Numerical study of resonant shallow flows past a lateral cavity: benchmarking the model with a new experimental data set

2020 ◽  
Author(s):  
Adrián Navas-Montilla ◽  
Sergio Martínez-Aranda ◽  
Antonio Lozano ◽  
Pilar García-Navarro
Keyword(s):  
Water Resources ◽  
Shallow Water ◽  
Large Scale ◽  
Numerical Study ◽  
Numerical Results ◽  
Small Scale ◽  
Coupling Mechanism ◽  
Data Set ◽  
Shallow Flows ◽  
Lateral Cavity

<p>Steady shallow flows past an open channel lateral cavity have been widely studied in the last years due to their engineering and environmental relevance, e.g. for river restoration purposes [1]. Such flows can induce the excitation of an eigenmode of a gravity standing wave inside the cavity, called seiche, which may be coupled with the shedding of vortices at the opening of the cavity. A complete understanding of such phenomenon is necessary as it may determine the mass exchange between the main channel and the cavity [2]. A numerical study of the resonant flow in a channel with a single lateral cavity is herein presented. Five different flow configurations at a fixed Froude number (Fr=0.8), measured in the laboratory [3], are used as a benchmark. Such experiments are reproduced using a high-order 2D depth-averaged URANS model based on the shallow water equations, assuming that shallow water turbulence is mainly horizontal [4]. The large-scale horizontal vortices are resolved by the model, whereas the effect of the small-scale turbulence is accounted for by means of a turbulence model. Water surface elevation and velocity measurements are used for comparison with the numerical results. A detailed comparison of the seiche amplitude distribution in the cavity-channel area is presented, showing a good agreement between the numerical results and the observations. Frequency analysis techniques are used to extract the relevant features of the flow. It is evidenced that the proposed model is able to reproduce the observed spatial distribution of oscillation nodes and anti-nodes, as well as the time-averaged flow field. The coupling mechanism between the gravity wave inside the cavity and the unstable shear layer at the opening of the cavity is also accurately captured. <br><br></p><p>[1] C. Juez, M. Thalmann, A. J. Schleiss & M. J.  Franca, Morphological resilience to flow fluctuations of fine sediment deposits in bank lateral cavities, Advances in Water Resources,  115 (2018) 44-59.</p><p>[2] I. Kimura & T. Hosoda, Fundamental properties of flows in open channels with dead zone, Journal of Hydraulic Engineering 123 (1997) 98-107.</p><p>[3] S. Martínez-Aranda, J. Fernández-Pato, D. Caviedes-Voullième, I. García-Palacín & P. García-Navarro, Towards transient experimental water surfaces: a new benchmark dataset for 2D shallow water solvers, Advances in water resources, 121 (2018) 130-149.</p><p>[4] A. Navas-Montilla, C. Juez, M.J. Franca & J. Murillo, Depth-averaged unsteady RANS simulation of resonant shallow flows in lateral cavities using augmented WENO-ADER schemes, Journal of Computational Physics, 24 (2019) 203-217.</p>

2D and 3D Multiscale Computational Modeling of Dynamic Microorgan Devices as Drug Screening Platforms

2015 ◽  
Author(s):  
Filippos Tourlomousis ◽  
Robert C. Chang
Keyword(s):  
Large Scale ◽  
Numerical Study ◽  
Numerical Results ◽  
Scale Model ◽  
Small Scale ◽  
Optimum Process ◽  
Shear Stresses ◽  
Enzymatic Reactions ◽  
Modeling Approach

