Spatial Variability of Physical Parameters and Processes in Two Field Soils

1991 ◽  
Vol 22 (5) ◽  
pp. 327-340 ◽  
Author(s):  
K. Høgh Jensen ◽  
J. C. Refsgaard
Keyword(s):  
Transport Model ◽  
Flow Direction ◽  
Measurement Data ◽  
Flow Simulation ◽  
Solute Concentration ◽  
Conclusive Evidence ◽  
Physical Parameters ◽  
Effective Parameters ◽  
The Mean ◽  
Tracer Experiments

A numerical analysis of solute transport in two spatially heterogeneous fields is carried out assuming that the fields are composed of ensembles of one-dimensional non-interacting soil columns, each column representing a possible soil profile in statistical terms. The basis for the analysis is the flow simulation described in Part II (Jensen and Refsgaard, this issue), which serves as input to a transport model based on the convection-dispersion equation. The simulations of the average and variation in solute concentration in planes perpendicular to the flow direction are compared to measurements obtained from tracer experiments carried out at the two fields. Due to the limited amount of measurement data, it is difficult to draw conclusive evidence of the simulations, but reliable simulations are obtained of the mean behaviour within the two fields. The concept of equivalent soil properties is also tested for the transport problem in heterogeneous soils. Based on effective parameters for the retention and hydraulic conductivity functions it is possible to predict the mean transport in the two experimental fields.

scholarly journals Spatial Variability of Physical Parameters and Processes in Two Field Soils

1991 ◽  
Vol 22 (5) ◽  
pp. 303-326 ◽  
Author(s):  
K. Høgh Jensen ◽  
J. C. Refsgaard
Keyword(s):  
Water Content ◽  
Flow Direction ◽  
Richards Equation ◽  
Physical Parameters ◽  
One Dimensional ◽  
Research Fields ◽  
Reasonable Degree ◽  
Soil Hydraulic Parameters ◽  
The Mean ◽  
Flow Variables

The horizontal variability of soil hydraulic parameters, water content and suction measured within two research fields in Denmark is analyzed and discussed. A numerical analysis of the flow in the two spatially heterogeneous fields is carried out by assuming that the fields are composed of ensembles of one-dimensional non-interacting soil columns, each column representing a possible soil profile in statistical terms. Flow predictions based on the classical Richards' equation are carried out for all columns, and the mean and standard deviation of water content and suction in planes perpendicular to the flow direction is derived and compared to measurements. The analysis shows that the model to a reasonable degree is able to describe most of the variation in flow variables within the two fields. The concept of equivalent soil properties is also investigated and applied to the two fields. Based on the average retention properties it is possible to predict the horizontal averages of flow variables within the fields.

A Reliable Method of Completing and Compensating the Results of Measurements of Flow Parameters in a Network of Headings / O Pewnej Metodzie Uzupełniania I Wyrównywania Wyników Pomiarów Parametrów Przepływu W Sieci Wyrobisk Górniczych

2015 ◽  
Vol 60 (1) ◽  
pp. 3-24 ◽  
Author(s):  
Wacław Dziurzyński ◽  
Andrzej Krach ◽  
Teresa Pałka
Keyword(s):  
Mathematical Model ◽  
Numerical Model ◽  
Air Flow ◽  
Aerodynamic Resistance ◽  
Measurement Data ◽  
Flow Simulation ◽  
Volumetric Flow Rate ◽  
Ventilation Network ◽  
Physical Parameters ◽  
Calculation Algorithms

Abstract Forecasting a ventilation process is based on two factors: using a validated software (Dziurzyński et al., 2011; Pritchard, 2010) and a properly prepared database encompassing the parameters describing the flow of air and gases, compatible with the adopted mathematical model of the VentGraph software (Dziurzyński, 2002). With a body of measurement data and a mathematical model for computer calculations and air flow simulation at our disposal, we proceed to develop a numerical model for a chosen network of mine headings. Preparing a numerical model of a ventilation network of a given mine requires providing a collection of data regarding the structure of the network and the physical properties of its elements, such as headings, fans, or stoppings. In the case of fire simulations, it is also necessary to specify the parameters describing the seat of a fire and the properties of the rocks of which the rock mass is comprised. The methods which are currently applied to this task involve manual ventilation measurements performed in headings; the results obtained in the course of these measurements constitute a basis for determining physical parameters, such as the aerodynamic resistance of a heading, density of the flow of air, or natural depression. Experience shows that - due to difficulties regarding accessibility of headings, as well as the considerable lengths of the latter - there are some nodes and headings in mines where such measurements are not performed. Thus, an attempt was made to develop a new methodology that would provide the missing data on the basis of some other available information concerning - for example - the air density, the geometry of headings and elevations. The adopted methodology suggests that one should start with balancing the air mass fluxes within the structure of a network of headings. The next step is to compile a database concerning the pressure values in the network nodes, based on the measurement results - and provide the missing pressure values on the basis of the available results of measurements carried out in adjacent nodes, as well as the pressure value calculated on the basis of the heading geometry and the given volumetric flow rate. The present paper discusses the methodology of compensating and balancing the volumetric air flow rates within a network of headings (Chapter 2) and the methodology of determining pressure values (Chapter 3) in the nodes of the network. The developed calculation algorithms - verified by means of sample calculations performed for a selected area of a mine ventilation network - were introduced into the VentGraph software system. The calculation results were presented in tabular form. The Summary section discusses the minuses and pluses of the adopted methodology.

