Wyniki wyszukiwania - Biblioteka Nauki

1

Geo-engineering computer simulation seems attractive but is it the real world?

100%

Sikora Z.

Studia Geotechnica et Mechanica

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2008

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tom Vol. 30, nr 1-2

165-172

EN

Correct formulation of the differential equation system for equilibrium conditions of subsoil, especially in terms of controlled numerical calculation, is discussed. The problem of solution stability is also considered. The solution of problems, which are ill-posed, have no practical value in the majority of cases and in this way the engineering prognosis can lead to a real disaster. The object of this paper is quite relevant if its application is taken into account. Numerical calculations of boundary value problems must often be performed as true predictions. Unfortunately, the ability to submit a reliable prediction seems to be lacking in geotechnical engineering. Several reasons, which may be responsible for this disappointing state, are described.

2

Influence of the Geometry Alteration of the Landslide Slope on its Stability: A Case Study in the Carnian Alps (Italy)

80%

Zabuski L. , Bossi G. , Marcato G.

Archives of Hydro-Engineering and Environmental Mechanics

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2017

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tom Vol. 64, nr 2

101--114

EN

The paper presents the principles of the slope reprofiling and proves the effectiveness of this stabilization measure. The case study of two adjacent landslides in the National Road 52 “Carnica” in the Tagliamento River valley, the Carnian Alps (462304900N, 124205100E) are the example allowing for illustration of this approach. The phenomena have been studied for more than a decade, making it possible to carry out a detailed geological and geomorphological reconstruction. That was done on the basis of a large amount of monitoring data collected during that period. Since the landslides are threatening an important road, countermeasure works to ameliorate the stability conditions of the slides need to be designed. The paper focuses on the creation of a numerical model consistent with monitoring data and capable of reconstructing the dynamics of both landslides. Two cross-sections, one for each landslide, were selected for the analysis. The geometry of the slip surface was determined on the basis of control points, such as slip surface readings from inclinometers, and geomorphological evidence for the contour. The FLAC2D code was used to evaluate the current stability of these landslides and to determine the effectiveness of changing the slope geometry by removing material from the upper part of the slope and putting it to the lowest part as reinforcement.

3

Numerical simulation of 3D flow through a control valve

80%

Badur J. , Banaszkiewicz M. , Karcz M. , Winowiecki M.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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1999

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tom nr 115

31--36

EN

The paper deals with numerical calculations of 3D flow through a control valve. The presented calculations were performed using commercial code FLUENT/UNS. The results of numerical simulations were compared with experimental data.

4

Analiza numeryczna pracy wymiennika ciepła z awaryjną nieszczelnością

80%

Pospolita W. , Cholewiński M.

Technical Issues

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2016

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tom nr 2

53--59

EN

Heat exchangers belong to the group of devices, whose proper operation is essential for the proper conduct of industrial processes. The growing influence of numerical methods in the design stage of exchanger, allows to optimize their design in terms of efficiency and meet the specified thermal parameters. A relatively new way to use numerical simulation is the study of unsteady heat transfer that characterized their work during failure. The article presents results of numerical analysis of the operation of a hypothetical heat exchanger with emergency leak of one of the coils. The effects of stream loss in the pipe and change of flow dynamics of entire system were taken into consideration. The importance of location of leak on the behavior of heat exchanger was also taken into account. The simulation was performed using the commercial software Autodesk Simulation CFD.

5

Numerical calculation of the expansion flow with spontaneous condensation in water vapour and moist air

80%

Chmielniak T. , Wróblewski W. , Dykas S.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Mechanika

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1999

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tom Z. 67

185--194

EN

A method for solving an expansion flow of the water steam and moist air is presented in the paper. The phenomenon of the homogenous condensation is also calculated. The gas is governed by the Euler equation, which are coupled with the system of partial differential equation describing the liquid phase. There is no slip between gas and water droplets. In this paper the real water vapour properties and functions in all regions were considered. It makes possible to model the condensation process more accurate. All governing equations are discretised by the cell-centered finite volume formulation. The numerical procedure is based on an explicit Godunov-type scheme. The method has been extensively tested including a one dimension test called the shock tube test, the expansion flow through a Laval nozzle and flow through the blade cascade of a turbine stator.

