scholarly journals The Role of Large-Scale Bedforms in Driftwood Storage Mechanism in Rivers

Water ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 811
Author(s):  
Takara Okitsu ◽  
Toshiki Iwasaki ◽  
Tomoko Kyuka ◽  
Yasuyuki Shimizu
Keyword(s):  
Large Scale ◽  
Field Measurements ◽  
Coupling Model ◽  
Two Dimensional ◽  
Watershed Scale ◽  
Storage Mechanism ◽  
Total Budget ◽  
Alternate Bars ◽  
River Reach

The quantification of driftwood deposition in rivers is important for understanding the total budget of driftwood at the watershed scale; however, it remains unclear how such driftwood storage in rivers contributes to the overall system because of the difficulties in undertaking field measurements. Herein, we perform numerical simulations of driftwood deposition within an idealized river reach with a sand-bed, to describe the role of large-scale bedforms, more specifically, alternate bars, multiple bars, and braiding, in driftwood storage in rivers. The numerical model we propose here is a coupling model involving a Lagrangian-type driftwood model and an Eulerian two-dimensional morphodynamic model for simulating large-scale bedforms (i.e., bars and braiding). The results show that the channel with a braiding pattern provides a wide area with enhanced capacity for deposition of driftwood, characterized by exposed mid-channel or in-channel bars, leading to high driftwood storage. The alternate bar is also a large bedform representing a sediment depositional element in rivers; however, because of the narrow exposed bar area and its downstream-migrating feature during floods, the alternate bars seem to contribute less to driftwood deposition in rivers. This suggests that the role of multiple bars and braiding is critically important for the driftwood deposition in rivers.

scholarly journals Supernova Explosions - The Role of a Rayleigh-Taylor Instability

1980 ◽  
Vol 58 ◽  
pp. 571-577
Author(s):  
J. Robert Buchler ◽  
Mario Livio ◽  
Stirling A. Colgate
Keyword(s):  
Large Scale ◽  
Supernova Explosion ◽  
Taylor Instability ◽  
Core Collapse ◽  
Two Dimensional ◽  
Supernova Explosions ◽  
Hydrodynamic Study ◽  
Rayleigh Taylor Instability ◽  
Energy And Momentum

AbstractA two dimensional hydrodynamic study indicates that convectively unstable gradients which develop during core collapse and bounce give rise to large scale core overturn. It is also shown that the concomitant release of neutrini can deposit large amounts of energy and momentum in the infalling envelope and give rise to a powerful supernova explosion.

Experimental and model-based evaluation of the role of denitrifying polyphosphate accumulating organisms at two large scale WWTPs in northern Poland

2006 ◽  
Vol 54 (8) ◽  
pp. 73-81 ◽  
Author(s):  
J. Makinia ◽  
K.-H. Rosenwinkel ◽  
M. Swinarski ◽  
E. Dobiegala
Keyword(s):  
Large Scale ◽  
Field Measurements ◽  
Model Parameters ◽  
Biological Phosphorus Removal ◽  
Batch Tests ◽  
Northern Poland ◽  
Real Wastewater ◽  
Polyphosphate Accumulating Organisms ◽  
Biological Phosphorus

The capabilities of denitrifying Polyphosphate Accumulating Organisms (DPAOs) in two large-scale plants in northern Poland performing enhanced biological phosphorus removal (EBPR) were evaluated in this study. A series of batch tests with the process biomass aimed at the measurements of phosphate release (with artificial substrate and real wastewater) and subsequent phosphate uptake under anoxic/aerobic conditions. The process kinetics were predicted using ASM2d implemented in the GPS-X ver. 4.0.2 simulation package. The results from one experimental series (summer) were used for the model calibration, whereas the results from another series (spring) were used for the model validation. The model parameters were also accurately confirmed by predictions of the accompanying field measurements in the full-scale bioreactors. The experimental and simulation results revealed that a relatively small fraction of PAO could denitrify (ηNO3,PAO=0.32). The denitrification rates associated with the anoxic storage of PP and the anoxic growth of PAO only constituted 16.0–21.0% of the denitrification rates associated with the anoxic activity of “ordinary” heterotrophs.

The Role of Streamwise Vorticity in the Control of Impinging Jets

2003 ◽  
Author(s):  
F. S. Alvi ◽  
H. Lou ◽  
C. Shih
Keyword(s):  
Velocity Field ◽  
Shear Layer ◽  
Acoustic Waves ◽  
High Speed ◽  
Feedback Loop ◽  
Large Scale ◽  
Field Measurements ◽  
Impinging Jets ◽  
Streamwise Vorticity

Supersonic impinging jets produce a highly unsteady flowfield leading to very high dynamic pressure loads on nearby surfaces. In earlier studies, we conclusively demonstrated that arrays of supersonic microjet, 400 μm in diameter, effectively disrupted the feedback loop inherent in high-speed impinging jet flows. This feedback disruption results in significant reductions in the adverse effects associated with such flows. In this paper, by primarily using detailed velocity field measurements, we examine the role of streamwise vorticity in order to better understand the mechanisms behind this control scheme. The velocity field measurements clearly reveal the presence of well-organized, streamwise vortices with the activation of microjets. This increase in streamwise vorticity is concomitant with a reduction in the azimuthal vorticity of the primary jet. We propose that the streamwise vorticity is mainly a result of the redirection of the azimuthal vorticity, which leads to a weakening of the large-scale structures in the primary jet. The appearance of strong vortices in the shear layer near the nozzle exit due to microjets further weakens the spatial coherence of the coupling between the acoustic waves and shear layer instability, while thickening the jet shear layer. All these effects are thought to be collectively responsible for the efficient disruption of the feedback loop using microjets.

