Pattern Formation and Instabilities in Particulate Suspensions

This study investigates the scaling criteria used to evaluate immiscible water and chemical floods, and miscible solvent injection and VAPEX processes by deriving dimensionless groups. We present findings from various flooding experiments and evaluate the interplay between viscous and capillary forces as functions of oil viscosity, injection velocity, and porous media characteristics. Updated dimensionless times, capillary numbers, and diffusion numbers were derived from the results of different core floods, which accurately predict recovery performance for different solvent and chemical types, injection rates, and rock properties. The capillary number (Nca) and dimensionless time (tD) are the most commonly used dimensionless numbers to characterize oil recovery performance in porous media. Nca balances forces at a given moment, and tD captures the displacement process over time. However, none of these individual numbers accurately correlate with the recovery factor. To address this, we incorporated viscosity ratios, oil density, reservoir thickness, porosity, and permeability, and adjusted the exponent for each term in new dimensionless numbers. We propose combined dimensionless scales to predict oil production in immiscible and miscible floods. The effect of each dimensionless group in our proposed numbers on oil recovery was examined through sensitivity analysis. The proposed updated dimensionless numbers successfully predicted oil recovery for water flooding, chemical flooding, and solvent injection in heavy oil systems. It was found that while traditional dimensionless numbers failed to accurately correlate with the recovery factor, our modified dimensionless numbers improved oil recovery prediction across varying viscosity ratios, solvent types, injection velocities, and core porosities and permeabilities. Incorporating oil density and reservoir height into Nenniger's dissolution term enabled the development of a new capillary number, Nca*, which improved the prediction of oil recovery during solvent injection processes. Our results showed increased recovery efficiency with higher Nca* values, as viscous forces overcame capillary forces. Dimensionless parameters provide accurate scaling from laboratory to field conditions. While extensive dimensionless analysis has been conducted on waterflooding, little work has focused on developing scaling laws for solvent flooding in heavy oil reservoirs. Our study demonstrated that the incorporation of viscosity ratio and dissolution term improved the accuracy of the existing dimensionless numbers in predicting oil production during immiscible and miscible flooding.

Chemical reaction, Dufour and Soret effects on the stability of magnetohydrodynamic blood flow conveying magnetic nanoparticle in presence of thermal radiation: A biomedical application

Comparison analysis of density wave oscillation type two-phase flow instability of superheated and saturated boiling tubes

The behavior of chlorobenzenes in Ise bay, estimated from their concentrations in various environmental media

Structural stability of transonic shock flows with external force in a divergent 3-D axisymmetric perturbed nozzle

Quasi-stationary flow structure in turbidity currents

Characteristic phenomenological behavior of MR fluids is typically modeled by Bingham’s equation, which has no fundamental connection to the microstructure of MR fluid and the fully coupled mechanical-electrical-magnetic equations. In this paper microstructurally, kinetic theory-based model of MR fluids (consisting of micro-sized ferrous particles suspended in a Newtonian fluid) are developed. For modeling these composite systems, dumbbell models in which two beads joined by an elastic connector are investigated. In these models the distributed forces from the carrier fluid and from the magnetic field on the suspended particle are idealized as being localized on beads. Microscale constitutive equations relating flow, stress, and particle orientation are produced by integrating the coupled equations governing forces, flow, and orientation over a representative volume of particles and carrier fluid. Coefficients in the constitutive equations are specified not by a fit to macroscale experimental flow measurement but rather in terms of primitive measurements of particle microstructure, carrier fluid, viscosity and density, and temperature. These new models for MR fluids are three dimensional and applicable to any flow geometry, while the Bingham plastic model is in general applicable only to shear flow. The models in this paper reduce to forms similar to Bingham’s model in a simple shear flow, but with coefficients which arise from fundamental electromagnetic considerations and microstructural features such as geometrical, magnetic and mechanical characterization of the particles, quantities measured primitively from the carrier fluid, magnetic field and temperature.