6

Flow analysis in centrifugal pump

80%

Altyntsev I. , Korczak A. , Synowiec T. , Bujok W. , Darłak M. , Kustosz R.

Computer Methods in Materials Science

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2011

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tom Vol. 11, No. 1

196-201

EN

The paper describes numerical and experimental study of centrifugal pump developed to assist left ventricle of the human heart. Usage of the modern computer software provides wide possibilities of studying complicated flow processes and visualization of the obtained results. The numerical pump model, based on theoretical study, was developed in Solid Edge. The mesh of the pump flow tract for numerical calculation was made in CFX-Mesh and ICEM CFD. The numerical calculations of the steady fluid flow in the centrifugal pump were performed to define the characteristics of the pump operating parameters at various flow rates. The construction of centrifugal pump flow tract was analyzed using Computational Fluid Dynamics (CFD) methods. Modifications of the geometry of flow tract were madę by pump's constructors. Changes concerned the pump flow analyses obtained from the numerical calculations. Dangerous areas in the flow, where the level of the shear stress achieved the maximal values, were defined. The character of the fluid flow in different parts of the pump was investigated. To perform the experimental validation of pump characteristics a laboratory stand was made. A series of measurements was performed to obtain pump performance characteristics. A comparison of the numerical calculation results and experimental measurements has shown differences between achieved results.

PL

W artykule przedstawiono numeryczne i eksperymentalne badania pompy odśrodkowej do wspomagania lewej komory serca człowieka. Korzystanie z nowoczesnych programów komputerowych oferuje szerokie możliwości w zakresie badań skomplikowanego procesu przepływu i wizualizacji uzyskanych wyników. Model numeryczny pompy, zbudowany na podstawie badań teoretycznych, został skonstruowany w programie Solid Edge. Siatka części przepływowej pompy dla obliczeń numerycznych została zbudowana w programach CFX-Mesh i ICEM CFD. Przeanalizowano konstrukcję pompy odśrodkowej wykorzystując metody obliczeniowej dynamiki płynów (CFD). Przeprowadzono numeryczne obliczenia ustalonego przepływu w pompie odśrodkowej, celem określenia charakterystyki parametrów pracy przy różnych parametrach przepływu. Zostały wykonane zmiany geometrii kanału przepływowego przez konstruktorów. Są one oparte na wynikach analizy przepływu w pompie, uzyskanych przy pomocy obliczeń numerycznych. Zdefiniowano niebezpieczne strefy w strumieniu, gdzie poziom naprężeń ścinających osiąga maksymalne wartości. Zbadano charakter przepływu cieczy w różnych elementach pompy. Celem otrzymania eksperymentalnych charakterystyk pompy, stworzono stanowisko laboratoryjne, na którym przeprowadzono serie pomiarów. Porównanie rezultatów obliczeń numerycznych i pomiarów eksperymentalnych pokazuje, że istnieje różnica między wynikami.

7

Viscoelastic unsteady lubrication of radial slide journal bearing at impulsive motion

70%

Miszczak A.

Polish Maritime Research

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2004

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tom nr 2

9-21

EN

This paper presents an analytical solution of velocity components of unsymmetrical oil flow and pressure distribution in radial journal bearing gap for hydrodynamic unsteady lubrication with viscoelastic oil. Numerical calculations are performed in Mathcad 11 Professional Program, with taking into account the method of finite differences. This meŹthod satisfies stability conditions of numerical solutions of partial differential equations and values of capacity forces occurring in cylindrical bearings. Exact calculations of presŹsure in journal bearing and its load capacity may be useful to prevent from premature wear tribological units of self ignition engines, especially those applied in ships.

8

Analytical solution for one-dimensional consolidation of unsaturated soils under dynamic load

70%

Liu Z.-Y. , Song Y. , Zhou F.-X. , Wang L.-Y.

