Wyniki wyszukiwania - Biblioteka Nauki

1

Evaluation of expansivity of Neogene clays and glacial tills from central Poland on the basis of suction tests

100%

Izdebska-Mucha D. , Wójcik E.

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2015

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tom Vol. 59, No. 3

593--602

EN

This paper presents the characteristics of the expansivity and quantitative prediction of heave of clay soils from Poland based on suction testing. 11 Neogene clays and 6 glacial tills, differing in genesis and plasticity, were analyzed to identify the expansive potential using eight empirical methods. The laboratory studies included measurements of soil-water characteristic curves and soil index properties. Data from water content, volume and suction measurements served to determine the suction compression index Ch and the suction-water content index Dh/Dw of the soils examined. The values of these indices are clearly dependent of the clay fraction content in tested soils. Compared with glacial tills, Neogene clays are expected to exhibit larger changes in volume due to changes in soil suction. Comparative results of the evaluation of expansivity suggest that the chosen classification methodologies provided consistent expansion ratings for glacial tills, while values for Neogene clays vary from low to very high. The lowest expansivity classes have been obtained from evaluation based on soil suction. The McKeen (1992) method has been adopted for calculations of the potential field heave of Neogene clays and glacial tills. In order to provide a rational estimation of expansive soil behavior, specialists should take into consideration the specific site and design features.

2

Effect of suction on the mechanical behaviour of unsaturated compacted clay-sand mixtures

100%

Bouchemella S. , Taibi S.

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2022

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tom Vol. 44, nr 3

175--189

EN

In this work, a series of unconfined compression tests at different water contents were performed to investigate the mechanical behaviour of clay–sand mixtures compacted in standard Proctor conditions. For studying the effect of water content and suction on unconfined compressive strength (UCS) and on strain secant modulus (E50 modulus) of these mixtures, drying–wetting paths were defined by measuring the soil–water characteristic curves (SWCCs) using osmotic and salt solution techniques and filter paper method. The results highlighted that an increase in sand content of the mixture leads to an increase in the maximum dry densities and a decrease in the optimum water content of the materials. However, at the given state, when clay is mixed with 25% of sand, the UCS and E50 modulus increase to 37% and 70%, respectively, compared to those of clayey samples. But when clay is mixed with 50% of sand, the UCS and E50 modulus decrease to 38% and 46%, respectively, compared to those of clayey samples. The results also indicate that the UCS and E50 increase with a decrease in the water content and an increase in suction, irrespective of the sand content.

3

Sprężysto-plastyczny model nienawodnionego ośrodka gruntowego

84%

Fedczuk P.

|

2007

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tom z. 111

141-148

PL

W pracy prezentuje się koncepcję modelu częściowo nawodnionego ośrodka gruntowego, uwzględniającego zjawisko ssania. Sprężysto-plastyczne zachowanie ośrodka, zdefiniowane w ramach teorii stanu krytycznego [l, 2] w formie rozwiniętej, opisuje rozszerzone przyrostowe równanie konstytutywne [3] (w postaci "naprężenie netto - odkształcenie i ssanie"). Model operuje równaniem powierzchni plastyczności sformułowanym przez Whelera i Shivakumara [4]. Prawo wzmocnienia (ograniczone do wariantu dla niezmiennej wartości ssania) wiąże przyrost plastycznej części wskaźnika porowatości z poziomem naprężenia i ssania.

EN

The paper presents the concept of soil medium model with partially saturation, taking into consideration the suction effect. Elasto-plastic behavior of medium, defined by critical state theory [l, 2] in extension form, has been described by extended incremental constitutive relation [3] (in form "net stress - strain and suction" relationship). The model operates equation of plastic surface formulated by Wheeler and Shivakumar [4]. Hardening rule (restricted to variant for constant value of suction) connects the increment of plastic part of void ratio with stress and suction levels.

4

Three dimensional MHD free convection flow and heat transfer through a vertical channel

84%

Guria M. , Ghara N. , Jana R. N.