scholarly journals Significance of Slippage and Electric Field in Mucociliary Transport of Biomagnetic Fluid

Lubricants ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 48
Author(s):  
Sufian Munawar
Keyword(s):  
Shear Stress ◽  
Flow Direction ◽  
Pressure Rise ◽  
Physical Parameters ◽  
Slippage Effect ◽  
Channel Surface ◽  
Electro Osmosis ◽  
Biomagnetic Fluid ◽  
Velocity Pressure ◽  
Metachronal Waves

Shear stress at the cilia wall is considered as an imperative factor that affects the efficiency of cilia beatings as it describes the momentum transfer between the fluid and the cilia. We consider a visco-inelastic Prandtl fluid in a ciliated channel under electro-osmotic pumping and the slippage effect at cilia surface. Cilia beating is responsible for the stimulation of the flow in the channel. Evenly distributed cilia tend to move in a coordinated rhythm to mobilize propulsive metachronal waves along the channel surface by achieving elliptic trajectory movements in the flow direction. After using lubrication approximations, the governing equations are solved by the perturbation method. The pressure rise per metachronal wavelength is obtained by numerically integrating the expression. The effects of the physical parameters of interest on various flow quantities, such as velocity, pressure gradient, pressure rise, stream function, and shear stress at the ciliated wall, are discussed through graphs. The analysis reveals that the axial velocity is enhanced by escalating the Helmholtz–Smoluchowski velocity and the electro-osmosis effects near the elastic wall. The shear stress at the ciliated boundary elevates with an increase in the cilia length and the eccentricity of the cilia structure.

scholarly journals Generation of Reverse Meniscus Flow by Applying An Electromagnetic Brake

2021 ◽  
Author(s):  
Alexander Vakhrushev ◽  
Abdellah Kharicha ◽  
Ebrahim Karimi-Sibaki ◽  
Menghuai Wu ◽  
Andreas Ludwig ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Lorentz Force ◽  
Applied Magnetic Field ◽  
Numerical Study ◽  
Flow Direction ◽  
Experimental Studies ◽  
Submerged Entry Nozzle ◽  
Mean Flow ◽  
Slab Caster ◽  
The Mean

AbstractA numerical study is presented that deals with the flow in the mold of a continuous slab caster under the influence of a DC magnetic field (electromagnetic brakes (EMBrs)). The arrangement and geometry investigated here is based on a series of previous experimental studies carried out at the mini-LIMMCAST facility at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The magnetic field models a ruler-type EMBr and is installed in the region of the ports of the submerged entry nozzle (SEN). The current article considers magnet field strengths up to 441 mT, corresponding to a Hartmann number of about 600, and takes the electrical conductivity of the solidified shell into account. The numerical model of the turbulent flow under the applied magnetic field is implemented using the open-source CFD package OpenFOAM®. Our numerical results reveal that a growing magnitude of the applied magnetic field may cause a reversal of the flow direction at the meniscus surface, which is related the formation of a “multiroll” flow pattern in the mold. This phenomenon can be explained as a classical magnetohydrodynamics (MHD) effect: (1) the closure of the induced electric current results not primarily in a braking Lorentz force inside the jet but in an acceleration in regions of previously weak velocities, which initiates the formation of an opposite vortex (OV) close to the mean jet; (2) this vortex develops in size at the expense of the main vortex until it reaches the meniscus surface, where it becomes clearly visible. We also show that an acceleration of the meniscus flow must be expected when the applied magnetic field is smaller than a critical value. This acceleration is due to the transfer of kinetic energy from smaller turbulent structures into the mean flow. A further increase in the EMBr intensity leads to the expected damping of the mean flow and, consequently, to a reduction in the size of the upper roll. These investigations show that the Lorentz force cannot be reduced to a simple damping effect; depending on the field strength, its action is found to be topologically complex.

scholarly journals Subdiffusive Reaction Model of Molecular Species in Liquid Layers: Fractional Reaction-Telegraph Approach