Journal of Theoretical and Applied Mechanics

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2023

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tom Vol. 61 nr 1

11--22

EN

Firstly, in this paper, based on the theory of the porous elastic medium and combined with the effective stress principle of unsaturated soil, a set of governing equations is established to describe consolidation of the unsaturated soil. Secondly, an analytical expression under any dynamic loads is obtained with the help of Laplace integral transformation. Finally, analysis of numerical examples under specific boundary conditions is made to discuss one-dimensional consolidation characteristics under harmonic loads and the influence of factors on the consolidation characteristics of unsaturated soil, such as excitation frequency and initial saturation.

9

The numerical calculations of influence of underpinning on foundations settlement

70%

Górski K. , Ignatowicz R. L. , Wierzbicki J. , Mazur R. , Mazurkiewicz J.

Studia Geotechnica et Mechanica

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2013

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tom Vol. 35, nr 4

47--64

EN

The paper presents numerical calculations of the influence of implementation technology for underpinning the footing on settlement, with the use of finite element method. Three cases of underpinning methods were taken for calculations, depending on the diameter of the jet grouting column and the order of works. The intensity of settlement of the base of the footing foundation is significantly influenced by the growth of Young’s modulus and the jet grouting column with time, until its complete curing and reaching final technological parameters.

10

Analysis of the influence of the changes in the value of dynamic viscosity coefficient in the direction of oil film thickness on the journal bearing load carrying capacity

70%

Miszczak A.

Journal of KONES

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2018

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tom Vol. 25, No. 3

355--362

EN

This article presents the results of numerical calculations of the hydrodynamic pressure distribution, load carrying capacity, friction force and friction coefficient of the slide journal bearing, if the assumed model of hydrodynamic lubrication takes into account the dependence of oil viscosity values on its temperature in all three directions of the adopted coordinate system, in particular, also across the thickness of the lubricant layer. This research considered the slide journal bearing lubricated with the Newtonian oil. The flow of oil was modelled as laminar and stationary. The bearing bushing had a full angle of wrap and its surfaces were smooth. In order to obtain hydrodynamic pressure distributions, the Reynolds type equation was numerically solved by application of the finite difference method (FDM). The numerical procedures for this research were prepared with the Mathcad 15 software. When adopting the classic models and simplifications for the hydrodynamic lubrication and a thin boundary layer, it is assumed, that the hydrodynamic pressure of lubricating oil does not depend on the position measured across the height of the lubrication gap. On the other hand, it is known, that the dynamic viscosity strongly depends on the temperature, which is a function of all three spatial variables. The aim of this work is to include, in the hydrodynamic lubrication model, the changes of viscosity in the direction of oil film thickness, and to investigate how it will affect the hydrodynamic pressure distribution and load carrying capacity of the journal bearing.

11

Analysis of the load carrying capacities and the friction force in the gap of the slide journal bearing lubricated with a non-Newtonian oil described by a power-law model

70%

Miszczak A.

Journal of KONES

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2016

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tom Vol. 23, No. 3

327--335

EN

In this paper, the author presents the results of numerical calculations of load carrying capacities and friction forces in the gap of the slide journal bearing lubricated with an oil on the non-Newtonian's properties. In the studies, the power-law model has been assumed to describe the relationship between the stress tensors and shear rate tensors. The analytical and numerical calculations have been performed for the plain bearing, non-porous with a full wrap angle. It has been assumed isothermal, laminar and steady flow of lubricant in the gap of a slide bearing. Numerical calculations have been performed for the Gumbel’s boundary conditions and dimensionless lengths of the bearings like L=b/R =2;1.5;1; ½ and ¼. The flow-rate index and coefficient of consistency have been adopted based on the results of experimental studies of changes of dynamic viscosity in terms of a shear rate. It has been assumed that the apparent viscosity depends only on the shear rate. Dynamic viscosity of the engine oil, used in a gasoline engine with a capacity of 1800 cm3, has been tested on the Haake Mars III rheometer. The analytical solutions presented in the paper were based on more general derivations carried out by Professor K. Wierzcholski in his article: ‘Non-linear hydrodynamic lubrication in conjugated fields’ (publication in printing). In this paper, the key quantities such as components of vector of the velocity, hydrodynamic pressure and temperature were presented in the form of convergent power series. The values of load carrying capacities and friction forces were determined and compared for the event where the oil has properties of Newtonian and non-Newtonian. Calculations have been made for the dimensionless quantities.

