Fluid Particle Separation Research Articles

Fluid-particle separation in a random flow described by the telegraph model

We study the statistics of the relative separation between two fluid particles in a spatially smooth and temporally random flow. The Lagrangian strain is modeled by a telegraph noise, which is a stationary random Markov process that can only take two values with known transition probabilities. The simplicity of the model enables us to write closed equations for the interparticle distance in the presence of a finite-correlated noise. In one dimension, we are able to find analytically the long-time growth rates of the distance moments and the senior Lyapunov exponent, which consistently turns out to be negative. We also find the exact expression for the Cramér function and show that it satisfies the fluctuation relation (for the probability of positive and negative entropy production) despite the time irreversibility of the strain statistics. For the two-dimensional incompressible isotropic case, we obtain the Lyapunov exponent (positive) and the asymptotic growth rates of the moments in two opposite limits of fast and slow strain. The quasideterministic limit (of slow strain) turns out to be singular, while a perfect agreement is found with the already-known delta-correlated case.

Separation and Concentration of Particles in Fluid Using Ultrasonic Standing Wave

This paper presents the theory, design, and evaluation of a smart device for the enhanced separation of particles mixed in fluid. The smart device takes advantage of the ultrasonic standing wave, which was generated by the operation of a piezoceramic PZT patch installed in the smart device. The details of the device design including the electro-acoustical modelling for separation and PZT transducer are described at first. Based on this design, the separation device was fabricated and evaluated. In the experiments, an optical camera with a zoom lens was used to monitor the position of particles within the separation channel layer in the device. The electric impedance of the PZT patch bonded on the separation device was measured .The device shows a strong levitation and separation force against 50μm diameter particles mixed with water at the separation channel in the device. Experimental results also showed that the device can work at both heavy and light sand particles mixed with water due to the generated standing wave field in the separation channel.

Methods of Solving Nonlinear Problems of Hydrodynamic Impact in Bounded Regions

The plane problem of separation impact on a plate floating on the surface of an ideal incompressible fluid in a bounded vessel is considered. In this problem the zone of contact between the body and the fluid is not known in advance and must be determined together with the fluid flow. As a result, the problem formulated is nonlinear and belongs to the class of free-boundary problems. The effect of vessel walls of different shapes on the fluid particle separation zone formed on the plate surface is studied. As examples, the problems for a layer or a truncated circular meniscus are considered.

Particle Separation Using Ultrasound Can Radically Reduce Embolic Load to Brain After Cardiac Surgery

Background Microembolism during cardiopulmonary bypass has been suggested as being the predominant cause of neurocognitive disorders after cardiac surgery. Shed blood, normally retransfused into the patient during cardiopulmonary bypass, is a major source of lipid microemboli in the brain capillaries. A newly developed technique based on acoustic standing-wave separation of particles in fluid in microchannels, with the capacity to remove lipid particles in blood, is presented. Methods A separator consisting of eight parallel, high-fidelity microfabricated channels was actuated with an ultrasound field to create a standing wave. Three different concentrations of lipid particles (diameter, 0.3 μm) were added to blood samples with increasing hematocrits and introduced into the separator channels to separate lipid particles and erythrocytes. Results The mean separation rates for lipid particles were 81.9% ± 7.6% and for erythrocytes 79.8% ± 9.9%, and both were related to the hematocrit level of the incoming blood sample. The procedure was atraumatic and did not cause hemolysis. Conclusions Particle separation by means of an acoustic standing-wave technique can be used for atraumatic and effective removal of lipid particles from blood, with the possible clinical implication of reducing neurocognitive complications after cardiopulmonary bypass.