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tom Vol. 15, no 4

1047-1063

EN

An analysis is made on the three dimensional MHD flow of a viscous incompressible fluid through a vertical channel in the presence of a uniform injection on the right plate and the left plate is subject to a periodic suction. The velocity and temperature fields are derived using the perturbation technique. It is observed that the primary velocity increases near the left plate and decreases near the right plate with an increase in the Reynolds number while it decreases with an increase in the magnetic parameter. It is seen that with an increase in the Prandtl number the primary velocity decreases whereas it increases with an increase in the Grashof number. It is seen that the magnitude of the secondary velocity increases in the range […] and thereafter decreases with an increase in the Reynolds number. It is also seen that the shear stress due to primary flow increases with an increase in either the Grashof number or Reynolds number but decreases with an increase in the Prandtl number. It is seen that the shear stress […] at the plate […] decreases with an increase in the magnetic parameter. Also, the magnitude of the shear stress due to cross flow increases with an increase in the Reynolds number. It is seen that the temperature at any point decreases with an increase in either the Prandtl number or Reynolds number. The rate of heat transfer in terms of the Nusselt number is also studied. Dimensional variables are indicated by dropping the asterisk and are defined in Eq.(2.8).

5

Radiation effect on three dimensional vertical channel flow

84%

Guria M. , Ghara N. , Jana R. N.

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tom Vol. 15, no 4

1065-1081

EN

An analysis is made of the three dimensional flow of viscous incompressible fluid through a vertical channel in the presence of a uniform injection on the right plate and a periodic suction velocity distribution on the left plate with radiation effect. The velocity and temperature fields are derived using the perturbation technique. It is found that the primary velocity decreases with an increase in the radiation parameter. It is seen that the shear stress due to primary flow increases with an increase in the Reynolds number but decreases with an increase in the radiation parameter. It is also seen that the temperature decreases with an increase in the radiation parameter. The rate of heat transfer in terms of the Nusselt number is also studied.

6

Heat transfer in oscillating flow through porous medium with dissipative heat

84%

Guria M.

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tom Vol. 27, no. 2

77--86

EN

In this paper, heat transfer in flow between two horizontal parallel porous plates through a porous medium when the upper plate oscillates in its own plane has been analyzed taking into account the effect of viscous dissipation. An increment in the Prandtl number or Reynolds number results in an increment of the temperature profile. With an increase in viscous dissipative heat the temperature distribution decreases.

7

Mechanism of biochar soil pore-gas-water interaction: gas properties of biochar-amended sandy soil at diferent degrees of compaction using KNN modeling

84%

Garg A. , Huang H. , Kushvaha V. , Madhushri P. , Kamchoom V. , Wani I. , Koshy N. , Zhu H.-H.

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tom Vol. 68, no. 1

207--217

EN

Soil compaction has contrasting efect on soil strength (i.e., positive) and vegetation growth (i.e., negative), respectively. Biochar has been utilized mostly in combination with soils in both agricultural felds (i.e., loose soils) and geo-structures (i.e., dense soil slopes, landfll cover) for improving water retention due to its microporous structure. Biochar is also found to be useful to reduce gas permeability in compacted soil recently. However, the efciency of biochar in reducing gas permeability in loose and dense soils is rarely understood. The objective of this study is to analyze efects of compaction on gas permeability in soil at diferent degrees of compaction (i.e., 65%, 80% and 95%) and also diferent biochar amendment contents (0%, 5% and 10%). Another aim is to identify relative signifcance of parameters (soil suction, water content, biochar content and compaction) in afecting gas permeability. Experiments were conducted before applying k-nearest neighbor (KNN) modeling technique for identifying relative signifcance of parameters. Biochar was synthesized from a coastal invasive species (water hyacinth), which has relatively no infuence on food chain (as unlike in biochar produced from biomass such as rice husk, straw, peanut shell). Based on measurements and KNN modeling, it was found that gas permeability of biochar-amended soil is relatively lower than that of soil without amendment. It was found from KNN model that for denser soils, higher amount of soil suction is mobilized for a signifcant increase in gas permeability as compared to loose soils. Among all parameters, soil suction is found to be most infuential in afecting gas permeability followed by water content and compaction.

