5,885 research outputs found
Numerical Investigation of Two-Phase Flow through a Fault
Imperial Users onl
Numerical simulation of bubble generation in a T-junction
We present a numerical study of the formation of mini-bubbles in a 2D T-junction by means of the fluid dynamics numerical code JADIM. Numerical simulations were carried out for different flow conditions, giving rise to results on the behavior of bubble velocity, void fraction, bubble generation frequency and length. Numerical results are compared with existing experimental data thanks to non-dimensional analysis
Phase-field simulation of core-annular pipe flow
Phase-field methods have long been used to model the flow of immiscible
fluids. Their ability to naturally capture interface topological changes is
widely recognized, but their accuracy in simulating flows of real fluids in
practical geometries is not established. We here quantitatively investigate the
convergence of the phase-field method to the sharp-interface limit with
simulations of two-phase pipe flow. We focus on core-annular flows, in which a
highly viscous fluid is lubricated by a less viscous fluid, and validate our
simulations with an analytic laminar solution, a formal linear stability
analysis and also in the fully nonlinear regime. We demonstrate the ability of
the phase-field method to accurately deal with non-rectangular geometry, strong
advection, unsteady fluctuations and large viscosity contrast. We argue that
phase-field methods are very promising for quantitatively studying moderately
turbulent flows, especially at high concentrations of the disperse phase.Comment: Paper accepted for publication in International Journal of Multiphase
Flo
Interface-Resolving Simulations of Gas-Liquid Two-Phase Flows in Solid Structures of Different Wettability
This PhD study is devoted to numerical investigations of two-phase flows on and through elementary and complex solid structures of varying wettability. The phase-field method is developed and implemented in OpenFOAM®. The numerical method/code is verified by a series of test cases of two-phase flows, and then applied to investigate: (1) droplet wetting on solid surfaces; (2) air bubble rising and interacting with cellular structures and (3) gas-liquid interfacial flows in foam structures
Faraday instability on a sphere: numerical simulation
We consider a spherical variant of the Faraday problem, in which a spherical
drop is subjected to a time-periodic body force, as well as surface tension. We
use a full three-dimensional parallel front-tracking code to calculate the
interface motion of the parametrically forced oscillating viscous drop, as well
as the velocity field inside and outside the drop. Forcing frequencies are
chosen so as to excite spherical harmonic wavenumbers ranging from 1 to 6. We
excite gravity waves for wavenumbers 1 and 2 and observe translational and
oblate-prolate oscillation, respectively. For wavenumbers 3 to 6, we excite
capillary waves and observe patterns analogous to the Platonic solids. For low
viscosity, both subharmonic and harmonic responses are accessible. The patterns
arising in each case are interpreted in the context of the theory of pattern
formation with spherical symmetry
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
One-dimensional modelling of mixing, dispersion and segregation of multiphase fluids flowing in pipelines
The flow of immiscible liquids in pipelines has been studied in this work in order to formulate
a one-dimensional model for the computer analysis of two-phase liquid-liquid flow in horizontal
pipes. The model simplifies the number of flow patterns commonly encountered in liquid-liquid
flow to stratified flow, fully dispersed flow and partial dispersion with the formation of one or
two different emulsions. The model is based on the solution of continuity equations for dispersed
and continuous phase; correlations available in the literature are used for the calculation of the
maximum and mean dispersed phase drop diameter, the emulsion viscosity, the phase inversion
point, the liquid-wall friction factors, liquid-liquid friction factors at interface and the slip
velocity between the phases. In absence of validated models for entrainment and deposition
in liquid-liquid flow, two entrainment rate correlations and two deposition models originally
developed for gas-liquid flow have been adapted to liquid-liquid flow. The model was applied
to the flow of oil and water; the predicted flow regimes have been presented as a function
of the input water fraction and mixture velocity and compared with experimental results,
showing an overall good agreement between calculation and experiments. Calculated values
of oil-in-water and water-in-oil dispersed fractions were compared against experimental data
for different oil and water superficial velocities, input water fractions and mixture velocities.
Pressure losses calculated in the full developed flow region of the pipe, a crucial quantity in
industrial applications, are reasonably close to measured values. Discrepancies and possible
improvements of the model are also discussed.
The model for two-phase flow was extended to three-phase liquid-liquid-gas flow within
the framework of the two-fluid model. The two liquid phases were treated as a unique liquid
phase with properly averaged properties. The model for three-phase flow thus developed was
implemented in an existing research code for the simulation of three-phase slug flow with the
formation of emulsions in the liquid phase and phase inversion phenomena. Comparisons with
experimental data are presented
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