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1

Non-isothermal constitutive relations and heat transfer equations of a two-phase medium

Uciechowska-Grakowicz A., Strzelecki T.

Studia Geotechnica et Mechanica

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2017

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Vol. 39, nr 3

67--78

EN

In the case of a two-phase medium – such as the soil, which consists of an elastic skeleton and is filled with pore fluids – stress and strain within the medium are dependent on both phases. Similarly, in the case of heat transfer, heat is conducted through the two phases at different rates, with an additional heat transfer between the phases. In the classical approach to modelling a porous medium, it is assumed that the fluid filling the pore space is water, which is incompressible. In the case of gas, the volume of which is strongly dependent on temperature and pressure, one should take this behavior into account in the constitutive relations for the medium. This work defines the physical relations of a two-phase medium and provides heat transfer equations, constructed for a porous, elastic skeleton with fluid-filled pores, which may be: liquid, gas, or mixture of liquid and a gas in non-isothermal conditions. The paper will present constitutive relations derived from the laws of irreversible thermodynamics, assuming that pores are filled with either a liquid or a gas. These relations, in the opinion of the authors, may be used as the basis for the construction of a model of the medium filled partly with a liquid and partly with a gas. It includes the possibility of independent heat transfer through any given two-phase medium phase, with the transfer of heat between the phases.

2

Numerical model of heat transfer in three phases of the poroelastic medium

Uciechowska-Grakowicz A., Strzelecki T.

Studia Geotechnica et Mechanica

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2016

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Vol. 38, nr 2

53—59

EN

In this paper, the results of numerical analysis of the thermal consolidation of a two phase medium, under the assumption of independent heat transfer in fluid and the solid phase of the medium, are presented. Three cases of pore fluid were considered: liquid, represented by water, and gas, represented by air and carbon dioxide. The mathematical model was derived from irreversible thermodynamics, with the assumption of a constant heat transfer between the phases. In the case of the accepted geometry of the classical dimensions of the soil sample and boundary conditions, the process leads to equalization of temperatures of the skeleton on the pore fluid. Heat transfer is associated with the fluid flow in the pores of the medium. In the case of gas as the pore fluid, a non-linear mathematical model of gas filtration through the pores of the medium was accepted. For the computing process, relationships between viscosity or density and temperature proposed by other authors were taken into account. Despite accepting mechanical constants of the solid phase that do not depend on temperature, the obtained model is nonlinear and develops the classical Biot–Darcy model.

3

Numerical analysis of road pavement thermal deformability, based on Biot viscoelastic model of porous medium

Bartlewska-Urban M., Zombroń M.

Studia Geotechnica et Mechanica

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2016

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Vol. 38, nr 1

15--22

EN

The following study presents numerical calculations for establishing the impact of temperature changes on the process of distortion of biphase medium represented using Biot consolidation equations with Kelvin–Voigt rheological skeleton presented, on the example of thermo-consolidation of a pavement of expressway S17. We analyzed the behavior of the expressway under the action of its own weight, dynamic load caused by traffic and temperature gradient. This paper presents the application of the Biot consolidation model with the Kelvin–Voigt skeleton rheological characteristics and the influence of temperature on the deformation process is taken into account. A three-dimensional model of the medium was created describing the thermal consolidation of a porous medium. The 3D geometrical model of the area under investigation was based on data obtained from the land surveying and soil investigation of a 200 m long section of the expressway and its shoulders.

4

Effect of variation of temperature field on the process of thermal consolidation of tailings pond “Żelazny Most”

Bartlewska-Urban M., Strzelecki T.

Studia Geotechnica et Mechanica

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2014

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Vol. 36, nr 2

57--65

EN

The following study presents numerical calculations for establishing an impact of temperature changes on the process of distortion of bi-phase medium. The Biot consolidation equations with Kelvin–Voigt rheological skeleton were used for that purpose. The process was exemplified by thermal consolidation of post floatation dump “Żelazny Most”. We analyzed the behavior of the landfill under the action of its own weight, forces of floating filtration and temperature gradient. Values of certain effective parameters of model were obtained during laboratory tests on material obtained from the landfill. The remaining data for mediums with similar characteristics were taken from literature. The results obtained from the stress state in the landfill allow the magnitude of plasticity potential to be specified based on known strength criteria. Change in the value sign of the plasticity potential clearly testifies to the emergence of an area of plasticity of material from landfill, however, this does not indicate the loss of stability of this hydrotechnical structure.

