Origin of idealized static thermodynamic forces inducing solid particle motion, orientation and related effects in a solute concentration gradient

1987 ◽  
Vol 83 (4) ◽  
pp. 1269 ◽  
Author(s):  
Ernest A. Boucher
Keyword(s):  
Solid Particle ◽  
Concentration Gradient ◽  
Particle Motion ◽  
Solute Concentration ◽  
Thermodynamic Forces

Solid particle motion in a standpipe as observed by Positron Emission Particle Tracking

2009 ◽  
Vol 194 (1-2) ◽  
pp. 58-66 ◽  
Author(s):  
Chian W. Chan ◽  
Jonathan Seville ◽  
Xianfeng Fan ◽  
Jan Baeyens
Keyword(s):  
Solid Particle ◽  
Particle Tracking ◽  
Particle Motion ◽  
Positron Emission

Solid-particle motion in two-dimensional peristaltic flows

1976 ◽  
Vol 73 (1) ◽  
pp. 77-96 ◽  
Author(s):  
Tin-Kan Hung ◽  
Thomas D. Brown
Keyword(s):  
Reynolds Number ◽  
Solid Particle ◽  
Particle Motion ◽  
Particle Transport ◽  
Particle Displacement ◽  
Two Dimensional ◽  
Single Bolus ◽  
Highly Nonlinear ◽  
Neutrally Buoyant ◽  
Gap Width

Some insight into the mechanism of solid-particle transport by peristalsis is sought experimentally through a two-dimensional model study (§ 2). The peristaltic wave is characterized by a single bolus sweeping by the particle, resulting in oscillatory motion of the particle. Because of fluid-particle interaction and the significant curvature in the wall wave, the peristaltic flow is highly nonlinear and time dependent.For a neutrally buoyant particle propelled along the axis of the channel by a single bolus, the net particle displacement can be either positive or negative. The instantaneous force acting upon the particle and the resultant particle trajectory are sensitive to the Reynolds number of the flow (§ 3 and 4). The net forward movement of the particle increases slightly with the particle size but decreases rapidly as the gap width of the bolus increases. The combined dynamic effects of the gap width and Reynolds number on the particle displacement are studied (§ 5). Changes in both the amplitude and the form of the wave have significant effects on particle motion. A decrease in wave amplitude along with an increase in wave speed may lead to a net retrograde particle motion (§ 6). For a non-neutrally buoyant particle, the gravitational effects on particle transport are modelled according to the ratio of the Froude number to the Reynolds number. The interaction of the particle with the wall for this case is also explored (§ 7).When the centre of the particle is off the longitudinal axis, the particle will undergo rotation as well as translation. Lateral migration of the particle is found to occur in the curvilinear flow region of the bolus, leading to a reduction in the net longitudinal transport (§ 8). The interaction of the curvilinear flow field with the particle is further discussed through comparison of flow patterns around a particle with the corresponding cases without a particle (§ 9).

Analytical Study of MHD Thermoconvective Waves through its Propagation

2017 ◽  
Vol 3 (01) ◽  
Author(s):  
Madan Lal
Keyword(s):  
Magnetic Field ◽  
Viscous Fluid ◽  
Concentration Gradient ◽  
Analytical Study ◽  
Solute Concentration ◽  
Horizontal Magnetic Field ◽  
Electrically Conducting ◽  
Specific Order ◽  
Waves Propagation ◽  
Propagation Of Waves

Following is the analytical study on the propagation of undamped thermoconvective waves, an electrically conducting viscous fluid is hypothesized which has the property of uniform horizontal magnetic field in heating the uniform vertical concentration gradient for a solute. It has seen that undamped thermoconvective waves propagation in a specific order, whereas the heating of fluid, is based on the solute concentration, this decreased vertically or show vertical pattern. If the heating of fluid takes place in upward manner the propagation of waves is highly effected, the above aspect proves hypothetically and has shown that its laboratory demonstration is also possible.

