Interphase Interaction Research Articles

Effect of vibration on structure and properties of polymeric membranes

The effect of structural memory in a wave field has been exemplarily studied by the IR-spectroscopy method on films made from mixtures of butadiene-styrene and acrylic latex as models of polymeric membranes. The strengthening of the interphase interaction in heterophase systems that can cause change of their local and transmitting mobility has been observed. It has been shown, that the response of polymeric dispersed systems and compositions on influence of nonlinear vibrations proves their influence on deformation properties, like orientation phenomena in solid polymers (where Rebinder's effect can take place) that it is possible to consider as a way of polymer modifications, including the obtaining of nanocomposites, polymeric biocarriers, etc.

Characteristics of nucleate boiling under conditions of pulsed heat release at the heater surface

This paper presents results of the experimental study for the initial stage of the explosive boiling, as well as an attempt to simulate them in order to clarify whether the existing approaches can be extended to the case of the non-stationary heat release. We present data on the onset of nucleate boiling (ONB) and nucleation density for pulsed heat release in the range from 0.56 to 2 MW/m2. To determine the dynamics of the temperature field under conditions of non-stationary nucleation, a numerical algorithm was implemented, which includes the calculation of the heat fluxes associated with the interphase interaction in the bubble neighborhood. It was shown that for the non-stationary case the previously developed approaches can be applied to numerically predict nucleate boiling characteristics using the Fourier number.

Nanoprticles of metals and their inorganic compounds obtained through interphase and redox-transmetalation interaction: application in medicine and pharmacology

Synthesis of nanoparticles of metals and their compounds with given morphology and dispersity for use in medicine, pharmacology, microelectronics, as well as subsequent research of their properties, is one of the current problems in the field of preparative inorganic chemistry. Interphase synthesis and redox-transmetalation reduction are as promising as the traditional precipitation from aqueous solutions, but not as researched. This study presents the results of a physicochemical analysis of nanoparticles of metals and their compounds obtained through chemical precipitation from aqueous solutions, interphase and redox-transmetalation interaction. Data describing the influence of phase composition and dispersity of copper and copper oxide (II) nanoparticles on their antimicrobial properties, as well as the results of researching the possibility to use magnetite magnetic fluids for mesenchymal stem cells marking, illustrate the application options synthe-sized nanoparticles find in pharmacology and medicine.

Nanoprticles of metals and their inorganic compounds obtained through interphase and redox-transmetalation interaction: application in medicine and pharmacology

Одной из актуальных проблем современной препаративной неорганической химии являются получение и исследование наночастиц металлов и их соединений с заданными морфологией и дисперсностью для использования в медицине, фармакологии, микроэлектронике. Наряду с традиционным осаждением из водных растворов перспективны, но менее изучены межфазный синтез и контактное восстановление. В работе представлены результаты физико-химического исследования наночастиц металлов и их соединений, полученных химическим осаждением из водных растворов, межфазным и контактным взаимодействием. Для иллюстрации использования синтезированных наночастиц в фармакологии и медицине приведены данные по влиянию фазового состава и дисперсности наночастиц меди и оксида меди (II) на их противомикробные свойства и результаты исследования возможности применения магнетитовых магнитных жидкостей для маркирования мезенхимальных стволовых клеток.

Dependence of the Osmotic Pressure and Electrical Conductivity of Soil Solutions on the Soil Water Content

The osmotic pressure and electrical conductivity were determined with the use of instrumental methods (centrifuging, conductometry, and cryoscopy) in equilibrium soil solutions as the functions of moisture (the mass ratio between solid and liquid phases) for the soils of different geneses and textures. These functions proved to have a nonlinear character with one extremum. A theoretical substantiation to this phenomenon is suggested. It is based on the concept of competing interphase interactions in soil and develops the classical ideas by A.A. Rode. Upon the low soil water content, surface (molecular and ion-electrostatic) forces of the solid phase bind water molecules and prevent them from hydrating ions and dissolving electrolyte salts in the soil solution; as a result, electrical conductivity and osmotic pressure values approach zero in this case. With an increase in the water content, water molecules escape gradually from the energy field of surface forces, and their activity (chemical potential) and dissolving capacity also increase. This results in the expected growth of the electrical conductivity and osmotic pressure of the equilibrium solution extracted from the soil. The maximum values of the studied parameters are observed at the water content approximately equal to the maximum molecular water capacity (or to the boundary zone, within which capillary gravitational forces influencing the soil liquid phase become prevailing over the surface interphase interaction forces). The further increase in the soil water content lowers the electrical conductivity and osmotic pressure of equilibrium solution because of dilution of the fixed mass of electrolyte salts. For quantitative description of the revealed functional dependence, we suggest an empirical mathematical model in the form of modified equation of lognormal distribution.