5

Thermal consolidation process of multiphase medium consisting of elastic skeleton, water, and water vapour

Strzelecki T., Uciechowska A.

Acta Geophysica

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2014

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Vol. 62, no. 5

1163--1178

EN

In the process of coal gasification, the phase transition from water to water vapour takes place as a result of high temperature. Thus, the parameters of the fluid flowing through the pores of the elastic skeleton change in a significant way. The goal of this work is to calculate the fluid flow process at a variable temperature using Finite Element Method and to determine the soil consolidation process taking place under its own weight and temperature changes. The mathematical model of thermal consolidation for a Biot body accounts for the phase transition of a liquid. Numerical calculations for a homogeneous and isotropic porous medium, consisting of two conventionally accepted layers, were carried out using the Flex PDE v.6 software. The obtained results are a first approximation of the actual processes taking place under complex geological conditions. They make it possible to determine, in approximation, the range of the phase transition and the influence of water vapour filtration on soil consolidation.

6

Numerical calculation of deformation of three dimensional sample in triaxial apparatus under external load and temperature field

Bartlewska-Urban M., Strzelecki T.

Studia Geotechnica et Mechanica

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2013

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Vol. 35, nr 1

27--40

EN

This study presents the results of calculations of the of thermo consolidation process of porous medium with the rheological Kelvin–Voigt skeleton, obtained numerically with the use of Flex.PDE. It is a continuation of the discussion on the phenomenon of thermal consolidation. A 3D problem considered boils down to solving the problem of the porous column filled with a liquid and treated by applying uniaxial compression load through a porous plate, allowing free flow of liquid from the center. To the sample affected by external lateral pressure. Numerical solution assumes compressing the sample at properly defined boundary conditions. The aim of this study was to describe the influence of external load and temperature gradient in the deformation tests for the case when the lateral surface is a good conductor of heat, and where the lateral surface of the sample does not conduct heat. The results obtained, in the context of further research, can also be used to determine the influence of other parameters of the state and model parameters on the process of thermo poroelasticity of the Biot model with rheological skeleton.

7

Thermal consolidation of porous medium with a rheological Kelvin–Voigt skeleton

Bartlewska-Urban M., Strzelecki T.

Studia Geotechnica et Mechanica

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2012

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Vol. 34, nr 3

17--35

EN

This study presents calculations results of thermal consolidation process of the porous medium with the rheological Kelvin–Voigt skeleton, obtained numerically with the use of Flex.PDE software. The investigated calculation scheme consisted of the porous column filled with a liquid. The vertical load was applied to the top surface of the column through a porous plate allowing the free flow of liquid through this surface. Numerical solution is based on compression of the sample at appropriately defined boundary conditions. The aim of this study was to describe the influence of external load and temperature gradient on the deformation tests progress at different values of three parameters: λ, rs and cv . The results obtained, in the context of further research, can also be used for the determination of the influence of other parameters of the state and model parameters on the process of thermo poroelasticity of Biot model with rheological skeleton.

8

Metoda tworzenia nowych bezsplotowych struktur tekstylnych

Kuchar M., Podsiedlik W., Słodowy J., Wiśniewski M.