Effect of Solute Concentration Gradients on the Onset of Convection: Uniform and Nonuniform Initial Gradients

1986 ◽  
Vol 108 (4) ◽  
pp. 776-782 ◽  
Author(s):  
M. Kaviany ◽  
M. Vogel
Keyword(s):  
Temperature Gradient ◽  
Concentration Gradient ◽  
Fluid Layer ◽  
Onset Time ◽  
Solute Concentration ◽  
Concentration Gradients ◽  
Linear Amplification ◽  
Onset Of Convection ◽  
Gradient Layer ◽  
Good Agreement

The time of the onset of convection in a fluid layer, which is initially stably stratified and then heated from below in a transient manner, is determined experimentally and analytically. The initial stratification is due to the presence of a solute concentration gradient. In addition to initial linear solute concentration distributions two other specific initial solute concentration distributions are considered. In Case 1, a zero gradient layer is located underneath a nonzero and uniform gradient layer. In Case 2, the zero gradient layer is on the top. The linear amplification theory is applied to the prediction of the onset time. Interferometry is used as a means of determining the onset time experimentally. It is shown that since the adverse temperature gradient is concentrated near the bottom, any nonuniformity in the solute concentration gradient in this region reduces the effectiveness of the gradient in delaying the onset. Experimental and predicted results are in good agreement.

scholarly journals Diffusiophoresis of a Colloidal Cylinder at Small Finite Péclet Numbers

2019 ◽  
Vol 3 (2) ◽  
pp. 44
Author(s):  
Chang ◽  
Keh
Keyword(s):  
Particle Velocity ◽  
Asymptotic Expansions ◽  
Concentration Gradient ◽  
Interfacial Layer ◽  
Fluid Velocity ◽  
Solute Concentration ◽  
Cylindrical Particle ◽  
Governing Equations ◽  
Nonelectrolyte Solution ◽  
Solute Convection

The diffusiophoretic migration of a circular cylindrical particle in a nonelectrolyte solution with a solute concentration gradient normal to its axis is analytically studied for a small but finite Péclet number . The interfacial layer of interaction between the solute molecules and the particle is taken to be thin, but the polarization of its mobile molecules is allowed. Using a method of matched asymptotic expansions, we solve the governing equations of conservation of the system and obtain an explicit formula for the diffusiophoretic velocity of the cylinder correct to the order . It is found that the perturbed solute concentration and fluid velocity distributions have the order , but the leading correction to the particle velocity has the higher order . The correction to the particle velocity to the order can be either positive or negative depending on the polarization parameter of the thin interfacial layer, establishing that the solute convection effect is complicated and can enhance or retard the diffusiophoretic motion. The particle velocity at can be about 17% smaller or 0.2% greater than that at . Under practical conditions, the solute convection effect on the diffusiophoretic velocity is much greater for a cylindrical particle than for a spherical particle, whose leading correction has the order .

Numerical modelling of solid particle motion using a new penalty method

2005 ◽  
Vol 47 (10-11) ◽  
pp. 1245-1251 ◽  
Author(s):  
T. N. Randrianarivelo ◽  
G. Pianet ◽  
S. Vincent ◽  
J. P. Caltagirone
Keyword(s):  
Numerical Modelling ◽  
Solid Particle ◽  
Particle Motion ◽  
Penalty Method

Investigation of the regularities of particle motion in a vortex air flow of radius variable in height

2020 ◽  
pp. 92-100
Author(s):  
S. P. Stepanenko ◽  
B. I. Kotov ◽  
R. A. Kalinichenko
Keyword(s):  
Flow Velocity ◽  
Solid Particle ◽  
Particle Motion ◽  
Equations Of Motion ◽  
Air Flow ◽  
Tangential Direction ◽  
Uniform Field ◽  
Fractionation Process ◽  
Conical Channel ◽  
Air Flow Velocity

Annotation Purpose. Improving the mathematical description of the motion of a solid particle in a vortex air flow for the case of changing the radius of twisting of the flow in the main direction. Methods. The specificity of the question under consideration determines the analytical method of research based on the compilation and analysis of the equations of motion of the particle, in the form of a sphere in the vortex air flow of a conical channel with uneven distribution of air flow velocity over height. Results. The motion of a solid particle in the air in the middle of a conical air-permeable surface is considered; air is sucked through the lateral surface of the cone with louver slits (holes) in the tangential direction, under the action of artificially created forces of the vortex air flow there is an effective intensification of grain fractionation. The obtained equation of particle motion under the action of vortex air flow allows to determine the dependence of material velocity in the grain material layer on a number of factors: geometric parameters of the separator, material feed angle, initial kinematic mode of the material and particle vitality coefficient. Conclusions. Based on the analysis of the force interaction of a particle of grain material with a vortex air flow, an improved mathematical model of particle motion in a non-uniform field of air flow velocity in a conical channel is obtained. Keywords: variable air velocity, trajectory, stability of forces, fractions, vortex air flow, fractionation process, grain mixture.

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