8

Three-dimensional oscillating flow between two parallel plates through a porous medium

84%

Guria M. , Ghara N. , Jana R. N.

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tom Vol. 18, no. 4

1025--1037

EN

An unsteady Couette flow between two parallel plates when upper plates oscillates in its own plane and is subjected to a constant suction and the lower plate to a injection velocity distribution through the porous medium has been analyzed. The approximate solution has been obtained using perturbation technique. It is seen that the primary velocity increases whereas the secondary velocity decreases with an increase in permeability parameter. It is also found that the primary velocity increases with an increase in the Reynolds number as well as the suction parameter. The magnitude of the secondary velocity increases near the stationary plate but decreases near the oscillating plate with an increase in the Reynolds number. Whereas, it increases with an increase in the suction parameter.

9

Bidirectionally stretched flow of Jeffrey liquid with nanoparticles, Rosseland radiation and variable thermal conductivity

84%

Archana M. , Gireesha B. J. , Rashidi M. M. , Prasannakumara B. C. , Gorla R. S. R.

Archives of Thermodynamics

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2018

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tom Vol. 39, no 4

33–-57

EN

Heat and mass transfer stretched flow of an incompressible, electrically conducting Jeffrey fluid has been studied numerically. Nanoparticles are suspended in the base fluid and it has many applications such as cooling of engines, thermal absorption systems, lubricants fuel cell, nanodrug delivery system and so on. Temperature dependent variable thermal conductivity with Rosseland approximation is taken into account and suction effect is employed in the boundary conditions. The governing partial differential equations are first transformed into set of ordinary differential equations using selected similarity transformations, which are then solved numerically using Runge-Kutta-Felhberg fourth-fifth order method along with shooting technique. The flow, heat and mass transfer characteristics with local Nusselt number for various physical parameters are presented graphically and a detailed discussion regarding the effect of flow parameters on velocity and temperature profiles are provided. It is found that, increase of variable thermal conductivity, radiation, Brownian motion and thermophoresis parameter increases the rate of heat transfer. Local Nusselt number has been computed for various parameters and it is observed that, in the presence of variable thermal conductivity and Rosseland approximation, heat transfer characteristics are higher as compared to the constant thermal conductivity and linear thermal radiation.

10

Radiation absorption and chemical reaction effects on Rivlin-Ericksen flow past a vertical moving porous plate

84%

Sravanthi C. S. , Gorla R. S. R.

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tom Vol. 24, no. 3

675--689

EN

An analysis has been carried out to study the combined effects of radiation absorption and chemical reaction on an incompressible, electrically conducting and radiating flow of a Rivlin-Ericksen fluid along a semi-infinite vertical permeable moving plate in the presence of a transverse applied magnetic field. It is assumed that the suction velocity, the temperature and the concentration at the wall are exponentially varying with time. The dimensionless governing equations for this investigation are solved analytically using two-term harmonic and non-harmonic functions. A comparison is made with the available results in the literature for a special case and our results are in very good agreement with the known results. A parametric study of the physical parameters is made and results are presented through graphs and tables. The results indicate that the fluid velocity and temperature could be controlled by varying the radiation absorption.

11

Sprężysto-plastyczny model gruntu nienawodnionego

67%

Fedczuk P.

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tom R. 72, nr 11

595--597

PL

Przedstawiono koncepcję sprężysto-plastycznego modelu częściowo nawodnionego gruntu. Model jest oparty na zmodyfikowanym równaniu powierzchni plastyczności Wheelera i Shivakumara. W przypadku zmiennej wartości ssania uogólnione prawo wzmocnienia wiąże przyrost plastycznej części wskaźnika porowatości z poziomem efektywnego naprężenia i ssania.

EN

The paper presents the concept of elasto-plastic model for partially saturated soil. The model operates equation of Wheeler and Shivakumar’s plastic surface. Generalized hardening rule, for changing value of suction, connects the increment of plastic part of void ratio with stress and suction levels.

