Mike Reeks

Newcastle University | NCL · School of Mechanical and Systems Engineering

Nationally approved emission factors of mass versus particle size for particulate emissions from UK MSW incinerators when converted to particle number versus size, indicate that nearly all (>90\%) of the emitted particles are ultra fine particles (ufps) < .1 micron in size. A similar result is true also of US MSW incinerators emissions. This would...

This Freeman Scholar article reviews the formulation and application of a kinetic theory for modeling the transport and dispersion of small particles in turbulent gas-flows, highlighting the insights and understanding it has provided and some of the long standing problems in the modeling of dispersed flows it has resolved. The theory has been devel...

This report summarizes the presentations and discussions conducted during the symposium, which was held under the aegis of the International Union of Theoretical and Applied Mechanics during 23–27 January 2012 in Bangalore, India.

We discuss the relation between three recent approaches of describing the dynamics and the spatial distribution of particles suspended in turbulent flows: phase-space singularities in the inertial particle dynamics (caustics), real-space singularities of the deformation tensor, and random uncorrelated motion. We discuss how the phase- and real-spac...

In this survey we consider the impact of turbulence on cloud formation from the cloud scale to the droplet scale. We assess progress in understanding the effect of turbulence on the condensational and collisional growth of droplets and the effect of entrainment and mixing on the droplet spectrum. The increasing power of computers and better experim...

We present a hybrid stochastic model for the resuspension of micron-size particles from multilayer deposits in a fully-developed turbulent boundary layer. The rate of removal of particles from any given layer depends upon the rate of removal of particles from the layer above which acts as a source of uncovering and exposure of particles to the resu...

The work described is concerned with the way micron-size particles attached to a surface are resuspended when exposed to a turbulent flow. An improved version of the Rock'n'Roll model (Reeks and Hall, 2001) is developed where this model employs a stochastic approach to resuspension involving the rocking and rolling of a particle about surface asper...

The HTR primary-system environment comprises nuclear graphites, alloys, dust (primarily carbonaceous) and high-purity helium. The amount of carbonaceous dust produced in a pebble-bed system would be considerably greater than one using a prismatic core with a significant contribution arising from the partially graphitized binder of the pebbles. The...

The Nuclear Decommissioning Authority (NDA) is developing a family of Standard Waste Transport Containers (SWTCs) for the transport of unshielded intermediate level radioactive waste packages. The SWTCs are shielded transport containers designed to carry different types of waste packages. The combination of the SWTC and the waste package is require...

The 6th FWP SARNET project launched a set of studies to enhance understanding and predictability of relevant-risk scenarios where uncertainties related to aerosol phenomena were still significant: retention in complex structures, such as steam generator by-pass SGTR sequences or cracks in concrete walls of an over-pressurised containment, and prima...

The way particles suspended in a turbulent flow are transported and segregated by turbulent structures is crucial in many atmospheric and industrial applications such as powder production and formation and growth of PM10 particulate. In recent years, this phenomenon has been studied from different viewpoints; lately, Osiptsov [1] proposed an altern...

Preferential concentration of inertial particles in turbulence is studied numerically by evaluating the Lagrangian compressibility of the particle velocity field using the "full Lagrangian method." This is compared with the "mesoscopic Eulerian particle velocity field" both in a direct numerical simulation of turbulence and in a synthetic flow fiel...

Important features associated with the segregration of particles in turbulent flow are investigated by considering the statistical distribution (phase-space number density) of particles subject to the combined effects of straining flow and stochastic forcing. A Fokker-Planck model is used to obtain results for the phase-space distributions of parti...

A theoretical model for predicting the droplet size distribution for electrostatic spray was described based on the information entropy method. The model was numerically calculated using the modified Newton-Raphson method. The present model can evaluate the droplet size distribution for a cone-jet mode electrostatic spray. The predicted results of...

Suspensions of small heavy particles in turbulent ows are found in a variety of natural and industrial applications such as droplets in clouds (1), soot particles in post combustion devices and reacting particles in chemical processs facilities (2). It is well known from experimental results (3), numerical simulations (4) and theoretical studies (5...

Introduction Computational modelling is assuming a greater and greater role in the study of multi-phase flows. Although it is not yet feasible to predict complex multi-phase flow fields over the full range of velocities and flow patterns, computational methods are helpful for a variety of reasons which include: They enable insights to be obtained o...

A simple mechanistic model for resuspension assuming a log-normal distribution of adhesive forces is used to analyse the resuspension measurements of a series of experiments reported in the literature covering a range of particle size from sub-micron to 30μm in both mono-layer and multi-layer deposits. Correlations are derived for the geometric mea...

Measurements are reported of the short-term resuspension of nominal 10 and alumina spheres and graphite particles from a polished stainless-steel flat plate in fully developed turbulent channel flow. Preliminary measurements were made of the normal and tangential forces holding the particles onto the surface. Whilst both forces had a broad spread a...

