Microflow
& Interfacial Transport (MIT) Laboratory
Our
group focuses on theoretical, numerical and experimental research on
fundamental mechanisms of transports (fluid mechanics, mass diffusion, heat
transfer, electro-kinetics…) with applications in energy resources
exploration and exploitation, waste protection and utilization,
interactions with life and health systems, space propulsion, and new
materials.
¨
Micro/nanoscale Flow and Interfacial Transport;
¨
Multiscale Multiphase/Multiphysico-chemical
transports in disordered materials;
¨
Multiscale and hierarchical modeling;
¨
Physics of complex fluids for engineering;
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Physics of heat transfer and non-equilibrium
thermodynamics at extreme scales (time
and space);
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Transport and coupling mechanisms.
Recent
highlights
|
Self-adaptive preferential flow control using dispersed polymers
in heterogeneous porous media |
Abstract:
Preferential flow which leads to non-uniform displacement, especially in heterogeneous
porous media, is usually unwelcome in most practical processes. We propose a
self-adaptive preferential flow control mechanism by using dispersed
polymers, which is supported strongly by experimental and numerical
evidences. Our experiments are performed on a microchip with heterogeneous
porous structures where oil is displaced by dispersed polymer microsphere
particles. Even though the size of particles is much smaller than the
pore-throat size, the diversion
effect
by the dispersed microspheres is still proved. Therefore, the plugging effect
is not the major mechanism for preferential flow control by dispersed
polymers. The mechanisms are further investigated by pore-scale modelling,
which indicates that the dispersed polymers exhibit an adaption ability to
pressure and resistance in the porous flow field. In such an intelligent way,
the displacing fluid with dispersed polymers smartly controls the
preferential flow by inducing pressure fluctuations, and demonstrates better
performances in both efficiency and economy aspects rather than the
traditional way with simply increasing the viscosity. These insights can be
applied to improve techniques in the fields, such as enhanced oil recovery
and soil wetting. Publication: C.Y. Xie,
W. Lei, M. Balhoff, M. Wang* and S. Chen. Journal
Fluid Mechanics 906: A10,
2021 (Cover Page) |
|
Enhanced oil recovery mechanism and recovery performance of
micro-gel particle suspensions by microfluidic experiments |
Abstract:
Micro-gel particle suspensions (MGPS) have been proposed for enhanced oil
recovery (EOR) in reservoirs with harsh conditions in recent years, yet the
mechanisms are still not clear because of the complex property of MGPS and
the complex geometry of rocks. In this paper, the micro-gel particle-based
flooding has been studied by our microfluidic experiments on both
bi-permeability micromodels and reservoir-on-a-chip. A method for
reservoir-on-a-chip design has been proposed based on QSGS (Quartet Structure
Generation Set) to ensure that the flow geometry on chip owns the most
important statistical features of real rock microstructures. In the
micromodel experiments with heterogeneous microstructures, even if the MGPS
has the same macroscopic rheology as the hydrolyzed polyacrylamides (HPAM)
solution for flooding, MGPS may lead to significant fluctuations of pressure
field caused by the non-uniform concentration distribution of particles. In
the reservoir-on-a-chip experiments, clustered oil trapped in the swept pores
can be recovered by MGPS because of pressure fluctuation, which hardly
happens in the HPAM flooding. Compared with the water-flooding, the HPAM
solution flooding leads to approximately 17% incremental oil recovery, while
the MGPS results in approximately 49.8% incremental oil recovery in the
laboratory. Publication: W. Lei, T.
Liu, C.Y. Xie, H.E. Yang, T.J. Wu, M. Wang*. Energy Science and Engineering 8: 986-998, 2020 (Cover Page) |
|
Does low-viscosity fracturing always create complex
fractures? |
Abstract: Lower-viscosity fluids are commonly believed to be able
to create more complex fractures in hydraulic fracturing, however, the
mechanism remains stubbornly unclear. We use a new grain-scale model with
accurate coupling of hydrodynamic forces to simulate the propagation of
fluid-driven fracturing. The results clarify that fracturing fluid with a
lower viscosity does not always create more complex fractures. The
heterogeneity in the rock exerts the principal control on systematic
evolution of fracture complexity. In homogeneous rock, low viscosity fluids
result in low breakdown pressure, but viscosity exerts little influence on
fracture complexity. However, in heterogeneous rock, lower viscosity can lead
to more complex network of fracturing. A regime map shows the dependence of
fracture complexity on the degree of rock heterogeneity where low viscosity
fracturing fluid more readily permeates weak defects and creates complex
fracture networks. Publication: Z.Q. Chen,
D. Elsworth and M. Wang*. Journal
Geophysical Research-Solid Earth 125(9): e2020JB020332, 2020 |
|
Temperature effects on electrical double layer at
solid-aqueous solution interface |
Abstract:
Despite the significant influence of solution temperature on the structure of
electrical double layer, the lack of theoretical model intercepts us to explain and predict the interesting
experimental observations. In this work, we study the structure of electrical
double layer as a function of thermo-chemical properties of the solution by
proposing a phenomenological temperature dependent surface complexation
model. We found that by introducing a buffer layer between the diffuse layer
and Stern layer, one can explain the sensitivity of zeta potential to
temperature for different bulk ion concentration. Calculation of the
electrical conductance as function of thermo-chemical properties of solution
reveals the electrical conductance not only is a function of bulk ion
concentration and channel height but also the solution temperature. The
present work model can provide deep understanding of micro and nanofluidic
devices functionality at different temperatures. Publication: A.
