scholarly journals Nonlinear effects of locally heterogeneous hydraulic conductivity fields on regional stream–aquifer exchanges

2015 ◽  
Vol 19 (11) ◽  
pp. 4531-4545 ◽  
Author(s):  
J. Zhu ◽  
C. L. Winter ◽  
Z. Wang
Keyword(s):  
Groundwater Flow ◽  
Effective Conductivity ◽  
Model Simulation ◽  
Three Dimensional ◽  
Small Scale ◽  
Heihe River ◽  
Effective Parameters ◽  
Aquifer Systems ◽  
Basin Scale ◽  
Local Grid

Abstract. Computational experiments are performed to evaluate the effects of locally heterogeneous conductivity fields on regional exchanges of water between stream and aquifer systems in the Middle Heihe River basin (MHRB) of northwestern China. The effects are found to be nonlinear in the sense that simulated discharges from aquifers to streams are systematically lower than discharges produced by a base model parameterized with relatively coarse effective conductivity. A similar, but weaker, effect is observed for stream leakage. The study is organized around three hypotheses: (H1) small-scale spatial variations of conductivity significantly affect regional exchanges of water between streams and aquifers in river basins, (H2) aggregating small-scale heterogeneities into regional effective parameters systematically biases estimates of stream–aquifer exchanges, and (H3) the biases result from slow paths in groundwater flow that emerge due to small-scale heterogeneities. The hypotheses are evaluated by comparing stream–aquifer fluxes produced by the base model to fluxes simulated using realizations of the MHRB characterized by local (grid-scale) heterogeneity. Levels of local heterogeneity are manipulated as control variables by adjusting coefficients of variation. All models are implemented using the MODFLOW (Modular Three-dimensional Finite-difference Groundwater Flow Model) simulation environment, and the PEST (parameter estimation) tool is used to calibrate effective conductivities defined over 16 zones within the MHRB. The effective parameters are also used as expected values to develop lognormally distributed conductivity (K) fields on local grid scales. Stream–aquifer exchanges are simulated with K fields at both scales and then compared. Results show that the effects of small-scale heterogeneities significantly influence exchanges with simulations based on local-scale heterogeneities always producing discharges that are less than those produced by the base model. Although aquifer heterogeneities are uncorrelated at local scales, they appear to induce coherent slow paths in groundwater fluxes that in turn reduce aquifer–stream exchanges. Since surface water–groundwater exchanges are critical hydrologic processes in basin-scale water budgets, these results also have implications for water resources management.

scholarly journals Nonlinear effects of locally heterogeneous hydraulic conductivity fields on regional stream–aquifer exchanges

2015 ◽  
Vol 12 (8) ◽  
pp. 7727-7764 ◽  
Author(s):  
J. Zhu ◽  
C. L. Winter ◽  
Z. Wang
Keyword(s):  
Effective Conductivity ◽  
Nonlinear Effects ◽  
Small Scale ◽  
Heihe River ◽  
Effective Parameters ◽  
Hydrologic Processes ◽  
Aquifer Systems ◽  
Coefficients Of Variation ◽  
Basin Scale ◽  
Local Grid

Abstract. Computational experiments are performed to evaluate the effects of locally heterogeneous conductivity fields on regional exchanges of water between stream and aquifer systems in the Middle Heihe River Basin (MHRB) of northwestern China. The effects are found to be nonlinear in the sense that simulated discharges from aquifers to streams are systematically lower than discharges produced by a base model parameterized with relatively coarse effective conductivity. A similar, but weaker, effect is observed for stream leakage. The study is organized around three hypotheses: (H1) small-scale spatial variations of conductivity significantly affect regional exchanges of water between streams and aquifers in river basins, (H2) aggregating small-scale heterogeneities into regional effective parameters systematically biases estimates of stream–aquifer exchanges, and (H3) the biases result from slow-paths in groundwater flow that emerge due to small-scale heterogeneities. The hypotheses are evaluated by comparing stream–aquifer fluxes produced by the base model to fluxes simulated using realizations of the MHRB characterized by local (grid-scale) heterogeneity. Levels of local heterogeneity are manipulated as control variables by adjusting coefficients of variation. All models are implemented using the MODFLOW simulation environment, and the PEST tool is used to calibrate effective conductivities defined over 16 zones within the MHRB. The effective parameters are also used as expected values to develop log-normally distributed conductivity (K) fields on local grid scales. Stream-aquifer exchanges are simulated with K fields at both scales and then compared. Results show that the effects of small-scale heterogeneities significantly influence exchanges with simulations based on local-scale heterogeneities always producing discharges that are less than those produced by the base model. Although aquifer heterogeneities are uncorrelated at local scales, they appear to induce coherent slow-paths in groundwater fluxes that in turn reduce aquifer–stream exchanges. Since surface water–groundwater exchanges are critical hydrologic processes in basin-scale water budgets, these results also have implications for water resources management.