The particle finite element method: a powerful tool to solve incompressible flows with free‐surfaces and breaking waves

AbstractParticle Methods are those in which the problem is represented by a discrete number of particles. Each particle moves accordingly with its own mass and the external/internal forces applied to it. Particle Methods may be used for both, discrete and continuous problems. In this paper, a Particle Method is used to solve the continuous fluid mechanics equations. To evaluate the external applied forces on each particle, the incompressible Navier–Stokes equations using a Lagrangian formulation are solved at each time step. The interpolation functions are those used in the Meshless Finite Element Method and the time integration is introduced by an implicit fractional‐step method. In this manner classical stabilization terms used in the momentum equations are unnecessary due to lack of convective terms in the Lagrangian formulation. Once the forces are evaluated, the particles move independently of the mesh. All the information is transmitted by the particles. Fluid–structure interaction problems including free‐fluid‐surfaces, breaking waves and fluid particle separation may be easily solved with this methodology. Copyright © 2004 John Wiley & Sons, Ltd.

Separation Impact on a Plate Floating on the Surface of an Ideal Incompressible Fluid in a Bounded Tank

The paper studies the planar problem of separation impact on a plate floating on the surface of an ideal incompressible fluid in a bounded tank. The problem is solved using an asymptotic method under the assumption that the immovable rigid walls of the tank are at a large distance from the plate. It is concluded that the tank walls of arbitrary shape have an ambiguous effect on the fluid particle separation zone formed on the plate surface is revealed. Examples of solutions are given.

Predicting the performance of air cyclones

Many empirical models for predicting the particle separation efficiency of cyclone separators have been presented by different investigators, but they are often limited in their use to the particular type of cyclones on which they were developed. This paper describes theoretical models and a numerical model for the analysis of the fluid flow and particle separation of cyclones and how they may be used in the design of new types of cyclones. The governing fluid and particulate flow equations have been analysed and numerically solved in order to predict the fluid flow and particle separation in cyclones. In addition, the key design parameters for the cyclones have been discussed as to their effect on the overall performance of the cyclone and general recommendations for the engineering design of cyclones have been suggested. Copyright © 2002 John Wiley & Sons, Ltd.

5502243 Hydrocarbonylation of dimethyl ether

This study evaluated the separation of particles suspended in power law fluids by applying a 10 mm hydrocyclone. Al2O3 particles were added to an aqueous polyacrylic acid solution to prepare 0.1 vol% suspensions with different flow behaviors. The effects of operating conditions, such as the inlet velocity, pressure drop, split ratio, and fluid flow behavior, on the fluid velocity distribution, particle trajectory, and particle separation efficiency were studied. The study applied a simulation in which the governing equations were coupled using the SIMPLE algorithm; the Reynolds stress model served as a turbulence model. The distributions of the fluid velocity and pressure were simulated using a segregated, steady-state, three-dimensional implicit numerical solver provided by ANSYS 15.0 software. The tangential velocity increased with the flow behavior index, n, at a fixed inlet velocity and split ratio. This effect was attributed to a lower molecular viscosity. The particle trajectories were simulated using a Lagrangian frame. The particle migration in the cylindrical part of the hydrocyclone dominated the particle separation efficiency. A reduction in the fluid n-value engendered a higher effective viscosity and lower tangential velocity, which caused fewer particle rotations and lower centrifugal effects, consequently lowering the opportunity for particles to collect in the underflow. The separation efficiency increased with the inlet velocity and particle size because of a higher centrifugal effect, but the influence of the inlet velocity was extremely small for a low fluid n-value. The total separation efficiency increased by approximately 40% as the n-value increased from 0.51 to 1.00. The simulated particle separation efficiency was highly consistent with experimental data. This verified the reliability of the simulation method and the validity of this method for understanding the effects of fluid flow behavior on particle separation performance.

Chainlike Formation of Particle Deposits in Fluid-Particle Separation

A theory is proposed for the formation and growth of particle dendrites on a collector placed in an aerosol or hydrosol stream. It is based on the interplay of two intrinsic properties of suspended particles: (i) their finite size and (ii) the randomness of the location of individual particles in the fluid stream. The results of simulations based on this theory resemble those obtained from experiments.