An asymptotic study of three-layered creeping flow and some geophysical applications

The Automated Hollow Fiber Ultrafiltration (AHFU) method is proposed here as a simple, efficient and rapid virus concentration technique from tap and drinking water sources. The results reported here extend the testing of the AHFU method to include two Picornaviruses [Poliovirus 2 (vaccine) and Echovirus 1] and Reovirus 3. Their respective mean virus recoveries from between 3 and 100 l of tap water is 88 ± 26, 79 ± 60, and 104 ± 48%. Various approaches including membrane surface modification, changes in backwash hydrodynamics, modification of the feed and backwash composition, and the use of S35-methionine labelled Poliovirus 2, are used to study the recovery of sorbed Poliovirus 2 from the hollow fiber/solution interface. An increase in the backwash pH to between 9.5 and 10.5 significantly improved Poliovirus 2 recovery. This, together with the labelled experiments, indicates that the virus-membrane interactions are probably electrostatic in nature. Convective polarization during filtration probably brings the virus close enough to the surface for these interactions to occur since virus losses were not detected for a non-permeation recycle experiment. Because very low Reynold's numbers are used, the flow is in the creeping-flow-regime for both filtration and backwashing (axial and radial). Unless significantly higher Reynolds could be used, enhanced recovery due to purely hydrodynamic forces is unlikely. High Reynold's numbers, of course, are limited by the pressure constraints of the hollow fibers.

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Kelvin–Helmholtz creeping flow at the interface between two viscous fluids

ANZIAM Journal ◽

10.21914/anziamj.v56i0.7575 ◽

2015 ◽

Vol 55 ◽

pp. 317

Author(s):

Lawrence Forbes ◽

Rhys Paul ◽

Michael Chen ◽

David Horsley

Keyword(s):

Creeping Flow ◽

Viscous Fluids

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Process characteristics of screw impellers with a draught tube for Newtonian liquids. Time of homogenization

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19812032 ◽

1981 ◽

Vol 46 (9) ◽

pp. 2032-2042 ◽

Cited By ~ 5

Author(s):

Pavel Seichter

Keyword(s):

Flow Regime ◽

Creeping Flow ◽

Energy Requirements ◽

Dimensionless Time ◽

Mixing Times ◽

Conductivity Method ◽

Draught Tube ◽

Process Characteristics ◽

Newtonian Liquids

A conductivity method has been used to assess the homogenization efficiency of screw impellers with draught tubes. The value of the criterion of homochronousness, i.e. the dimensionless time of homogenization, in the creeping flow regime of Newtonian liquids is dependent on the geometrical simplexes of the mixing system. In particular, on the ratio of diameters of the vessel and the impeller and on the ratio of the screw lead to the impeller diameter. Expression have been proposed to calculate the mixing times. Efficiency has been examined of individual configurations of screw impellers. The lowest energy requirements for homogenization have been found for the system with the ratio D/d = 2.

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Process characteristics of screw impellers with a draught tube for Newtonian liquids. Pumping capacity of the impeller

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19812021 ◽

1981 ◽

Vol 46 (9) ◽

pp. 2021-2031 ◽

Cited By ~ 6

Author(s):

Pavel Seichter

Keyword(s):

Viscous Liquid ◽

Energy Criterion ◽

Velocity Profiles ◽

Newtonian Liquid ◽

Creeping Flow ◽

Geometrical Arrangement ◽

Draught Tube ◽

Process Characteristics ◽

Newtonian Liquids

Velocity profiles and pumping capacity have been determined using a thermistor anemometer in a vessel equipped with a screw impeller. In region of the creeping flow of a Newtonian liquid, i.e. for Re <15, the dimensionless pumping capacity is dependent on the geometrical arrangement of the mixing system. The efficiency was assessed of individual configuration from the value energy criterion expressing the dimensionless power requirements for recirculation of a highly viscous liquid in a vessel equipped with a screw impeller.