Air mass exchange across the polar vortex edge during a simulated major stratospheric warming

1995 ◽  
Vol 13 (7) ◽  
pp. 745-756 ◽  
Author(s):  
G. Günther ◽  
M. Dameris
Keyword(s):  
Cross Sections ◽  
Middle Atmosphere ◽  
Model Simulation ◽  
Mechanistic Model ◽  
Three Dimensional ◽  
Polar Vortex ◽  
Small Scale ◽  
Stratospheric Warming ◽  
Air Masses ◽  
Physical And Chemical

Abstract. The dynamics of the polar vortex in winter and spring play an important role in explaining observed low ozone values. A quantification of physical and chemical processes is necessary to obtain information about natural and anthropogenic causes of fluctuations of ozone. This paper aims to contribute to answering the question of how permeable the polar vortex is. The transport into and out of the vortex ("degree of isolation") remains the subject of considerable debate. Based on the results of a three-dimensional mechanistic model of the middle atmosphere, the possibility of exchange of air masses across the polar vortex edge is investigated. Additionally the horizontal and vertical structure of the polar vortex is examined. The model simulation used for this study is related to the major stratospheric warming observed in February 1989. The model results show fair agreement with observed features of the major warming of 1989. Complex structures of the simulated polar vortex are illustrated by horizontal and vertical cross sections of potential vorticity and inert tracer. A three-dimensional view of the polar vortex enables a description of the vortex as a whole. During the simulation two vortices and an anticyclone, grouped together in a very stable tripolar structure, and a weaker, more amorphous anticyclone are formed. This leads to the generation of small-scale features. The results also indicate that the permeability of the vortex edges is low because the interior of the vortices remain isolated during the simulation.

scholarly journals Heihe Watershed Allied Telemetry Experimental Research (HiWATER): Scientific Objectives and Experimental Design

2013 ◽  
Vol 94 (8) ◽  
pp. 1145-1160 ◽  
Author(s):  
Xin Li ◽  
Guodong Cheng ◽  
Shaomin Liu ◽  
Qing Xiao ◽  
Mingguo Ma ◽  
...  
Keyword(s):  
Experimental Design ◽  
Experimental Research ◽  
Water Resource Management ◽  
Model Simulation ◽  
Interdisciplinary Studies ◽  
Heihe River ◽  
Observation Data ◽  
Science Data ◽  
Basin Scale ◽  
Research Plan

A major research plan entitled “Integrated research on the ecohydrological process of the Heihe River Basin” was launched by the National Natural Science Foundation of China in 2010. One of the key aims of this research plan is to establish a research platform that integrates observation, data management, and model simulation to foster twenty-first-century watershed science in China. Based on the diverse needs of interdisciplinary studies within this research plan, a program called the Heihe Watershed Allied Telemetry Experimental Research (HiWATER) was implemented. The overall objective of HiWATER is to improve the observability of hydrological and ecological processes, to build a world-class watershed observing system, and to enhance the applicability of remote sensing in integrated ecohydrological studies and water resource management at the basin scale. This paper introduces the background, scientific objectives, and experimental design of HiWATER. The instrumental setting and airborne mission plans are also outlined. The highlights are the use of a flux observing matrix and an eco-hydrological wireless sensor network to capture multiscale heterogeneities and to address complex problems, such as heterogeneity, scaling, uncertainty, and closing water cycle at the watershed scale. HiWATER was formally initialized in May 2012 and will last four years until 2015. Data will be made available to the scientific community via the Environmental and Ecological Science Data Center for West China. International scientists are welcome to participate in the field campaign and use the data in their analyses.

scholarly journals Dynamics of eddying abyssal mixing layers over rough topography

