Computer Simulation of Thermomigration Process

1997 ◽  
Vol 490 ◽  
Author(s):  
V. Yu. Gershanov ◽  
S. I. Garmashov ◽  
A. R. Minyaev ◽  
A. V. Beletskaya
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Computer Simulation ◽  
Thermal Gradient ◽  
Thermal Conditions ◽  
Diffuse Interface ◽  
Cross Sectional ◽  
Nucleation Mechanisms ◽  
Liquid Phase Composition ◽  
Sectional Shape

ABSTRACTMathematical model of thermomigration of liquid inclusions through a crystal under stationary and non-stationary thermal conditions is presented. It is assumed that the mass-transfer is provided by diffusion only, the crystallization and dissolution processes are carried out in accordance with the diffuse interface mechanism for atomic-rough (non-singular) interfaces and screw-dislocation or two-dimension nucleation mechanisms for singular interfaces.The package of computer programs based on this model enables simulation of the evolution of the cross-sectional shape of cylindrical liquid inclusions. It is possible to simulate the cases of various inclusion sizes, various relationship between the interface and volume mass-transfer restrictions, various liquid phase composition, thermal gradient under stationary and non-stationary thermal conditions as well. The main results of the simulation are presented.

scholarly journals О скорости термомиграции жидких цилиндрических включений в кристалле в стационарных тепловых условиях

2019 ◽  
Vol 61 (12) ◽  
pp. 2303
Author(s):  
С.И. Гармашов
Keyword(s):  
Temperature Gradient ◽  
Cross Section ◽  
Interfacial Energy ◽  
Thermal Conditions ◽  
Cross Sectional Area ◽  
Cylindrical Inclusion ◽  
Sectional Area ◽  
Cross Sectional ◽  
Nonmonotonic Dependence ◽  
Sectional Shape

Based on model ideas about the cross-sectional shape of a liquid cylindrical inclusion migrating through a crystal under the action of a temperature gradient in the case of the stationary thermal conditions, the dependences of the velocity and cross-sectional shape of the inclusion on its cross-sectional area have been calculated and analyzed for different values of the specific interfacial energy, the degree of its anisotropy, and the degree of difficulty of interface processes. The possibility of a nonmonotonic dependence of the velocity of the cylindrical inclusion on the area and thickness of its cross section has been shown.

scholarly journals Cross-Sectional Performance of Hollow Square Prisms with Rounded Edges

Symmetry ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 996
Author(s):  
Hiroyuki Shima ◽  
Nao Furukawa ◽  
Yuhei Kameyama ◽  
Akio Inoue ◽  
Motohiro Sato
Keyword(s):  
Mechanical Properties ◽  
Mathematical Model ◽  
Cross Sections ◽  
Cross Sectional ◽  
Hollow Section ◽  
Buckling Resistance ◽  
The Cross ◽  
The Stability ◽  
External Forces ◽  
Sectional Shape

Hollow-section columns are one of the mechanically superior structures with high buckling resistance and high bending stiffness. The mechanical properties of the column are strongly influenced by the cross-sectional shape. Therefore, when evaluating the stability of a column against external forces, it is necessary to reproduce the cross-sectional shape accurately. In this study, we propose a mathematical method to describe a polygonal section with rounded edges and vertices. This mathematical model would be quite useful for analyzing the mechanical properties of plants and designing plant-mimicking functional structures, since the cross-sections of the actual plant culms and stems often show rounded polygons.

The Capillarity Influence On Shape Of Small Liquid Inclusions Enclosed In A Solid Under Non-Stationary Thermal Conditions

2000 ◽  
Vol 648 ◽  
Author(s):  
Vladimir Yu. Gershanov ◽  
Sergey I. Garmashov ◽  
Andrey R. Minyaev ◽  
Nickita E. Ivanov ◽  
Irina Yu. Nosuleva
Keyword(s):  
Analytical Model ◽  
Interfacial Energy ◽  
Thermal Conditions ◽  
Liquid Inclusion ◽  
Capillary Effect ◽  
Sectional Area ◽  
Cross Sectional ◽  
Anisotropic Crystal ◽  
Inclusion Shape ◽  
Sectional Shape

AbstractAn analytical model taking into account the influence of capillarity on the process of changing the cross-sectional shape of a cylindrical liquid inclusion enclosed in an anisotropic crystal under non-stationary thermal conditions is suggested. It is shown that the capillary effect confines the possibilities for controlling the inclusion shape under non-stationary thermal conditions. The capillarity influence becomes stronger with decreasing cross-sectional area and increasing interfacial energy. The results of calculations of the limit inclusion shape under different thermal conditions are presented and discussed.

