Particle Dispersion in Homogeneous Isotropic Turbulence PDF Download
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Author: Thomas Burgener
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Thomas Burgener
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Kyle David Squires
Publisher:
ISBN:
Category :
Languages : en
Pages : 308
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Author: Renwei Mei
Publisher:
ISBN:
Category :
Languages : en
Pages : 636
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Book Description
A solution to particle dispersion in an isotropic turbulence under Stokes drag, Basset force and gravitational force is obtained in closed form using the independence approximation. The Basset force has no effect on the fluid velocity structure seen by the particles or the long-time particle diffusivities. It does affect the intensities of particle motion for particles with large settling rate and with response time comparable to the turbulence integral time scale. A solution for particles dispersion in isotropic turbulence with non-Stokesian drag and gravitational force is obtained. The time constants of the particle fluctuation in the directions parallel and perpendicular to the gravity are anisotropic. Turbulence increases particle response time constants and reduces settling velocity. Influence of the nonlinear drag, particle response time constants and settling rate on particle dispersion are investigated. Monte-Carlo simulations are performed for particle motions in an isotropic turbulence with non-Stokesian drag. Pseudo-turbulence is generated using random Fourier modes representation. Statistical averages are obtained from more than 5000 particles. The results of the simulation validate the preceeding analysis in the non-Stokesian drag range. The influence of turbulence structure on the dispersions of fluid and particle is examined. In addition to the integral length and time scales, the functional form of the energy spectrum is also important in describing the dispersions of both fluid and particles. Numerical solution for unsteady flow over a sphere indicates that the added-mass force at finite Reynolds number is the same as in the creeping flow and the potential flow. The classical Stokes solution is not valid at small frequency, $omega$, and the corresponding Basset force is proportional to $omega$, instead of $sqrt{omega}$. The Basset-force term has a kernel decays faster than (t- $tau$)$sp{-1/2}$ at large time. The use of the steady state drag coefficient with the instantaneous velocity is justified to approximate the quasi-steady drag on particles. Limiting behavior of the unsteady drag on a sphere at small frequency and low Reynolds number is obtained using matched asymptotic expansions. The modified Basset-force term at finite Re is constructed. It has a kernel decays as (t- $tau$)$sp{-2}$ at large times.
Author: J. P. Minier
Publisher:
ISBN:
Category : Dispersion
Languages : en
Pages : 300
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Author: Renwei Mei
Publisher:
ISBN:
Category : Mechanics, Applied
Languages : en
Pages : 61
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Author: S. Balachandar
Publisher: Springer Science & Business Media
ISBN: 1402049773
Category : Science
Languages : en
Pages : 443
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Book Description
The book provides a broad overview of the full spectrum of state-of-the-art computational activities in multiphase flow as presented by top practitioners in the field. It starts with well-established approaches and builds up to newer methods. These methods are illustrated with applications to a broad spectrum of problems involving particle dispersion and deposition, turbulence modulation, environmental flows, fluidized beds, bubbly flows, and many others.
Author: Bernard Geurts
Publisher: Springer Science & Business Media
ISBN: 1402062184
Category : Science
Languages : en
Pages : 409
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Book Description
This book contains a selection of the papers that were presented at the EUROMECH colloquium on particle-laden flow held at the University of Twente in 2006. The multiscale nature of this challenging field motivated the calling of the colloquium and reflects the central importance that the dispersion of particles in a flow has in various geophysical and environmental problems. The spreading of aerosols and soot in the air, the growth and dispersion of plankton blooms in seas and oceans, or the transport of sediment in rivers, estuaries and coastal regions are striking examples.
Author: Leonid I. Zaichik
Publisher: John Wiley & Sons
ISBN: 3527626263
Category : Science
Languages : en
Pages : 318
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Book Description
The only work available to treat the theory of turbulent flow with suspended particles, this book also includes a section on simulation methods, comparing the model results obtained with the PDF method to those obtained with other techniques, such as DNS, LES and RANS. Written by experienced scientists with background in oil and gas processing, this book is applicable to a wide range of industries -- from the petrol industry and industrial chemistry to food and water processing.
Author: Kenneth T. Kiger
Publisher:
ISBN:
Category :
Languages : en
Pages : 368
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Book Description
The transport of heavy, polydispersed particles and the inter-phase transfer of kinetic energy is measured experimentally in a turbulent shear layer. Specifically, fundamental/subharmonic forcing and conditional-averaging techniques were used to study the particle/turbulence interaction with the large-scale, spanwise, coherent vortices, starting from their initial roll-up through the first pairing event. It is shown that the pairing event plays a homogenizing role on the particulate field, but the amount of homogenization is strongly dependent upon the particle's viscous relaxation time, the eddy turnover time, as well as the time the particles are allowed to interact with each scale prior to a pairing event. Thus, even though the smaller size particles become well-mixed across the structure, the larger sizes are still dispersed in an inhomogeneous fashion. The dispersed/carrier phase coupling was examined through the measurement of conditionally-averaged kinetic energy transfer (which results from the work done to accelerate or decelerate the dispersed phase), as well as the conditionally-averaged particle dissipation (energy dissipated by shear deformation in the carrier phase due to the relative slip between the particles and the carrier fluid).
Author: Udayshankar Kundur Menon
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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When anisotropic particles settle in isotropic turbulence, the inertial torque due to their settling favors broadside alignment while turbulence favors orientation dispersion. This process leads, for example, to the anisotropic scattering of electromagnetic radiations in icy clouds due to the oprientation dustribution of ice crystals, which can have needle-like or disk-like shapes. We study two types of particles amenable to the use of slender-body theory (Batchelor 1970, Khayat and Cox 1989): fibers and planar triads consisting of three connected rods. In our approach we use slendr-body theory to model these high aspect ration particles and use stochastic models to describe the fluid flow. For particles smaller than the Kolmogorov scale, the effect of turbulence can be described in terms of a temporally fluctuating local linear flow field following the motion of the particle. When the settling velocity is small compared with the Kolmogorov velocity, the particle samples the fluid velocity gradients along a Lagrangian path, and our simulations employ the stochastic velocity gradient model og Girimaji and Pope (1990). When the setting velocity is large compared with the Kolmogorov velocity, the large inertial torque causes the particle to acheive a quasi-steady orientation with respect to the local velocity gradient allowing analytical predictions of the small orientaional dispersion away from the preferred horizontal alignment. Through our simulations and theory, we identify a settling parameter Sf and an asymptotic power-law dependence of orientational variance on the same. We eventually compare our simulation results to experiments and derived theoretical asymtotes.
