Constant Viscosity Research Articles

Growth and morphology of thermally assisted sinterable zirconia nanoparticle tribofilm

Tribofilm formation mechanisms of a novel zirconia (ZrO2) nanoparticle antiwear additive were investigated. Spherical ZrO2 nanoparticles 5 nm in diameter with organic capping ligands were dispersed in a polyalphaolefin (PAO) synthetic base oil and tested between AISI 52100 steel counterfaces in a ball-on-disk tribometer under boundary lubrication contact conditions. Film formation was studied as a function of temperature, using PAO blends to maintain constant viscosity across the different temperatures. A temperature dependence was found, with higher temperatures assisting initial tribofilm growth and maintaining the steady-state tribofilm thickness. Findings are consistent with previous reports indicating the primary mechanism of tribofilm growth for zirconium oxide is nanoparticle capture at the sliding interface followed by particle accumulation and sintering.

Effect of matrix solidification on the structure formation in electromagnetic suspensions

For suspensions with electromagnetic particles exposed to an external field, we examine the effect of the solidification of the suspending medium on the formation of particle structures, representative of the curing of a photo-reactive resin during stereolithography. To that end, Brownian Dynamics (BD) simulations are examined in which the solidification of the suspending medium can be incorporated by increasing its viscosity in the course of time. For illustrative purposes, it is assumed that the viscosity function is known apriori in explicit and parametrized form, however, experimental data can be used as well. It is demonstrated that one can study the effects of the viscosity increase by a transformation of time, akin to the time–temperature superposition principle, but here also in the presence of thermal noise on the suspended particles. Therefore, instead of performing BD simulations with a continuously increasing viscosity (computationally inefficient), we advocate performing simulations at a constant (low) viscosity and subsequently transform time (nonlinearly) for re-interpretation of the simulation results. So doing, one can predict the formation of particle structures during on-going solidification of the suspending medium. In practice, the viscosity increase is so drastic that further evolution of the particle structure can be considered as arrested after the characteristic transition-time of the viscosity is reached. Semi-quantitative rules of thumb are formulated for the 3D-printing practitioner.Graphical

Effect of MHD and viscosity variation on the couplestress squeeze film between curved circular plate and a flat porous plate

A theoretical study of MHD with viscosity variation on the squeeze film attributes of a curved circular plate and a flat porous plate using couple stress fluid is examined in this paper. The Reynolds equation in modified is inferred and same is solved to get the expression for film pressure, load supporting capacity and response time in non-dimensional form. As per the computed results, the squeeze film attributes are improved by using a non-Newtonian fluid as a lubricant in association with a magnetic effect. Also, the impact of viscosity variation enhances the squeeze film attributes in comparison with constant viscosity whereas the permeability factor declines the pressure, load supporting capacity and response time as compared to non-porous case.

An immersed [formula omitted]-[formula omitted] element for Stokes interface problems and the optimal convergence analysis

This paper presents and analyzes an immersed finite element (IFE) method for solving Stokes interface problems with a piecewise constant viscosity coefficient that has a jump across the interface. In the method, the triangulation does not need to fit the interface and the IFE spaces are constructed from the traditional CR−P0 element with modifications near the interface according to the interface jump conditions. We prove that the IFE basis functions are unisolvent on arbitrary triangles without any angle conditions and the IFE spaces have the optimal approximation capabilities, although the proof is challenging due to the coupling of the velocity and the pressure. The stability and the optimal error estimates of the proposed IFE method are also derived rigorously. The constants in the error estimates are shown to be independent of the interface location relative to the triangulation. Numerical examples are provided to verify the theoretical results.

