ABOUT THE PARAMETERS OF THE DIELECTRIC MODEL OF SOILS USED IN THE SMOS ALGORITHM

2021 ◽  
pp. 95-102
Author(s):  
P. P. Bobrov ◽  
T. A. Belyaeva ◽  
E. S. Kroshka ◽  
O. V. Rodionova
Keyword(s):  
Experimental Data ◽  
Relaxation Time ◽  
Relaxation Process ◽  
Soil Water ◽  
Specific Conductivity ◽  
Bound Water ◽  
Debye Model ◽  
Dielectric Model ◽  
True Values

The features of the four-component refractive dielectric model of moist soils are considered. Typical values of the parameters of the Debye model of bound water obtained by processing experimental data using this model are given. The reasons why the parameters of the Debye model of free soil water in this model differ from the true values of these parameters are explained. It is shown that the excess of the static permeability and specific conductivity values relative to the true values is caused by the Maxwell – Wagner relaxation process with a relaxation time of sev-eral nanoseconds.

Modeling of dielectric relaxation in clays at negative and positive temperatures

2021 ◽  
Vol 64 (1) ◽  
pp. 58-63
Author(s):  
A.V. Repin ◽  
◽  
O.V. Rodionova ◽  
E.S. Kroshka ◽  
◽  
...  
Keyword(s):  
Experimental Data ◽  
Dielectric Constant ◽  
Relaxation Process ◽  
Bound Water ◽  
Complex Dielectric Constant ◽  
Distilled Water ◽  
Frequency Range ◽  
Water Ice ◽  
Free And Bound Water ◽  
The Relationship

Experimental data on measuring the complex dielectric constant (CDP) of clays with full moistening with distilled water in the frequency range from 1 kHz to 8.5 GHz at temperatures from -15 to +25 °C are presented. The modeling of the dependences of is carried out by a multirelaxation model that takes into account the relaxation of free and bound water, as well as relaxation at the bound water - mineral and bound water - air boundaries. It is shown that at temperatures below -5 °C, a relaxation process appears in the CDP spectrum due to polarization at the bound water - ice or ice - mineral interface. The relationship between the parameters of this relaxation process and the petrophysical characteristics of the rock is found.

Generalized refractive mixing dielectric model of moist soils considering ionic relaxation of soil water

2013 ◽  
Vol 56 (3) ◽  
pp. 319-324 ◽  
Author(s):  
V. L. Mironov ◽  
P. P. Bobrov ◽  
S. V. Fomin ◽  
A. Yu. Karavaiskii
Keyword(s):  
Soil Water ◽  
Dielectric Model

scholarly journals A thermodynamic formulation of root water uptake

2016 ◽  
Vol 20 (8) ◽  
pp. 3441-3454 ◽  
Author(s):  
Anke Hildebrandt ◽  
Axel Kleidon ◽  
Marcel Bechmann
Keyword(s):  
Soil Water ◽  
Water Uptake ◽  
Water Distribution ◽  
Bound Water ◽  
Root Water Uptake ◽  
Flow Path ◽  
Thermodynamic Evaluation ◽  
Entire Flow ◽  
Soil Water Distribution

Abstract. By extracting bound water from the soil and lifting it to the canopy, root systems of vegetation perform work. Here we describe how root water uptake can be evaluated thermodynamically and demonstrate that this evaluation provides additional insights into the factors that impede root water uptake. We derive an expression that relates the energy export at the base of the root system to a sum of terms that reflect all fluxes and storage changes along the flow path in thermodynamic terms. We illustrate this thermodynamic formulation using an idealized setup of scenarios with a simple model. In these scenarios, we demonstrate why heterogeneity in soil water distribution and rooting properties affect the impediment of water flow even though the mean soil water content and rooting properties are the same across the scenarios. The effects of heterogeneity can clearly be identified in the thermodynamics of the system in terms of differences in dissipative losses and hydraulic energy, resulting in an earlier start of water limitation in the drying cycle. We conclude that this thermodynamic evaluation of root water uptake conveniently provides insights into the impediments of different processes along the entire flow path, which goes beyond resistances and also accounts for the role of heterogeneity in soil water distribution.

scholarly journals Thermodynamic Analysis of Relaxation Model for Non-Equilibrium Phase Behavior of Hydrocarbon Mixtures

2021 ◽  
Vol 2090 (1) ◽  
pp. 012138
Author(s):  
I M Indrupskiy ◽  
P A Chageeva
Keyword(s):  
Relaxation Time ◽  
Phase Behavior ◽  
Relaxation Process ◽  
Thermodynamic Analysis ◽  
Balance Equation ◽  
Equilibrium Phase ◽  
Characteristic Relaxation Time ◽  
Relaxation Model ◽  
Entropy Balance ◽  
Non Equilibrium

Abstract Mathematical models of phase behavior are widely used to describe multiphase oil and gas-condensate systems during hydrocarbon recovery from natural petroleum reservoirs. Previously a non-equilibrium phase behavior model was proposed as an extension over generally adopted equilibrium models. It is based on relaxation of component chemical potentials difference between phases and provides accurate calculations in some typical situations when non-instantaneous changing of phase fractions and compositions in response to variations of pressure or total composition is to be considered. In this paper we present a thermodynamic analysis of the relaxation model. General equations of non-equilibrium thermodynamics for multiphase flows in porous media are considered, and reduced entropy balance equation for the relaxation process is obtained. Isotropic relaxation process is simulated for a real multicomponent hydrocarbon system with different values of characteristic relaxation time using the non-equilibrium model implemented in the PVT Designer module of the RFD tNavigator simulation software. The results are processed with a special algorithm implemented in Matlab to calculate graphs of the total entropy time derivative and its constituents in the entropy balance equation. It is shown that the constituents have different signs, and the greatest influence on the entropy is associated with the interphase flow of the major component of the mixture and the change of the total system volume in the isotropic process. The characteristic relaxation time affects the rate at which the entropy is approaching its maximum value.

scholarly journals Monitoring water content changes in a soil profile with TDR-probes at just three depths - How well does it work?