12

Zjawisko pękania lamelarnego w ujęciu numerycznym

70%

Niezgodziński T. , Kubiak T. , Młotkowski A.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Mechanika

|

2001

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tom Z. 73

233-239

PL

W niniejszej pracy rozpatrywano zachowanie sie modelu numerycznego struktury perlityczno-ferrytycznej stali z wtrąceniami niemetalicznymi w postaci pasmowej. Nagromadzenie takich wtrąceń może prowadzić do pęknięć lameralnych - równoległych do powierzchni blachy. Model numeryczny zbudowano dla trzech warstw wtrąceń ułożonych w różnorodny sposób, a następnie obciążono wzdłuż i w poprzek wtrąceń pasmowych. Otrzymane wyniki obliczeń numerycznych potwierdziły teorię, że pękanie lamelarne powstaje w wyniku dużych odkształceń prostopadłych do pasm wtrąceń; zjawisko to występuje przy dużej koncentracji wtrąceń oraz niekorzystnym ich ułożeniu względem siebie.

EN

In this paper behavior of numerical model of ferritic structure with non-metallic inclusion in band distributed was analyzed. Concentration of non-metallic inclusion occur lamellar teatring - parallel to surface of sheet. Analyzed model was loaded in directionparallel or perpendicular to band of inclusion. The results of numerical calculation confirm theory that lamellar tearing appear when load casuses large strain in direction perpendicular to band of inclusion. Lamellar tearing phenomenon appear only in specific cases: specific distribution of non-metallic inclusion and inclusion concentration.

13

Dissipation of pore water pressure in the theory of Biot

70%

Kaminski R. , Wozniak M.

Annals of Warsaw Agricultural University. Land Reclamation

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1986

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tom 22

14

Heat and mass transfer in two-phase gas-droplet turbulent developing flow in a tube

70%

Terekhov V. , Pakhomov M.

Archives of Thermodynamics

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2002

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tom Vol. 23, no 4

59-80

EN

A computation model is developed, where flow dynamics together with heat and mass transfer in a turbulent two-phase gas-droplet developing tube flow are numerically studied. Turbulent characteristics of the gas phase were calculated using the Nagano-Tagawa LRN k - model. It is shown that, with increasing initial droplet diameter the heat transfer between the duct surface and the vapour-gas mixture becomes much less intense, whereas the wall friction increases only insignificantly. The computed flow-dynamics and heat and mass transfer data are compared with previously reported experimental and numerical results, and a fairly good agreement between the compared data is obtained.

15

Support parameters optimization and engineering application of roadway with broken-expand surrounding rock in deep

70%

Yu W.-J. , Wu G.-S.

Mining Science

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2017

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tom Vol. 24

267--285

EN

Aiming at the deformation characteristics and the support problem of deep high stress broken-expand surrounding rock, the secondary support of the deep roadway engineering of Fenglong coal mine in Jiangxi Province, China, is carried out to optimize the parameters. First of all, according to the characteristics of deep roadway deformation in Fenglong coal mine, the specific support scheme was put forward on the basis of the original support, then, the secondary support parameters and the support time are designed. The softening strength parameters of the surrounding rock in the roadway are obtained by using the piecewise linear strain softening model and the dilatancy angle of the rock mass. Considering the strength effect of cable anchor, the calculation equation and support strength index ID concept of anchor cable are put forward, and the corrected calculation parameters of anchorage effect are given. Then, the numerical calculation is carried out for 16 schemes, meanwhile, the optimal scheme of the comprehensive evaluation index Es of roadway engineering stability is adopted. The influence of different anchoring effect on the stability of roadway and different secondary displacement value on the stability of roadway are analyzed respectively. Finally, the optimized support scheme is used to carry out the engineering practice, the results of monitoring the deformation of roadway by cross method show that the deformation value is within the controllable range, which can better control the roadway deformation.

16

Method of multivariate sample allocation in agricultural surveys

70%

Kozak M.

Colloquium Biometryczne

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2004

|

tom 34

17

Analysis of the dynamic response of offshore floating wind power platforms in waves

70%

Li J. , Xie Y. , Wu W. , Zhang C.