Viscoelastic and Viscoplastic Glucose Theory (VGT #34): Applying VEGT and Viscoelastic Perturbation Model and Using Carbs/Sugar Intake Amount Along with Post-Meal Walking K-Steps as Two Constant Viscosity Factors to Predict Two LEGT PPG Values from 8/8/2018 to 2/26/2022 Based on GH-Method: MathPhysical Medicine (No. 615)

The author has studied strength of materials and theory of elasticity through his undergraduate courses at the University of Iowa (UI). He also conducted research work and earned a master’s degree in Biomechanics under Professor James Andrews. In 1970-1971, he used a combined spring and dashpot model to simulate the behaviors of human joints, bones, muscles, and tendons, where he took some related courses at the UI School of Medicine, to investigate the soldier-weapon biophysical interactions during the Vietnam war era. Next, he went to MIT to pursue his PhD study under Professor Norman Jones, who taught him theory of plasticity and dynamic plastic behaviors of various structure elements. To further his education, he took additional graduate courses in various fields of fluid dynamics, thermodynamics, bridge design using energy absorption pad, and soil mechanics under earthquake forces which deal with “time-dependent issues”. Since then, many advancements have been made in the biomechanics branch, especially with human body live tissues that possess certain viscoelastic characteristics, such as bones, muscles, cartilages, tendons (connect bone to muscle), ligaments (connect bone to bone), fascia, and skin. For example, the author suffered plantar fasciitis for many years. He understood that calf stretching exercises or wearing the night splint dorsiflexes forefoot, at the back of the foot, increases plantar fascia tension to offer stress-relief from the pain. This model where muscles and tendons connect the lower leg and foot is a form of viscoelastic study for medical problem solving. When dealing with human internal organs, it is not easy to conduct live experiments to obtain accurate measurements for the biomedical material properties. Blood itself is a viscous material (time-dependent) and its viscosity factor may fall between water, honey, syrup, or gel. However, the author’s research focus is on “glucose” where the blood sugar amount is produced by the liver and carried by red blood cells, not the blood itself. It is nearly impossible to measure the material geometry or material properties to determine the viscosity of glucose, like in engineering research work. Although postprandial plasma glucose (PPG) is strongly influenced by both energy input via carbs/sugar intake amount (~60%) and energy output via post-meal exercise level (~40%). Fundamentally, the PPG level is also dependent upon the individual's health conditions in regard to liver cells and pancreatic beta cells, which produce glucose and release insulin to control the glucose level in blood. Therefore, the author selects a combined value of (carbs/sugar grams and post-meal walking k-steps with respective weighting factors of GH-Modulus as the viscosity factor (η). Based on this knowledge, he applies the “concept” of viscoelasticity and viscoplasticity” to construct an analogy model of time-dependent glucose behaviors.

Viscoelastic and Viscoplastic Glucose Theory (VGT #33): Applying VGT and Viscoelastic Perturbation Model and Using the Combined Values from Carbs/ Sugar Intake Amount with GH.p-Modulus and Post-Meal Walking k-Steps with GH.w-Modulus as the Constant Viscosity Factor to Predict the K-line PPG Values from 8/8/2018 to 2/25/2022 Based on GH-Method: Math-Physical Medicine (No. 614)

The author has studied strength of materials and theory of elasticity through his undergraduate courses at the University of Iowa (UI). He also conducted research work and earned a master’s degree in Biomechanics under Professor James Andrews. In 1970-1971, he used a combined spring and dashpot model to simulate the behaviors of human joints, bones, muscles, and tendons, where he took some related courses at the UI School of Medicine, to investigate the soldier-weapon biophysical interactions during the Vietnam war era. Next, he went to MIT to pursue his PhD study under Professor Norman Jones, who taught him theory of plasticity and dynamic plastic behaviors of various structure elements. To further his education, he took additional graduate courses in various fields of fluid dynamics, thermodynamics, bridge design using energy absorption pad, and soil mechanics under earthquake forces which deal with “time-dependent issues”. Since then, many advancements have been made in the biomechanics branch, especially with human body live tissues that possess certain viscoelastic characteristics, such as bones, muscles, cartilages, tendons (connect bone to muscle), ligaments (connect bone to bone), fascia, and skin. For example, the author suffered plantar fasciitis for many years. He understood that calf stretching exercises or wearing the night splint dorsiflexes forefoot, at the back of the foot, increases plantar fascia tension to offer stress-relief from the pain. This model where muscles and tendons connect the lower leg and foot is a form of viscoelastic study for medical problem solving. When dealing with human internal organs, it is not easy to conduct live experiments to obtain accurate measurements for the biomedical material properties. Blood itself is a viscous material (time-dependent) and its viscosity factor may fall between water, honey, syrup, or gel. However, the author’s research focus is on “glucose” where the blood sugar amount is produced by the liver and carried by red blood cells, not the blood itself. It is nearly impossible to measure the material geometry or material properties to determine the viscosity of glucose-like in engineering research work. Although postprandial plasma glucose (PPG) is strongly influenced by both energy input via carbs/sugar intake amount (~60%) and energy output via post-meal exercise level (~40%). Fundamentally, the PPG level is also dependent on the individual's health conditions in regard to liver cells and pancreatic beta cells, which produce glucose and release insulin to control the glucose level in blood. Therefore, the author selects a combined value of (carbs/sugar grams and post-meal walking k-steps with weighting factors of GH-Modulus as the viscosity factor (η). Based on this knowledge, he applies the “concept” of viscoelasticity and viscoplasticity” to construct an analogy model of time-dependent glucose behaviors.