Understanding the physics of a three-phase contact line between gas, liquid, and solid is important for numerous applications. At the macroscale, the response of a three-phase contact line to an external force action is often characterized by a contact angle hysteresis, and several models are presented in the literature for its description. Yet, there is still a need for more information about such model applications at the nanoscale. In this study, a molecular dynamics approach was used to investigate the shape of a liquid droplet under an external force for different wetting regimes. In addition, an analytic model for describing the droplet shape was developed. It gives us the possibility to evaluate the receding and advancing wetting angle accurately. With our modeling, we found that the interplay between capillary forces and viscous forces is crucial to characterize the droplet shape at the nanoscale. In this frame, the importance of the rolling movement of the interface between liquid and vapor was pointed out. We also demonstrate that in the range of the external forces when capillary forces are most significant compared to others, hysteresis is well described by the macroscale Cox–Voinov model.

<p>Functionalities and structural properties of multiphase polymeric materials can be modified by imposing external forces to the mixture undergoing phase separation resulting in non-uniform anisotropic microstructures. Anisotropic heterogeneous polymeric materials have practical engineering applications such as anisotropic porous polymer membranes and switchable holographic polymer-dispersed liquid crystal films. Anisotropy can be generated by applying singly or in combination, an external force like shear flow, electric or magnetic field, surface effect, controlled chemical reaction, concentration gradient, or temperature gradient to a polymer solution undergoing phase separation. In this study, the self-condensation polymerization of a monomer in a monomer-solvent mixture and phase separation of the system were simultaneously modeled and simulated. The numerical Galerkin finite-element method was applied to develop the mathematical model. Short-range surface potential, long-range surface potential, and linear temperature and concentration gradients were applied singly and also simultaneously to the system undergoing the polymerization-induced phase separation (PIPS). The expected non- uniform structures were achieved. A comprehensive parametric study was carried out by investigating the effects of diffusivity, temperature gradient, concentration gradient, and surface potential parameter on the lag time, process time, morphology development, thickness of the wetting layer, and the extent of anisotropy of the system. The size analysis and structural characterization of the phase-separated system were also carried out using ImageJ 1.51j8 which is an image processing and analysis software. The numerical results are in good agreement with published experimental data.</p>

Immiscible displacements in porous media with both capillary and viscous effects can be characterized by two dimensionless numbers, the capillary number C, which is the ratio of viscous forces to capillary forces, and the ratio M of the two viscosities. For certain values of these numbers, either viscous or capillary forces dominate and displacement takes one of the basic forms: (a) viscous fingering, (b) capillary fingering or (c) stable displacement. We present a study in the simple case of injection of a non-wetting fluid into a two-dimensional porous medium made of interconnected capillaries. The first part of this paper presents the results of network simulators (100 × 100 and 25 × 25 pores) based on the physical rules of the displacement at the pore scale. The second part describes a series of experiments performed in transparent etched networks. Both the computer simulations and the experiments cover a range of several decades in C and M. They clearly show the existence of the three basic domains (capillary fingering, viscous fingering and stable displacement) within which the patterns remain unchanged. The domains of validity of the three different basic mechanisms are mapped onto the plane with axes C and M, and this mapping represents the ‘phase-diagram’ for drainage. In the final section we present three statistical models (percolation, diffusion-limited aggregation (DLA) and anti-DLA) which can be used for describing the three ‘basic’ domains of the phase-diagram.

CO2 storage potential during CO2 enhanced oil recovery in sandstone reservoirs

This study investigates the heat transfer enhancement by electrohydrodynamic (EHD) in a rectangular channel with various geometric and operational parameters in a wide NEHD range of 0.4–5. Here, NEHD is a dimensionless number, describing the ratio of electrostatic, inertial, and viscous forces. Two working regimes in EHD are identified: inertial and electrostatic regimes. The results show that the barrier effect exists only in the inertial regime; however, the interference effect occurs in the electrostatic regime. The barrier effect relies heavily on NEHD rather than the dimensionless distance between electrodes l* and the dimensionless channel width H* because the thermal boundary layer cannot be disturbed sufficiently by a small electrostatic force; however, the interference effect depends on l* and H* rather than NEHD due to the stagnant area initiated only by a strong interaction between adjacent emitting electrodes. A new effect, the “blocking effect,” is found in the electrostatic regime. The mechanism of the blocking effect is different from that of the barrier and interference effects. The blocking effect is initiated by a giant vortex, which “blocks” the airflow flowing toward the downstream channel. The average Nusselt number of channels can be reduced by at least 8%, 13%, and 5% for the barrier, interference, and blocking effects, respectively. A working spectrum of EHD-induced heat transfer enhancement in a rectangular channel is provided under NEHD and channel area coupling conditions. We believe the spectrum can help in designing EHD-induced heat transfer enhancement because it provides theoretical guidance for avoiding the three effects.