2022 ◽  
Author(s):  
Henri Drake ◽  
Xiaozhou Ruan ◽  
Raffaele Ferrari ◽  
Andreas Thurnherr ◽  
Kelly Ogden ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Three Dimensional ◽  
Small Scale ◽  
One Dimensional ◽  
Basin Scale ◽  
Dimensional Boundary ◽  
Mid Atlantic Ridge ◽  
Non Local ◽  
The One ◽  
Abyssal Mixing

The abyssal overturning circulation is thought to be primarily driven by small-scale turbulent mixing. Diagnosed watermass transformations are dominated by rough topography "hotspots", where the bottom-enhancement of mixing causes the diffusive buoyancy flux to diverge, driving widespread downwelling in the interior—only to be overwhelmed by an even stronger upwelling in a thin Bottom Boundary Layer (BBL). These watermass transformations are significantly underestimated by one-dimensional sloping boundary layer solutions, suggesting the importance of three-dimensional physics. Here, we use a hierarchy of models to generalize this one-dimensional boundary layer approach to three-dimensional eddying flows over realistically rough topography. When applied to the Mid-Atlantic Ridge in the Brazil Basin, the idealized simulation results are roughly consistent with available observations. Integral buoyancy budgets isolate the physical processes that contribute to realistically strong BBL upwelling. The downwards diffusion of buoyancy is primarily balanced by upwelling along the canyon flanks and the surrounding abyssal hills. These flows are strengthened by the restratifying effects of submesoscale baroclinic eddies on the canyon flanks and by the blocking of along-ridge thermal wind within the canyon. Major topographic sills block along-thalweg flows from restratifying the canyon trough, resulting in the continual erosion of the trough's stratification. We propose simple modifications to the one-dimensional boundary layer model which approximate each of these three-dimensional effects. These results provide \textit{local} dynamical insights into mixing-driven abyssal overturning, but a complete theory will also require the non-local coupling to the basin-scale circulation.

Combination of Basin Scale Data Analysis and Numerical Simulations for the Interpretation of the Coexistence of Thermal Water and Hydrocarbon Accumulations

2020 ◽  
Author(s):  
Hana Ben Mahrez ◽  
Zsóka Szabó ◽  
Tímea Havril ◽  
Brigitta Czauner-Zentai ◽  
Judit Mádl-Szőnyi
Keyword(s):  
Data Analysis ◽  
Groundwater Flow ◽  
Thermal Water ◽  
Driving Forces ◽  
Three Dimensional ◽  
Dispersive Transport ◽  
2D Simulation ◽  
Basin Scale ◽  
Dependent Flow ◽  
Density Dependent Flow

<p>During the evolutionary stages of sedimentary basins, different processes are active. Secondary migration means the movement from the source area to the trap and it has most likely the tendency to move along with water. Thus, the secondary migration of petroleum is directly affected by the different driving forces which also influence the ambient groundwater (Tóth 1988). In other words, understanding the regional groundwater flow systems and driving forces may support petroleum exploration. In this theoretical framework, a hydrogeological evaluation of the broader environment of Ebes-Hajdúszoboszló area(Eastern Hungary, Pannonian basin) was executed on the interpretation of the coexistence of thermal water and hydrocarbon accumulations in the specific area.</p><p>The study is based on the application of two different methods. At first a basin-scale hydrogeological evaluation of the recent fluid flow condition including archive hydraulic, chemical, borehole temperature data interpretation, and regional pressure field evaluation was carried out. These data confirmed the superposition of an over-pressured flow regime driven by tectonic compression and compaction and the upwelling of fluids in the gravity driven-flow system in the upper part (Zentai-Czauner et al., 2018).</p><p>The data analysis could provide initial understanding and conceptual framework for 2D numerical evaluation of superposition of the topography differences and overpressure as driving forces It was carried out using the Heat Flow Smoker software version 7.0 developed by (Molson, 2014) which can simulate density-dependent flow and advective-dispersive transport of thermal energy, mass or residence time in three-dimensional porous or fractured media.</p><p>The interpretation of the 2D simulation of the cross-section was compared with the results of the data analysis and it can show the relationship between the hydrocarbon accumulations and the existence of thermal water is due to groundwater flow.</p><p>The regional data analysis and subsequent 2D simulation could confirm the favorable conditions for hydraulic trapping of hydrocarbons and the heat accumulation in groundwater due to advective heat transport.</p><p>This work is part of a project that has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 810980.</p><p><strong>Keywords:</strong></p><p>Groundwater-flow, thermal water, hydraulic trapping, hydrocarbons, migration, accumulation.</p><p><strong>References:</strong></p><ul><li>Szabó Zs., Zentai-Czauner B., Mádl-Szőnyi J., 2018 Hydrogeological evaluation of the broader environment of Ebes concession area for the understanding of recent fluid flow conditions, final report of Vermillion Energy Hungary.</li> <li>Toth J., 1988, Groundwater and hydrocarbon migration, in back, W., Rosenshein, J. S., and Seaber, P. R., eds., Hydrogeology: Boulder, Colorado, Geological Society of America, The geology of North America, v. O-2, chap. 48, pp. 485-502.</li> <li>John W. Molson, 2019. Heat Flow Smoker, Version 7.0, density-dependent flow and advective-dispersive transport of thermal energy, mass or residence time in three-dimensional porous or fractured porous media, université Laval, University of Waterloo.</li> </ul><p> </p>