On the cross-sectional shape of the cellulose crystallites in the tunicate Halocynthia papillosa

1990 ◽  
Vol 48 (3) ◽  
pp. 566-567
Author(s):  
J.-F. Revol ◽  
Y. Van Daele ◽  
F. Gaill
Keyword(s):  
Contrast Imaging ◽  
Animal Kingdom ◽  
Bright Field ◽  
Field Mode ◽  
Cross Sectional ◽  
Ultrathin Sections ◽  
The Cross ◽  
Sectional Shape ◽  
Valonia Ventricosa ◽  
C Nmr

The only form of cellulose which could unequivocally be ascribed to the animal kingdom is the tunicin that occurs in the tests of the tunicates. Recently, high-resolution solid-state l3C NMR revealed that tunicin belongs to the Iβ form of cellulose as opposed to the Iα form found in Valonia and bacterial celluloses. The high perfection of the tunicin crystallites led us to study its crosssectional shape and to compare it with the shape of those in Valonia ventricosa (V.v.), the goal being to relate the cross-section of cellulose crystallites with the two allomorphs Iα and Iβ.In the present work the source of tunicin was the test of the ascidian Halocvnthia papillosa (H.p.). Diffraction contrast imaging in the bright field mode was applied on ultrathin sections of the V.v. cell wall and H.p. test with cellulose crystallites perpendicular to the plane of the sections. The electron microscope, a Philips 400T, was operated at 120 kV in a low intensity beam condition.

Computer Simulation of the Response of Amperometric Biosensors in Stirred and non Stirred Solution

2003 ◽  
Vol 8 (1) ◽  
pp. 3-18 ◽  
Author(s):  
R. Baronas ◽  
F. Ivanauskas ◽  
J. Kulys
Keyword(s):  
Mathematical Model ◽  
Computer Simulation ◽  
Finite Difference ◽  
Mass Transport ◽  
Enzyme Reaction ◽  
Analyte Concentration ◽  
Amperometric Biosensors ◽  
Finite Difference Technique ◽  
Enzyme Layer ◽  
Biosensor Response

A mathematical model of amperometric biosensors has been developed to simulate the biosensor response in stirred as well as non stirred solution. The model involves three regions: the enzyme layer where enzyme reaction as well as mass transport by diffusion takes place, a diffusion limiting region where only the diffusion takes place, and a convective region, where the analyte concentration is maintained constant. Using computer simulation the influence of the thickness of the enzyme layer as well the diffusion one on the biosensor response was investigated. The computer simulation was carried out using the finite difference technique.

Automated 3D measurement of fiber cross section morphology in handsheets

2012 ◽  
Vol 27 (2) ◽  
pp. 264-269 ◽  
Author(s):  
Christian Lorbach ◽  
Ulrich Hirn ◽  
Johannes Kritzinger ◽  
Wolfgang Bauer
Keyword(s):  
Image Analysis ◽  
Cross Section ◽  
Cross Sections ◽  
Image Plane ◽  
3D Measurement ◽  
Cross Sectional ◽  
Fiber Cross Section ◽  
Fiber Wall ◽  
Sectional Shape ◽  
Cross Section Geometry

Abstract We present a method for 3D measurement of fiber cross sectional morphology from handsheets. An automated procedure is used to acquire 3D datasets of fiber cross sectional images using an automated microtome and light microscopy. The fiber cross section geometry is extracted using digital image analysis. Simple sample preparation and highly automated image acquisition and image analysis are providing an efficient tool to analyze large samples. It is demonstrated that if fibers are tilted towards the image plane the images of fiber cross sections are always larger than the true fiber cross section geometry. In our analysis the tilting angles of the fibers to the image plane are measured. The resulting fiber cross sectional images are distorted to compensate the error due to fiber tilt, restoring the true fiber cross sectional shape. We use an approximated correction, the paper provides error estimates of the approximation. Measurement results for fiber wall thickness, fiber coarseness and fiber collapse are presented for one hardwood and one softwood pulp.