The pulsating jet is a common working mode in electrohydrodynamic printing (EHDP), and this process is highly influenced by operating parameters and material properties. In this paper, we investigated the behavior of pulsating jets in liquids with varying physical properties through numerical simulations. We established an electrohydrodynamic (EHD) solver and employed a charge flux restriction step to ensure a realistic distribution of free charges. Our simulations revealed three different ejection regimes: an oscillating cone (OC), a choked jet (CJ), and a stable cone–jet (SJ). We found that the ejection regime is primarily determined by three dimensionless numbers related to liquid properties: the Ohnesorge number, Q0εr/Q, and Q0/(QRe). Based on these dimensionless numbers, we analyzed the influence of liquid properties on pulsating jets in OC and CJ. In OC, the jet's breakage is mainly attributed to the significant oscillation of the Taylor cone, a phenomenon primarily influenced by viscosity and conductivity. In CJ, the emission of the jet is terminated due to the excessive resistant force in the cone–jet transition region. For liquids with low to medium viscosity, the dominant resistant force is either the polarization force or the viscous force depending on whether εrRe is larger or smaller than 1, respectively. In the cases of high viscosity liquids, the viscous force always plays a major role as the primary resistance. These findings provide deeper insight into the physical mechanisms of pulsating jets.

The fundamental aspects of Water Alternating Gas (WAG) injection are still not well understood. There are a few applications in fractured media and these show potential1. This study looks at the sensitivity of production to reservoir and fluid properties on a pattern scale using tools derived from experimental design. Also a look has been taken into the drive mechanisms in the fractured media that play an important role during WAG injection. Earlier studies claimed that WAG injection in fractured reservoirs is not the best improved oil recovery (IOR) method2. However when the conditions are fully understood and the injection is modeled correctly, it is optimal in some fractured reservoirs. The proper modeling of fractured reservoirs remains difficult. The standard dual porosity formulation in commercial simulators is based on a continuous matrix grid overlaid by a continuous fracture grid. The transfer of fluid from matrix to fracture is described by a transfer function. The heart of this transfer function is the shape factor, sigma. As can be seen in a fine-scale grid, the shape factor is different for different reservoir properties and injection types. The upscaling of this sigma from the fine-scale grid to the pattern scale model is important for correct modeling. This study performs several fine scale single porosity simulations to properly upscale the flow model to a dual system. The process of determining sensitivities in an organized manner on properly upscaled models will be shown here with a limited number of parameters. Fractured reservoirs can be divided into different categories3. Based on a fine grid model of one type of fractured media, a dual porosity model with varying parameters is set up. This yields recovery outputs across a range of reservoir properties that are represented by two dimensionless numbers. These numbers represent the capillary over viscous and gravity over viscous forces. By looking into the mechanisms that are behind the recovery in different balances of forces, an insight into when and why WAG is working is given.

We have investigated experimentally the competition between viscous, capillary, and gravity forces during drainage in a two-dimensional synthetic porous medium. The displacement of a mixture of glycerol and water by air at constant withdrawal rate has been studied. The setup can be tilted to tune gravity, and pressure is recorded at the outlet of the model. Viscous forces tend to destabilize the displacement front into narrow fingers against the stabilizing effect of gravity. Subsequently, a viscous instability is observed for sufficiently large withdrawal speeds or sufficiently low gravity components on the model. We predict the scaling of the front width for stable situations and characterize it experimentally through analyses of the invasion front geometry and pressure recordings. The front width under stable displacement and the threshold for the instability are shown, both experimentally and theoretically, to be controlled by a dimensionless number F which is defined as the ratio of the effective fluid pressure drop (i.e., average hydrostatic pressure drop minus viscous pressure drop) at pore scale to the width of the fluctuations in the threshold capillary pressures.