Alizadeh and M. Wang*. Electrophoresis
41, 1067-1072, 2020 (cover page inside) |
|
Dispersion of Charged Solute in Charged Micro- and
Nanochannel with Reversible Sorption |
Abstract: We study dispersion
of a charged solute in a charged micro- and nanochannel with reversible
sorption and derive an analytical solution for mass fraction in the fluid,
transport velocity and dispersion coefficient. We discuss the effect of
sorption and electrical double layer (EDL) on solute transport and show that
the coupling between sorption and EDL gives rise to charge-dependent
transport even for a thin double layer. However, in this case it can be
reduced to a simple non-charge-dependent case by introducing the intrinsic
sorption equilibrium constant. Publication: L. Zhang,
M.A. Hesse and M. Wang*. Electrophoresis
40: 838-844, 2019 (Cover page) |
|
Transport mechanism of deformable micro-gel particle
through micropores with mechanical properties characterized by AFM |
Abstract: Deformable
micro-gel particles (DMP) have been used to enhanced oil recovery (EOR) in
reservoirs with unfavourable conditions. Direct pore-scale understanding of
the DMP transport mechanism is important for further improvements of
its EOR performance. To consider the interaction between soft particle and fluid
in complex pore-throat geometries, we perform an Immersed Boundary-Lattice
Boltzmann (IB-LB) simulation of DMP passing through a
throat. A spring-network model is used to capture the deformation of DMP. In
order to obtain appropriate simulation parameters that represent the real mechanical
properties of DMP, we propose a procedure
via fitting the DMP elastic modulus data measured by the nano-indentation
experiments using Atomic
Force Microscope (AFM). The pore-scale modelling obtains
the critical pressure of the DMP for different particle-throat diameter
ratios and elastic modulus. It is found that two-clog particle transport mode is observed in a
contracted throat, the relationship
between the critical pressure and the elastic modulus/particle-throat
diameter ratio follows a power law.
The particle-throat diameter ratio shows
a greater impact on the critical pressure difference than the elastic modulus of particles. Publication: W.H. Lei,
C. Xie, T.J. Wu, X.C. Wu and M. Wang*. Scientific
Reports 9: 1453, 2019 |
|
Direct simulation of electroosmosis around a spherical
particle with inhomogeneously acquired surface charge |
Abstract: Uncovering electroosmosis around an inhomogeneously
acquired charge spherical particle in a confined space could provide detailed
insights into its broad applications from biology to geology. In the present
study, we developed a direct simulation method with the effects of
inhomogeneously acquired charges on the particle surface considered, which
has been validated by the available analytical and experimental data.
Modeling results reveal that the surface charge and zeta potential, which are
acquired through chemical interactions, strongly depend on the local solution
properties and the particle size. The surface charge and zeta potential of
the particle would significantly vary with the tangential positions on the
particle surface by increasing the particle radius. Moreover, regarding the
streaming potential for a particle-fluid-tube system, our results uncover
that the streaming potential has a reverse relation with the particle size in
a micro or nanotube. To explain this phenomenon, we present a simple relation
that bridges the streaming potential with the particle size and tube radius,
zeta potential, bulk and surface conductivity. This relation could predict
good results specifically for higher ion concentrations and provide deeper
understanding of the particle size effects on the streaming potential
measurements of the particle-fluid-tube system. Publication: A. Alizadeh and M. Wang*. Electrophoresis 38: 580-595, 2017 (cover page) |
|
Electrokinetic mechanism of wettability alternation at
oil-water-rock interface |
Abstract: Design
of ions for injection water may change the wettability of oil-brine-rock (OBR)
system, which has very important applications in enhanced oil recovery.
