@article {Simula.simula.376,
title = {Computational Aspects of Multiscale Simulation With the Lumped Particle Framework},
journal = {Communications in Computational Physics},
volume = {12},
number = {4},
year = {2012},
pages = {1257-1274},
abstract = {First introduced in [2], the lumped particle framework is a flexible and numerically efficient framework for the modelling of particle transport in fluid flow. In this paper, the frame- work is expanded to simulate multicomponent particle-laden fluid flow. This is accomplished by introducing simulation protocols to model particles over a wide range of length and time scales. Consequently, we present a time ordering scheme and an approximate approach for ac- celerating the computation of evolution of different particle constituents with large differences in physical scales. We apply the extended framework on the temporal evolution of three parti- cle constituents in sand-laden flow, and horizontal release of spherical particles. Furthermore, we evaluate the numerical error of the lumped particle model. In this context, we discuss the Velocity-Verlet numerical scheme, and show how to apply this to solving Newton{\textquoteright}s equations within the framework. We show that the increased accuracy of the Velocity-Verlet scheme is not lost when applied to the lumped particle framework.},
author = {Al-Khayat, Omar and Hans Petter {Langtangen}}
}
@inproceedings {Simula.simula.374,
title = {An OpenMP-Enabled Parallel Simulator for Particle Transport in Fluid Flows},
journal = {Proceedings of the International Conference on Computational Science, ICCS 2011},
volume = {4},
year = {2011},
pages = {1475-1484},
publisher = {Elsevier Science},
type = {Conference},
address = { },
abstract = {By using C/C++ programming and OpenMP parallelization, we implement a newly developed numerical strategy for simulating particle transport in sparsely particle-laden fluid flows. Due to its highly dynamic property of the chosen numerical framework, the implementation needs to properly handle the moving, merging and splitting of a large number of particle lumps. We show that a careful division of the entire computational work into a set of distinctive tasks not only produces a clearly structured code, but also allows taskwise parallelization through appropriate use of OpenMP compiler directives. The performance of the OpenMP-enabled parallel simulator is tested on representative architectures of multicore-based shared memory, by running a large case of particle transport in a pipe flow. Attention is also given to a number of performance-critical features of the simulator.},
doi = {10.1016/j.procs.2011.04.160},
author = {Wei, Wenjie and Al-Khayat, Omar and Cai, Xing},
editor = {Sato, M. and Matsuoka, S.}
}
@article {Simula.sc.812,
title = {Particle Collisions in a Lumped Particle Model},
journal = {Communications in Computational Physics},
volume = {10},
number = {4},
year = {2011},
month = {October},
pages = {823-843},
abstract = {{This paper presents an extension of the lumped particle model in [1] to include the effects of particle collisions. The lumped particle model is a flexible framework for the model- ing of particle laden flows, that takes into account fundamental features, including advection, diffusion and dispersion of the particles. In this paper, we transform a binary collision model and concepts from kinetic theory into a collision procedure for the lumped particle framework. We apply this new collision procedure to investigate numerically the role of particle collisions in the hindered settling effect. The hindered settling effect is characterized by an increase in the effective drag coefficient CD that influences each particle in the flow. This coefficient is given by CD = (1 {-} \varphi){-}n CD , where \varphi is the volume fraction of particles, CD is the drag coefficient for a single particle, and n \simeq 4.67 for creeping flow. We obtain an approximation for CD /CD by calculating the effective work done by collisions, and comparing that to the work done by the drag force. In our numerical experiments, we observe a minimal value of n = 3.0. Moreover, by allowing high energy dissipation, an approximation for the classical value for creeping flow},
doi = {10.4208},
author = {Al-Khayat, Omar and Are Magnus {Bruaset} and Hans Petter {Langtangen}}
}
@article {Simula.SC.576,
title = {A Lumped Particle Modeling Framework for Simulating Particle Transport in Fluids},
journal = {Communications in Computational Physics},
volume = {8},
number = {1},
year = {2010},
pages = {115-142},
abstract = {This paper presents a lumped particle model for simulating a large number of particles. The lumped particle model is a flexible framework in modeling particle flows, embodying fundamental features that are intrinsic in particle laden flow, including advection, diffusion and dispersion. In this paper, the particles obey a simplified version of the Bassinet-Boussinesq-Oseen equation for a single spherical particle. However, instead of tracking the individual dynamics of each particle, a weighted spatial averaging procedure is used where the external forces are applied to a {\textquoteleft}{\textquoteleft}lump{\textquoteright}{\textquoteright} of particles, from which an average position and velocity is derived. The temporal evolution of the particles is computed by partitioning the lumped particle into smaller entities, which are then transported throughout the physical domain. These smaller entities recombine into new particle lumps at their target destinations. For particles prone to the effects of Brownian motion or similar phenomena, a symmetric spreading of the particles is included as well. Numerical experiments show that the lumped particle model reproduces the effects of Brownian diffusion and uniform particle transport by a fluid and gravity. The late time scale diffusive nature of particle motion is also reproduced.},
