Search results for "numerical [Methods]"
showing 10 items of 500 documents
Digital rock physics, chemistry, and biology: challenges and prospects of pore-scale modelling approach
2021
Abstract Conventional and unconventional hydrocarbon rocks have complicated pore structures with heterogeneities distributed over various length scales (from nanometre to centimetre or even larger scales). Effective characterization of the properties of such rocks based on their digital twins is a challenging task. Digital rock physics (DRP) can be used to quantify the structural and morphological parameters of rocks directly and predict flow transport properties at the pore scale. Digital rock chemistry (DRC) or biology (DRB) applies when the changes in pore structures are due to interaction with solutes or microbial activities. Fluid–rock interactions or microbial activities complicate fl…
Interference Effects in Photodetachment of F- in a Strong Circularly Polarized Laser Pulse
2007
A numerical simulation of photodetachment of F{sup -} by a circularly polarized laser pulse has been accomplished by using a Keldysh-type approach. The numerical results are in agreement with measurements of photoelectron energy spectra recently reported in the literature. The features exhibited by the spectra are traced back to quantum interference effects, in the same spirit as in a double-slit experiment in the time doma0008.
Multipole solitary wave solutions of the higher-order nonlinear Schrödinger equation with quintic non-Kerr terms
2013
We consider a high-order nonlinear Schrodinger (HNLS) equation with third- and fourth-order dispersions, quintic non-Kerr terms, self steepening, and self-frequency-shift effects. The model applies to the description of ultrashort optical pulse propagation in highly nonlinear media. We propose a complex envelope function ansatz composed of single bright, single dark and the product of bright and dark solitary waves that allows us to obtain analytically different shapes of solitary wave solutions. Parametric conditions for the existence and uniqueness of such solitary waves are presented. The solutions comprise fundamental solitons, kink and anti-kink solitons, W-shaped, dipole, tripole, and…
Simple absorbing layer conditions for shallow wave simulations with Smoothed Particle Hydrodynamics
2013
Abstract We study and implement a simple method, based on the Perfectly Matched Layer approach, to treat non reflecting boundary conditions with the Smoothed Particles Hydrodynamics numerical algorithm. The method is based on the concept of physical damping operating on a fictitious layer added to the computational domain. The method works for both 1D and 2D cases, but here we illustrate it in the case of 1D and 2D time dependent shallow waves propagating in a finite domain.
Unsteady turbulence in plane channel flow
2011
Abstract Direct numerical simulations were conducted for oscillating flow with zero time mean (reciprocating flow) in a plane channel subject to a harmonic forcing term of varying amplitude and frequency. The results confirmed the existence of four flow regimes (laminar, “disturbed laminar”, intermittently turbulent, and fully turbulent) depending on the above parameters. The flow behaviour was found to depend on the complex interplay of mean and turbulence quantities, as described by the closed loop formed by the streamwise Reynolds-averaged momentum equation in conjunction with the exact transport equations for the turbulent (Reynolds) stresses. A crucial role in this loop appeared to be …
Numerical Models of Blackbody-Dominated GRBs
2015
Blackbody-dominated (BBD) gamma-ray bursts (GRBs) are events characterized by the absence of a typical afterglow, long durations and the presence of a significant thermal component following the prompt gamma-ray emission. GRB 101225A (the `Christmas burst') is a prototype of this class. A plausible progenitor system for it, and for the BBD-GRBs, is the merger of a neutron star (NS) and a helium core of an evolved, massive star. Using relativistic hydrodynamic simulations we model the propagation of an ultrarelativistic jet through the enviroment created by such a merger and we compute the whole radiative signature, both thermal and non-thermal, of the jet dynamical evolution. We find that t…
High Energy Emission from Shocks Due to Jets and Accretion in Young Stars with Disks: Combining Observations, Numerical Models, and Laboratory Experi…
2018
High energy emission from young stars with disks, with all their components due to accretion and outflow activity, can have a deep impact on the evolution of their disks and on the formation of exo-planetary systems. An inter-disciplinary approach, which combines multi-wavelength observations, magnetohydrodynamical models, and laboratory experiments, allows us to get a more complete description of the accretion/ejection phenomena characterizing young stars. We discuss the case of the HH 154 jet, its X-ray emission localized at the base of the jet and its complex morphology, comparing observations, models, and laser experiments. We present the comparison between magnetohydrodynamical models …
Direct numerical simulation of MR suspension: The role of viscous and magnetic interactions between particles
2009
A numerical method is developed with aim to simulate the magnetorheological (MR) suspension taking into account realistic magnetic forces. The MR suspension is described by spherical particles with nonlinear magnetic properties suspended in a shear flow. Inertia effects, Brownian motion and buoyancy forces are neglected. The hydrodynamic interaction between close particles is taken into account approximately. Results of some test simulations are presented.
Numerical test of finite-size scaling predictions for the droplet condensation-evaporation transition
2016
We numerically study the finite-size droplet condensation-evaporation transition in two dimensions. We consider and compare two orthogonal approaches, namely at fixed temperature and at fixed density, making use of parallel multicanonical simulations. The equivalence between Ising model and lattice gas allows us to compare to analytical predictions. We recover the known background density (at fixed temperature) and transition temperature (at fixed density) in the thermodynamic limit and compare our finite-size deviations to the predicted leading-order finite-size corrections.
Discrete-ring vortex solitons
2010
We study analytically and numerically the existence and stability of discrete vortex solitons in the circular arrays of nonlinear optical waveguides, governed by the discrete nonlinear Schrodinger equation. Stable vortex breathers with periodically oscillating topological charge are identified and a continuous interpolating map is constructed which allows to recover trajectories of individual phase dislocations in the form of hyperbolic avoided crossings.