2021 ◽  
Vol 5 (2) ◽  
pp. 51
Author(s):  
Ashraf M. Tawfik ◽  
Mohamed Mokhtar Hefny
Keyword(s):  
Molecular Species ◽  
Transport Model ◽  
Mean Square Displacement ◽  
Telegraph Equation ◽  
Reaction Model ◽  
Simulation Techniques ◽  
Experimental Works ◽  
The Mean ◽  
Classical Transport ◽  
Fractional Reaction

In recent years, different experimental works with molecular simulation techniques have been developed to study the transport of plasma-generated reactive species in liquid layers. Here, we improve the classical transport model that describes the molecular species movement in liquid layers via considering the fractional reaction–telegraph equation. We have considered the fractional equation to describe a non-Brownian motion of molecular species in a liquid layer, which have different diffusivities. The analytical solution of the fractional reaction–telegraph equation, which is defined in terms of the Caputo fractional derivative, is obtained by using the Laplace–Fourier technique. The profiles of species density with the mean square displacement are discussed in each case for different values of the time-fractional order and relaxation time.

Computed Effects of Rotor-Induced Swirl on Brush Seal Performance—Part 2: Bristle Force Analysis

1996 ◽  
Vol 118 (4) ◽  
pp. 920-926 ◽  
Author(s):  
M. C. Sharatchandra ◽  
D. L. Rhode
Keyword(s):  
Inclination Angle ◽  
Flow Direction ◽  
Flow Simulation ◽  
Companion Paper ◽  
Navier Stokes ◽  
Brush Seal ◽  
Swirl Flows ◽  
Lift Off ◽  
Square Configuration ◽  
Periodic Module

This paper analytically investigates the aerodynamic bristle force distributions in brush seals used in aircraft gas turbine engines. These forces are responsible for the onset of bristle tip lift-off from the rotor surface which significantly affects brush seal performance. In order to provide an enhanced understanding of the mechanisms governing the bristle force distributions, a full Navier-Stokes flow simulation is performed in a streamwise periodic module of bristles corresponding to the staggered square configuration. As is the case with a companion paper (Sharatchandra and Rhode, 1996), this study has the novel feature of considering the combined effects of axial (leakage) and tangential (swirl) flows. Specifically, the effects of intra-bristle spacing and bristle inclination angle are explored. The results indicate that the lifting bristle force increases with reduced intra-bristle spacing and increased inclination angle. It was also observed that increases in the axial or tangential flow rates increased the force component in the normal as well as the flow direction.

Detection and Analysis of Rats’ Bioelectromagnetic Signal

2014 ◽  
Vol 536-537 ◽  
pp. 13-17
Author(s):  
Hong Long Cao ◽  
Fen Ju Qin ◽  
Xue Guan Liu ◽  
He Ming Zhao
Keyword(s):  
Standard Deviation ◽  
Automatic System ◽  
Measurement Method ◽  
Measurement Accuracy ◽  
Biological Activities ◽  
Measurement Data ◽  
Measured Data ◽  
The Mean ◽  
Frequency Window ◽  
Window Effects

In this paper, we designed an automatic system and automatic test software, and they can carry out Kunming rats bioelectromagnetic measurement in standard status and anesthesia automatically in anechoic chamber where the electromagnetic field outside is shielded, the reflection wave is absorbed, and the measurement accuracy will be improved. We get a great number of measurement data with frequency-sweep measurement method. The mean and standard deviation of amplitudes vs. frequencies is calculated and analyzed. The results show the measurement method is feasible. We have plotted the means of measured data as multiple sets of Y values in a series of bars with standard deviations bars included and distributed in the frequency axis of X. It is found that the fluctuation of the mean and standard deviation in some frequencies is not evident which may explain frequency window effects, while in other frequencies, such a fluctuation can be obviously observed, which may suggest that bioelectromagnetic signal is influenced by biological activities (standard and anaesthesia status) in these frequency points.

Effects of Pin Shape and Array Orientation on Heat Transfer and Pressure Loss in Pin Fin Arrays

1984 ◽  
Vol 106 (1) ◽  
pp. 252-257 ◽  
Author(s):  
D. E. Metzger ◽  
C. S. Fan ◽  
S. W. Haley
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Pressure Loss ◽  
Flow Direction ◽  
Circular Cross Section ◽  
Cycle Performance ◽  
Mean Flow ◽  
Pin Fin ◽  
The Mean ◽  
Cooling Air