Polish Maritime Research

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2020

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tom nr 4

17--25

EN

Floating wind power platforms are in constant motion due to waves when deployed at sea. This motion directly affects the stability and safety of the platform. Therefore, it is very important to study the laws governing the platform’s dynamic response. In this paper, the dynamic characteristics of an offshore floating wind power platform were analysed under nine different sets of operating conditions using a numerical calculation method. Following this, a scaled 1:50 platform model was tested in a tank. Model tests were carried out with different wave conditions, and dynamic response data for the platform were measured and analysed. The hydrodynamic variation rules of floating wind power generation platform in waves were obtained. Some effective measures for maintain the stability and safety of wind power platforms are put forward that can provide a reference for dynamic stability research and the design of floating wind power platforms in the future.

18

Numeryczne obliczenia prądu włączania transformatora energetycznego

60%

Horiszny J.

Przegląd Elektrotechniczny

|

2004

|

tom R. 80, nr 10

909-912

PL

W artykule przedstawiono wyniki obliczeń numerycznych prądu włączania jednofazowego transformatora energetycznego, przeprowadzone przy użyciu programu symulacyjnego ATP. Model układu zrealizowano w postaci obwodowej. Uzyskane rezultaty potwierdziły zależność wartości szczytowej prądu włączania od takich czynników, jak wartość i kierunek strumienia szczątkowego w rdzeniu transformatora, faza napięcia zasilającego, przebieg charakterystyki magnesowania w obszarze nasycenia.

EN

The article shows numerical calculation results of a single phase transformer's inrush current. Circuital model of the system in ATP simulation program was created for this purpose. The results confirmed that the maximum value of inrush current depends upon the value and direction of residual flux in the transformer's core, phase of the voltage and the shape of current-flux characteristic in the saturation region.

19

Nowy sposób monitorowania ilości ścieków dopływających do oczyszczalni

60%

Łomotowski J. , Paluch-Puk M.

Gaz, Woda i Technika Sanitarna

|

2012

|

tom Nr 5

224-227

PL

Oryginalny sposób wyliczania szeregu czasowego dobowych zagregowanych sum minutowych objętości ścieków dopływających do oczyszczalni w oparciu o chwilowe pomiary ilości dopływających ścieków. Opracowana metoda jest prosta w zakresie obliczeń numerycznych a wygładzony szereg czasowy dobowych sum dopływu ścieków do oczyszczalni pozwala wyciągnąć informacje o stanie hydraulicznym systemu kanalizacyjnego, ilości wód deszczowych i przypadkowych przedostających się do sieci kanalizacyjnej i istnieniu oscylacji w dopływie ścieków do oczyszczalni o okresach dłuższych niż doba.

EN

The original method of calculation of the aggregated time series of daily sums of minute volume of wastewater flowing into wastewater treatment based on instantaneous measurements of the quantities of sewage. The method is simple for numerical calculations and smoothed time series of daily sums of sewage inflow to the sewage can draw information about the state of the hydraulic system of sewerage, storm water quantity and accidental entering the sewerage system and the existence of oscillations in the flow of sewage to the treatment periods longer than a day.

20

Danger of flashovers to electric equipment located on roofs of buildings struck by lightning

60%

Markowska R.

Przegląd Elektrotechniczny

|

2012

|

tom R. 88, nr 8

48-51

EN

Threats of flashovers to electrical equipment located on roofs of buildings struck by lightning and application of different methods for estimation of separation distances for protection of this equipment are analyzed and compared. Large, few-storey buildings with different external LPS (Lightning Protection Systems) are taken into considerations. The analyses are based on the results of numerical calculations, confronted with the results of approximate procedures proposed in the European and international standards on lightning protection EN/IEC 62305-3.

PL

Analizowane są zagrożenia przeskokami iskrowymi do urządzeń i instalacji elektrycznych na dachach obiektów budowlanych trafionych przez wyładowania piorunowe oraz różne metody szacowania odstępów izolacyjnych w celu ochrony tych urządzeń. Analizy bazują na wynikach obliczeń numerycznych oraz zaleceniach europejskich i międzynarodowych normach ochrony odgromowej EN/IEC 62305-3.