Extrusion-Based 3D Printing for Pharmaceuticals: Contemporary Research and Applications

2019 ◽  
Vol 24 (42) ◽  
pp. 4991-5008 ◽  
Author(s):  
Mohammed S. Algahtani ◽  
Abdul Aleem Mohammed ◽  
Javed Ahmad
Keyword(s):  
Cosmetic Surgery ◽  
Fused Deposition Modeling ◽  
Personalised Medicine ◽  
Organ Transplant ◽  
Three Dimensional ◽  
Dosage Forms ◽  
Release Profile ◽  
Small Scale ◽  
Drug Release Profile ◽  
Fused Deposition

Three-dimensional printing (3DP) has a significant impact on organ transplant, cosmetic surgery, surgical planning, prosthetics and other medical fields. Recently, 3 DP attracted the attention as a promising method for the production of small-scale drug production. The knowledge expansion about the population differences in metabolism and genetics grows the need for personalised medicine substantially. In personalised medicine, the patient receives a tailored dose and the release profile is based on his pharmacokinetics data. 3 DP is expected to be one of the leading solutions for the personalisation of the drug dispensing. This technology can fabricate a drug-device with complicated geometries and fillings to obtain the needed drug release profile. The extrusionbased 3 DP is the most explored method for investigating the feasibility of the technology to produce a novel dosage form with properties that are difficult to achieve using the conventional industrial methods. Extrusionbased 3 DP is divided into two techniques, the semi-solid extrusion (SSE) and the fused deposition modeling (FDM). This review aims to explain the extrusion principles behind the two techniques and discuss their capabilities to fabricate novel dosage forms. The advantages and limitations observed through the application of SSE and FDM for fabrication of drug dosage forms were discussed in this review. Further exploration and development are required to implement this technology in the healthcare frontline for more effective and personalised treatment.

scholarly journals Quantification of Measurement and Model Effects in Monopile Foundation Scour Protection Experiments

2021 ◽  
Vol 9 (6) ◽  
pp. 585
Author(s):  
Minghao Wu ◽  
Leen De Vos ◽  
Carlos Emilio Arboleda Chavez ◽  
Vasiliki Stratigaki ◽  
Maximilian Streicher ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Flow Field ◽  
Three Dimensional ◽  
Small Scale ◽  
Maximum Wave Height ◽  
Chaotic Flow ◽  
The Mean ◽  
Scour Protection ◽  
Damage Number ◽  
Measurement Effects

The present work introduces an analysis of the measurement and model effects that exist in monopile scour protection experiments with repeated small scale tests. The damage erosion is calculated using the three dimensional global damage number S3D and subarea damage number S3D,i. Results show that the standard deviation of the global damage number σ(S3D)=0.257 and is approximately 20% of the mean S3D, and the standard deviation of the subarea damage number σ(S3D,i)=0.42 which can be up to 33% of the mean S3D. The irreproducible maximum wave height, chaotic flow field and non-repeatable armour layer construction are regarded as the main reasons for the occurrence of strong model effects. The measurement effects are limited to σ(S3D)=0.039 and σ(S3D,i)=0.083, which are minor compared to the model effects.

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