author = {Al-Khayat, Omar and Are Magnus {Bruaset} and Hans Petter {Langtangen}}
}
@misc {Simula.cg.30,
title = {A Lumped Particle Modeling Framework for the Transport of Particles},
howpublished = {Talk at CBC workshop on Tsunami Modelling},
year = {2010},
month = {June},
author = {Al-Khayat, Omar}
}
@phdthesis {Simula.simula.36,
title = {Mesoscale Modeling of Particle Flow},
year = {2010},
month = {May 2010},
school = {University of Oslo},
type = {phd},
isbn = {ISSN 1501-7710},
author = {Al-Khayat, Omar}
}
@misc {Simula.cg.32,
title = {A Multiscale Lumped Particle Modeling Framework for the Simulation of Turbidity Currents},
howpublished = {Poster at the 7th EGU General Assembly, vol 12, Vienna},
year = {2010},
author = {Al-Khayat, Omar}
}
@misc {Simula.SC.216,
title = {A Coupled Lattice Boltzmann Model for a Turbulent Sand-Laden Fluid Flow},
howpublished = {Talk at the DSFD conference in Brazil},
year = {2008},
month = {August},
abstract = {his talk describes a novel numerical modelling approach to simulate a sand-laden, highly turbulent fluid flow, also known as a turbidity current, with the Lattice Boltzmann method. Turbidity currents are sediment laden, highly turbulent submarine flows that are often triggered by catastrophic events like tsunamis or earthquakes. When a tur- bidity current comes to rest, the heaviest, coarsest grains settle first and the finest, lightest grains settle last. These deposits are called Turbidites. Turbidity currents constitute an important factor in the transport of clastic sediments into deep waters . Deposits from such flows are common in the deep water areas throughout the world and many of them constitute important petroleum reservoirs. The modelling and prediction of such deposits are therefore of prime interest both in the academic community and in the industry.Traditionally, turbidity currents have been modelled as a multiphase fluid flow in terms of continuum physics in a partial differential equation setting. Numerous models exist, and they are almost without exception based on traditional computational fluid dynamics (CFD). These are based on the assumption that the fluid and other quantities are in principle a continuum. Although improvement has been made, such models are associated with challenges. It is for instance difficult phenomenologically to describe and model the dynamics, deposition and erosion of sand particles in complex fluid flow from a traditional CFD approach.We will introduce a framework for modelling turbidity currents and turbidite development. The fluid phase is modeled by the Lattice Boltzmann equation, and the sand dynamics is described by the Basset-Boussinesq-Oseen (BBO) for spherical particles in a turbulent fluid. The two phases interact non-linearly through momentum exchange. We will describe basic features of the model and give an overview of the numerical implementation. Current status and outlook on the development process will be reported as well.},
author = {Al-Khayat, Omar and Hans Petter {Langtangen} and Are Magnus {Bruaset}}
}
@misc {Simula.SC.214,
title = {Numerical Modeling of Turbidity Flow With the Lattice Boltzmann Method},
howpublished = {Talk at the Computational Geoscience workshop},
year = {2008},
month = {June 6},
author = {Al-Khayat, Omar and Are Magnus {Bruaset} and Hans Petter {Langtangen}}
}
@misc {Simula.SC.218,
title = {Numerical Python},
howpublished = {Four day course at the University of Erlangen},
year = {2008},
month = {February},
author = {Hans Petter {Langtangen} and Al-Khayat, Omar and Are Magnus {Bruaset}}
}
@misc {Simula.SC.176,
title = {Particle-Based Methods in the Modelling of Turbidity Currents and Turbidites},
howpublished = {Talk at the 33rd IGC Congress in Oslo},
year = {2008},
month = {August},
author = {Al-Khayat, Omar and Tore M. {L{\o}seth} and Are Magnus {Bruaset} and Hans Petter {Langtangen}}
}
@misc {Simula.SC.84,
title = {Introduction to Particle Based Lattice Boltzmann Methods},
howpublished = {Minisymposium Talk},
year = {2007},
month = {July},
abstract = {Introduction at a Minisymposium session at ICIAM07},
author = {Al-Khayat, Omar}
}
@misc {Simula.SC.85,
title = {Lattice Boltzmann Method and Turbidity Flow Modeling},
howpublished = {Talk at MekIT{\textquoteright}07: Fourth National Conference on Computational Mechanics},
year = {2007},
author = {Al-Khayat, Omar and Are Magnus {Bruaset} and Hans Petter {Langtangen}}
}
@inproceedings {Simula.SC.20,
title = {Lattice Boltzmann Method and Turbidity Flow Modeling},
journal = {MekIT{\textquoteright}07 : Fourth National Conference in Computational Mechanics},
year = {2007},
month = {May},
pages = {213-228},
publisher = {Tapir Academic Press},
type = {Conference},
abstract = {We discuss the Lattice Boltzmann method (LBM), which provides a new way of thinking on complex, multiphase fluid flow problems. We present the basics of the LBM as well as its origins in the Cellular Automata. The particle-based nature of the LBM makes it well suited to study fluid-boundary interfaces. We then commence to sketch advanced applications like particle suspension problems and we show how the LBM can be applied on turbidity currents, a challenging fluid flow problem. We show that the LBM has a good deal of versatility in modeling physical systems.},
isbn = {978-82-519-2235-7},
author = {Al-Khayat, Omar and Are Magnus {Bruaset} and Hans Petter {Langtangen}},
editor = {Bj{\o}rn H. {Skallerud} and H. I. {Andersson}}
}
@mastersthesis {Al-khayat.2005.2,
title = {Introduction to the Theory of the Cosmic Microwave Background},
year = {2005},
month = {june},
publisher = {University of Oslo},
type = {masters},
abstract = {The thesis presents an in depth study of the physical and numerical aspects of the Cosmic Microwave Background. New analytic results are analyzed numerically to check correspondance with public codes.},
author = {Al-Khayat, Omar}
}