39,170 research outputs found
Lattice Boltzmann simulations of fluid flow in continental carbonate reservoir rocks and in upscaled rock models generated with multiple-point geostatistics
Microcomputed tomography (mu CT) and Lattice Boltzmann Method (LBM) simulations were applied to continental carbonates to quantify fluid flow. Fluid flow characteristics in these complex carbonates with multiscale pore networks are unique and the applied method allows studying their heterogeneity and anisotropy. 3D pore network models were introduced to single-phase flow simulations in Palabos, a software tool for particle-based modelling of classic computational fluid dynamics. In addition, permeability simulations were also performed on rock models generated with multiple-point geostatistics (MPS). This allowed assessing the applicability of MPS in upscaling high-resolution porosity patterns into large rock models that exceed the volume limitations of the mu CT. Porosity and tortuosity control fluid flow in these porous media. Micro-and mesopores influence flow properties at larger scales in continental carbonates. Upscaling with MPS is therefore necessary to overcome volume-resolution problems of CT scanning equipment. The presented LBM-MPS workflow is applicable to other lithologies, comprising different pore types, shapes, and pore networks altogether. The lack of straightforward porosity-permeability relationships in complex carbonates highlights the necessity for a 3D approach. 3D fluid flow studies provide the best understanding of flow through porous media, which is of crucial importance in reservoir modelling
A GPU-accelerated package for simulation of flow in nanoporous source rocks with many-body dissipative particle dynamics
Mesoscopic simulations of hydrocarbon flow in source shales are challenging,
in part due to the heterogeneous shale pores with sizes ranging from a few
nanometers to a few micrometers. Additionally, the sub-continuum fluid-fluid
and fluid-solid interactions in nano- to micro-scale shale pores, which are
physically and chemically sophisticated, must be captured. To address those
challenges, we present a GPU-accelerated package for simulation of flow in
nano- to micro-pore networks with a many-body dissipative particle dynamics
(mDPD) mesoscale model. Based on a fully distributed parallel paradigm, the
code offloads all intensive workloads on GPUs. Other advancements, such as
smart particle packing and no-slip boundary condition in complex pore
geometries, are also implemented for the construction and the simulation of the
realistic shale pores from 3D nanometer-resolution stack images. Our code is
validated for accuracy and compared against the CPU counterpart for speedup. In
our benchmark tests, the code delivers nearly perfect strong scaling and weak
scaling (with up to 512 million particles) on up to 512 K20X GPUs on Oak Ridge
National Laboratory's (ORNL) Titan supercomputer. Moreover, a single-GPU
benchmark on ORNL's SummitDev and IBM's AC922 suggests that the host-to-device
NVLink can boost performance over PCIe by a remarkable 40\%. Lastly, we
demonstrate, through a flow simulation in realistic shale pores, that the CPU
counterpart requires 840 Power9 cores to rival the performance delivered by our
package with four V100 GPUs on ORNL's Summit architecture. This simulation
package enables quick-turnaround and high-throughput mesoscopic numerical
simulations for investigating complex flow phenomena in nano- to micro-porous
rocks with realistic pore geometries
Efficient prediction of broadband trailing edge noise and application to porous edge treatment
Trailing edge noise generated by turbulent flow traveling past an edge of an
airfoil is one of the most essential aeroacoustic sound generation mechanisms.