On the development of noise-producing large-scale wavelike eddies in a plane turbulent jet

1975 ◽  
Vol 70 (2) ◽  
pp. 353-368 ◽  
Author(s):  
Lee-Or Merkine ◽  
J. T. C. Liu
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Thickness ◽  
Large Scale ◽  
Frequency Parameter ◽  
Turbulent Jet ◽  
Two Dimensional ◽  
Fine Scale ◽  
Mean Flow ◽  
Potential Core

In this paper we study the development of large-scale wavelike eddies in a two-dimensional turbulent jet, extending earlier work on the mixing region (Liu 1974). The basic mean flow develops from one of mixing-region type with an initially specified boundary-layer thickness into a fully developed jet. This study brings out the role of the varicose and sinuous modes as they develop in a growing mean flow. In general, it is found that, for a given frequency parameter, the varicose mode has a shorter streamwise lifetime than the sinuous mode. For lower frequencies, the latter persists past the end of the potential core only to become subject to dissipation by the enhanced fine-scale turbulent activity in that region.

Two-dimensional atom-phonon coupling model for spin conversion: role of metastable states

2011 ◽  
Vol 83 (2) ◽  
pp. 115-132 ◽  
Author(s):  
J. A. Nasser ◽  
S. Topçu ◽  
L. Chassagne ◽  
M. Wakim ◽  
B. Bennali ◽  
...  
Keyword(s):  
Coupling Model ◽  
Metastable States ◽  
Two Dimensional ◽  
Phonon Coupling ◽  
Spin Conversion

The Role of Sense of Direction and Other Factors During Navigation in a Large-Scale, Unconstrained Environment

2013 ◽  
Author(s):  
Elisabeth J. Ploran ◽  
Ericka Rovira ◽  
James C. Thompson ◽  
Raja Parasuraman
Keyword(s):  
Large Scale ◽  
Sense Of Direction

Magnetic Properties of xCeO2•(50 − x) PbO•50B2O3 Glasses and Glass Ceramics

2017 ◽  
Vol 13 (1) ◽  
pp. 4486-4494 ◽  
Author(s):  
G.El Damrawi ◽  
F. Gharghar
Keyword(s):  
Magnetic Properties ◽  
Large Scale ◽  
Glass Ceramics ◽  
Magnetic Behavior ◽  
Crystal Formation ◽  
Dual Roles ◽  
Effective Agent ◽  
Ordered Structures ◽  
Essential Change

Cerium oxide in borate glasses of composition xCeO2·(50 − x)PbO·50B2O3 plays an important role in changing both microstructure and magnetic behaviors of the system. The structural role of CeO2 as an effective agent for cluster and crystal formation in borate network is clearly evidenced by XRD technique. Both structure and size of well-formed cerium separated clusters have an effective influence on the structural properties. The cluster aggregations are documented to be found in different range ordered structures, intermediate and long range orders are the most structures in which cerium phases are involved. The nano-sized crystallized cerium species in lead borate phase are evidenced to have magnetic behavior.  The criteria of building new specific borate phase enriched with cerium as ferrimagnetism has been found to keep the magnetization in large scale even at extremely high temperature. Treating the glass thermally or exposing it to an effective dose of ionized radiation is evidenced to have an essential change in magnetic properties. Thermal heat treatment for some of investigated materials is observed to play dual roles in the glass matrix. It can not only enhance alignment processes of the magnetic moment but also increases the capacity of the crystallite species in the magnetic phases. On the other hand, reverse processes are remarked under the effect of irradiation. The magnetization was found to be lowered, since several types of the trap centers which are regarded as defective states can be produced by effect of ionized radiation. 

The Impact of Quantitative Easing on Emerging Markets – Literature Review

e-Finanse ◽  
2018 ◽  
Vol 14 (4) ◽  
pp. 67-76
Author(s):  
Piotr Bartkiewicz
Keyword(s):  
Emerging Markets ◽  
Large Scale ◽  
Empirical Literature ◽  
Quantitative Easing ◽  
Methodological Choices ◽  
The Subject ◽  
Methodological Approaches ◽  
The Impact ◽  
Sufficient Precision

AbstractThe article presents the results of the review of the empirical literature regarding the impact of quantitative easing (QE) on emerging markets (EMs). The subject is of interest to policymakers and researchers due to the increasingly larger role of EMs in the world economy and the large-scale capital flows occurring after 2009. The review is conducted in a systematic manner and takes into consideration different methodological choices, samples and measurement issues. The paper puts the summarized results in the context of transmission channels identified in the literature. There are few distinct methodological approaches present in the literature. While there is a consensus regarding the direction of the impact of QE on EMs, its size and durability have not yet been assessed with sufficient precision. In addition, there are clear gaps in the empirical findings, not least related to relative underrepresentation of the CEE region (in particular, Poland).

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