The ability to incorporate three-dimensional (3D) hepatocyte-laden hydrogel constructs using layered fabrication approaches into devices that can be perfused with drugs enables the creation of dynamic microorgan devices (DMDs) that offer an optimal analog of the in vivo liver metabolism scenario. The dynamic nature of such in vitro metabolism models demands reliable numerical tools to determine the optimum process, material, and geometric parameters for the most effective metabolic conversion of the perfused drug into the liver microenvironment. However, there is a current lack of literature that integrates computational approaches to guide the optimum design of such devices. The groundwork of the present numerical study has been laid by our previous study [1], where the authors modeled in 2D an in vitro DMD of arbitrary dimensions and identified the modeling challenges towards meaningful results. These constructs are hosted in the chamber of the microfluidic device serving as walls of the microfluidic array of channels through which a fluorescent drug substrate is perfused into the microfluidic printed channel walls at a specified volumetric flow rate assuring Stokes flow conditions (Re<<1). Due to the porous nature of the hydrogel walls, a metabolized drug product is collected at the outlet port. A rigorous FEM based modeling approach is presented for a single channel parallel model geometry (1 free flow channel with 2 porous walls), where the hydrodynamics, mass transfer and pharmacokinetics equations are solved numerically in order to yield the drug metabolite concentration profile at the DMD outlet. The fluid induces shear stresses are assessed both in 3D, with only 27 cells modeled as single compartment voids, where all of the enzymatic reactions are assumed to take place. In this way, the mechanotransduction effect that alters the hepatocyte metabolic activity is assessed for a small scale model. This approach overcomes the numerical limitations imposed by the cell density (∼1012 cells/m3) of the large scale DMD device. In addition, a compartmentalization technique is proposed in order to assess the metabolism process at the subcellular level. The numerical results are validated with experiments to reveal the robustness of the proposed modeling approach and the necessity of scaling the numerical results by preserving dynamic and biochemical similarity between the small and large scale model.

Experimental study of resonant shallow flows past a lateral cavity: a benchmark test for high-resolution numerical models

2020 ◽  
Author(s):  
Sergio Martínez Aranda ◽  
Adrián Navas-Montilla ◽  
Antonio Lozano ◽  
Pilar García-Navarro
Keyword(s):  
Experimental Study ◽  
High Resolution ◽  
Water Resources ◽  
Water Surface ◽  
Numerical Models ◽  
Resonance Phenomenon ◽  
Data Set ◽  
River Bank ◽  
Shallow Flows ◽  
Lateral Cavity

&lt;p&gt;&lt;span&gt;The study of resonant shallow flows past a lateral cavity is of great relevance due to their interest in civil and environmental engineering [1]. Such flows exhibit the presence of a standing gravity wave, called seiche, which is coupled with the shedding of vortices at the opening of the cavity. A complete understanding of such phenomenon is necessary as it may determine the mass exchange between the main channel and the cavity [2]. &lt;/span&gt;&lt;span&gt;A better insight into this phenomenon helps to improve the design and implementation of innovative river bank restoration techniques&lt;/span&gt;&lt;span&gt;. An experimental study of the resonant flow in a laboratory flume with a single lateral cavity is herein presented. Five different flow configurations at a fixed Froude number (Fr=0.8) are considered. The main novelty of the present work is the use of a pioneering non-intrusive experimental technique [3] to measure the water surface at the channel-cavity region. This optical technique offers high resolution 2D data in time and space of the water surface evolution, allowing to determine the relevant features of the seiche oscillation, i.e. spatial distribution of oscillation nodes and anti-nodes, oscillation modes and amplitude of the oscillation. Such data are supplemented with Particle Image Velocimetry measurements to perform a more detailed study of the resonance phenomenon. High-resolution two-dimensional amplitude oscillation maps of the seiche phenomenon are presented for the experimental water depth. Experimental velocity fields inside the cavity are presented and confirm the inherent coupling between the unstable shear layer at the opening of the cavity and the gravity standing wave. The high quality of the experimental data reported in this work makes this data set a suitable benchmark for numerical simulation models in order to evaluate their performance in the resolution of turbulent resonant shallow flows.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;[1] C. Juez, M. Thalmann, A. J. Schleiss &amp; M. J. Franca, Morphological resilience to flow fluctuations of fine sediment deposits in bank lateral cavities, Advances in Water Resources, 115 (2018) 44-59.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;[2] I. Kimura &amp; T. Hosoda, Fundamental properties of flows in open channels with dead zone, Journal of Hydraulic Engineering 123 (1997) 98-107.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;[3] S. Mart&amp;#237;nez-Aranda, J. Fern&amp;#225;ndez-Pato, D. Caviedes-Voulli&amp;#232;me, I. Garc&amp;#237;a-Palac&amp;#237;n &amp; P. Garc&amp;#237;a-Navarro, Towards transient experimental water surfaces: a new benchmark dataset for 2D shallow water solvers, Advances in water resources, 121 (2018) 130-149.&lt;/span&gt;&lt;/p&gt;

