scholarly journals Hydraulic and transport parameter assessment using column infiltration experiments

2016 ◽  
Author(s):  
A. Younes ◽  
T. A. Mara ◽  
M. Fahs ◽  
O. Grunenberger ◽  
Ph. Ackerer
Keyword(s):  
Pressure Head ◽  
Solute Concentration ◽  
Richards Equation ◽  
Transport Parameter ◽  
State Variables ◽  
Transport Parameters ◽  
Uncertainty Range ◽  
Infiltration Experiment ◽  
Statistical Calibration

Abstract. In the present work, we study the quality of the statistical calibration of hydraulic and transport soil properties using an infiltration experiment in which, over a given period, tracer-contaminated water is injected into a laboratory column filled with a homogeneous soil. The numerical model is based on the Richards' equation for solving water flow and the advection-dispersion equation for solving solute transport. Several state variables (e.g., water content, solute concentration, pressure head) are measured during the experiment. Statistical calibration of the computer model is then carried out for different data sets and injection scenarios with the DREAM(ZS) Markov Chain Monte Carlo sampler. The results show that the injection period has a significant effect on the quality of the estimation, in particular, the posterior uncertainty range. The hydraulic and transport parameters of the investigated soil can be estimated from the infiltration experiment using the concentration and cumulative outflow, which are measured non-intrusively. A significant improvement of the identifiability of the parameters is observed when the pressure data from measurements taken inside the column are also considered in the inversion.

scholarly journals Hydraulic and transport parameter assessment using column infiltration experiments

2017 ◽  
Vol 21 (5) ◽  
pp. 2263-2275 ◽  
Author(s):  
Anis Younes ◽  
Thierry Mara ◽  
Marwan Fahs ◽  
Olivier Grunberger ◽  
Philippe Ackerer
Keyword(s):  
Solute Concentration ◽  
Model Parameters ◽  
Transport Parameter ◽  
Residual Water ◽  
Transport Parameters ◽  
Uncertainty Range ◽  
Injection Duration ◽  
Longitudinal Dispersivity ◽  
The Impact

Abstract. The quality of statistical calibration of hydraulic and transport soil properties is studied for infiltration experiments in which, over a given period, tracer-contaminated water is injected into an hypothetical column filled with a homogeneous soil. The saturated hydraulic conductivity, the saturated and residual water contents, the Mualem–van Genuchten shape parameters and the longitudinal dispersivity are estimated in a Bayesian framework using the Markov chain Monte Carlo (MCMC) sampler. The impact of the kind of measurement sets (water content, pressure inside the column, cumulative outflow and outlet solute concentration) and that of the solute injection duration is investigated by analyzing the calibrated model parameters and their confidence intervals for different scenarios. The results show that the injection period has a significant effect on the quality of the estimation, in particular, on the posterior uncertainty range of the parameters. All hydraulic and transport parameters of the investigated soil can be well estimated from the experiment using only the outlet concentration and cumulative outflow, which are measured non-intrusively. An improvement of the identifiability of the hydraulic parameters is observed when the pressure data from measurements taken inside the column are also considered in the inversion.

scholarly journals Transport Parameter Correlations for Digitally Created PEFC Gas Diffusion Layers by Using OpenPNM

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1141
Author(s):  
Ángel Encalada-Dávila ◽  
Mayken Espinoza-Andaluz ◽  
Julio Barzola-Monteses ◽  
Shian Li ◽  
Martin Andersson
Keyword(s):  
Fuel Cell ◽  
Energy Conversion ◽  
Transport Phenomena ◽  
Electrical Energy ◽  
Gas Diffusion ◽  
Polymer Electrolyte Fuel Cell ◽  
Carbon Paper ◽  
Transport Parameter ◽  
Transport Parameters ◽  
Depth Analysis

A polymer electrolyte fuel cell (PEFC) is an electrochemical device that converts chemical energy into electrical energy and heat. The energy conversion is simple; however, the multiphysics phenomena involved in the energy conversion process must be analyzed in detail. The gas diffusion layer (GDL) provides a diffusion media for reactant gases and gives mechanical support to the fuel cell. It is a complex medium whose properties impact the fuel cell’s efficiency. Therefore, an in-depth analysis is required to improve its mechanical and physical properties. In the current study, several transport phenomena through three-dimensional digitally created GDLs have been analyzed. Once the porous microstructure is generated and the transport phenomena are mimicked, transport parameters related to the fluid flow and mass diffusion are computed. The GDLs are approximated to the carbon paper represented as a grouped package of carbon fibers. Several correlations, based on the fiber diameter, to predict their transport properties are proposed. The digitally created GDLs and the transport phenomena have been modeled using the open-source library named Open Pore Network Modeling (OpenPNM). The proposed correlations show a good fit with the obtained data with an R-square of approximately 0.98.

scholarly journals Multi-source data assimilation for physically-based hydrological modeling of an experimental hillslope