Numerical study on liquid-solid flow characteristics in inverse circulating fluidized beds

The flow behavior of particles in inverse liquid-solid circulating fluidized beds was simulated using the Eulerian-Eulerian approach incorporating the kinetic theory of granular flow. The Syamlal-O’Brien drag model was used to account for the interphase interaction between the liquid and solids phases. A detailed description of the model equations used in this work has been presented. Predicted results were compared with the experimental data obtained by other group members. A good agreement between the numerical simulations and experimental results has been achieved. The inverse flow characteristics of particles were studied using a single type of particles and multiple types of particles with different densities under different liquid velocities and solids flow rates. The results indicated that for the particles with different densities, 950 kg/m3, 850 kg/m3 and 640 kg/m3, the cross-sectional average solids holdup along the axis was uniform and the radial flow structures at different bed heights were identical. Particles moved from the walls to the center at the top region of the bed. Such tendency diminished as the particles move downwards. The axial velocities of solid particles were higher in the center and lower near the walls. For the particles with a density of 28 kg/m3, due to the randomly generated vortexes of particles, the solids holdup radial distributions and the velocities of particles were more irregular. For the mixed particles with two different densities of 850 kg/m3 and 950 kg/m3, the trend of solids holdup radial distribution, and the trend of the lateral and axial velocities of each particle group were similar to those in the simulation using the single-density particles.

Comparison of liquid-solid flow characteristics in upward and downward circulating fluidized beds by CFD approach

The flow behaviors of the particles in the upward and downward liquid-solid circulating fluidized beds were simulated by Eulerian-Eulerian approach incorporating the kinetic theory of granular flow. The Syamlal-O’Brien drag model was used to account for the interphase interaction between the liquid and solids phases. The numerical results agreed well with the experimental data obtained by other group members, successfully validating the numerical approach. The hydrodynamic characteristics of the particles with different densities and sizes in the upward and downward circulating fluidized beds were compared in detail under different liquid velocities and solids flow rates. The results indicated that there were many hydrodynamic similarities in the upward and downward circulating fluidized beds. However, due to the deviation of the standard drag curve, the drag force on the lighter particles in the downward liquid-solid circulating fluidized bed became different, leading to random and irregular particle flow behaviors. The predicted average solids holdups matched well with the results by an empirical model proposed by Sang and Zhu and the matching degree between the numerical results and the model was larger than 85%, further proving that the Sang and Zhu model is widely applicable.

Sexual Behavior of the Desert Locust During Intra- and Inter-Phase Interactions

Mating and reproduction behaviors and strategies are fundamental aspects of an organism’s evolutionary and ecological success. In locusts, intra- as well as inter-phase reproductive interactions among gregarious and solitarious locust populations have a major impact on the locust population dynamics. However, practically all previous work on locust sexual behavior has been limited to the gregarious phase. Here we provide a first detailed description of pre-copulatory behavior of solitarious desert locusts. We compare our findings with those of previous reports of pre-copulatory behavior of gregarious locusts, focusing on the behavioral elements that serve in inter-sex signaling and communication. We also studied inter-phase (mixed pairs) reproductive interactions. Solitarious males were found to invest more in pre-copulatory courtship and signaling compared to their gregarious counterparts; and solitarious females played a more dominant role in the inter-sex communication than gregarious females. The solitarious females were also less likely to demonstrate rejection-related behavioral patterns than gregarious females. As a consequence of the particular characteristic behavior of each phase, the most successful among intra- and inter-phase pairs were gregarious males with solitary females. Least successful were solitary males paired with gregarious females, indicating a strong asymmetry in inter-phase reproductive interactions.

On the interphase and intra-phase interaction of particles and gas in a layer of granular materials behind shock wave

The work is devoted to the analysis of physical mechanisms of lifting a layer of granular material in the flow behind shock wave. Based on experimental data physical processes are considered behind a shock wave traveling above a dust layer, leading to its rise: the escape of single particles from the layer and the formation of an intermediate layer or fluidized bed between a dense layer and a suspension, the collision of particles in the fluidized bed and its ascent, the influence of a dense suspension on the flow behind the shock wave, and the effect of unsteady flow on the rise of the layer. A physical model of the process is proposed that allows predicting the rate and height of the rise of a layer of granular material at an early stage of interaction with the flow behind incident shock wave.