Managing the impacts of mining on Ghana’s water resources from a legal perspective

2018 ◽  
Vol 1 (3) ◽  
pp. 156-165 ◽  
Author(s):  
Nasirudeen Abdul Fatawu
Keyword(s):  
Surface Water ◽  
Water Resources ◽  
Environmental Protection Agency ◽  
Large Scale ◽  
Small Scale ◽  
Mining Activities ◽  
Protection Agency ◽  
Environmental Laws ◽  
Mining Areas ◽  
Legal Perspective

Recent floods in Ghana are largely blamed on mining activities. Not only are lives lost through these floods, farms andproperties are destroyed as a result. Water resources are diverted, polluted and impounded upon by both large-scale minersand small-scale miners. Although these activities are largely blamed on behavioural attitudes that need to be changed, thereare legal dimensions that should be addressed as well. Coincidentally, a great proportion of the water resources of Ghana arewithin these mining areas thus the continual pollution of these surface water sources is a serious threat to the environmentand the development of the country as a whole. The environmental laws need to be oriented properly with adequate sanctionsto tackle the impacts mining has on water resources. The Environmental Impact Assessment (EIA) procedure needs to bestreamlined and undertaken by the Environmental Protection Agency (EPA) and not the company itself.

Mapping global water projects: improving access to donor investment information on the web

Water Policy ◽  
2003 ◽  
Vol 5 (3) ◽  
pp. 203-212
Author(s):  
J. Lisa Jorgensona
Keyword(s):  
Water Resources ◽  
Web Sites ◽  
Large Scale ◽  
Technical Assistance ◽  
Water Withdrawal ◽  
Small Scale ◽  
Water Projects ◽  
Essential Information ◽  
Water Project ◽  
The Web

This paper discusses a series of discusses how web sites now report international water project information, and maps the combined donor investment in more than 6000 water projects, active since 1995. The maps show donor investment:  • has addressed water scarcity,  • has improved access to improvised water resources,  • correlates with growth in GDP,  • appears to show a correlation with growth in net private capital flow,  • does NOT appear to correlate with growth in GNI. Evaluation indicates problems in the combined water project portfolios for major donor organizations: •difficulties in grouping projects over differing Sector classifications, food security, or agriculture/irrigation is the most difficult.  • inability to map donor projects at the country or river basin level because 60% of the donor projects include no location data (town, province, watershed) in the title or abstracts available on the web sites.  • no means to identify donor projects with utilization of water resources from training or technical assistance.  • no information of the source of water (river, aquifer, rainwater catchment).  • an identifiable quantity of water (withdrawal amounts, or increased water efficiency) is not provided.  • differentiation between large scale verses small scale projects. Recommendation: Major donors need to look at how the web harvests and combines their information, and look at ways to agree on a standard template for project titles to include more essential information. The Japanese (JICA) and the Asian Development Bank provide good models.

A numerical study of the transition of jet diffusion flames

1990 ◽  
Vol 431 (1882) ◽  
pp. 301-314 ◽  
Keyword(s):  
Reynolds Number ◽  
Diffusion Coefficient ◽  
Large Scale ◽  
Numerical Study ◽  
Small Scale ◽  
Surface Model ◽  
Flame Surface ◽  
Transition Mechanism ◽  
Air Stream ◽  
Scale Fluctuation