2018 ◽  
Author(s):  
Anna Botto ◽  
Enrica Belluco ◽  
Matteo Camporese
Keyword(s):  
Soil Moisture ◽  
Data Assimilation ◽  
Hydrological Modeling ◽  
Nonlinear Models ◽  
Pressure Head ◽  
Richards Equation ◽  
Hydrological Models ◽  
Filter Performance ◽  
Trade Offs ◽  
Source Data

Abstract. Data assimilation has been recently the focus of much attention for integrated surface-subsurface hydrological models, whereby joint assimilation of water table, soil moisture, and river discharge measurements with the ensemble Kalman filter (EnKF) have been extensively applied. Although the EnKF has been specifically developed to deal with nonlinear models, integrated hydrological models based on the Richards equation still represent a challenge, due to strong nonlinearities that may significantly affect the filter performance. Thus, more studies are needed to investigate the capabilities of the EnKF to correct the system state and identify parameters in cases where the unsaturated zone dynamics are dominant, as well as to quantify possible tradeoffs associated with assimilation of multi-source data. Here, the model CATHY (CATchment HYdrology) is applied to reproduce the hydrological dynamics observed in an experimental two-layered hillslope, equipped with tensiometers, water content reflectometer probes, and tipping bucket flow gages to monitor the hillslope response to a series of artificial rainfall events. Pressure head, soil moisture, and subsurface outflow are assimilated with the EnKF in a number of scenarios and the challenges and issues arising from the assimilation of multi-source data in this real-world test case are discussed. Our results demonstrate that the EnKF is able to effectively correct states and parameters even in a real application characterized by strong nonlinearities. However, multi-source data assimilation may lead to significant trade-offs: the assimilation of additional variables can lead to degradation of model predictions for other variables that were otherwise well reproduced. Furthermore, we show that integrated observations such as outflow discharge cannot compensate for the lack of well-distributed data in heterogeneous hillslopes.

scholarly journals Evolutionary Observer Ensemble for Leak Diagnosis in Water Pipelines

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 913 ◽  
Author(s):  
A. Navarro ◽  
J. A. Delgado-Aguiñaga ◽  
J. D. Sánchez-Torres ◽  
O. Begovich ◽  
G. Besançon
Keyword(s):  
Heuristic Method ◽  
Pressure Head ◽  
Search Space ◽  
Observation Error ◽  
State Variables ◽  
Test Bed ◽  
Interior Node ◽  
Water Pipelines ◽  
Exponentially Stable ◽  
Integral Observation

This work deals with the Leak Detection and Isolation (LDI) problem in water pipelines based on some heuristic method and assuming only flow rate and pressure head measurements at both ends of the duct. By considering the single leak case at an interior node of the pipeline, it has been shown that observability is indeed satisfied in this case, which allows designing an observer for the unmeasurable state variables, i.e., the pressure head at leak position. Relying on the fact that the origin of the observation error is exponentially stable if all parameters (including the leak coefficients) are known and uniformly ultimately bounded otherwise, the authors propose a bank of observers as follows: taking into account that the physical pipeline parameters are well-known, and there is only uncertainty about leak coefficients (position and magnitude), a pair of such coefficients is taken from a search space and is assigned to an observer. Then, a Genetic Algorithm (GA) is exploited to minimize the integration of the square observation error. The minimum integral observation error will be reached in the observer where the estimated leak parameters match the real ones. Finally, some results are presented by using real-noisy databases coming from a test bed plant built at Cinvestav-Guadalajara, aiming to show the potentiality of this method.

Numerical Simulation Analysis of the Cold Bending Forming Technology Based on DEFORM

2012 ◽  
Vol 490-495 ◽  
pp. 3353-3357 ◽  
Author(s):  
Xiao Bing Xu ◽  
Hong Run Luo
Keyword(s):  
Simulation Analysis ◽  
Pipe Production ◽  
State Variables ◽  
Technical Parameters ◽  
Forming Technology ◽  
Cold Bending ◽  
Bent Pipe ◽  
Deformation Speed ◽  
3D Software

In this paper, the accurate numerical simulations using the DEFORM-3D software are carried out in terms of the cold bending pipe technology. Correspondingly, the changes of state variables are gained, such as the stress, the strain, the material deformation speed, the damage severity and so on. Meanwhile, the important technical parameters concerned with the quality of pipe bending formation like the speed of the punch press, the friction coefficient and the friction types are comprehensively analyzed. Thus, it can be realized in practice to control and optimize the quality of the bent pipe production

Evaluating Chemical Toxicity of Surface Disposal of LILW-SL in Belgium

2008 ◽  
Vol 1107 ◽  
Author(s):  
D. Mallants ◽  
L. Wang ◽  
E. Weetjens ◽  
W. Cool
Keyword(s):  
Transport Model ◽  
Chemical Elements ◽  
Near Field ◽  
Distribution Coefficients ◽  
Small Scale ◽  
Transport Parameter ◽  
Chemical Toxicity ◽  
Transport Parameters ◽  
Field Environment ◽  
Waste Container

