Presence Of Suspended Particles Research Articles

Stability of superposed viscous-viscoelastic (Rivlin-Ericksen) fluids in the presence of suspended particles through a porous medium

The Rayleigh-Taylor instability of a Newtonian viscous fluid overlying a Rivlin-Ericksen viscoelastic fluid containing suspended particles in a porous medium is considered. As in both Newtonian viscous-viscoelastic fluids the system is stable in the potentially stable case and unstable in the potentially unstable case, this holds for the present problem also. The effects of a variable horizontal magnetic field and a uniform rotation are also considered. The presence of magnetic field stabilizes a certain wave-number band, whereas the system is unstable for all wave-numbers in the absence of the magnetic field for the potentially unstable configuration. However, the system is stable in the potentially stable case and unstable in the potentially unstable case for highly viscous fluids in the presence of a uniform rotation.

Quantification of nisin in flow-injection immunoassay systems

A monoclonal-antibody-based, sequential competitive-flow-injection immunoassay system in expanded-bed mode has been developed for the determination of nisin. The system allows the determination of nisin in the presence of suspended particles without any significant interference, illustrating its potential for on-line monitoring of fermentation processes or the analysis of food matrices. The dose response range of the system when operated in expanded-bed mode was 6–90 μM. The detection limit under packed-bed conditions was 3 μM. The results correlated well with the results from conventional ELISA in the analysis of samples of processed cheese. When milk samples, fermentation samples and buffer were spiked with nisin, the mean recoveries were 86% for milk samples, 96% for fermentation samples and 98% for buffer solution.

Snowdrift Suspension And Atmospheric Turbulence. Part II: Results Of Model Simulations

An atmospheric surface-layer model is used to investigate the interactionbetween suspended snow particles and the near-surface flow. Themodel incorporates the effects of upward diffusion, gravitational settling and sublimation of snow particles in 48 size classes, the effects of snowdrift sublimation on the heat and moisture budget of the surface layer, and the buoyancy destruction of turbulent kinetic energy (TKE) caused by the presence of suspended particles. A new term in the E-e closure model representing the buoyancy destruction due to suspended particles is included in the prognostic equation for TKE. Generally, model results indicate that the presence of suspended particles causes significant decreases in TKE, the dissipation rate, turbulent length scales and eddy exchange coefficients (up to 40%). It is found that the reduction in the eddy exchangecoefficients is due mainly to reductions in turbulent length scales. Theassociated particle Richardson number peaks near the saltation-suspensioninterface, but at higher levels in the surface layer the particle-induced buoyancy can also significantly affect the flow. A detailed analysis of the various snowdrift quantities, the TKE budget and the particle buoyancy effects on the flow is presented.

Snowdrift suspension and atmospheric turbulence. Part I: Theoretical background and model description

Snowdrift is one of the manymanifestations of two-phase flow, in which theinteraction between suspended particles and theambient fluid brings about some interesting features.Specifically, the drag required to keep particles insuspension against the downward gravitational pullrequires expenditure of turbulent kinetic energy(TKE). Other effects include the increased density of theair-snow mixture and the stable thermal stratificationcaused by the snowdrift sublimation-induced cooling.An atmospheric surface-layer model that includes snowdriftsuspension is described that includes the effects ofupward diffusion, gravitational settling andsublimation of snow particles in 48 size classes, theeffects of snowdrift sublimation on the heat andmoisture budget of the surface layer and the dampingof turbulence in the presence of suspended particles. Thewell-known E-e closure model is applied toevaluate the eddy exchange coefficient, with a newterm representing buoyancy reduction induced by thestably stratified suspended particle profile includedin the prognostic equation for TKE.

Stability of Two Superposed Viscoelastic (Walters B') Fluid-Particle Mixtures in Porous Medium

The stability of the plane interface separating two viscoelastic (Walters B') superposed fluids in por-ous medium in the presence of suspended particles is considered. For the case of two uniform Walters B' fluids separated by a horizontal boundary, the system is found to be stable or unstable under certain conditions for the stable configuration. However, the system is found to be unstable for the unstable configuration. The case of an exponentially varying density is also considered. For the stable stratifica-tion, the system is found to be stable or unstable under certain conditions, whereas the system is found to be unstable for the unstable stratification. The behaviour of growth rates with respect to suspended particle, number density, and medium permeability is examined analytically.