Problemy Eksploatacji

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2011

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nr 4

195-206

PL

Przedstawiono realizację idei nowego systemu wytwarzania płaskich bezsplotowych wyrobów włókienniczych przy ciągłym ruchu organów wyko-nawczych urządzenia wytwórczego - bez tworzenia przesmyku. Brak splotu wyrobu tekstylnego uzyskano przez zaplatanie nitki wątkowej (rowingu szklanego z powłoką PCV) na wynoszonych lokalnie kołkach na obwodzie bębna pobierającego z ramy natykowej nitki osnowowe (takie same jak nitka wątkowa) i dociskanie nimi przez opasanie wątku do powierzchni bębna. Przewidziano konsolidację termiczną wyrobu płaskiego w postaci siatki budowlanej. Dla uzyskania postępu zaplatania rowingu wątkowego zaplanowano wysuwanie po jednej stronie bębna pojedynczego kołka, a po drugiej - dwóch jednocześnie. Jako mechanizm wodzący wątek przewidziano przekładnię cięgnową o stałej prędkości obwodowej z wodzikiem przymocowanym do cięgna. Wykonano projekt stanowiska badawczego do tworzenia bezsplotowych wyrobów płaskich składającego się z posadowionych na ramie następujących zespołów: - bębna z układem napędowym, - zespołu wodzenia nitki wątkowej, - zespołu odbioru wyrobu, - dwóch kulowych popychaczy obrotowych. Kulowe popychacze obrotowe realizują ruchy wynoszenia kołków, a napęd otrzymują od bębna - poprzez zazębienie kulek z wgłębieniami w czołach wysuwanych kołków. Zgłoszenie patentowe tego wynalazku (nr P.394865) zostało zarejestrowane w Urzędzie Patentowym RP. Wykonano część mechaniczną stanowiska badawczego oraz zbudowano na bazie sterowników PLC i falowników prądowych układy sterowania. Badania wytwarzania tekstylnych wyrobów bezsplotowych przeprowadzono wg planu ujmującego 2 rodzaje rowingu w osłonie PCV, prędkość obwodową bębna do 1,5 m/min, napięcie nitek do 80 N i temperatury podczas procesu zgrzewania do 600°C. Określono optymalne dla stanowiska badawczego parametry procesu wytwórczego. Uzyskany płaski bezsplotowy wyrób włókienniczy poddano ocenie geometrycznej (regularności podziałki siatki) i wytrzymałościowej. Stwierdzono pozytywne własności wytworzonego wyrobu bezsplotowego, wysoką wytrzymałość na rozrywanie i bardzo mały rozrzut wyników, co świadczy o dobrej powtarzalności procesu technologicznego.

EN

As the aim of work the realisation of the system of producing the new weaveless textile fabrics with the continuous movements of the generating elements of machine without forming the shed has been set. The performed actions involved: - Designing the test rig for production of the weaveless textile structures, - Production and verification of the test rig producing the weaveless textile structures, - Tests of the technological parameters for the producing the weaveless flat textile fabrics, - Identification of properties of the produced weaveless textile structures. The weaveless structure of the textile fabric has been made through wrapping the weft (the PCV covered glass roving) around the locally shifted pins that are assembled in the rings on sides of the drum, which takes out the warp threads (also the PCV covered glass rovings) from creel that press the weft thread to the surface of the drum. The weft and warp threads have been consolidated thermally to the fabric - a building grid. In order to achieve the progress in wrapping the weft thread its wrapping has been made on a single pin shifted on the one side of the drum and two pins moved on the opposite side. As a mechanism carrying the weft thread a roller chain transmission with a constant circumferential velocity, which has benn provided with a feeder, has been utilised. The design of a test rig for producing the weaveless textile fabrics has been made. The test rig consists of the following assemblies with their load-carrying structure: - Drum with is driving unit, - Weft feeding set with its driving unit, - Take-up set of the fabric, - Two ball rotating actuators. The ball rotating actuators realize the pins shifting. They are driven from the rotating drum - through their meshing with holes in pins. The patent application for this invention has been registered in the Patent Office of the Republic of Poland (No P.394865). The creel with its load-carrying structure with ball bearing systems and friction brakes has been designed. The test rig for the weaveless fabrics and creel have been produced in the Department of Textile Techniques of the Institute for Sustainable Techologies - National Research Institute. The control systems of the test device have been developed with usage of the PLC systems that govern: - The setting of the velocities of the drum and the feeder and synchronise the mutual position of these components, - The conditions of the thermal consolidation of the fabric. The test rig for generating the weaveless structures has been verified in the series of tests. A number of the design changes were introduced and as a result the proper action of thee rig has been achieved. The tests of the producing the weaveless textile fabrics have been performed according to the research plan involving 2 types of the PCV coated glass roving, the circumferential velocity of the main drum up to 1.5 m/min, tension of the threads up to 80 N and temperature of the thermal consolidation up to 600°C. The optimum parameters of the production process have been determined. The weaveless textile fabric has been tested for its geometric features (regularity of the grid) and its straight (tension tests) The good properties of the new fabric have been confirmed and very limited scatter of the test results has been shown, which demonstrates the good repatibilty of the production process.