The effects of silica aerogel on the rheological behaviour and polymer matrix structure of Rigid Polyurethane foams

The incorporation of silica aerogel particles into the isocyanate used to prepare Rigid Polyurethane composite foams drastically modifies its rheological behaviour. The isocyanate changes from being a Newtonian fluid of constant viscosity (0.3 Pa s at 25 °C) to a non-linear power-law material with complex viscosity decreasing from 104 to 101 Pa s with a slope −1 versus frequency. The change in response is caused by the formation of a percolated network of particles at contents above 2.5 wt% of aerogel. Moreover, the addition of aerogel significantly slows down the modulus-build up kinetics and vitrification of the matrix by approximately 4.5 min with every 1 wt% of aerogel added. For the foam with 3.0 wt% of aerogel, the combination of high viscosity at early reaction times coupled with the slow modulus build-up impedes the drainage which leads to a decrease in the fraction of material in the struts of the matrix.

Counter-flow phenomena studied by nuclear magnetic resonance (NMR) velocimetry and flow simulations

Flow patterns including counter-flow and flow reversal effects have been studied by a combination of nuclear magnetic resonance flow imaging and numerical modeling using the finite volume method in the open-source computational fluid mechanics package OpenFOAM. Two cylindrical geometries have been used: In a concentric double-cylinder system the flow reversal under oscillatory rotation of the inner cylinder has been followed, and the time evolution of the flow reversal has been studied. We find extended periods of counter-rotating flow in the gap where fluid in the inner part of the gap follows the new direction of the rotor, while the outer part takes a longer time until the viscous forces transmit the reverted flow direction outwards. The radial position of the reversal of flow direction has been monitored as a function of the oscillation angle after the turning point. In the second cylindrical geometry, the rotating bob is placed off the center and a counter-rotating vortex is detected in the wider part of the gap. At constant viscosity and eccentricity, the position of the center of the vortex was found to depend on the rotation frequency of the bob. Qualitative and quantitative agreement between experiment and laminar (nonturbulent) flow simulations has been obtained for both steady-state flow using the Semi-Implicit Method for Pressure Linked Equations (SIMPLE) algorithm and time-dependent flow using the Pressure Implicit with Splitting of Operators (PISO) algorithm.

Caries-inhibiting Effect of Microencapsulated Active Components in Pit and Fissure Sealants.