RBRH ◽  
2020 ◽  
Vol 25 ◽  
Author(s):  
Jens Hagenau ◽  
Vander Kaufmann ◽  
Heinz Borg
Keyword(s):  
Time Delay ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
High Precision ◽  
Soil Profile ◽  
Reliable Data ◽  
Short Term ◽  
True Values ◽  
Daily Changes

ABSTRACT TDR-probes are widely used to monitor water content changes in a soil profile (ΔW). Frequently, probes are placed at just three depths. This raises the question how well such a setup can trace the true ΔW. To answer it we used a 2 m deep high precision weighing lysimeter in which TDR-probes are installed horizontally at 20, 60 and 120 cm depth (one per depth). ΔW-data collected by weighing the lysimeter vessel were taken as the true values to which ΔW-data determined with the TDR-probes were compared. We obtained the following results: There is a time delay in the response of the TDR-probes to precipitation, evaporation, transpiration or drainage, because a wetting or drying front must first reach them. Also, the TDR-data are more or less point measurements which are then extrapolated to a larger soil volume. This frequently leads to errors. For these reasons TDR-probes at just three depths cannot provide reliable data on short term (e.g. daily) changes in soil water content due to the above processes. For longer periods (e.g. a week) the data are better, but still not accurate enough for serious scientific studies.

scholarly journals Molecular Association of Tetramethylurea and Chlorobenzene Molecules in Microwave Frequency Range

2010 ◽  
Vol 65 (10) ◽  
pp. 854-858
Author(s):  
Vimal Sharma ◽  
Nagesh Thakur
Keyword(s):  
Relaxation Time ◽  
Dielectric Relaxation ◽  
Viscous Flow ◽  
Relaxation Process ◽  
Binary Mixtures ◽  
Variation Method ◽  
Dielectric Relaxation Time ◽  
Flow Process ◽  
Dielectric Relaxation Process ◽  
Energy Parameters

The dielectric constant ε´ and dielectric loss ε´´ of the binary mixtures of tetramethylurea (TMU) and chlorobenzene (CB) have been calculated at 9.883 GHz by using standard standing microwave techniques. Gopalakrishna’s single frequency concentration variation method has been used to calculate dipole moment μ and dielectric relaxation time τ for different mole fractions of TMU in the binary mixture at different temperatures of 25 °C, 30 °C, 35 °C, and 40 °C. The variation of dielectric relaxation time with the mole fraction of TMU in the whole concentration range of the binary mixtures was found to be non-monotonic. The solute-solute and solute-solvent type of molecular associations may be proposed based upon above observations. Using Eyring rate equations the energy parameters ΔH, ΔF, and ΔS for the dielectric relaxation process and the viscous flow process have been calculated at the given temperatures. It is found from the comparison of energy parameters that, just like the viscous flow process, the dielectric relaxation process can also be treated as a rate process.

A Soil Water Characteristic Curve Model Considering Urea Concentration

2013 ◽  
Vol 798-799 ◽  
pp. 157-160
Author(s):  
You Le Wang ◽  
Dong Fang Tian ◽  
Gai Qing Dai ◽  
Yao Ruan ◽  
Lang Tian
Keyword(s):  
Experimental Data ◽  
Water Content ◽  
Soil Water ◽  
Exponential Function ◽  
Characteristic Curve ◽  
Urea Concentration ◽  
Exponential Functions ◽  
Valuable Data ◽  
Soil Water Characteristic Curve ◽  
Curve Model

A new soil water characteristic curve (SWCC) model considering urea concentration is presented in the paper. Two assumptions are used to obtain the model. One is SWCC which could be described by exponential functions in the experiments. Another is relationship between the parameters of exponential functions and urea concentration which is linear based on experimental data. In the research, we have carried out some experiments of SWCC and obtained some valuable data which could affect urea concentration. By using linear fitting, an exponential function between water content and suction and urea concentration is established.

Soil Water Characteristic Curve for a Granite Residual Soil: Experimental and Numerical Results

2011 ◽  
Vol 312-315 ◽  
pp. 1172-1177 ◽  
Author(s):  
A. Topa Gomes ◽  
A. Viana Da Fonseca ◽  
A. Silva Cardoso
Keyword(s):  
Experimental Data ◽  
Soil Water ◽  
Characteristic Curve ◽  
Residual Soil ◽  
Seepage Analysis ◽  
Soil Water Characteristic Curve ◽  
Granite Residual Soil ◽  
Definition Of ◽  
Paper Method ◽  
Geotechnical Problems

The seepage analysis in geotechnical problems, namely in excavations, was typically performed assuming saturated conditions in the ground. It is now know that the flow in the non saturated part of the ground assumes also relevant importance and hence it is vital to characterize its behaviour. The Soil Water Characteristic Curve (SWCC) of the soil is probably the most important parameter in defining this behaviour and particularly for estimating the permeability of the soil. This paper presents the definition of the SWCC for a granite residual soil using pressure plates and the filter paper method. Based on experimental data some equations are adjusted and the results obtained are discussed. At the end of the paper some predictions of the non saturated permeability of the ground are also performed.

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