Generalized stress framework for unsaturated soil: demonstration and discussion

The long-lived debate on the principle of effective stress is rooted in the obscure physical significance of stresses. For the sakes of clarifying stress concepts and establishing a reasonable principle of effective stress, unsaturated soil is divided into six phases and the bearing structure of it, named generalized soil structure, is defined based on considering soil as a special structure. Then the essence of effective stress equation, named stress relation equation, is derived according to analysis of interphase interactions and independent-phase equilibrium. The stress relation equation indicates the corresponding relation between two series of stress variables used in mixed and multiphase continuum models, respectively. Furthermore, a reasonable concept of suction stress is redefined to describe interparticle connection properties. Then, a generalized stress framework is constructed by associating stress relation equation with suction stress. After demonstrating the concept of neutral stress, a generalized principle of effective stress is established and the total soil skeleton stress is searched out, which is the predominant stress controlling the strength and deformation of soil. Finally, the collapse phenomenon is analyzed and the time- and spatial-dependent stress frameworks are developed.

Numerical study of pebble recirculation in a two-dimensional pebble bed of stationary atmosphere using LB-IB-DEM coupled method

The pebble bed is one type of the core of the high temperature gas-cooled reactor (HTGR), which is regarded as the candidate of the generation IV advanced reactor. It is important to explore the gas-pebble flow characteristics and the pebble recirculation under the helium atmosphere. In this work, we presented a lattice Boltzmann (LB) method – immersed boundary (IB) method – discrete element method (DEM) coupled approach to simulate a test facility of pebble bed under the recirculation mode of operation. After model validation by an experiment of sphere sedimentation, the process of pebble recirculated at five constant rates are simulated. The correlations of gas motion and pebble motion in the upper and lower half beds are analyzed to uncover the inter-phase relationships for such intermittent pebble flows. Based on the systematic analyses of the two-phase flows, including the mean field and r.m.s field, the historical variation, inter-correlation, and the spectrum and phase space representations, we found sufficient evidences for the characteristics of intermittency, simultaneity, periodicity, and linear dependence for the inter-phase interaction of gas-pebble flows.

Determination of choking in the EMMS model

This paper investigates the relationship between the two choking criteria in the energy minimization multi-scale (EMMS) model. An improved GPU solver for the EMMS model is used to facilitate the related calculation. Both choking criteria agree well with the experiments in literature, and the predictions are almost identical to each other. The study confirms that both criteria define the critical conditions in terms of the breakdown of the fully heterogeneous structures. This structural change is due to the enhanced inter-phase interaction with increasing gas velocities at given solid flow rate. According to the numerical calculation, the solution space and the clustering constraint are visualized to consolidate the impact of structural changes on choking.

Research of inter-phase interaction in ZOL-silicate paints

It was suggested to use polysilicate solutions obtained by mixing liquid glass and silicic acid sol as a binder in the manufacture of sili- cate paints. Information is provided on the mechanism for increasing the operational properties of coatings based on sol silicate paint. It has been revealed that polysilicate solutions form membranes characterized by higher tensile strength due to an increase in the fraction of high-polymer fractions of silicic anions in the structure of the polysilicate binder in comparison with liquid glass. The results of a study on the interphase interaction between the pigment and the film-forming agent are given. It is shown that potassium polysilicate solutions form a smaller contact angle on the surface of the pigment (filler) and are characterized by greater work of wetting and adhesion to the filler (pigment).

On the effects of landslide deformability and initial submergence on landslide-generated waves

This paper represents a numerical study on the effects of landslide initial submergence and its geotechnical and rheological properties on the characteristics of landslide-generated waves (LGWs) and landslide deformation. A number of 117 numerical experiments are performed using a two-layer Coulomb Mixture Flow (2LCMFlow) model on a real-sized numerical flume as a simplified cross section of the Maku dam reservoir, located in the Northwest of Iran. Three different initial locations are considered for landslide representing a subaerial (SAL), a semi-submerged (SSL), and a submarine (SML) landslide. Based on the numerical results, the majority of SMLs and in some cases SSLs generate tsunami waves with a larger wave trough than the wave crest. The maximum negative wave amplitudes of LGWs caused by SMLs (SMLGWs) can be up to 55% larger than that for SALs. LGWs caused by SALs (SALGWs) commonly have a higher wave crest than the wave trough. In 70% of cases, the maximum wave crests of SALGWs are larger than that for LGWs caused by SSLs (SSLGWs) and SMLGWs. While, in the rest 30% of simulations, the maximum SSLGW crests are up to 60% larger than SALGWs. Due to the landslide inter-phase interactions in combination with its basal and internal friction resistances, only 10–40% of the SAL initial mass contributes in LGW generation process. Energy transfer from landslide into water is about 0.5–7.5% for SMLs, 6–17.2% for SSLs, and 5–15% for SALs. The final deposit of SMLs generally has a short and thick profile while SALs and SSLs elongate more and travel longer distances. Finally, a Coulomb mixture product parameter, PCM, is defined to relate the maximum LGW heights to the considered landslide properties.