The aim of the present in vitro study was to examine the caries-inhibiting effect of a pit and fissure sealant (PFS) containing ion-releasing microcapsules under cariogenic conditions in a biofilm artificial mouth. Forty-eight human third molars were divided into four groups (n=12 per group). Fissures were extended with burs and sealed with experimental PFS. The four groups of specimens were treated as follows: 1) EPFS 1: EPFS (Premier Dental) of increasing viscosity, containing microcapsules loaded with remineralizing agents (calcium, phosphate, and fluoride ions); 2) US: fluoride-releasing PFS (UltraSeal XT plus, UltraDent Products, South Jordan, UT, USA); 3) EPFS 2: experimental PFS of constant viscosity containing microcapsules loaded with calcium, phosphate, and fluoride ions; and 4) FT: glass ionomer cement (GIC) (GC Fuji Triage CAPSULE WHITE glass ionomer cement, GC Europe NV, Leuven, Belgium). FT and US were used as control groups. EPFS 1 and EPFS 2 were the experimental groups. Specimens were stored in distilled water for 14 days at 37°C, subjected to 10,000 thermocycles (5°C and 55°C) and finally exposed to microbiological cycling in a Streptococcus mutans-based artificial mouth for 10 days. Replicas were made for scanning electron microscopic (SEM) evaluation and specimens were cut for fluorescence microscopy. Overall demineralization depths at the margin of Fuji Triage were significantly shallower than in the other groups (p<0.05). Overall demineralization depths adjacent to the experimental pit and fissure sealant EPFS 2 (59±15 μm) were comparable to the values of the resin-based pit and fissure sealant UltraSeal XT plus (58±10 μm, p≥0.05). SEM revealed surface roughness of the GIC-based PFS. The experimental PFS with microcapsules containing active components for remineralization did not show a caries-inhibiting effect compared to a fluoride-releasing resin-based PFS. Lower demineralization depths adjacent to GIC sealants indicate an anticariogenic effect through fluoride ion release.

A thermal management of Darcy-Forchheimer SWCNT–MWCNT Cross hybrid nanofluid flow due to vertical stretched cylinder with and without inertia effects

Heat transfer from a surface enshrouded in a porous medium through which non-Newtonian hybrid nanofluid is flowing is of great practical importance in several fields of engineering. Cross fluid model is implemented due to its significant properties like yield stress features, flow in regions of both low and high shear rates, finite viscosity and time constant. Especially, convective flows in a porous medium are of considerable interest in view of the present and potential utilization of geothermal energy, solar energy, etc. for power production. The purpose of this paper is to present the numerical solutions of boundary-layer equations describing the steady free convection flow of non-Newtonian hybrid nanofluid in a saturated porous medium described by Forchheimer extended Darcy’s law. Flow and heat transfer characteristics with and without inertia effects are explored. Percentage of heat transfer rate (HTR) enhancement is obtained. The major outcomes of the study are that velocity of Cross hybrid nanofluid exhibits opposite effects in response to amplification of Weissenberg number and porosity parameter in both presence and absence of inertia. The heat transfer rate for quadratic radiation contributes to moderate response. Further, percentage enhancement of heat transfer rate is greater subject to disparate Weissenberg number compared to that of Brinkman number.

STAROBINSKY MODEL WITH A VISCOUS FLUID

The article considers some cosmological solutions of the Starobinsky model for a flat inhomogeneous viscous Universe. The first section contains a brief of the F(R)&nbsp; theory of gravity. One of the most common examples of F(R)&nbsp;gravity with a high degree of curvature is the Starobinsky model. For the Starobinsky &nbsp;F(R)=aR+bR2&nbsp;model, the cosmological model of a flat and homogeneous Universe is considered. For the Friedmann-Robertson-Walker metric, the Lagrange function is defined, and the corresponding equations are determined by the Euler-Lagrange equations and the Hamilton energy condition. Using the equation of state for inhomogeneous viscous fluid, we considered two cases of the viscosity parameter when the state parameter is constant. Next, using the results obtained, we determined the dynamics of the Hubble parameter H. At constant viscosity,&nbsp; has a negative value of the Hubble parameter and decreases with time along a hyperbola, while the viscosity parameter with proportional dependence on&nbsp;H has a positive value that decreases along a hyperbola. If we compare it with the well-known de Sitter solution describing the accelerated expansion of the Universe and take into account that time in physics should only be positive, then the change in the Hubble parameter for the viscosity with proportional dependence on&nbsp;H&nbsp;occurs later. An analysis of this solution shows that at a certain point in time the acceleration of the Universe turns into a process of instantaneous compression. However, in the end, the result is similar to the de Sitter solution tends to zero, i.e. the Universe stops accelerating. Based on the results obtained, a graph was constructed with respect to the de Sitter solution. The analysis was carried out according to the graph. These results are useful for describing the accelerated expansion of the modern Universe and do not contradict modern astronomical observations.

