Simulation of deterministic energy-balance particle agglomeration in turbulent liquid-solid flows

An efficient technique to simulate turbulent particle-laden flow at high mass loadings within the four-way coupled simulation regime is presented. The technique implements large-eddy simulation, discrete particle simulation, a deterministic treatment of inter-particle collisions, and an energy-balanced particle agglomeration model. The algorithm to detect inter-particle collisions is such that the computational costs scale linearly with the number of particles present in the computational domain. On detection of a collision, particle agglomeration is tested based on the pre-collision kinetic energy, restitution coefficient, and van der Waals’ interactions. The performance of the technique developed is tested by performing parametric studies on the influence of the restitution coefficient (en = 0.2, 0.4, 0.6, and 0.8), particle size (dp = 60, 120, 200, and 316 μm), Reynolds number (Reτ = 150, 300, and 590), and particle concentration (αp = 5.0 × 10−4, 1.0 × 10−3, and 5.0 × 10−3) on particle-particle interaction events (collision and agglomeration). The results demonstrate that the collision frequency shows a linear dependency on the restitution coefficient, while the agglomeration rate shows an inverse dependence. Collisions among smaller particles are more frequent and efficient in forming agglomerates than those of coarser particles. The particle-particle interaction events show a strong dependency on the shear Reynolds number Reτ, while increasing the particle concentration effectively enhances particle collision and agglomeration whilst having only a minor influence on the agglomeration rate. Overall, the sensitivity of the particle-particle interaction events to the selected simulation parameters is found to influence the population and distribution of the primary particles and agglomerates formed

Derrick Laster v. Charles Samuels

USDC for the District of New Jerse

Effect of flow pattern at pipe bends on corrosion behaviour of low carbon steek and its challenges

Recent design work regarding seawater flow lines has emphasized the need to identify, develop, and verify critical relationships between corrosion prediction and flow regime mechanisms at pipe bend. In practice this often reduces to an pragmatic interpretation of the effects of corrosion mechanisms at pipe bends. Most importantly the identification of positions or sites, within the internal surface contact areas where the maximum corrosion stimulus may be expected to occur, thereby allowing better understanding, mitigation, monitoring and corrosion control over the life cycle. Some case histories have been reviewed in this context, and the interaction between corrosion mechanisms and flow patterns closely determined, and in some cases correlated. Since the actual relationships are complex, it was determined that a risk based decision making process using selected ‘what’ if corrosion analyses linked to ‘what if’ flow assurance analyses was the best way forward. Using this in methodology, and pertinent field data exchange, it is postulated that significant improvements in corrosion prediction can be made. This paper outlines the approach used and shows how related corrosion modelling software data such as that available from corrosion models Norsok M5006, and Cassandra to parallel computational flow modelling in a targeted manner can generate very noteworthy results, and considerably more viable trends for corrosion control guidance. It is postulated that the normally associated lack of agreement between corrosion modelling and field experience, is more likely due to inadequate consideration of corrosion stimulating flow regime data, rather than limitations of the corrosion modelling. Applications of flow visualization studies as well as computations with the k-ε model of turbulence have identified flow features and regions where metal loss is a maximu

Large Eddy Simulation of Particle Agglomeration with Shear Breakup in Turbulent Channel Flow

A systematic technique is developed for studying particle dynamics as induced by a turbulent liquid flow, in which transport, agglomeration, and breakup are considered. An Eulerian description of the carrier phase obtained using large eddy simulation is adopted and fully coupled to a Lagrangian definition of the particle phase using a pointwise discrete particle simulation. An efficient hard-sphere interaction model with deterministic collision detection enhanced with an energy-balance agglomeration model was implemented in an existing computational fluid dynamic code for turbulent multiphase flow. The breakup model adopted allows instantaneous breakup to occur once the transmitted hydrodynamic stress within an agglomerate exceeds a critical value, characterised by a fractal dimension and the size of the agglomerate. The results from the developed technique support the conclusion that the local turbulence kinetic energy, its dissipation rate, and the agglomerate fractal dimension control the kinetics of the agglomeration and de-agglomeration processes, and as well as defining with time the morphology of the particles and their resultant transport. Overall, the results are credible and consistent with the expected physical behavior and with known theories