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Model of vortex flow of charge in a vessel with turbine impeller

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19871888 ◽

1987 ◽

Vol 52 (8) ◽

pp. 1888-1904

Author(s):

Miloslav Hošťálek ◽

Ivan Fořt

Keyword(s):

Boundary Conditions ◽

Equations Of Motion ◽

Theoretical Data ◽

Eddy Diffusion ◽

Quantitative Agreement ◽

Creeping Flow ◽

Model Parameters ◽

Mean Flow ◽

Two Dimensional Flow ◽

Vorticity Transport

A theoretical model is described of the mean two-dimensional flow of homogeneous charge in a flat-bottomed cylindrical tank with radial baffles and six-blade turbine disc impeller. The model starts from the concept of vorticity transport in the bulk of vortex liquid flow through the mechanism of eddy diffusion characterized by a constant value of turbulent (eddy) viscosity. The result of solution of the equation which is analogous to the Stokes simplification of equations of motion for creeping flow is the description of field of the stream function and of the axial and radial velocity components of mean flow in the whole charge. The results of modelling are compared with the experimental and theoretical data published by different authors, a good qualitative and quantitative agreement being stated. Advantage of the model proposed is a very simple schematization of the system volume necessary to introduce the boundary conditions (only the parts above the impeller plane of symmetry and below it are distinguished), the explicit character of the model with respect to the model parameters (model lucidity, low demands on the capacity of computer), and, in the end, the possibility to modify the given model by changing boundary conditions even for another agitating set-up with radially-axial character of flow.

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Convective diffusion to a slowly rotating spherical electrode; Basic model for Re → O, Pe → ∞

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19831571 ◽

1983 ◽

Vol 48 (6) ◽

pp. 1571-1578 ◽

Cited By ~ 1

Author(s):

Ondřej Wein

Keyword(s):

Boundary Layer ◽

Flow Regime ◽

Peclet Number ◽

Convective Diffusion ◽

Creeping Flow ◽

Péclet Number ◽

Spherical Electrode ◽

Basic Model ◽

Boundary Layer Solution ◽

Layer Solution

Theory has been formulated of a convective rotating spherical electrode in the creeping flow regime (Re → 0). The currently available boundary layer solution for Pe → ∞ has been confronted with an improved similarity description applicable in the whole range of the Peclet number.

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Formation and Destruction of Platelet Aggregates in Viscometric Flow

10.1055/s-0039-1689398 ◽

1975 ◽

Author(s):

H. Rieger ◽

H. Schmid-Schönbein

Keyword(s):

Initial Rate ◽

Aggregate Stability ◽

Creeping Flow ◽

Experimental Conditions ◽

Shear Rates ◽

Independent Variables ◽

Lower Shear ◽

Platelet Aggregates ◽

Blood Elements ◽

Shape Changes

Even after pseudopodia formation platelets - unlike all other known formed blood elements - remain dispersed in stasis and creeping flow and become aggregated only in the presence of a minimum amount of shearing. The “rheoaggregometer” (Rieger et al., Pflüger’s Archiv, 343, R 33, 1973) allows to measure the minimum shear rates necessary for platelet aggregation (PA), as well as the initial rate and the maximum extent of PA in citrated PRP.PA is quantified photometrically as a function of variable shear rates. The initial rate of PA steadily increases with increasing shear rates up to 460 sec-1. However, the maximal extent of PA (indicating the mechanical integrity of formed aggregates) saturates at about 35 sec-1 and then decreases because of a destruction of formed aggregates and of prevention of further PA. The aggregability of the platelets, as reflected by various degrees of shape changes, is enhanced by a drop of temperature and a rise in pH as well as by the so called aggregating agents (e.g. epinephrine 10-6 up to 10-9 M/l) : consecutively lower shear rates (lower effects of collision) are necessary to induce PA. In citrated PRP stable platelet aggregates are produced only within a defined range of shear rates. Platelet aggregability and aggregate stability are independent variables influenced by different experimental conditions.

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