Surface In Porous Medium Research Articles

Numerical investigation of nanofluid flow over a bidirectional stretching surface in porous media

AbstractFlow‐induced by bidirectional stretching surfaces has significant applications in various engineering processes. This study aims to address the research gap in understanding the three‐dimensional flow of nanofluid over a flat bidirectional stretching surface in a porous medium considering both axisymmetric and non‐axisymmetric scenarios. The analysis incorporates the effects of radiation, internal heat sources, viscous dissipation, and Joule heating. A single‐phase approach is utilized to model the problem. The governing nonlinear PDEs are non‐dimensionalized and transformed into a set of ordinary differential equations using appropriate proportional similarity transformations. A numerical solution is obtained using an implicit finite difference scheme. Using graphical representations, the influence of the Eckert and Prandtl numbers, along with parameters such as permeability, stretching, radiation, and heat sources, is inspected. The study reveals that porosity and magnetic parameters reduce fluid velocity while enhancing the temperature distribution. Conversely, the Eckert number, radiation, and heat source parameters increase the nanofluid temperature. Furthermore, the dimensionless friction coefficient and Nusselt numbers at the boundary are illustrated and computed. These findings offer valuable insights into the fluid dynamics and heat transfer characteristics of the system, enhancing the comprehension of these complex phenomena.

Thermal and magnetic influences on the hybrid nanofluid flow over exponentially elongating/contracting curved surfaces in porous media: a comprehensive study

Thermal and magnetic influences on the hybrid nanofluid flow over exponentially elongating/contracting curved surfaces in porous media: a comprehensive study

Physical modeling of organics-contaminated groundwater remediation by ozone micro-nano-bubbles enhanced oxidation

Ozone micro-nano-bubbles (MNBs) enhanced oxidation is a promising in-situ remediation technology for organics-contaminated groundwater. The transport behavior of MNBs and contaminant removal effect in actual groundwater scene is not yet comprehensively understood, although one-dimensional column experiments and batch tests were conducted to investigate the migration of MNBs and contaminant degradation in previous studies. Here, a novel two-dimensional (2D) physical modeling facility was developed, which can characterize the tempo-spatial distribution of MNBs and contaminant in groundwater. The facility was used to explore the migration of MNBs under different hydraulic gradients and the removal of methyl orange, a representative organic pollutant, using ozone MNBs. The experimental results show that groundwater flow velocity has a significant influence on the migration behavior of MNBs. A model including groundwater flow, MNBs transport, and dissolved gas transport can well capture the migration and distribution of MNBs under different hydraulic gradients. The longitudinal and transverse dispersivities of the MNBs were calculated to be 1.14 cm and 0.18 cm, respectively. MNBs are able to migrate with groundwater flow to long distances and exhibit strong dispersion in the lateral and longitudinal directions. The increase in hydraulic gradient greatly enhances the transport of MNBs in groundwater and relieves the deposited MNBs on the surface of porous media. At a hydraulic gradient increasing from 0.033 to 0.1, the range of influence of MNBs increased from about 80 cm × 40 cm to 140 cm × 39 cm after 36 h of injection of oxygen MNBs water. The methyl orange in groundwater is effectively removed by ozone MNBs enhanced oxidation, showing the remarkable remediation ability of ozone MNBs. The area of influence and pollutant removal of the ozone MNBs expanded with injection, and the area of influence was approximately 48 cm × 30 cm after 48 h of treatment. We also discuss the effect of groundwater matrix on ozone MNB migration and degradation of contaminants. The 2D model tests illustrate the mechanism of MNB migration and indicate that ozone MNBs enhanced oxidation technology has great potential in the remediation of organics-contaminated groundwater.

Understanding the role of flux chamber configuration in the measurement of VOC emissions from porous media

The accurate quantification of volatile organic compound (VOC) emission rates from porous media to the air is a challenging problem, as measurements are affected by the chemical and physical characteristics of the porous media, and the operating parameters of the sampling device itself. The main objective of this study is to investigate how flux chamber (the most commonly used sampling device) configurations influence emission rate measurement from three selected porous media. Various parameters were studied, including sweep air flow rate, presence of a mixing fan, headspace volume and thickness of media. Controlled experiments focused on the behaviour of two VOCs commonly found in area sources: acetic acid and 1-butanol. Sweep gas flow rate emerged as the most influential factor, inducing turbulence and dilution over porous media surfaces and impacting emission rate measurements more significantly than headspace volume and fan installation. Variations in porous media properties also affected mass transfer, with emissions from coco coir showing higher mass transfer as its porosity and particle size facilitated gas transportation. While behaviour of acetic acid emission through the media supported the diffusion theory, emission of 1-butanol was affected by a combination of factors, highlighting the role of both diffusive and advective transport mechanisms. Understanding how flux chamber setups and porous media properties influence emission rates is crucial for accurately interpreting data. This knowledge also guides the design of studies, especially when investigating complex sources like biosolids and organic-amended soil.