A numerical study on the transition from laminar to turbulent of two-dimensional fuel jet flames developed in a co-flowing air stream was made by adopting the flame surface model of infinite chemical reaction rate and unit Lewis number. The time dependent compressible Navier–Stokes equation was solved numerically with the equation for coupling function by using a finite difference method. The temperature-dependence of viscosity and diffusion coefficient were taken into account so as to study effects of increases of these coefficients on the transition. The numerical calculation was done for the case when methane is injected into a co-flowing air stream with variable injection Reynolds number up to 2500. When the Reynolds number was smaller than 1000 the flame, as well as the flow, remained laminar in the calculated domain. As the Reynolds number was increased above this value, a transition point appeared along the flame, downstream of which the flame and flow began to fluctuate. Two kinds of fluctuations were observed, a small scale fluctuation near the jet axis and a large scale fluctuation outside the flame surface, both of the same origin, due to the Kelvin–Helmholtz instability. The radial distributions of density and transport coefficients were found to play dominant roles in this instability, and hence in the transition mechanism. The decreased density in the flame accelerated the instability, while the increase in viscosity had a stabilizing effect. However, the most important effect was the increase in diffusion coefficient. The increase shifted the flame surface, where the large density decrease occurs, outside the shear layer of the jet and produced a thick viscous layer surrounding the jet which effectively suppressed the instability.

scholarly journals Hyplant-Derived Sun-Induced Fluorescence—A New Opportunity to Disentangle Complex Vegetation Signals from Diverse Vegetation Types

2019 ◽  
Vol 11 (14) ◽  
pp. 1691 ◽  
Author(s):  
Subhajit Bandopadhyay ◽  
Anshu Rastogi ◽  
Uwe Rascher ◽  
Patrick Rademske ◽  
Anke Schickling ◽  
...  
Keyword(s):  
Plant Communities ◽  
Large Scale ◽  
Temporal Dynamics ◽  
Vegetation Indices ◽  
Spatial Diversity ◽  
Small Scale ◽  
Data Set ◽  
Area Index ◽  
Heterogeneous Landscape ◽  
Large Heterogeneity

Hyperspectral remote sensing (RS) provides unique possibilities to monitor peatland vegetation traits and their temporal dynamics at a fine spatial scale. Peatlands provide a vital contribution to ecosystem services by their massive carbon storage and wide heterogeneity. However, monitoring, understanding, and disentangling the diverse vegetation traits from a heterogeneous landscape using complex RS signal is challenging, due to its wide biodiversity and distinctive plant species composition. In this work, we aim to demonstrate, for the first time, the large heterogeneity of peatland vegetation traits using well-established vegetation indices (VIs) and Sun-Induced Fluorescence (SIF) for describing the spatial heterogeneity of the signals which may correspond to spatial diversity of biochemical and structural traits. SIF originates from the initial reactions in photosystems and is emitted at wavelengths between 650–780 nm, with the first peak at around 687 nm and the second peak around 760 nm. We used the first HyPlant airborne data set recorded over a heterogeneous peatland area and its surrounding ecosystems (i.e., forest, grassland) in Poland. We deployed a comparative analysis of SIF and VIs obtained from differently managed and natural vegetation ecosystems, as well as from diverse small-scale peatland plant communities. Furthermore, spatial relationships between SIF and VIs from large-scale vegetation ecosystems to small-scale peatland plant communities were examined. Apart from signal variations, we observed a positive correlation between SIF and greenness-sensitive VIs, whereas a negative correlation between SIF and a VI sensitive to photosynthesis was observed for large-scale vegetation ecosystems. In general, higher values of SIF were associated with higher biomass of vascular plants (associated with higher Leaf Area Index (LAI)). SIF signals, especially SIF760, were strongly associated with the functional diversity of the peatland vegetation. At the peatland area, higher values of SIF760 were associated with plant communities of high perennials, whereas, lower values of SIF760 indicated peatland patches dominated by Sphagnum. In general, SIF760 reflected the productivity gradient on the fen peatland, from Sphagnum-dominated patches with the lowest SIF and fAPAR values indicating lowest productivity to the Carex-dominated patches with the highest SIF and fAPAR values indicating highest productivity.

Magnetic coupling of waves and oscillations in the lower solar atmosphere: can the tail wag the dog?