Presents a new approach to the way small particles are resuspended from a surface exposed to a turbulent flow. In contrast to current force balance models, this approach recognises the influence of turbulent energy transferred to a particle from the resuspending flow. This energy maintains the particle in motion on the surface within a surface adhe...

A transport equation for the particle phase space density (probability density function (pdf) kinetic equation) is derived for the motion of a dilute suspension of particles in a turbulent flow. The underlying particle equation of motion is based upon a Langevin equation but with a non-white noise driving force derived from an Eulerian aerodynamic...

A technique for solving a certain class of partial differential equations is used to obtain exact solutions for particle dispersion in an unbounded Gaussian random flow field in which the mean flow is a simple shear and the turbulence is homogeneous and stationary. Results are compared with those of a simple random walk simulation and those obtaine...

Measurements are reported of the resuspension of 10 and 20 micron alumina spheres and graphite particles from a polished stainless steel flat plate in fully developed turbulent channel flow. Preliminary measurements were made of the normal and tangential forces holding the particles onto the surface. Whilst both forces had a broad spread and were o...

A set of continuum equations modelling the dispersed particle phase will be derived. This set represents conservation of mass, momentum and energy within a fixed elemental volume. These are obtained from a transport equation for a probability density function describing the average particle behaviour.

The steady-state transport and deposition of "high inertia" particles in turbulent duct flow is studied. A relatively simple yet fundamental PDF (probability density function) equation (kinetic equation) is proposed as a model for such systems together with models describing perfectly and partially adsorbing boundaries. Using the idea of particle m...

The work presented follows on from a previous study in which a kinetic approach was used to generate the continuum equations for a dilute dispersed phase of noncolliding particles in a nonuniform turbulent flow. Here this approach is used to derive forms for the Reynolds stresses and the fluctuating interphase momentum transfer for particles at equ...

The continuum equations of a dispersed phase of solid, noncolliding particles in a nonuniform turbulent gas flow are derived from a kinetic equation for the transport of the average phase space density 〈W(v,x,t)〉 for particles with velocity v and position x at time t. The crucial feature of this equation is the form given for the phase space diffus...

The work described is part of a long-term study in pursuit of a kinetic equation for particles suspended in a turbulent flow. This equation represents the transport of the average particle phase space density and can be used to derive the continuum equations and constitutive relations for a two-fluid model of a dispersed particle flow and to establ...

A Fokker-Planck equation describing the transport of particles in turbulent flows is considered. The initial value problem with perfectly absorbing boundary conditions on the wall is solved by introducing a characteristic line in phase space. It is found that the solution domain in phase space decomposes into three regions which are connected by tw...

This paper proposes an integro-differential equation to describe the decay of particle gas-borne concentration in recirculating turbulent flows which are fully mixed. Its application to the decay of gas-borne concentration for particles injected into the primary circuit of an Advanced Gas Cooled Reactor is considered. The novel aspect of this work...

Previous works have used the fluctuation–dissipation theorem to evaluate the diffusion coefficient for particles in a turbulent flow which differs from the commonly accepted value. This calculation is reexamined and it is concluded that fluctuation–dissipation expressing energy equipartition is inappropriate for hydrodynamic turbulence.

This paper examines in detail a recent particle-based theory for the low temperature deposition of carbon observed in the Windscale advanced gas-cooled reactor (WAGR). A crucial feature of the theory is the variation of carbon deposition with thermal flux due to thermophoresis. Detailed calculations of the heat flux and flow over ribbed fuel pin su...

A calculation of the asymptotic particle diffusion coefficient in an unbounded stationary homogeneous turbulent flow is performed for a particle subjected to both added mass and Basset history forces, as well as the normal Stokes drag. The original value obtained by Tchen is shown to be in error by an additional term which for a sphere of diameter...

A statistical model for the resuspension of small particles by a turbulent fluid is presented. The approach is similar to the escape of Brownian particles from a potential well. Particles are released from the well when they receive enough energy from the local interaction of the turbulent eddies to escape over a potential barrier formed from the a...

Recent measurements of particle deposition velocities on the walls of a pipe in turbulent flow (Liu and Agarwal, 1974) show a decline with increasing particle size beyond a critical particle size. A stochastic model of particle deposition is presented which explains this result. As in other models, the deposition process is composed of turbulent di...

This volume contains the papers that were presented at the Fifth International Symposium on Gas-Solid Flows. The symposium included seven invited addresses that cover the major areas of interest within the field of gas-solid flows. The contributed papers cover a very broad range of topics, including analytical developments, full numerical simulatio...

This book contains papers that were presented at the Fourth International Symposium on Gas-Solid Flows. It is organized under the following headings: Simulation of gas-solid flows; Chaos and analytical developments; Applications; Experimental studies; Particle-wall and particle-particle interactions; Gas-solid transport and metering; Fluidized beds...