obtained by
ultrasound velocity profiler (UVP) showed that similar distributions were
maintained, with low dissipation. The results indicate that the turbidity
current progressed in a quasi-stationary state, which enabled long-distance
sediment transport. To understand the mechanisms behind the quasi-stationary
flow, we analyzed the forces acting on the turbidity current. We found that
under particular densities of suspended particles, the gravitational force is
balanced by the viscous forces along the slope direction. We conclude that this
specific force balance induces the quasi-stationary flow structure, enabling
the long-distance transport of a substantial amount of sediment downstream with
low dissipation.
Keywords: Turbidity current; Velocity field; Mass
valance; Image processing; Ultrasound Doppler velocity profiling; Flume
experiment
10 、Influence of
surface roughness of dune bedforms on flow and turbulence characteristics
Veysel
Sadan Ozgur Kirca, Seyed Mahdi Saghebian, Kiyoumars Roushangar, Oral Yagci
Pages
666-678
https://doi.org/10.1016/j.ijsrc.2020.06.003
https://www.sciencedirect.com/science/article/pii/S1001627920300676
Abstract
The current paper investigates the
flow and turbulence characteristics over dune bed forms by means of laboratory
experiments, where spatially dense and temporally high frequency velocity
measurements were done. Although similar studies are available in the
literature, the focus and novelty of the current study is to assess the
influence of surface roughness of the dune bed forms on the near bed flow. For
direct comparison, two different surface roughness heights over idealized,
fixed-shaped, high-angled dune bed forms were tested; one with a
hydraulically-smooth surface, and the other with a fully-rough surface. Spatial
variation of time-averaged flow as well as turbulence statistics were examined,
which was complemented by streamline plots and spectral analyses. The results
are interpreted from sediment entrainment and sediment transport points of view.
The results show that increased dune surface roughness reduces the near bed
flow velocity, but increases the flow velocities at upper regions. The upward
directed flow near the dune crests becomes stronger in the case of smooth
surface, while the re-attachment point moves further downstream compared to the
rough wall case. It is concluded that the roughness of the dune surface affects
the near bed flow and turbulence characteristics qualitatively and
quantitatively, which is shown to have direct consequences on sediment
entrainment characteristics.
Keywords:
Bedforms;
Dunes; Friction drag; Turbulence; Grain roughness; Form drag