Formation of a strong negative wake behind a helical swimmer in a viscoelastic fluid

We investigate the effects of helical swimmer shape (i.e. helical pitch angle and tail thickness) on swimming dynamics in a constant viscosity viscoelastic (Boger) fluid via a combination of particle tracking velocimetry, particle image velocimetry and three-dimensional simulations of the finitely extensible nonlinear elastic model with Peterlin approximation (FENE-P). The 3D-printed helical swimmer is actuated in a magnetic field using a custom-built rotating Helmholtz coil. Our results indicate that increasing the swimmer tail thickness and pitch angle enhances the normalized swimming speed (i.e. ratio of swimming speed in the Boger fluid to that of the Newtonian fluid). Strikingly, unlike the Newtonian fluid, the viscoelastic flow around the swimmer is characterized by formation of a front–back flow asymmetry that is characterized by a strong negative wake downstream of the swimmer's body. Evidently, the strength of the negative wake is inversely proportional to the normalized swimming speed. Three-dimensional simulations of the swimmer with the FENE-P model with conditions that match those of experiments, confirm formation of a similar front–back flow asymmetry around the swimmer. Finally, by developing an approximate force balance in the streamwise direction, we show that the contribution of polymer stresses in the interior region of the helix may provide a mechanism for swimming enhancement or diminution in the viscoelastic fluid.

The influence of the viscosity of crude oil on liquid-dynamic noise characteristics in the volute shell of oil transfer pump

This paper aims to study the influence of the viscosity of crude oil on the liquid-dynamic noise characteristics using ANSYS Fluent. The RNG k-ɛ model is used for simulating the static pressure distribution characteristics of crude oil in the centrifugal pump. The LES S-L model is used for simulating the transient characteristics of crude oil in the centrifugal pump. The results show that the viscosity of crude oil is the primary factor affecting the static pressure distribution and the transient characteristics of crude oil in the centrifugal pump. The lower the viscosity of the crude oil is, the greater the change in static pressure is. The maximum static pressure peak appears nearby the tongue of oil transfer pump. The static pressure critical viscosity affecting the inner wall of the volute shell is 1728mPa.s. According to the viscosity test data provided by related literature, A 3-step mathematical characterization model is proposed to describe the relationship between the viscosity and the corresponding water content of crude oil. It can be used to compute the crude oil viscosity parameter as a given value in ANSYS Fluent program. The maximum relative deviation is 2.62%. A transmit method is proposed by heating up the pre-stable and post-stable crude oil twice to keep the viscosity constant in the whole progress of crude oil transmit. It will be beneficial to energy saving.

Oil droplet breakup during pressure swirl atomization of emulsions: Influence of emulsion viscosity and viscosity ratio

The atomization of oil-in-water emulsions for spray drying is a common task in food engineering. During atomization with pressure swirl atomizers, the emulsions are subjected to high stresses that can lead to deformation and breakup not only of the liquid itself but also of the disperse oil droplets therein. In this study, the effect of the viscosity ratio λ of the emulsion (0.2–33) and of the emulsion viscosity (5–50 mPa⋅s) on oil droplet breakup during atomization was investigated at atomization pressures between 50 and 250 bar. A systematic influence of λ on the oil droplet size was observed with maximum oil droplet breakup for λ between 0.2 and 1.2. At a constant viscosity ratio of ∼ 1, the resulting oil droplet size was almost independent of the emulsion viscosity, even when volume flow rates and spray droplet sizes during atomization showed a clear dependence on this parameter. A model based on existing knowledge on droplet breakup in laminar shear flow is developed, by which oil droplet sizes after atomization can be predicted. This model may serve as a tool to control oil droplet size after atomization by defining appropriate atomization conditions and emulsion formulation. This is especially relevant for spray drying applications in which the oil droplet size in the powder is an important quality parameter. • Viscosity ratio λ influences oil droplet breakup during pressure swirl atomization. • At λ ∼ 1 the emulsion viscosity per se has little influence on oil droplet breakup. • Oil droplet breakup follows the theory of droplet breakup in laminar shear flow. • A model is proposed that serves as a tool to predict oil droplet breakup.

