Hydrological Responses to Anthropogenic Disturbance in Peatlands: a Numerical Approach

2020 ◽  
Author(s):  
Meseret Menberu ◽  
Anna-Kaisa Ronkanen ◽  
Hannu Marttila ◽  
Ali Torabi Haghighi ◽  
Bjørn Kløve
Keyword(s):  
Water Table ◽  
Three Dimensional ◽  
Ground Surface ◽  
Numerical Approach ◽  
Weather Data ◽  
Hydrological Responses ◽  
Long Term Storage ◽  
Physically Based ◽  
The Impact ◽  
Restoration Measures

<p>Peatland ecosystems are complex mosaics and located often in low-lying transitional zones between terrestrial and aquatic ecosystems. Peatlands in its pristine state play a significant role in regulating the hydrological, biogeochemical and ecological functions and act as long-term storage for carbon. However, up to 20% of the global peatland resources have been disturbed for a variety of human land uses (e.g., forestry and agriculture) and lost their natural functions. In this research, we tested the effectiveness and applicability of a physically-based three-dimensional fully integrated surface-subsurface numerical model (HydroGeosphere, HGS) to study hydrological disturbances in peatlands. The model was specifically implemented to assess the impact of artificial drainage and subsequent restoration on the hydrological responses (runoff and water table) of a previously disturbed, now restored (ditches-blocked) peatland catchment (about 11.4 ha) located in Western Finland. The hydrological data included two years before restoration (drained condition) and one year after restoration (ditches-blocked) collected during frost-free periods. The model domain was discretized with seven vertical finite element layers of 146744 nodes and 255206 elements to represent the ditch networks (drained condition) and blocked ditches (restored condition) in the model realistically. The HGS model was run for the two disturbed conditions (drained and restored) using forcing weather data collected in 2016, 2017 and 2018. In all the years, simulated runoff in drained conditions was significantly higher than simulated at restored conditions. The simulated water table level in restored conditions was significantly closer to the ground surface than in drained conditions, which agreed with the observed water table data. The results indicated that three-dimensional models, such as the HGS can be implemented to evaluate the effect of restoration measures on the hydrological response of peatland catchments. Thus, high-resolution physically-based models have the potential to improve our understanding of the complex hydrology of disturbed habitats spatially. Understating the spatial dependence of peatlands to inputs from groundwater and surrounding upland areas could further help us improve restoration measures.</p>

scholarly journals Hybrid Analytical and Numerical Approach for Modeling Fluid Flow in Simplified Three-Dimensional Fracture Networks

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
D. Roubinet ◽  
S. Demirel ◽  
E. B. Voytek ◽  
X. Wang ◽  
J. Irving
Keyword(s):  
Fluid Flow ◽  
Three Dimensional ◽  
Fracture Network ◽  
Numerical Approach ◽  
Fracture Networks ◽  
Surrounding Matrix ◽  
Mesh Free ◽  
Fracture Scale ◽  
The Impact ◽  
Numerical Approaches

Modeling fluid flow in three-dimensional fracture networks is required in a wide variety of applications related to fractured rocks. Numerical approaches developed for this purpose rely on either simplified representations of the physics of the considered problem using mesh-free methods at the fracture scale or complex meshing of the studied systems resulting in considerable computational costs. Here, we derive an alternative approach that does not rely on a full meshing of the fracture network yet maintains an accurate representation of the modeled physical processes. This is done by considering simplified fracture networks in which the fractures are represented as rectangles that are divided into rectangular subfractures such that the fracture intersections are defined on the borders of these subfractures. Two-dimensional analytical solutions for the Darcy-scale flow problem are utilized at the subfracture scale and coupled at the fracture-network scale through discretization nodes located on the subfracture borders. We investigate the impact of parameters related to the location and number of the discretization nodes on the results obtained, and we compare our results with those calculated using reference solutions, which are an analytical solution for simple configurations and a standard finite-element modeling approach for complex configurations. This work represents a first step towards the development of 3D hybrid analytical and numerical approaches where the impact of the surrounding matrix will be eventually considered.

scholarly journals Modelling of shallow water table dynamics using conceptual and physically based integrated surface-water–groundwater hydrologic models

2019 ◽  
Vol 23 (5) ◽  
pp. 2245-2260 ◽  
Author(s):  
Mohammad Bizhanimanzar ◽  
Robert Leconte ◽  
Mathieu Nuth
Keyword(s):  
Shallow Water ◽  
Groundwater Recharge ◽  
Water Table ◽  
Soil Column ◽  
Three Dimensional ◽  
Vertical Plane ◽  
Dimensional Case ◽  
Shallow Water Table ◽  
Mike She ◽  
Physically Based