Electrodeposited Tl2 O 3‐Matrix Composites: I. Effect of the Dispersed Phase on Nucleation and Growth of the Matrix

The electrodeposition of composites has been performed by anodic oxidation of ions in the presence of suspended particles. This study, aimed at obtaining and characterizing new electrocatalytic materials for oxygen evolution reaction, has shown that particles enhance the rate of nucleation and growth of the matrix. At each potential, induction times are shorter and kinetic constants are higher in the presence of than in its absence. The chronoamperometric transients measured during composite deposition are compatible with instantaneous nucleation and 3D growth. Scanning electron microscopy and energy dispersive X‐ray analyses data show that particles become effectively embedded in the deposit from the early stages of its formation and act as centers of preferential growth for the matrix, so that the content is higher near the electrode/composite interface than in the bulk. composites are compared with other systems for which nucleation and growth of the matrix is unaffected by the dispersed phase.

Impact of turbulence and turbidity on the grazing rate of the rotifer Brachionus calyciflorus (Pallas)

The impact of turbulence and turbidity on Brachionus calyciflorus grazing rate was determined in short feeding periods (10 min), using labelled Chlorella pyrenoidosa. The response to water motion of B. calyciflorus depends on it physiological state: the grazing rate of recently fed amictic females stomach green (with one or two eggs) is significantly reduced in agitated environments compared with non-agitated environments. In contrast, the grazing rate of starved amictic females is not reduced by water motion, whatever its velocity (V1=0.18 m s−1 and V2=0.22 m s−1). In the presence of suspended particles (3–6-μm silica beads), a larger reduction in grazing rate is observed in agitated water at any water velocity (V1=0.18 m s−1 or V2=0.22 m s−1), than in stagnant water. A synergy between turbulence and turbidity is unfavourable to feeding of rotifers.

Effect of Suspended Particles on Crystallization Fouling in Plate Heat Exchangers

The presence of suspended particles in solutions significantly affects the crystallization rate. This study investigates the effects of calcium sulphate (crystallizing) particles and alumina (noncrystallizing) particles on calcium sulphate crystallization fouling in a plate heat exchanger. Calcium sulphate particles are formed during the preparation of calcium sulphate solution due to breakage of calcium sulphate crystals growing on the heat transfer surface. These suspended particles settle on the heat transfer surface and act as nuclei. The availability of extra nucleation sites increases the crystallization rate significantly. These particles can be removed with a filter, and the removal of the particles prevents this extra assistance available for crystallization. Therefore, the crystallization rate is reduced markedly. Alumina particles were purposely added during the preparation of calcium sulphate solutions. These particles attach loosely to the heat transfer surface compared with crystalline deposits which adhere strongly. Therefore, calcium sulphate crystals growing on these particles are removed easily. Also, alumina particles settling on the growth faces of calcium sulphate crystals may act as a distorting agent. This slows down the growth of the crystals.

Control of clogging in drip irrigation with stored treated municipal sewage effluent

Emitter clogging is a major problem incurred in the operation of drip irrigation systems, especially when these systems utilize treated wastewater effluent stored in surface reservoirs. In an attempt to seek solutions to the problems arising from the presence of suspended particles, algae, zooplankton and other organisms in the reservoirs, as well as to prevent clogging in the supply lines and in downstream sections of the drip laterals, a series of filter and drip emitter clogging trials was set up. The trials were conducted with two water supplies. The first (1987–1990) was water from the Kfar Barukh reservoir, which stores storm run-off, treated sewage effluent and National Carrier water. The second (1991–1992) was water from the Burgata reservoir, which stores only secondary effluents. This paper reports on the performance of manual and automatic screens, discs and media filters and of different types of emitters, as well as on the effect of chemical treatments designed to control clogging.