BLENDS OF ALIPHATIC POLYAMIDES WITH FUNCTIONALIZED POLYOLEFINS: INTERPHASE INTERACTIONS, FEATURES OF THE RHEOLOGICAL BEHAVIOR OF MELTS, STRUCTURE AND MECHANICAL PROPERTIES

The effect of addition of functionalized polyolefins (fPO) in an amount of 28 wt. % – mixtures of polyethylene and copolymer of ethylene with higher olefin containing 0.43 and 0.77 wt. % grafted monomer having two carboxyl groups in its composition – to aliphatic polyamides PA6 and PA66 on the structural features, the rheological behavior of melts and the mechanical properties of mixed materials was investigated. The materials studied were prepared by reactive mixing of the components in a melt in an extrusion reactor. It is shown that mixtures of PA66/fPO are characterized by more significant changes in the characteristics under analysis compared with those based on PA6 when the concentration of a grafted monomer is varied. An abnormally sharp increase (by more than two decimal orders) of the melt viscosity of a mixture of PA66 with fPO containing 0.77 wt. % of the grafted monomer, compared with the viscosity of initial PA66, is due to the specificity of the interphase interactions in the mixtures.

Development of a mathematical model for submarine granular flows

An Eulerian-Eulerian two-phase model based on a collisional-frictional law for the granular stress is proposed for the description of underwater granular flows and is applied to the collapses of immersed granular columns, which can be viewed as an idealized physical model of submarine landslides. In the mathematical model, the kinetic theory for dry granular flows is extended to take into account the particle-fluid interaction when formulating the collisional stress in the granular material, while the frictional stress is modeled based on an existing relation obtained by statistically averaging the individual contact forces among cohesionless particles. The drag force and the virtual-mass force are considered to represent the inter-phase interaction. The two-phase model is then employed to simulate the laboratory experiments of the collapses of granular columns immersed in an ambient liquid with an emphasis on the effect of the initial packing condition of the granular particles. It has been shown that the computed collapsing process of granular columns is in very good agreement with the experimental observations, and the proposed model can well capture the dynamic features of underwater granular flows. The effects of fluid pressure, drag force, and particle and fluid properties on the granular collapse are also discussed. It is demonstrated that the interstitial fluid flow plays a significant role in the collapsing process.

Suspensions of finite-size neutrally buoyant spheres in turbulent duct flow

We study the turbulent square duct flow of dense suspensions of neutrally buoyant spherical particles. Direct numerical simulations (DNS) are performed in the range of volume fractions $\unicode[STIX]{x1D719}=0{-}0.2$, using the immersed boundary method (IBM) to account for the dispersed phase. Based on the hydraulic diameter a Reynolds number of 5600 is considered. We observe that for $\unicode[STIX]{x1D719}=0.05$ and 0.1, particles preferentially accumulate on the corner bisectors, close to the corners, as also observed for laminar square duct flows of the same duct-to-particle size ratio. At the highest volume fraction, particles preferentially accumulate in the core region. For plane channel flows, in the absence of lateral confinement, particles are found instead to be uniformly distributed across the channel. The intensity of the cross-stream secondary flows increases (with respect to the unladen case) with the volume fraction up to $\unicode[STIX]{x1D719}=0.1$, as a consequence of the high concentration of particles along the corner bisector. For $\unicode[STIX]{x1D719}=0.2$ the turbulence activity is reduced and the intensity of the secondary flows reduces to below that of the unladen case. The friction Reynolds number increases with $\unicode[STIX]{x1D719}$ in dilute conditions, as observed for channel flows. However, for $\unicode[STIX]{x1D719}=0.2$ the mean friction Reynolds number is similar to that for $\unicode[STIX]{x1D719}=0.1$. By performing the turbulent kinetic energy budget, we see that the turbulence production is enhanced up to $\unicode[STIX]{x1D719}=0.1$, while for $\unicode[STIX]{x1D719}=0.2$ the production decreases below the values for $\unicode[STIX]{x1D719}=0.05$. On the other hand, the dissipation and the transport monotonically increase with $\unicode[STIX]{x1D719}$. The interphase interaction term also contributes positively to the turbulent kinetic energy budget and increases monotonically with $\unicode[STIX]{x1D719}$, in a similar way as the mean transport. Finally, we show that particles move on average faster than the fluid. However, there are regions close to the walls and at the corners where they lag behind it. In particular, for $\unicode[STIX]{x1D719}=0.05,0.1$, the slip velocity distribution at the corner bisectors seems correlated to the locations of maximum concentration: the concentration is higher where the slip velocity vanishes. The wall-normal hydrodynamic and collision forces acting on the particles push them away from the corners. The combination of these forces vanishes around the locations of maximum concentration. The total mean forces are generally low along the corner bisectors and at the core, also explaining the concentration distribution for $\unicode[STIX]{x1D719}=0.2$.