12

Badania wstępne wpływu odsysania mieszaniny parowo-powietrznej na efektywność wymiany ciepła między chłodziwem a podgrzewaną powierzchnią

67%

Sobczak M. , Zapałowicz Z.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

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2014

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tom z. 86 [290], nr 2

249--256

PL

W pracy przedstawiono budowę stanowiska badawczego, metodykę pomiarów i obliczeń oraz wstępne wyniki badań doświadczalnych chłodzenia podgrzewanej powierzchni strugami wody. Celem pracy jest wstępna analiza wpływu procesu odsysania mieszaniny parowo-powietrznej na intensywność procesu odparowania filmu wodnego. Nagrzana powierzchnia chłodzona jest trzema strugami wody wytwarzanymi w zakraplaczach zamontowanych w płytce i ustawionych w wierzchołkach trójkąta równobocznego. Natężenie przepływu wody jest ustalone. W środku tego trójkąta umieszczono sondę połączoną z pompą próżniową, zadaniem której jest usunięcie powstałej nad powierzchnią filmu pary wodnej i otaczającego układ powietrza atmosferycznego. Strugi wody chłodzą powierzchnię roboczą grzejnika wykonanego z bloku miedzianego o wymiarach 0,04×0,04×0,02 m. Eksperyment przeprowadzono dla temperatury podgrzewanej powierzchni zmieniającej się w zakresie od 50÷100°C. Na podstawie analizy uzyskanych wstępnych wyników badań oszacowano, że odsysanie mieszaniny parowo-powietrznej z nad warstwy filmu cieczowego zwiększa się intensywność odparowania chłodziwa (wody) o około 25÷50%.

EN

The paper presents test stand structure, measurement and calculation methodology and initial results of investigation of preheated surface cooling by water stream The aim of this article is preliminary analysis of influence of steam-air mixture evacuation on the intensity of water film evaporation. The hot surface is cooling by three streams of water. Streams are produced in droppers mounted in plate and located in the vertices of a equilateral triangle. The water flow rate is stationary. In the center of triangle is mounted the probe connected to a vacuum pump that is used for evacuation of steam-air mixture from above the hot surface and atmospheric air surrounding the system. Streams of water cooling the heater surface made of cooper block with the dimensions: 0.04×0.04×0.02 m). The surface temperature of block is changed in the range from 50°C to 100°C. Based on the results of preliminary investigations itwas stated that the suction of steam-air mixture from above the liquid film layer enhancement the water film evaporation about 25÷50%.

13

Analiza wplywu strumienia masy cieczy oraz obciazenia rurociagu mlecznego na wartosc sredniego podcisnienia ssania w kubku udojowym dojarki rurociagowej

67%

Skalska D. , Szlachta J. , Luberanski A.

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nr 1

75-87

14

Wpływ odsysania mieszaniny parowo-powietrznej na efektywność procesu chłodzenia strumieniem kropel

67%

Sobczak M. , Zapałowicz Z.

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tom z. 88 [293], nr 1

55--64

PL

W pracy przedstawiono budowę stanowiska badawczego, metodykę pomiarów i obliczeń oraz wstępne wyniki badań doświadczalnych procesu chłodzenia podgrzewanej powierzchni strumieniem kropel wody, gdy powstająca mieszanina parowo-powietrzna jest odsysana z zamkniętej przestrzeni otaczającej grzejnik. Badania przeprowadzono dla trzech wariantów procesu chłodzenia grzejnika tj. przy zastosowaniu bocznego odsysania powstającej mieszaniny przestrzeni nad ogrzewaną powierzchnią, przy odsysaniu tej mieszaniny z wnętrza tej przestrzeni oraz w warunkach, gdy mieszanina powietrzno-parowa nie jest odsysana. Celem pracy jest analiza wpływu miejsca odsysania mieszaniny parowo-powietrznej oraz czasu na intensywność procesu odparowania filmu wodnego. Eksperyment przeprowadzono dla temperatury podgrzewanej powierzchni wynoszącej 90°C. Na podstawie analizy wstępnych wyników badań doświadczalnych oszacowano, że odsysanie mieszaniny parowo-powietrznej z wnętrza przestrzeni zwiększa intensywność odparowania chłodziwa (wody) o około 5÷30%, gdy czas chłodzenia wzrasta trzykrotnie. Zmiana miejsca odsysania mieszaniny parowo-powietrznej nie zmienia istotnie intensywności odparowania filmu wodnego.