2005 ◽  
Vol 364 (1839) ◽  
pp. 351-381 ◽  
Author(s):  
Robert Erdélyi
Keyword(s):  
Magnetic Fields ◽  
Solar Atmosphere ◽  
Acoustic Waves ◽  
Large Scale ◽  
Magnetic Coupling ◽  
Small Scale ◽  
Coupling Mechanism ◽  
Frequency Shifts ◽  
Characteristic Features ◽  
Lower Solar Atmosphere

Can the ubiquitously magnetic solar atmosphere have any effect on solar global oscillations? Traditionally, solar atmospheric magnetic fields are considered to be somewhat less important for the existence and characteristic features of solar global oscillations ( p , f and the not-yet-observed g -modes). In this paper, I demonstrate the importance of the presence of magnetism and plasma dynamics for global resonant oscillations in the solar atmosphere. In particular, in the lower part of the solar atmosphere there are both coherent and random components of magnetic fields and velocity fields, each of which contribute on its own to the line widths and frequency variations of solar global acoustic waves. Changes in the coherent large-scale atmospheric magnetic fields cause frequency shifts of global oscillations over a solar cycle. The random character of the continuously emerging, more localized, magnetic carpet (i.e. small-scale, possibly even sub-resolution, loops) gives rise to additional frequency shifts. On the other hand, random and organized surface and sub-surface flows, like surface granulation, meridional flows or differential rotation, also affect the coupling mechanism of global oscillations to the lower magnetic atmosphere. The competition between magnetic fields and flows is inevitable. Finally, I shall discuss how solar global oscillations can resonantly interact with the overlaying inhomogeneous lower solar atmosphere embedded in a magnetic carpet. Line width broadening and distorsion of global acoustic modes will be discussed. The latter is suggested to be tested and measured by using ring-analysis techniques.

Coral reef development drives molluscan diversity increase at local and regional scales in the late Neogene and Quaternary of the southwestern Caribbean

Paleobiology ◽  
2007 ◽  
Vol 33 (1) ◽  
pp. 24-52 ◽  
Author(s):  
Kenneth G. Johnson ◽  
Jonathan A. Todd ◽  
Jeremy B. C. Jackson
Keyword(s):  
Environmental Change ◽  
Shallow Water ◽  
Large Scale ◽  
Environmental Changes ◽  
Marine Biota ◽  
Environmental Distribution ◽  
Data Set ◽  
Ecological Response ◽  
Local Diversity ◽  
Late Neogene

The late Neogene was a time of major environmental change in Tropical America. Global cooling and associated oceanographic reorganization and the onset and intensification of glaciation in the Northern Hemisphere during the past ten million years coincided with the uplift of the Central American isthmus and resulting changes in regional oceanographic conditions. Previous analyses of patterns of taxonomic turnover and the shifting abundances of major ecological guilds indicated that the regional shallow-water marine biota responded to these environmental changes through extinction and via a restructuring of local benthic food webs, but it is not clear whether this ecological response had an effect on the diversity of molluscan assemblages in the region. Changes in regional and local diversity are often used as proxies for similar ecological response to environmental change in large-scale paleontological studies, but a clear relationship between diversity and ecological function has rarely been demonstrated in marine systems dominated by mollusks. To explore this relationship, we have compiled a data set of the stratigraphic and environmental distribution of genera of mollusks in large new collections of fossil specimens from the late Neogene and Recent of the southwestern Caribbean. Analysis of a selection of ecological diversity measures indicates that within shelf depths, assemblages from deeper water (51–200 m) were more diverse than shallow-water (<50 m) assemblages in the Pliocene. Lower diversity for shallow-water assemblages is caused by increased dominance of a few superabundant taxa in each assemblage. This implies that studies of diversity of shelf benthos need to control for relatively fine scaled environmental conditions if they are to avoid interpreting artifacts of uneven sampling as true change of diversity. For shallow-water assemblages only, there was significant increase in local and regional diversity of bivalve assemblages after the late Pliocene. No parallel increase in gastropods could be detected, but this likely is because sample size was inadequate for documenting the diversity of gastropod assemblages following a steep post-Pliocene decline of average gastropod abundance. Both the increasing bivalve diversity and the decrease in average abundance of gastropod taxa correspond to an interval of increasing carbonate deposition and reef building in the region, and are likely a result of increased fine-scale habitat heterogeneity controlled by the local distribution of carbonate buildups. Each of these results demonstrates that documenting the ecological response of tropical marine ecosystems to regional environmental change requires a large volume of fine-scaled samples with detailed paleoenvironmental control. Such data sets are rarely available from the fossil record.