Modeling of aerated upflow fixed bed reactors for nitrification

1999 ◽  
Vol 39 (4) ◽  
pp. 85-92 ◽  
Author(s):  
J. Behrendt
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Liquid Phase ◽  
Gas Phase ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Bulk Liquid ◽  
Initial Value ◽  
Fixed Bed Reactors ◽  
Number Of Cells

A mathematical model for nitrification in an aerated fixed bed reactor has been developed. This model is based on material balances in the bulk liquid, gas phase and in the biofilm area. The fixed bed is divided into a number of cells according to the reduced remixing behaviour. A fixed bed cell consists of 4 compartments: the support, the gas phase, the bulk liquid phase and the stagnant volume containing the biofilm. In the stagnant volume the biological transmutation of the ammonia is located. The transport phenomena are modelled with mass transfer formulations so that the balances could be formulated as an initial value problem. The results of the simulation and experiments are compared.

Validation of mathematical model of electrothermal calculation of DC catenary on the basis of scale model

2018 ◽  
Vol 77 (4) ◽  
pp. 222-229 ◽  
Author(s):  
A. V. Paranin ◽  
A. B. Batrashov
Keyword(s):  
Mathematical Model ◽  
Operating Conditions ◽  
Scale Model ◽  
Contact Network ◽  
Scaled Model ◽  
Cross Sectional ◽  
Current Collection ◽  
Topological Features ◽  
Study Results ◽  
Real Physical Process

The article compares the results of calculation of the finite element simulation of current and temperature distribution in the scale model of the DC catenary with the data of laboratory tests. Researches were carried on various versions of the structural design of catenary model, reflecting the topological features of the wire connection, characteristic of the DC contact network. The proportions of the cross-sectional area of the scaled model wires are comparable to each other with the corresponding values for real DC catenary. The article deals with the operating conditions of the catenary model in the modes of transit and current collection. When studying the operation of the scale catenary model in the transit mode, the effect of the structural elements on the current distribution and heating of the wires was obtained. Within the framework of the scale model, theoretical assumptions about the current overload of the supporting cable near the middle anchoring have been confirmed. In the current collection mode, the experimental dependences of the current in the transverse wires of the scale model are obtained from the coordinate of the current collection point. Using the model it was experimentally confirmed that in the section of the contact wire with local wear, not only the temperature rise occurs but also the current redistribution due to the smaller cross section. Thus, the current share in other longitudinal wires of the scale model increases and their temperature rises. Scale and mathematical models are constructed with allowance for laboratory clamps and supporting elements that participate in the removal of heat from the investigated wires. Obtained study results of the scale model allow to draw a conclusion about the adequacy of the mathematical model and its correspondence to the real physical process. These conclusions indicate the possibility of applying mathematical model for calculating real catenary, taking into account the uneven contact wear wire and the armature of the contact network.

Study of Correctly Expanded Sonic Jet with Air Tabs

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Arun Prasad R ◽  
Thanigaiarasu S ◽  
Sembaruthi M ◽  
Rathakrishnan E
Keyword(s):  
Numerical Study ◽  
Cross Sectional ◽  
Potential Core ◽  
Convergent Nozzle ◽  
Jet Mixing ◽  
Pressure Profiles ◽  
Constant Diameter ◽  
Sonic Jet ◽  
Sectional Shape ◽  
Length Reduction

AbstractThe present numerical study is to understand the effect of air tabs located at the exit of a convergent nozzle on the spreading and mixing characteristics of correctly expanded sonic primary jet. Air tabs used in this study are two secondary jets issuing from constant diameter tubes located diametrically opposite at the periphery of the primary nozzle exit, normal to the primary jet. Two air tabs of Mach numbers 1.0 to 1.4, in steps of 0.1 are considered in this study. The mixing modification caused by air tabs are analysed by considering the mixing of uncontrolled (free) primary jet as a reference. Substantial enhancement in jet mixing is achieved with Mach 1.4 air tabs, which results in 80 % potential core length reduction. The total pressure profiles taken on the plane (YZ) normal to the primary jet axis, at various locations along the primary jet centreline revealed the modification of the jet cross sectional shape by air tabs. The stream-wise vortices and bifurcation of the primary jet caused by air tabs are found to be the mechanism behind the enhanced jet mixing.

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