Abstract. We present a new conceptual scheme of the interaction between unsaturated and saturated zones of the MOBIDIC (MOdello Bilancio Idrologico DIstributo e Continuo) hydrological model which is applicable to shallow water table conditions. First, MODFLOW was coupled to MOBIDIC as the physically based alternative to the conceptual groundwater component of the MOBIDIC–MODFLOW. Then, assuming a hydrostatic equilibrium moisture profile in the unsaturated zone, a dynamic specific yield that is dependent on the water table level was added to MOBIDIC–MODFLOW, and calculation of the groundwater recharge in MOBIDIC was revisited using a power-type equation based on the infiltration rate, soil moisture deficit, and a calibration parameter linked to the initial water table depth, soil type, and rainfall intensity. Using the water table fluctuation (WTF) method for a homogeneous soil column, the parameter of the proposed groundwater recharge equation was determined for four soil types, i.e. sand, loamy sand, sandy loam, and loam under a pulse of rain with different intensities. The fidelity of the introduced modifications in MOBIDIC–MODFLOW was assessed by comparison of the simulated water tables against those of MIKE SHE, a physically based integrated hydrological modelling system simulating surface and groundwater flow, in two numerical experiments: a two-dimensional case of a hypothetical watershed in a vertical plane (constant slope) under a 1 cm d−1 uniform rainfall rate and a quasi-real three-dimensional watershed under 1 month of a measured daily rainfall hyetograph. The comparative analysis confirmed that the simplified approach can mimic simple and complex groundwater systems with an acceptable level of accuracy. In addition, the computational efficiency of the proposed approach (MIKE SHE took 180 times longer to solve the three-dimensional case than the MOBIDIC–MODFLOW framework) demonstrates its applicability to real catchment case studies.

scholarly journals Predicting Lake Eutrophication Responses to Multiple Scenarios of Lake Restoration: A Three-Dimensional Modeling Approach

Water ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 994 ◽  
Author(s):  
Yanping Wang ◽  
Weiping Hu ◽  
Zhaoliang Peng ◽  
Ye Zeng ◽  
Karsten Rinke
Keyword(s):  
Water Quality ◽  
Drinking Water ◽  
Three Dimensional ◽  
Water Transfer ◽  
Nutrient Concentrations ◽  
Observation Data ◽  
Nutrient Reduction ◽  
Effective Measure ◽  
The Impact ◽  
Restoration Measures

To improve the water quality and alleviate the eutrophication of Lake Yangchenghu, the third largest freshwater body within the Lake Taihu basin in China and an important source of drinking water, nutrient reduction strategies should be urgently addressed by decision makers, since virtually no improvement of water quality has taken place since the mid-1990s. Due to the lack of sufficient observation data and simulation results, a vertically compressed three-dimensional numerical model, the EcoTaihu model, was used to study the impact of three restoration measures on the water quality—namely, total nitrogen (TN), total phosphorus (TP) and biomass of phytoplankton (BP)—of Lake Yangchenghu: (i) total nutrient reduction, (ii) intensification of flushing by water transfer, and (iii) spatial adjustment of inflow channels. In particular, the spatial effects of the three restoration measures on the water quality were investigated. The results showed that the EcoTaihu model is applicable to other shallow lakes in China. The water quality responses to the different restoration scenarios showed significant spatio-temporal differences. The reduction of nutrient loads from inflows appeared to be the most effective measure for controlling the eutrophication and algal blooms in Lake Yangchenghu. The effectiveness of water transfer on the improvement of water quality for TN and TP was more influenced by the differences of nutrient concentrations between the transferred water and lake water, rather than flow rate, since no proportionate increase of improvement was observable in the case of larger transferred rates (60 m3 s−1). The spatial narrowing of inflowing rivers in the southwestern lake could preferentially improve the water quality in the southern bay of the western lake, but would also result in a deterioration trend of water quality in the total lake and drinking water abstraction areas.

CFD Modeling Effects on Unsteady Multistage Simulation for a Transonic Axial Compressor

2011 ◽  
Author(s):  
Mai Yamagami ◽  
Hidekazu Kodama ◽  
Dai Kato ◽  
Naoki Tsuchiya ◽  
Yasuo Horiguchi ◽  
...  
Keyword(s):  
Performance Prediction ◽  
High Speed ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Turbulence Models ◽  
Numerical Approach ◽  
Path Model ◽  
Cfd Modeling ◽  
Geometry Modeling ◽  
The Impact

Unsteady three-dimensional multistage calculations are performed for a highly loaded, high-speed axial compressor to investigate the impact of real geometry modeling and different numerical approaches on the accuracy of the performance prediction. First, two features of the real geometries are separately compared with the calculation which consists of a pure flow path model except that rotor tip clearances are considered. One treats leakage generated by part gaps between variable stator vanes and the annulus lines. Another incorporates seal cavities to model leakage underneath the shrouded stators. Then, the influence of different numerical approach with different turbulence models is also investigated. Discussion on the impact of the CFD modeling on the performance prediction focuses on the prediction accuracies of stage operating points and spanwise mixing. It is suggested that a realistic simulation of turbulent-type flow unsteadiness in a multistage machine is important for an accurate prediction of spanwise mixing phenomena.