Photoimage Formation in a TiO2 Particle‐Incorporated Prussian Blue Film

An indium‐tin oxide (ITO) electrode coated with prussian blue (PB) film containing particles ( electrode) was prepared by electrochemical deposition of PB in the presence of suspended particles. Irradiation of the prepared film with a high pressure mercury arc lamp in a solution containing methanol as an electron donor caused photoinduced reduction of PB to colorless prussian white (PW). Irradiation of a spot on the film, however, did not restrict the reduction of PB to the irradiated part, rather the reduction area spread beyond the irradiation zone, the extent being larger with increasing irradiation time. The electron transport from the photoproduced PW to the surrounding PB through the conducting ITO substrate was found to be responsible for the observed spread. Area‐selective photoreduction of PB to PW was successfully achieved by inserting a thin ferrocenylmethyltrimethylammonium (FA)‐bound Nafion between the and ITO to give a /Nafion[FA]/ITO electrode. The preparation of this bilayer electrode was accomplished by electrochemically depositing a layer onto a Nafion[FA]‐coated ITO electrode. FA in the Nafion layer blocked electrochemical reduction of PB to PW, but mediated oxidation of the photoproduced PW. White images were successfully formed in the blue films of the bilayer electrodes by irradiation under open‐circuit condition.

Instability of Two Maxwellian Viscoelastic Superposed Fluids with Suspended Particles and Variable Magnetic Field in Porous Medium

Abstract Instability of the plane interface between two viscoelastic (Maxwellian) superposed conducting fluids in the presence of suspended particles and variable horizontal magnetic field in porous medium is studied. The cases of two fluids of uniform densities, viscosities, magnetic fields, and suspended particles number densities separated by a horizontal boundary; and of exponentially varying density, viscosity, suspended particles number density, and magnetic field are considered. It is found that the stability criterion is independent of the effects of viscoelasticity, medium porosity, and suspended particles but is dependent on the orientation and magnitude of the magnetic field. The magnetic field succeeds in stabilizing a certain range of wavenumbers which were unstable in the absence of the magnetic field. The system is found to be stable for potentially stable configuration/stratifications. The growth rates are found to increase (for certain wavenumbers) and decrease (for other wavenumbers) wit...

Effects of sediment loading on food perception and ingestion by freshwater copepods

Seasonal influx of suspended sediments to lakes is common in many aquatic systems, particularly during periods of high flow. Suspended particles not only affect visibility and net primary productivity, as light penetration is reduced, but may also affect the ability of herbivorous zooplankton to locate and ingest food. In Swan Lake, an oligotrophic lake in northwestern Montana, the dose association between zooplankton population development and seasonal maxima in turbidity levels suggests that the community present during peak turbidity is minimally impacted by suspended sediments. This report presents the results of laboratory investigations into the effect of suspended sediments on feeding by the copepod Diaptomus ashlandii, the dominant zoo‐plankter in Swan Lake. Ingestion rate for copepods feeding on 32P labeled algae was significantly reduced in the presence of suspended particles at all turbidity levels tested (5 to 200 NTU's) compared to ingestion rate in the absence of suspended particles (0 NTU's).

Monitoring Particle Sizes with Rotating Disc Electrodes: Measurement of the Dissolution Kinetics of Calcite

The presence of suspended particles in solution causes an enhancement of the mass transport to a rotating disc electrode, the magnitude of which is dependent on the volume fraction of the particulate material. By monitoring the transport limited current due to the reduction/oxidation of a suitable electroactive substrate in the presence of dissolving particles the change in the size of the latter with time may be monitored, thus allowing the rate of dissolution to be inferred. Experiments conducted on the dissolution of calcite at pH 7 are shown to give kinetic data in excellent agreement with that deduced by independent means.

Rayleigh-Taylor Instability of Two Superposed Conducting Fluids in the Presence of a Variable Magnetic Field and Suspended Particles

The instability of two superposed fluids in the presence of suspended particles is studied. It is found that the system is unstable for sufficiently long waves, however large the applied magnetic field may be, provided the initial configuration is top-heavy density wise. Also, the potentially stable system remains stable for the case of two superposed fluids in the presence of a variable magnetic field and suspended particles.