scholarly journals Impact Assessment of Orography on the Extreme Precipitation Event of July 2010 over Pakistan: A Numerical Study

2015 ◽  
Vol 2015 ◽  
pp. 1-20 ◽  
Author(s):  
Khan Muhammad Tahir ◽  
Yan Yin ◽  
Yong Wang ◽  
Zaheer A. Babar ◽  
Dong Yan
Keyword(s):  
Large Scale ◽  
Extreme Event ◽  
Numerical Study ◽  
Deep Convection ◽  
Temporal Distribution ◽  
Precipitation Event ◽  
Windward Side ◽  
Small Scale ◽  
Extreme Rainfall Event ◽  
Synoptic Conditions

The topography influences monsoon precipitation and gives rise to significant rainfall events in South Asia. The physical mechanism involved in such events includes mechanical uplifting, thermodynamics, small scale cloud processes, and large scale atmospheric circulations. The investigation into orographic precipitation is pursued by synoptic and model analysis. Deep convection occurs as warm moist airflow is channeling over steep mountains. WRF model coupled with Morrison double moment scheme is used to assess the relative impact of topography on extreme rainfall event of 26–30 July 2010 in Pakistan. Two sensitivity tests with full topography (CTL) and reduced topography by 50% (LOW) are carried out. Two distinct precipitation zones over Hindukush and Himalaya mountains are identified. The topographic changes significantly affect moisture divergence and spatial and temporal distribution of precipitation. A low level jet is created on windward side of big mountains, yielding enhanced moisture flux and instability. Eddy kinetic energy significantly changes with orographic height. Energy flux created further unstabilized atmosphere and deep convection, producing wide spread heavy rainfall in the area in Himalaya foothills. Under the set synoptic conditions, orographic orientation enhanced the moisture accumulation and deep convection, resulting in occurrence of this extreme event.

scholarly journals Interaction between Crustal-Scale Darcy and Hydrofracture Fluid Transport: A Numerical Study

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Tamara de Riese ◽  
Paul D. Bons ◽  
Enrique Gomez-Rivas ◽  
Till Sachau
Keyword(s):  
Fluid Flow ◽  
Numerical Model ◽  
Transport Mechanism ◽  
Large Scale ◽  
Fluid Transport ◽  
Numerical Study ◽  
Ballistic Transport ◽  
Accretionary Prism ◽  
Small Scale ◽  
Porous Flow

Crustal-scale fluid flow can be regarded as a bimodal transport mechanism. At low hydraulic head gradients, fluid flow through rock porosity is slow and can be described as diffusional. Structures such as hydraulic breccias and hydrothermal veins both form when fluid velocities and pressures are high, which can be achieved by localized fluid transport in space and time, via hydrofractures. Hydrofracture propagation and simultaneous fluid flow can be regarded as a “ballistic” transport mechanism, which is activated when transport by diffusion alone is insufficient to release the local fluid overpressure. The activation of a ballistic system locally reduces the driving force, through allowing the escape of fluid. We use a numerical model to investigate the properties of the two transport modes in general and the transition between them in particular. We developed a numerical model in order to study patterns that result from bimodal transport. When hydrofractures are activated due to low permeability relative to fluid flux, many hydrofractures form that do not extend through the whole system. These abundant hydrofractures follow a power-law size distribution. A Hurst factor of ~0.9 indicates that the system self-organizes. The abundant small-scale hydrofractures organize the formation of large-scale hydrofractures that ascend through the whole system and drain fluids in large bursts. As the relative contribution of porous flow increases, escaping fluid bursts become less frequent, but more regular in time and larger in volume. We propose that metamorphic rocks with abundant veins, such as in the Kodiak accretionary prism (Alaska) and Otago schists (New Zealand), represent regions with abundant hydrofractures near the fluid source, while hydrothermal breccias are formed by the large fluid bursts that can ascend the crust to shallower levels.

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