Physically-based oscillations of the Laurentide under glacial conditions.

2020 ◽  
Author(s):  
Daniel Moreno ◽  
Javier Blasco ◽  
Jorge Álvarez-Solas ◽  
Alexander Robinson ◽  
Marisa Montoya
Keyword(s):  
Three Dimensional ◽  
Ice Sheet ◽  
Ice Streams ◽  
Ice Dynamics ◽  
Future Evolution ◽  
Basal Friction ◽  
Wide Range ◽  
Physically Based ◽  
Friction Parameters ◽  
The Impact

<p>The climate during the last glacial period was far from stable. Evidence has shown the presence of layers of ice-rafted debris (IRD) in deep sea sediments, which have been interpreted as quasi-periodic episodes of massive iceberg calving from the Laurentide Ice Sheet (LIS). Several mechanisms have been proposed, yet the ultimate cause of these events is still under debate. In fact, one of the main sources of uncertainty and diversity in model response is the choice of basal friction law. Therefore, it is essential to determine the impact of this feature in glacial transport and erosion, deposition of sediments and ice streams among others. We herein study the effect of a wide range of basal friction parameters and laws under glacial conditions over the LIS. In addition, the impact of the thermodynamic state of the ice is taken into account by means of two independent procedures: a two-valued friction coefficient approach and an active basal hydrology. The aim is to determine under what conditions, if any, physically-based oscillations are possible in a three-dimensional hybrid ice-sheet model. Increasing our understanding of both basal friction laws and basal hydrology will improve not only reconstructions of paleo ice dynamics but also help to constrain the potential future evolution of current ice sheets.</p>

scholarly journals Three-Dimensional Water-Based Magneto-Hydrodynamic Rotating Nanofluid Flow over a Linear Extending Sheet and Heat Transport Analysis: A Numerical Approach

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 5133
Author(s):  
Azad Hussain ◽  
Mubashar Arshad ◽  
Aysha Rehman ◽  
Ali Hassan ◽  
S. K. Elagan ◽  
...  
Keyword(s):  
Differential Equations ◽  
Comparative Study ◽  
Skin Friction ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Nanofluid Flow ◽  
Two Phase ◽  
Transport Analysis ◽  
The Impact ◽  
Phase Fluid

This comparative study inspects the heat transfer characteristics of magnetohydrodynamic (MHD) nanofluid flow. The model employed is a two-phase fluid flow model. Water is utilized as the base fluid, and zinc and titanium oxide (Zn and TiO2) are used as two different types of nanoparticles. The rotation of nanofluid is considered along the z-axis, with velocity ω*. A similarity transformation is used to transform the leading structure of partial differential equations to ordinary differential equations. By using a powerful mathematical BVP-4C technique, numerical results are obtained. This study aims to describe the possessions of different constraints on temperature and velocity for rotating nanofluid with a magnetic effect. The outcomes for the rotating nanofluid flow and heat transference properties for both types of nanoparticles are highlighted with the help of graphs and tables. The impact of physical concentrations such as heat transference rates and coefficients of skin friction are examined. It is noted that rotation increases the heat flux and decreases skin friction. In this comparative study, Zn-water nanofluid was demonstrated to be a worthy heat transporter as compared to TiO2-water nanofluid.

scholarly journals Experimental and Numerical Analysis of Conical Projectile Impact on Inconel 718 Plates

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 638 ◽  
Author(s):  
Marcos Rodríguez-Millán ◽  
Antonio Díaz-Álvarez ◽  
Richard Bernier ◽  
María Henar Miguélez ◽  
José Antonio Loya
Keyword(s):  
Inconel 718 ◽  
Failure Mechanisms ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Numerical Approach ◽  
Impact Behavior ◽  
Ballistic Limit ◽  
3D Numerical Model ◽  
Global And Local ◽  
The Impact

This paper analyses the impact behavior of Inconel 718 through experimental and numerical approach. Different conical projectiles were tested in order to obtain the ballistic curves and failure mechanisms. A three-dimensional (3D) numerical model corresponding to the experimental tests was developed using the Johnson–Cook constitutive model. The experimental data (residual velocities, global, and local perforation mechanisms) were successfully predicted with the numerical simulations. The influence of the projectile’s nose angle was found to be important when designing ballistic protections. The projectile with the narrowest angle, 40°, developed a ballistic limit approximately 10 m/s lower than the projectile with a 72° nose. The use of double-nose projectile for the same nose angle, 72°, led to a ballistic limit 12 m/s lower than that obtained for the single nose.