Reynolds number effects on particle agglomeration in turbulent channel flow

The work described in this paper employs large eddy simulation and a discrete element method to study particle-laden flows, including particle dispersion and agglomeration, in a horizontal channel. The particle-particle interaction model is based on the Hertz- Mindlin approach with Johnson-Kendall-Roberts cohesion to allow the simulation of Van der Waals forces in a dry air flow. The influence of different flow Reynolds numbers, and therefore the impact of turbulence, on particle agglomeration is investigated. The agglomeration rate is found to be strongly influenced by the flow Reynolds number, with most of the particle-particle interactions taking place at locations close to the channel walls, aided by the higher turbulence and concentration of particles in these regions

The impact of coupling and particle volume fraction on fluid-particle interactions in a turbulent channel flow

Direct numerical simulation, facilitated by a spectral element method, is used to predict a multi-phase fluid flow through a channel at a shear Reynolds number of 300. Following validation of single-A nd multi-phase flow results against other DNS predictions available in the literature, a channel flow is simulated utilising a Lagrangian particle tracker to model 300,000 particles with a diameter of 100 'Ým, having a density ratio equivalent to that of water to glass, and a particle volume fraction of approximately 0.01%. This flow is calculated using multiple levels of coupling between the particles and the flow; one-way, two-way and four-way. The mean streamwise velocity of the fluid and the particles, along with the shear and normal stresses, are compared for the different coupling methods, with the differences between them analysed and, although small, they are found to be consistent across the channel. A second set of runs is performed using in excess of 2 million particles in order to facilitate a tenfold increase in the particle volume fraction, to 0.1%, with the particles expected in this case to have a greater impact upon the properties of the fluid. The statistics of the fluid and particles in these simulations are then compared with those from the simulation with a lower concentration of particles in order to determine the magnitude of the effect the particles have on the fluid in this flow. The effects of the different couplings on the flow are much greater in this case due to the increased number of particles affecting the flow. Also, the presence of the particles is seen to increase the turbulence levels of the fluid, especially in the streamwise direction. The accuracy of the simulations clearly increases with the level of coupling. However, the speed of the simulations decreases. One way of achieving decreased run times, for both volume fraction cases, is to use a faster stochastic version of the particle tracking code for four-way coupling. This is tested, replacing the Lagrangian collision mechanics in the four-way coupled simulations with a probabilistically-determined mechanistic model. For the lower volume fraction, the normal stresses of the particles are exaggerated somewhat using the stochastic method. The simulation time is decreased compared to the Lagrangian approach, although the results presented suggest that the stochastic method requires further refinement

Leaving the Street: Young Fathers Move from Hustling to Legitimate Work

This report explores employment and hustling among men in Fathers at Work, a three-year national demonstration designed to help low-income, noncustodial fathers secure living-wage jobs, increase their involvement with their children and manage their child support obligations. As part of P/PVs evaluation of the initiative, researchers undertook an in-depth interview study. When they learned that more than three quarters of all Fathers at Work participants had been convicted of a crime, they focused the interview study on 27 men who had relied on hustlingprimarily selling drugs, but also other illegal activitiesas a source of income. The report describes how the men became involved in hustling and what led them to seek alternatives. Participants hustling and work experiences are detailed, with four distinct patterns emergingresearchers found that these patterns appeared to influence early employment outcomes. The report closes with a look at the ongoing challenges faced by the men, and recommendations for programs working with similar populations

On the effect of static and dynamic particle size distribution on flow turbulence modulation

The effect of an evolving particle size distribution due to particle agglomeration and breakup, and the direction and absence of gravitational acceleration, on flow turbulence modulation is investigated using large eddy and discrete particle simulation of a turbulent channel flow. The results are compared with the case in which the particle size distribution is static and where only inter-particle collision is allowed. Due to the small particle Stokes number considered, inherent in a solid-liquid flow, and the small simulation time, only small effects were observed for the static versus dynamic particle size distribution on the fluid turbulence. For vertical channel flows, however, the influence of flow direction and gravity lead to different particle segregation patterns which, together with changes in wall shear stresses and mass flow rate due to buoyancy effects, do affect the flow turbulence and the evolution of inter-particle collisions, collision efficiency and agglomerate breakup

The Tiger Vol. VI No.19 - 1911-03-07

https://tigerprints.clemson.edu/tiger_newspaper/1062/thumbnail.jp

GSU View, April 3, 2018

GSU Men\u27s Basketball Championship Banners, Amber Brooks and Tiana Mericle named to CCAC All-Academic Team, Interview with Men\u27s Basketball Coach Tony Bates, interview with Mike Reilly and Jim Reilly; Interview with Jeffrey Alfano