AbstractONDRAF/NIRAS is developing and evaluating a surface disposal concept for low and intermediate level short-lived radioactive waste (LILW-SL) at Dessel, Belgium. In support of ONDRAF/NIRAS's assignment, SCK•CEN carried out long-term performance assessment calculations for the inorganic non-radioactive components that are present in LILW-SL. This paper summarizes the results obtained from calculations that were done for a heavily engineered surface disposal facility at the nuclear zone of Mol/Dessel. The calculations address the migration of chemotoxic elements from the disposed waste to groundwater.Screening calculations were performed first to decide which non-radioactive components could potentially increase concentrations in groundwater to levels above the groundwater standards. On the basis of very conservative calculations, only 6 out of 41 chemical elements could not be classified as having a negligible impact on man and environment. For each of these six elements (B, Be, Cd, Pb, Sb, and Zn), the source term was characterized in terms of its chemical form (i.e., metal, oxide, or salt), and a macroscopic transport model built that would capture the small-scale dissolution processes relevant to element release from a cementitious waste container. Furthermore, reliable transport parameters in support of the convection-dispersion-retardation (CDR) transport calculations were determined. This included derivation of (1) solubility for a cementitious near field environment based on thermodynamic equilibrium calculations with The Geochemist's Workbench, and (2) distribution coefficients based on a compilation of literature values. Scoping calculations illustrated the effects of transport parameter uncertainty on the rates at which inorganic components in LILW-SL leach to groundwater.

scholarly journals Two Simultaneous Leak Diagnosis in Pipelines Based on Input–Output Numerical Differentiation

Sensors ◽  
2021 ◽  
Vol 21 (23) ◽  
pp. 8035
Author(s):  
Adrián Navarro-Díaz ◽  
Jorge-Alejandro Delgado-Aguiñaga ◽  
Ofelia Begovich ◽  
Gildas Besançon
Keyword(s):  
State Vector ◽  
Pressure Head ◽  
Numerical Differentiation ◽  
State Variables ◽  
Test Bed ◽  
Water Shortages ◽  
Third Order ◽  
Large Cities ◽  
Noise Rejection ◽  
Derivatives Of

This paper addresses the two simultaneous leak diagnosis problem in pipelines based on a state vector reconstruction as a strategy to improve water shortages in large cities by only considering the availability of the flow rate and pressure head measurements at both ends of the pipeline. The proposed algorithm considers the parameters of both leaks as new state variables with constant dynamics, which results in an extended state representation. By applying a suitable persistent input, an invertible mapping in x can be obtained as a function of the input and output, including their time derivatives of the third-order. The state vector can then be reconstructed by means of an algebraic-like observer through the computation of time derivatives using a Numerical Differentiation with Annihilatorsconsidering its inherent noise rejection properties. Experimental results showed that leak parameters were reconstructed with accuracy using a test bed plant built at Cinvestav Guadalajara.

scholarly journals Investigating stratospheric changes between 2009 and 2018 with aircraft, AirCores, and a global model focusing on CFC-11

2020 ◽  
Author(s):  
Johannes C. Laube ◽  
Emma C. Leedham Elvidge ◽  
Karina E. Adcock ◽  
Bianca Baier ◽  
Carl A. M. Brenninkmeijer ◽  
...  
Keyword(s):  
Quantitative Analysis ◽  
Stratospheric Ozone ◽  
Sampling Technique ◽  
Cost Effective ◽  
Global Scale ◽  
Global Model ◽  
Uncertainty Range ◽  
Model Driven ◽  
Mixing Ratios

Abstract. We present new observations of trace gases in the stratosphere based on a cost-effective sampling technique that can access much higher altitudes than aircraft. The further development of this method now provides detection of species with abundances in the parts per trillion (ppt) range and below. We obtain mixing ratios for six gases (CFC-11, CFC-12, HCFC-22, H-1211, H-1301, and SF6), all of which are important for understanding stratospheric ozone depletion and circulation. After demonstrating the quality of the data through comparisons with ground-based records and aircraft-based observations we combine them with the latter to demonstrate its potential. We first compare it with results from a global model driven by three widely used meteorological reanalyses. Secondly, we focus on CFC-11 as recent evidence has indicated renewed atmospheric emissions of that species relevant on a global scale. Because the stratosphere represents the main sink region for CFC-11, potential changes in stratospheric circulation and troposphere-stratosphere exchange fluxes have been identified as the largest source of uncertainty for the accurate quantification of such emissions. Our observations span over a decade (up until 2018) and therefore cover the period of the slowdown of CFC-11 global mixing ratio decreases measured at the Earth's surface. The spatial and temporal coverage of the observations is insufficient for a global quantitative analysis, but we do find some trends that are in contrast with expectations; indicating that the stratosphere may have contributed to the slower concentration decline in recent years. Further investigating the reanalysis-driven model data we find that the required dynamical changes in the stratosphere required to explain the apparent change in tropospheric CFC-11 emissions after 2013 are possible, but with a very high uncertainty range. This is partly caused by the high variability of mass flux from the stratosphere to the troposphere, especially at time scales of a few years, and partly by large differences between runs driven by different reanalysis products, none of which agree with our observations well enough for such a quantitative analysis.

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