Laminar Flow Of Suspension Research Articles

Separation of magnetic particles in channel flows by BEM

AbstractIn‐line separation of suspensions can become difficult in case of particles with comparable values of densities. For flows in micro devices in such cases gravitational settling is inefficient, and other separation techniques must be applied. In case of magneto active particles, the action of Kelvin magnetic force in a non‐uniform magnetic field could be used in order to achieve a higher degree of particles separation. The contribution therefore deals with Euler‐Lagrangian formulation of dilute two‐phase flows. The Boundary element based computational algorithm solves the incompressible Navier‐Stokes equations written in velocity‐vorticity formulation. The non‐uniform magnetic field is defined analytically for the case of a set of long thin wires. The particle trajectories are computed by applying the 4th order Runge‐Kutta method. The computed test case consists of a narrow channel with laminar flow of suspension under Re = 1 − 10. Particle trajectories under the influence of a non‐uniform magnetic field are computed for the case of magnetite and aluminium particles suspended in water. The efficiency of separation on basis of particle trajectories for different values of Re number and magnetic field strength is performed, clearly indicating superior separation of magneto active particles. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Laminar Flow of Suspensions in the Entrance Region of a Diffuser

An analytical investigation of the mechanics of deposition of fine particles in a two-dimensional diffuser from the diffuser to inlet to the point of separation has been made. The deposition of suspensions in a diffuser was found to depend strongly on the electrostatic charge parameter and the diffuser angle. The analysis is restricted to laminar flow of dilute suspensions with diffusive, electrostatic, and surface adhesive effects. The implicit finite difference method was utilized to obtain a solution of the governing equations.

Study on the Tubular Pinch Effect in a Pipe Flow : I. Lateral migration of a single particle in laminar poiseuille flow

In laminar flow of suspensions through a circular tube, particles migrate into a concentric annular region with the radius about 0.6 of the tube radius. This phenomenon is well-known as the tubular pinch effect. To clarify the mechanism, the influences of relative particle-fluid velocity, Reynolds number and particle diameter on radial particle displacement (lateral migration) were investigated by measuring the motion of a suspended spherical particle in laminar flow through a circular tube. Consequently, it was found that the motions of particles could be classified by the particle Reynolds number. And, especially, the relation between the particle Reynolds number and the equilibrium radial position of particles and the existence of critical particle Reynolds number for shifting from unilateral migration to bilateral migration were clarified.

Mechanical production of metamorphic banding—a critical appraisal

SummaryThe mechanical process for producing foliation (banding) in metamorphic rocks, as proposed by Schmidt (1932), is shown to be inadequate. Examples in the literature ascribed to the mechanism are insufficiently supported and the metallurgical analogy for the process is found to be false. A possible restatement of a mechanical process by analogy with particle interaction effects during the laminar flow of suspensions is discussed. Evidence from metamorphic rocks indicates, however, that the modified mechanical process cannot be responsible for common metamorphic layering.

The laminar flow of suspensions in tubes

The conception of viscosity as action per unit volume is used in the analysis of the flow of a suspension or macromolecular solution in a tube. The flow mechanism adduced involves the postulation of molecular vortices of which the suspended particles or molecules form the nuclei. This mechanism is used as a basis for the derivation of a relationship between the specific viscosity of the suspension and the linear dimensions of the vortices. The laws of Einstein, Staudinger, Huggins and their co-workers are derived simply and as special cases of this relationship. The law relating viscosity with concentration is also derived with reference to the same mechanism. This law assumes the form ηsp = an + bn2 where a and b are constants and ηsp and n are respectively the specific viscosity and molecular concentration of the solution. It is shown to be in good agreement with typical experimental results. The effect of the aspect ratio of the suspended particles or molecules is also considered and it is shown that the longest particle dimension rotates in a plane normal to the vortex axis. Although no quantitative relationship between viscosity and velocity gradient has been derived the mechanism is observed to lead to results in qualitative agreement with the experimental data.