It is of great interest for noise problems in various areas of industrial
application. First principle based CAA with short response time are needed in
the industrial design process for reliable prediction of spectral differences
in turbulent-boundary-layer trailing-edge noise due to design modifications. In
this paper, an aeroacoustic method is studied, resting on a hybrid CFD/CAA
procedure. In a first step RANS simulation provides a time-averaged solution,
including the mean-flow and turbulence statistics such as length-scale,
time-scale and turbulence kinetic energy. Based on these, fluctuating sound
sources are then stochastically generated by the Fast Random Particle-Mesh
Method to simulate in a second CAA step broadband aeroacoustic sound. From
experimental findings it is well known that porous trailing edges significantly
lower trailing edge noise level over a large range of frequencies reaching up
to 8dB reduction. Furthermore, sound reduction depends on the porous material
parameters, e.g. geometry, porosity, permeability and pore size. The paper
presents first results for an extended hybrid CFD/CAA method including porous
materials with prescribed parameters. To incorporate the effect of porosity, an
extended formulation of the Acoustic Perturbation Equations with source terms
is derived based on a reformulation of the volume averaged Navier-Stokes
equations into perturbation form. Proper implementation of the Darcy and
Forchheimer terms is verified for sound propagation in homogeneous and
anisotropic porous medium. Sound generation is studied for a generic symmetric
NACA0012 airfoil without lift to separate secondary effects of lift and camber
on sound from those of the basic edge noise treatments.Comment: 37 page
Dynamic development of hydrofracture
Many natural examples of complex joint and vein networks in layered sedimentary rocks are hydrofractures that form by a combination of pore fluid overpressure and tectonic stresses. In this paper, a two-dimensional hybrid hydro-mechanical formulation is proposed to model the dynamic development of natural hydrofractures. The numerical scheme combines a discrete element model (DEM) framework that represents a porous solid medium with a supplementary Darcy based pore-pressure diffusion as continuum description for the fluid. This combination yields a porosity controlled coupling between an evolving fracture network and the associated hydraulic field. The model is tested on some basic cases of hydro-driven fracturing commonly found in nature, e.g., fracturing due to local fluid overpressure in rocks subjected to hydrostatic and nonhydrostatic tectonic loadings. In our models we find that seepage forces created by hydraulic pressure gradients together with poroelastic feedback upon discrete fracturing play a significant role in subsurface rock deformation. These forces manipulate the growth and geometry of hydrofractures in addition to tectonic stresses and the mechanical properties of the porous rocks. Our results show characteristic failure patterns that reflect different tectonic and lithological conditions and are qualitatively consistent with existing analogue and numerical studies as well as field observations. The applied scheme is numerically efficient, can be applied at various scales and is computational cost effective with the least involvement of sophisticated mathematical computation of hydrodynamic flow between the solid grains
Microscopic Motion of Particles Flowing through a Porous Medium
We use Stokesian Dynamics simulations to study the microscopic motion of
particles suspended in fluids passing through porous media. We construct model
porous media with fixed spherical particles, and allow mobile ones to move
through this fixed bed under the action of an ambient velocity field. We first
consider the pore scale motion of individual suspended particles at pore
junctions. The relative particle flux into different possible directions
exiting from a single pore, for two and three dimensional model porous media is
found to approximately equal the corresponding fractional channel width or
area. Next we consider the waiting time distribution for particles which are
delayed in a junction, due to a stagnation point caused by a flow bifurcation.
The waiting times are found to be controlled by two-particle interactions, and
the distributions take the same form in model porous media as in two-particle
systems. A simple theoretical estimate of the waiting time is consistent with
the simulations. We also find that perturbing such a slow-moving particle by
another nearby one leads to rather complicated behavior. We study the stability
of geometrically trapped particles. For simple model traps, we find that
particles passing nearby can ``relaunch'' the trapped particle through its
hydrodynamic interaction, although the conditions for relaunching depend
sensitively on the details of the trap and its surroundings.Comment: 16 pages, 19 figure
Liquid spreading in trickle-bed reactors: Experiments and numerical simulations using Eulerian--Eulerian two-fluid approach
Liquid spreading in gas-liquid concurrent trickle-bed reactors is simulated
using an Eulerian twofluid CFD approach. In order to propose a model that
describes exhaustively all interaction forces acting on each fluid phase with
an emphasis on dispersion mechanisms, a discussion of closure laws available in
the literature is proposed. Liquid dispersion is recognized to result from two
main mechanisms: capillary and mechanical (Attou and Ferschneider, 2000;
Lappalainen et al., 2009- The proposed model is then implemented in two
trickle-bed configurations matching with two experimental set ups: In the first
configuration, simulations on a 2D axisymmetric geometry are considered and the
model is validated upon a new set of experimental data. Overall pressure drop
and liquid distribution obtained from -ray tomography are provided for
different geometrical and operating conditions. In the second configuration, a
3D simulation is considered and the model is compared to experimental liquid
flux patterns at the bed outlet. A sensitivity analysis of liquid spreading to
bed geometrical characteristics (void-fraction and particles diameter) as well
as to gas and liquid flow rates is proposed. The model is shown to achieve very
good agreement with experimental data and to predict, accurately, tendencies of
liquid spreading for various geometrical bed characteristics and/or phases
flow-rates
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