H-principle for the 2-dimensional incompressible porous media equation with viscosity jump

In this work we extend the results in [6,32] on the 2D IPM system with constant viscosity (Atwood number $A_{\mu}=0$) to the case of viscosity jump ($|A_{\mu}|<1$). We prove a h-principle whereby (infinitely many) weak solutions in $C_tL_{w^*}^{\infty}$ are recovered via convex integration whenever a subsolution is provided. As a first example, non-trivial weak solutions with compact support in time are obtained. Secondly, we construct mixing solutions to the unstable Muskat problem with initial flat interface. As a byproduct, we check that the connection, established by Sz\'ekelyhidi for $A_{\mu}=0$, between the subsolution and the Lagrangian relaxed solution of Otto, holds for $|A_{\mu}|<1$ too. For different viscosities, we show how a pinch singularity in the relaxation prevents the two fluids from mixing wherever there is neither Rayleigh-Taylor nor vorticity at the interface.

Effect of magnetic field and heat transfer on peristaltic flow of a micropolar fluid through a porous medium

This paper presents a numerical study of the peristaltic flow of a micropolar fluid through a porous medium have been studied under the long-wavelength and low Reynolds number approximation. The system of differential equations is solved numerically using the NDSolve Mathematica. The numerical study investigates the effects of magnetic field, heat transfer on the peristaltic flow of a micropolar fluid through a porous medium induced by sinusoidal peristaltic waves traveling down the channel wall in symmetric channel. The effects of various parameters like coupling number, the Hartman number, the micropolar parameter, the permeability, the viscosity constant of the classical fluid dynamics and the thermal radiation, etc. on velocity profiles, temperature and micropolar rotation. Numerical results are computed and discussed numerically and presented through graphs. The impacts of pertinent parameters on the aforementioned quantities are examined by plotting graphs on the basis of computational results. The results indicate that the effect of parameters is very pronounced.

Analysis of an unfitted mixed finite element method for a class of quasi-Newtonian Stokes flow

We propose and analyze an unfitted method for a dual-dual mixed formulation of a class of Stokes models with variable viscosity depending on the velocity gradient, in which the pseudoestress, the velocity and its gradient are the main unknowns. On a fluid domain Ω with curved boundary Γ we consider a Dirichlet boundary condition and employ an approach previously applied to the Stokes equations with constant viscosity, which consists of approximating Ω by a polyhedral computational subdomain Ωh, not necessarily fitting Ω, where a Galerkin method is applied to compute solution. Furthermore, to approximate the Dirichlet data on the computational boundary Γh, we make use of a transferring technique based on integrating the discrete velocity gradient. Then the associated Galerkin scheme can be defined by employing Raviart–Thomas of order k≥0 for the pseudostress, and discontinuous polynomials of degree k for the velocity and its gradient. For the a priori error analysis we provide suitable assumptions on the mesh near the boundary Γ ensuring that the associated Galerkin scheme is well-posed and optimally convergent with O(hk+1). Next, for the case when Γh is taken as a piecewise linear interpolation of Γ, we develop a reliable and quasi-efficient residual-based a posteriori error estimator. Numerical experiments verify our analysis and illustrate the performance of the associated a posteriori error indicator.

Hemorheological and biochemical study in patients with liver cirrhosis

In this study, rheological techniques are used to measure the flow properties of blood from 52 patients with liver cirrhosis. A comparative analysis included a control group (23 persons) to determine the stage of the disease in cirrhotic patients. An important correlation relating the blood biochemical composition with the rheological response was found. Two rheological techniques were employed: simple shear-flow and small amplitude oscillatory shear. The “whole blood viscosity” (WBV) exhibits non-Newtonian shear-thinning behavior. Cirrhotic patients show low WBV levels as well as low values of viscoelastic response compared to those of the control group. Viscosity curves in decompensated cirrhotic patients tend toward a Newtonian behavior (constant viscosity) at high shear rates. Regarding the complex viscosity, there are clear differences between compensated and decompensated patients. The viscoelastic response reveals a change in the slope of the elastic modulus (G′) with frequency as compared to the response of the control group. In general, blood elasticity was observed to decrease as the disease progresses (i.e., blood tends to become less elastic, becoming a Newtonian fluid in advanced cirrhotic patients). These results represent a promising alternative to evaluate the incidence of cirrhosis in patients using fast, inexpensive, and noninvasive tests to confirm liver cirrhosis diseases.