Modern high-performance gas turbine engines operate at high turbine inlet temperatures and require internal convection cooling of many of the components exposed to the hot gas flow. Cooling air is supplied from the engine compressor at a cost to cycle performance and a design goal is to provide necessary cooling with the minimum required cooling air flow. In conjunction with this objective, two families of pin fin array geometries which have potential for improving airfoil internal cooling performance were studied experimentally. One family utilizes pins of a circular cross section with various orientations of the array with respect to the mean flow direction. The second family utilizes pins with an oblong cross section with various pin orientations with respect to the mean flow direction. Both heat transfer and pressure loss characteristics are presented. The results indicate that the use of circular pins with array orientation between staggered and inline can in some cases increase heat transfer while decreasing pressure loss. The use of elongated pins increases heat transfer, but at a high cost of increased pressure loss. In conjunction with the present measurements, previously published results were reexamined in order to estimate the magnitude of heat transfer coefficients on the pin surfaces relative to those of the endwall surfaces. The estimate indicates that the pin surface coefficients are approximately double the endwall values.

scholarly journals An advanced scheme for wet scavenging and liquid-phase chemistry in a regional online-coupled chemistry transport model

2013 ◽  
Vol 13 (3) ◽  
pp. 1177-1192 ◽  
Author(s):  
C. Knote ◽  
D. Brunner
Keyword(s):  
Aqueous Phase ◽  
Climate Model ◽  
Transport Model ◽  
Measurement Data ◽  
Coupled System ◽  
Cloud Microphysics ◽  
Microphysics Scheme ◽  
Meteorological Model ◽  
Wet Scavenging ◽  
Phase Chemistry

Abstract. Clouds are reaction chambers for atmospheric trace gases and aerosols, and the associated precipitation is a major sink for atmospheric constituents. The regional chemistry-climate model COSMO-ART has been lacking a description of wet scavenging of gases and aqueous-phase chemistry. In this work we present a coupling of COSMO-ART with a wet scavenging and aqueous-phase chemistry scheme. The coupling is made consistent with the cloud microphysics scheme of the underlying meteorological model COSMO. While the choice of the aqueous-chemistry mechanism is flexible, the effects of a simple sulfur oxidation scheme are shown in the application of the coupled system in this work. We give details explaining the coupling and extensions made, then present results from idealized flow-over-hill experiments in a 2-D model setup and finally results from a full 3-D simulation. Comparison against measurement data shows that the scheme efficiently reduces SO2 trace gas concentrations by 0.3 ppbv (−30%) on average, while leaving O3 and NOx unchanged. PM10 aerosol mass was increased by 10% on average. While total PM2.5 changes only little, chemical composition is improved notably. Overestimations of nitrate aerosols are reduced by typically 0.5–1 μg m−3 (up to −2 μg m−3 in the Po Valley) while sulfate mass is increased by 1–1.5 μg m−3 on average (up to 2.5 μg m−3 in Eastern Europe). The effect of cloud processing of aerosols on its size distribution, i.e. a shift towards larger diameters, is observed. Compared against wet deposition measurements the system tends to underestimate the total wet deposited mass for the simulated case study.

A computed method for noninvasive MRI assessment of pulmonary arterial hypertension

2004 ◽  
Vol 96 (2) ◽  
pp. 463-468 ◽  
Author(s):  
Eric Laffon ◽  
Christophe Vallet ◽  
Virginie Bernard ◽  
Michel Montaudon ◽  
Dominique Ducassou ◽  
...  
Keyword(s):  
Arterial Pressure ◽  
Pulmonary Arterial Pressure ◽  
Cross Sectional Area ◽  
Physical Parameters ◽  
Sectional Area ◽  
Biophysical Parameters ◽  
Cross Sectional ◽  
Mean Pulmonary Arterial Pressure ◽  
Pulmonary Arterial ◽  
The Mean

The present method enables the noninvasive assessment of mean pulmonary arterial pressure from magnetic resonance phase mapping by computing both physical and biophysical parameters. The physical parameters include the mean blood flow velocity over the cross-sectional area of the main pulmonary artery (MPA) at the systolic peak and the maximal systolic MPA cross-sectional area value, whereas the biophysical parameters are related to each patient, such as height, weight, and heart rate. These parameters have been measured in a series of 31 patients undergoing right-side heart catheterization, and the computed mean pulmonary arterial pressure value (PpaComp) has been compared with the mean pressure value obtained from catheterization (PpaCat) in each patient. A significant correlation was found that did not differ from the identity line PpaComp = PpaCat ( r = 0.92). The mean and maximal absolute differences between PpaComp and PpaCat were 5.4 and 11.9 mmHg, respectively. The method was also applied to compute the MPA systolic and diastolic pressures in the same patient series. We conclude that this computed method, which combines physical (whoever the patient) and biophysical parameters (related to each patient), improves the accuracy of MRI to noninvasively estimate pulmonary arterial pressures.

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