Lateral Migration and Orientation of Elliptical Particles in Poiseuille Flows (original) (raw)
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Lateral Migration and Rotational Motion of Elliptic Particles in Planar Poiseuille Flow
Simulations of elliptic particulate suspensions in the planar Poiseuille flow are performed by using the lattice Boltzmann equation. Effects of the multi-particle on the lateral migration and rotational motion of both neutrally and non-neutrally buoyant elliptic particles are investigated. Low and intermediate total particle volume fraction f(sub a) = 13%, 15%, and 40% are considered in this work.
A numerical study of the lateral migration of spherical particles in Poiseuille flow
Engineering Analysis with Boundary Elements, 1994
The lateral migration of spherical particles in Poiseuille flow at low but non-zero Reynolds numbers is studied numerically by the boundary element method. A particular solution method to remove the domain integral associated with the nonlinear convection terms is discussed. For nonneutrally buoyant spheres, the numerical results confirm for the most part that the lateral velocity is towards the wall if the particle velocity leads the undisturbed Poiseuille velocity and is towards the axis if the particle velocity lags the undisturbed Poiseuille velocity. However, the numerical results contradict this general trend in the vicinity of the tube axis.
Journal of Computational Science and Technology, 2008
Numerical simulations are performed using the lattice Boltzmann method for particulate suspension in a plane channel flow at low and moderate Reynolds numbers in order to investigate the blood cell behavior in microvascular flows. The simulation results of three types of particle volume fractions indicate the existence of an important relationship between the Reynolds number and the variance of the particles. When the particle volume fraction is small, it is found that the particles are concentrated between the centerline and the wall, that is, the Segré-Silberberg effect occurs. On the other hand, as the particle volume fraction becomes larger, this effect disappears and the variance of the particles increases. In the case of an inelastic collision, the number of the particles that flow near the wall increases and the variance of the particle distribution decreases in comparison with the case of the elastic collision.
Sedimentation of an elliptic rigid particle in a yield-stress fluid: A Lattice-Boltzmann simulation
Physics of Fluids
Sedimentation of a single, two-dimensional, rigid, elliptic particle in a biviscous fluid contained in a finite, closed-ended channel is studied in this work using the lattice-Boltzmann method. The main objective of the work is to numerically investigate the role played by a fluid's yield stress on the trajectory, orientation, and terminal velocity of such a particle for different density and aspect ratios. Numerical results suggest that a new mode of settling might emerge for yield-stress fluids, which is nonexistent for Newtonian fluids. That is, a particle released from the rest state at the midplane with a prescribed, nonzero, inclination angle (with respect to the horizontal line) migrates toward the left side-wall (if the inclination angle is positive) soon after it is released but changes course after a short while and moves back toward the centerline where the voyage started. However, while for Newtonian fluids the particle eventually returns to the centerline and continues its free fall with a horizontal orientation, for yield-stress fluids, the particle might finally lodge at a specific distance away from the centerline and continue its fall assuming a nonhorizontal orientation. The offset position is predicted to be a function of the Bingham number and the density ratio but independent of the initial inclination angle.
Lattice-Boltzmann simulations of particle transport in a turbulent channel flow
International Journal of Heat and Mass Transfer, 2018
The lattice-Boltzmann Method (LBM) is employed to directly simulate the transport of particles approximated as 'point particles' in a turbulent channel flow. Prior experimental studies have shown that particles preferentially move toward the wall or center in a pipe flow depending on their Stokes number (St). The simulations are carried out for a range of St and they reproduce the observed experimental behavior. Since the only effect that can influence the transport in the cross-flow direction is turbulence in the context of the simulation framework adopted here, it is concluded that turbophoresis is responsible for the behavior.
Lattice Boltzmann analysis of micro-particles transport in pulsating obstructed channel flow
Dispersion and deposition of microparticles are investigated numerically in a channel in the presence of a square obstacle and inlet flow pulsation. Lattice Boltzmann method (LBM) is used to simulate the flow field and modified Euler method is employed to calculate particles trajectories with the assumption of one-way coupling. The forces of drag, gravity, Saffman lift and Brownian motion are included in the particles equation of motion. The effects of pulsation amplitude (AMP), Strouhal number and particles Stokes number (Stk) are rigorously studied on particles dispersion and deposition efficiency. Flow vortex shedding and particles dispersion patterns together with the averaged fluid–particle relative velocity and deposition efficiency plots are all discussed thoroughly. The results show that increment of pulsation amplitude enforces the vortices to form closer to the obstacle until their shape deteriorates as Strouhal number ratio (SNR) rises. The average recirculation length shrinks to its minimum at each studied Amp when SNR escalates to 2. Various behaviors are categorized for dispersion pattern of particles when Stokes number changes from 0.001 to 4. Deposition efficiency is indirectly related to Amp for Stk ≤ 2 while for higher Stokes numbers (2 < Stk ≤ 4) they show direct relationship. Deposition pattern becomes rather independent of SNR at Amp = 0.1. The grid independency test was performed for the LBM analysis, and simulation code was successfully verified against credible benchmarks.
Computers & Fluids, 2019
Particle-resolved direct numerical simulations (PR-DNS) of particle-laden turbulent flow in a channel are carried out to understand the effect of particle Stokes number (St) on their motion. The study focuses on particles which are larger than the Kolmogorov scale. The forces that impact this motion are factored into the discussion. The lattice-Boltzmann method (LBM) is employed for the simulations. The scheme employed is able to resolve the surface of the particle and a method is adopted to account for the exchange of momentum between the particles and fluid as the particles move on fixed lattices. The simulations show that particles with relatively lower St move preferentially toward the wall while those with higher St exhibit a relatively uniform concentration.
Numerical simulation of microparticles transport in a concentric annulus by Lattice Boltzmann Method
Dispersion and removal of micro aerosol particles are investigat ed numerically in a horizontal concentric annulus by Lattice Boltzmann Method and Lagrangian Runge–Kutta procedure with the assumption of one-way coupling. Drag, buoyancy, gravity, shear lift, Brownian motion and thermophoretic are forces that are included in particle equation of motion. All simulations were performed at Rayleigh number of 104 and particles specific density of 1000. The effect of aspect ratio and particles diameter were determined on particles behavior such as removal and dispersion. Results show that recirculation power increases by decreasing of cylinders gap. Particles move in a thinner quasi-equilibrium region by increasing of their diameter and decreasing of cylinders gap. Brownian motion is dominant removal mechanism in particle with diameter of 1 micrometer.
Bulletin of the American Physical Society, 2006
Inertial migration of neutrally buoyant particles in a square duct has been investigated by numerical simulation in the range of Reynolds numbers from 100 to 1000. Particles migrate to one of a small number of equilibrium positions in the cross-sectional plane, located near a corner or at the center of an edge. In dilute suspensions, trains of particles are formed along the axis of the flow, near the planar equilibrium positions of single particles. At high Reynolds numbers ͑Reജ 750͒, we observe particles in an inner region near the center of the duct. We present numerical evidence that closely spaced pairs of particles can migrate to the center at high Reynolds number.
Numerical study of particle migration in tube and plane Poiseuille flows
2006
The lateral migration of a single spherical particle in tube Poiseuille flow is simulated by ALE scheme, along with the study of the movement of a circular particle in plane Poiseuille flow with consistent dimensionless parameters. These particles are rigid and neutrally buoyant. A lift law se s s