Solution to Three-Dimensional Indeterminate Contact and Impact With Friction Using Rigid Body Constraints

2015 ◽  
Author(s):  
Adrian Rodriguez ◽  
Abhishek Chatterjee ◽  
Alan Bowling
Keyword(s):  
Rigid Body ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Impact Behavior ◽  
Impact Event ◽  
Slip Direction ◽  
Rocking Block ◽  
Post Impact ◽  
Contact And Impact ◽  
The Impact

This work analyzes three-dimensional multibody systems undergoing indeterminate contact and impact in the presence of Coulomb friction. A discrete approach is used to analyze the impact behavior upon detection of the impact events during simulation. During an impact event, the velocities of the impact points describe the systems state and can be studied to characterize the nature of impact and determine the post-impact behavior of the system. The velocities of the impact points during an impact event can be described in terms of the impulses at those points. This work uses Amontons-Coulombs law of friction and rigid body constraints to develop a technique for reducing the number of impulses required to compute the velocities of the impact point during the impact event. Indeterminacies associated with slip direction arise, when Coulombs friction is considered. Therefore, a numerical approach is used to evolve the slip direction along with the slip velocity, with respect to a normal impulse. The work-energy theorem is used to detect the end of the impact event, and determine the post-impact velocities of the system. Examples of a three-dimensional rocking block and a sphere impacting a corner are analyzed to demonstrate the proposed methodology.

Analyzing the Impact of X-Ray Tomography on the Reliability of Integrated Circuits

2015 ◽  
Author(s):  
Halit Dogan ◽  
Md Mahbub Alam ◽  
Navid Asadizanjani ◽  
Sina Shahbazmohamadi ◽  
Domenic Forte ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Integrated Circuit ◽  
3D Imaging ◽  
Three Dimensional ◽  
Serial Sectioning ◽  
Promising Technique ◽  
Flash Memories ◽  
X Ray ◽  
3D Information ◽  
The Impact

Abstract X-ray tomography is a promising technique that can provide micron level, internal structure, and three dimensional (3D) information of an integrated circuit (IC) component without the need for serial sectioning or decapsulation. This is especially useful for counterfeit IC detection as demonstrated by recent work. Although the components remain physically intact during tomography, the effect of radiation on the electrical functionality is not yet fully investigated. In this paper we analyze the impact of X-ray tomography on the reliability of ICs with different fabrication technologies. We perform a 3D imaging using an advanced X-ray machine on Intel flash memories, Macronix flash memories, Xilinx Spartan 3 and Spartan 6 FPGAs. Electrical functionalities are then tested in a systematic procedure after each round of tomography to estimate the impact of X-ray on Flash erase time, read margin, and program operation, and the frequencies of ring oscillators in the FPGAs. A major finding is that erase times for flash memories of older technology are significantly degraded when exposed to tomography, eventually resulting in failure. However, the flash and Xilinx FPGAs of newer technologies seem less sensitive to tomography, as only minor degradations are observed. Further, we did not identify permanent failures for any chips in the time needed to perform tomography for counterfeit detection (approximately 2 hours).

Drawdowns at the Free Water Table During Pumping Tests in Artesian and Semiartesian Aquifers

1980 ◽  
Vol 11 (3-4) ◽  
pp. 159-168 ◽  
Author(s):  
Henrik Kærgaard
Keyword(s):  
Water Table ◽  
Free Water ◽  
Pumping Test ◽  
Water Withdrawal ◽  
Specific Yield ◽  
Minor Role ◽  
Long Term Effects ◽  
Long Term Storage ◽  
Term Storage

In an earlier paper I have shown an example of how long term drawdowns can be used for the computation of long term storage in artesian and semiartesian areas. In most cases the long term storage is more or less equivalent to the specific yield at the water table; the storage mechanisms of consolidation playing a minor role in long term situations. The specific yield in artesian areas is a very important parameter in the prediction of long term effects of ground water withdrawal. Especially the stream depletion will often mainly be governed by draw-downs in upper nonpumped aquifers near the water table, and these drawdowns depend to a great extent on the specific yield at the water table. A determination of long term storage will often necessitate long term draw-down data, however, under certain circumstances a determination can be made on the basis of a pumping test of limited duration (3-5 weeks) provided drawdown observations at the water table can be made. In this paper some formulas dealing with water table drawdowns in different geohydrologic systems are reviewed, and two cases in which these formulas have been used in practice are presented.

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