Qualitative analysis of the processes of aerosol propagation in a containment

Characteristic times of the removal of aerosols are evaluated for different processes of deposition. Gas flows in a containment in the presence of suspended particles of various concentrations have been analyzed. A mathematical model is suggested for describing the propagation and deposition of aerosols under the conditions of large-scale convection.

Rayleigh-taylor instability of viscoelastic fluids with suspended particles in porous medium in hydromagnetics

The instability of the plane interface between two viscoelastic (Oldroydian) superposed conducting fluids permeated with suspended particles in porous medium is studied when the whole system is immersed in a uniform magnetic field. The dispersion relation for the Oldroydian viscoelastic fluid is obtained which also yields dispersion relations for Maxwellian and Newtonian fluids in special cases, in the presence of suspended particles in porous medium in hydromagnelics. The system is found to be stable for potentially stable case. The presence of magnetic field stabilizes certain wave number band whereas the system was unstable for all wave numbers in the absence of magnetic field, for the potentially unstable configuration. The growth rates increase (for certain wave numbers) and decrease (for other wave numbers) with the increase in stress relaxation time, strain retardation time, suspended particles number density and medium permeability.

Zn and Cu removal kinetics in estuarine waters

The time-dependent removal of dissolved Zn and Cu in the presence of suspended particles has been studied in the laboratory using conditions closely resembling the aquatic environment encountered in the Tamar Estuary. The metals were removed from both river water and low salinity waters and the uptake profiles were of an exponential form. The removal profiles were interpreted in terms of a reversible, heterogeneous, pseudo-first order reaction, for which the forward and reverse rate constants were evaluated. The forward rate constants for Zn were salinity dependent and varied between 0.08 h −1 and 0.61 h −1 . In contrast, the rate constants for Cu ranged from 0.10 h −1 to 0.75 h −1 and in freshwater they were dependent on the suspended particle concentration. The reaction response times, τ resp (defined as the time for the attainment of 63% of a new equilibrium), were 1 to 10 h for Zn and 1 to 8 h for Cu. These values were compared with calculated flushing times of the Tamar Estuary and a new interpretation of field observations of the non-conservative behaviour of dissolved Zn and Cu in the Tamar Estuary was evolved.

Double-diffusive convection with fine dust

The effect of fine dust (suspended particles) is considered on the thermosolutal convection. The principle of exchange of stabilities is satisfied for thermal Rayleigh number greater than or equal to solute Rayleigh number. If the solute Rayleigh number exceeds the thermal Rayleigh number, the oscillatory modes may come into play. The effect of stable solute gradient has a stabilizing effect whereas the effect of suspended particles is to destabilize the layer. The effect of a uniform rotation is also considered and is found to have a stabilizing effect in the presence of suspended particles on the thermosolutal convection.

Stability of stratified fluid in porous medium in the presence of suspended particles and variable magnetic field

General equations governing the stability of stratified fluid in a stratified porous medium in the presence of suspended particles and variable horizontal magnetic field, separately, have been derived. Assuming stratifications in density, viscosity, suspended particles number density, medium porosity, medium permeability and a magnetic field of exponential form the dispersion relations have been obtained. Systems have been found to be stable for stable stratifications and unstable for unstable stratifications. A system which was unstable in the absence of magnetic field can be completely stabilized by a magnetic field for a certain wave-number range. The behaviour of growth rates with respect to fluid viscosity, medium permeability, suspended particles number density and magnetic field has been examined analytically.

Thermosolutal-convective instability of a stellar atmosphere in the presence of suspended particles

Thermosolutal-convective instability of a stellar atmosphere is considered in the presence of suspended particles. The criteria for monotonic instability are derived which are found to hold good in the presence of uniform rotation and uniform magnetic field, separately, on the thermosolutal-convective instability in the presence of suspended particles.