Simulation of Scale Inhibitor Squeeze Treatments in a Polymer Flooded Reservoir

Summary This study aims to demonstrate the changes to scale inhibitor squeeze lifetimes in a polymer flooded reservoir vs. a waterflooded reservoir. A squeeze campaign was designed for the base waterflood system, then injection was switched to polymer flooding (PF) at early and late field life. The squeeze design strategy was adapted to maintain full scale protection under the new system. During the field life, the production of water is a constant challenge. Both in terms of water handling, but also the associated risk of mineral scale deposition. Squeeze treatment is a common technique, where a scale inhibitor is injected to prevent the formation of scale. The squeeze lifetime is dictated by the adsorption/desorption properties of the inhibitor chemical, along with the water rate at the production well. The impact on the adsorption properties and changes to water rate on squeeze lifetime during PF are studied using reservoir simulation. A 2D 5-spot model was used in this study, which is considered a reasonable representation of a field reservoir under waterflooding (WF)/PF. It was observed that when applying polymer (HPAM) flooding, with either a constant viscosity or with polymer degradation. The study concludes that the number of squeeze treatments was significantly reduced as compared to the waterflood case. This is due to the significant delay in water production induced by the polymer flood. When the polymer flood was initiated later in field life, after 0.5 PV (reservoir PVs) water injection, resulting in 70% water cut approximately, the number of squeeze treatments required was still lower than the waterflood base case. However, it was also observed that in all cases, at later stages of field life the positive impact of PF on squeeze lifetime begin to diminish, due in part to the polymer breakthrough, which results in higher water viscosity in the production near-wellbore region. Preventing the overflush to be as effective transporting the scale inhibitor. This study represents the first coupled reservoir simulation/squeeze treatment design for a polymer flooded reservoir. It has been demonstrated that in over the course of a field lifetime, PF will in fact reduce the number of squeeze treatments required even with a potential reduction in inhibitor adsorption. This highlights an opportunity for further optimization and a key benefit of PF in terms of scale management, aside from the EOR.

Study of Rayleigh-Taylor instability in viscosity-stratified fluid layers

The Rayleigh-Taylor instability in viscosity varying fluid layers is studied. A heavier fluid layer is superimposed on a lighter fluid layer. Both the fluid layers are bounded between two parallel isothermal horizontal walls. Out of the two walls, one wall is isothermally heated, while the other wall is isothermally cooled. The Rayleigh-Taylor instability is studied for axisymmetric configuration. Viscosities of both the fluids are considered to be varying with temperature. The effect of viscosity ratio, temperature ratio, heating location, Prandtl number and Weber number on the instability is studied. When the viscosity of fluid layers vary with temperature, the configuration becomes more unstable compared to that for constant viscosity fluid layers. For varying viscosity fluid layers the spike undergoes large deformations. At lower viscosity ratios, mushroom shaped spike is formed with elongated skirt structure. Whereas, at higher viscosity ratios, spike with fluid column structure is formed. It is found that increasing viscosity ratio shows stabilizing effect. Increasing temperature ratio is found to show destabilizing effect with complex spike structure formation at high temperature ratios. In top wall heating configuration, formation of mushroom shaped spike and skirt of the spike occurs earlier in a thinner and elongated form compared to that of bottom wall heating configuration. Prandtl number showed insignificant effect on the instability. For the parameter values of the study, when Weber is lower than 55 the configuration is stable and does not undergo instability. Overall, surface tension has shown stabilizing effect on the instability.