EN

The paper presents test stand, research methodology and preliminary results of an experimental cooling of hot surface by stream of water droplets when the resulting steam-air mixture is sucked - off from the confined space surrounding the heater. Experiments were carried out for three cases of cooling process. In the first case steam-air mixture was sucked off from the confined space over heated surface through the outlet at the lateral surface of glass cover, in the second case mixture was sucked off from the center of the confined space over the hot surface and in the third case mixture in question was not sucked off. The vacuum pump was used for suction of steam-air mixture. The paper is aimed at analysis of effect location of steam-air suction point and time on intensity of water film evaporation. The temperature of the heating plate surface during experiments of 90°C. Based on preliminary analysis of the experimental results it was estimated that suction of vapor – air mixture from the interior of the confined space increases the intensity of cooling fluid (water) evaporation of approximately 5-30%, when the cooling time is increased threefold. Change in location of vapor-air suction mixture point enables to increase the intensity of water film evaporation is too high.

15

Problems of dust removal from multi-cyclones of engine air cleaners in cross-country motor vehicles

67%

Dziubak T.

Archiwum Motoryzacji

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2017

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tom Vol. 76, nr 2

37--62

EN

The organization of the process of extracting dust (by suction) from inertial intake air cleaners of internal combustion (IC) engines of motor vehicles has been discussed. The ejector configurations used in the dust removal systems have been demonstrated. Examples of contaminant extraction systems based on the ejection effect have been presented. The notion of dust suction ratio has been defined. The impact of this ratio on the filter restriction and air filtration efficiency characteristics of individual cyclones has been analysed. The impact of the dust extraction from the dust settling chamber of an inertial air cleaner (multi-cyclone) on the filtration efficiency has been explained. The impact of the dust extraction from the dust settling chamber on the unevenness of dust suction from individual cyclones of a multi-cyclone has been analysed and the reasons for the unevenness have been shown. The analysis results visualizing the impact of the unevenness of suction on the filtration efficiency of a multi-cyclone combined with a nonwoven fabric filter element have been quoted. The methods aimed at the obtaining of relatively even flow rates of the streams sucked off from individual cyclones have been analysed. It has been shown that even flow rates of the suction streams flowing out from individual cyclones can be obtained by appropriately modifying the structure of the multi-cyclone’s dust settling chamber.

PL

Omówiono organizację procesu odsysania pyłu z bezwładnościowych filtrów powietrza wlotowego silników spalinowych pojazdów mechanicznych. Przedstawiono stosowane konfiguracje ejektorów w układach odsysania pyłu. Omówiono przykłady układów ejekcyjnego odsysania zanieczyszczeń. Zdefiniowano stopień odsysania pyłu. Przeanalizowano jego wpływ na charakterystykę przepływową i skuteczności filtracji powietrza pojedynczych cyklonów. Wyjaśniono zjawisko wpływu odsysania pyłu z osadnika filtru bezwładnościowego (multicyklonu) na skuteczność filtracji. Przeanalizowano wpływ odsysania pyłu z osadnika na nierównomierność odsysania z pojedynczych cyklonów multicyklonu oraz pokazano przyczyny nierównomierności. Przytoczono wyniki obrazujące wpływ nierównomierności odsysania na skuteczność filtracji multicyklonu i wkładu włókninowego. Przeanalizowano metody prowadzące do uzyskania względnej równomierności strumieni odsysanych z pojedynczych cyklonów. Wykazano, że równomierne wartości strumieni odsysania z pojedynczych cyklonów można uzyskać poprzez odpowiednią zmianę struktury osadnika pyłu multicyklonu.