Though ion-tuned wettability has been verified by various experiments, the
mechanism is still not clear. In this review paper, we first present a
comprehensive summarization of possible wettability alteration mechanisms,
including fines migration or dissolution, multicomponent ion-exchange (MIE),
electrical double layer (EDL) interaction between rock and oil, and repulsive
hydration force. To clarify the key mechanism, we introduce a complete frame
of theories to calculate attribution of EDL repulsion to wettability
alteration by assuming constant binding forces (no MIE) and rigid smooth
surface (no fines migration or dissolution). The frame consists of three
parts: the classical Gouy-Chapman model coupled with interface charging
mechanisms to describe EDL in oil-brine-rock systems, three methods with
different boundary assumptions to evaluate EDL interaction energy, and the
modified Young-Dupré equation to link EDL interaction energy with contact
angle. The quantitative analysis for two typical oil-brine-rock systems
provides two physical maps that show how the EDL interaction influences
contact angle at different ionic composition. The result indicates that the
contribution of EDL interaction to ion-tuned wettability for the studied
system is not quite significant. The classical and advanced experimental work
using microfabrication is reviewed briefly on the contribution of EDL
repulsion to wettability alteration and compared with the theoretical
results. It is indicated that the roughness of real rock surface may enhance
EDL interaction. Finally we discuss some pending questions, perspectives and
promising applications based on the mechanism. Publication: H. Tian and M. Wang*. Surface
Science Reports 72:
369-391, 2017 (cover page) |
|
Phonon hydrodynamics and its applications in nanoscale heat
transport |
Abstract: Phonon
hydrodynamics is an effective macroscopic method to study heat transport in
dielectric solid and semiconductor. It has a clear and intuitive physical
picture, transforming the abstract and ambiguous heat transport process into
a concrete and evident process of phonon gas flow. Furthermore, with the aid
of the abundant models and methods developed in classical hydrodynamics,
phonon hydrodynamics becomes much easier to implement in comparison to the
current popular approaches based on the first-principle method and kinetic
theories involving complicated computations. Therefore, it is a promising
tool for studying micro- and nanoscale heat transport in rapidly developing
micro and nano science and technology. However, there still lacks a
comprehensive account of the theoretical foundations, development and
implementation of this approach. This work represents such an attempt in
providing a full landscape, from physical fundamental and kinetic theory of
phonons to phonon hydrodynamics in view of descriptions of phonon systems at
microscopic, mesoscopic and macroscopic levels. Thus a systematical kinetic
framework, summing up so far scattered theoretical models and methods in
phonon hydrodynamics as individual cases, is established through a frame of a
Chapman-Enskog solution to phonon Boltzmann equation. Then the basic tenets
and procedures in implementing phonon hydrodynamics in nanoscale heat
transport are presented through a review of its recent wide applications in
modeling thermal transport properties of nanostructures. Finally, we discuss
some pending questions and perspectives highlighted by a novel concept of
generalized phonon hydrodynamics and possible applications in micro/nano
phononics, which will shed more light on more profound understanding and credible
applications of this new approach in micro- and nanoscale heat transport
science. Publication: Y.Y. Guo and M. Wang*. Physics Reports 595: 1-44, 2015 (cover
page) |
|
Predictions of
effective physical properties of complex multiphase materials |
Abstract: Theoretical
prediction of effective properties for multiphase material systems is very
important not only to analysis and optimization of material performance, but
also to new material designs. This review first examines the issues,
difficulties and challenges in prediction of material behaviors by
summarizing and critiquing the existing major analytical approaches dealing
with material property modeling. The focus then shifts to some recent
advances in numerical methodology that are able to predict more accurately
and efficiently the effective physical properties of multiphase materials
with complex internal microstructures. A random generation-growth algorithm
is highlighted for reproducing multiphase microstructures, statistically
equivalent to the actual systems, based on the geometrical and morphological
information obtained from measurements and experimental estimations. Then a
high-efficiency lattice Boltzmann solver for the corresponding governing
equations is described which, while assuring energy conservation and the
appropriate continuities at numerous interfaces in a complex system, has demonstrated
its numerical power in yielding accurate solutions. Various applications are
provided to validate the feasibility, effectiveness and robustness of this
new methodology by comparing the predictions with existing experimental data
from different transport processes, accounting for the effects due to
component size, material anisotropy, internal morphology and multiphase
interactions. The examples given also suggest even wider potential
applicability of this methodology to other problems as long as they are
governed by the similar partial differential equation(s). Thus, for given
system composition and structure, this numerical methodology is in essence a
model built on sound physics principles with prior validity, without resorting to ad hoc empirical treatment. Therefore, it
is useful for design and optimization of new materials, beyond just
predicting and analyzing the existing ones. Publication: M. Wang and N. Pan*. Materials
Science and Engineering: R: Reports 63: 1-30, 2008 (cover page) |