Numerical simulation of flow behavior of particles in a gas-solid stirred fluidized bed

Flow behavior of particles is simulated by means of two-fluid model combining with kinetic theory of granular flow in a gas-solid stirred fluidized bed with a frame impeller. The Huilin-Gidaspow drag model is used to obtain the interphase interaction of gas and solids phases. The moving reference frame is used to simulate the rotation of numerical domain. Simulated results are compared with experimental data measured by Jiajun Wang et al. (2013) in a gas-solid stirred fluidized bed. The comparisons show that the present model can capture the gas-solid flow with mechanical agitation. The distributions of bed pressure drop, standard deviations of the differential pressure between different bed heights, particle velocity vectors and solids volume fraction are predicted. The effects of agitation speed and particle density on flow behavior of particles are analyzed. Simulations indicate the bed expansion ratio is increased, and then decreased with an increase of agitation speed. Increasing the mechanical agitation, the movements of particles are intensified, especially, the lateral movements of particles according to the distribution of particle velocity vectors. Moreover, the granular temperatures are increased with an increase of agitation speed and a decrease of particle density. Present investigations provide the detailed hydrodynamic characteristics of gas and particles and bed expansion with different agitation speeds and particle densities in a stirred fluidized bed.

About Thermodynamic Theory of Water Retention Capacity and Dispersity of Soils

On the basis of thermodynamic concept on competitive interphase interactions, the idea is forwarded about the ionic-electrostatic mechanism of water retention capacity and aggregative stability of fine solid particles in soil physical systems. The author applies modern data on the nanostructure of colloidal disperse complex of soil physical systems in the gel form, i.e., in the form of noncapillary two-phase system of resistant to aggregation particles separated by solvate layers. Disputable questions are discussed about the role of surface energy and hydration of cations in water retention as well as about the relationship between the matrix (disjoining) and the osmotic water pressures. The fundamental ionic-electrostatic model of water retention capacity is analyzed for the colloidal-disperse bodies in the areas of sorptive and film water on the water retention curve (WRC) in the form of interaction between thermodynamic potential (disjoining pressure), water content, and dispersity (effective specific surface area) of the solid phase. On the basis of this model, the potential dependence is shown between the dispersity and the mobile thermodynamic factors (i.e., temperature, charge, and concentration of ions in the electrical double layer), and the method of estimating the effective specific surface area from the WRC is proposed as an alternative to the commonly adopted BET method. For standard conditions, under which the dispersed system with monomolecular liquid layer maintains its aggregative stability, the specific surface area is calculated according to the WRC slope (the angle coefficient in semi-logarithmic coordinates) and the value of the effective size of water molecules. Simultaneously with the dispersity assessment from the WRC, the energy indices of interphase interactions— the generalized Hamaker constant and the surface tension at the solid–liquid interphase—are determined.

Drift velocity in sediment-laden downward jets

The drift velocity, defined as the velocity of individual phase relative to the water–sediment mixture, is a key variable in two-phase mixture model. In this paper, a relation for the drift velocity in sediment-laden jets, expressed as a power series of the nozzle Stokes number, was derived by using the perturbation approach. It shows that except the gravity and turbulent diffusion, effects of particle inertia, inter-phase interaction, and other forces contained in the first-order particle inertial corrections also play significant roles in sediment-laden jet flows. Based on the relation for the drift velocity, the velocity and concentration distribution were obtained from the similarity solutions for sediment-laden jets. The calculated concentration and velocity profiles agree well with the experimental observations in literature. Furthermore, analysis on the sediment diffusion coefficient shows that the fluid turbulence is not the only driving force for the sediment diffusion in sediment-laden jets; the effect of particle turbulence on the behavior of sediment-laden jets is also significant with the increasing of particle inertia.