Radiative flow of clay nanoparticles on the lubricity of Williamson drilling fluids across a vertical surface in a Darcy-Brinkman porous medium

Drilling fluids are essential for extracting gases and oils from rocks and soil. To increase drilling fluid efficiency, clay nanoparticles are crucial. The use of clay particles in drilling fluids increases their thermal conductivity, viscosity, and boiling point, hence giving resilience to high temperatures and controlling fluid costs. Therefore, this research examines the convection radiative flow and heat transfer incorporated in the Williamson nanofluid with a heat source/sink. The effective thermophysical properties of clay nanofluid are represented quantitatively by using Maxwell-Garnett and Brinkman's formulas. The leading PDEs with physical boundary conditions that control the flow phenomena are predetermined. These PDEs are converted into ODEs using the similarity method, and dual solutions are then found by using an effective bvp4c solver. The effects of mixed convective, permeability, Williamson constraint, heat source/sink, nanoparticle volume fraction, and radiation parameters were all thoroughly studied quantitatively and theoretically. The Nusselt number and skin friction are calculated and displayed in tabular form as well as graphical form along with the velocity and temperature profiles. Multiple solutions are observed in the shrinkable sheet as well as the buoyancy assisting flow. The findings demonstrate that the Nusselt number rises noticeably when volume concentration increases. In addition, the permeability parameter expands the boundary layer thickness in the lower solution, while the contrary behavior is observed in the upper solution.

Unsteady MHD‐radiative thin film flow with heat transfer over a stretching surface in porous media

AbstractThis study conducts a computational analysis to explore how magnetic fields, radiation, heat, and mass transfer collectively influence a horizontal stretching sheet within a porous medium. The research focuses on elucidating the dynamics of thin film flow through the formulation of time‐dependent equations and subsequent transformation of fluid flow equations into ordinary differential equations via similarity transformation. The numerical solution is attained employing the Runge–Kutta fourth‐order method coupled with a shooting technique. MATLAB software is utilized to generate graphs and numerical values, offering a detailed representation of engineering‐relevant physical quantities in tabular form. The investigation revealed notable trends associated with varying parameters. Increasing unsteadiness parameters lead to a reduction in velocity, temperature, and concentration fields, while the temperature distribution demonstrates a positive correlation with radiation parameters. Moreover, elevated Prandtl numbers and unsteadiness parameters correspond to augmented heat and mass flux, respectively. Of particular significance is the observed heightened heat transfer rate during the transition from a Prandtl number of 1 (representing air) to 2 (representing oil), alongside an increased mass transfer rate with the escalation in Schmidt number from 0.62 (representing hydrogen) to 0.78 (representing ammonia). A comparative analysis of the numerical findings with existing literature demonstrates excellent agreement, affirming the validity and relevance of the present study. These insights offer valuable implications for understanding and optimizing heat and mass transfer processes in porous media, with potential applications in various engineering and scientific domains.

External velocity and dissipative flow of clay nanoparticles on the lubricity of drilling fluids across a vertical surface in a Darcy-Brinkman porous medium with thermal radiation

Drilling fluids are important in the extraction of oils and gases through rocks and soil. Clay nanoparticles are essential for enhancing drilling fluid efficiency. The thermal conductivity, viscosity, and boiling point of drilling fluids increase when clay nanoparticles are incorporated, providing resistance to high temperatures and regulating fluid costs. This article illustrates the convection heat transfer in drilling nanofluid while taking into account the significant presence of clay nanoparticles in the fluid with viscous dissipation, thermal radiation, and heat source/sink. The efficient thermophysical characteristics of clay nanofluid are expressed mathematically using Maxwell-Garnett and Brinkman’s formulas. The partial differential equations (PDEs) with physical boundary conditions that control the flow phenomena are predetermined. The similarity technique is employed to transmute these PDEs into ordinary differential equations (ODEs) and then an efficient boundary value problem fourth-order (bvp4c) solver is utilized to find dual solutions. The Nusselt number and skin friction are calculated and displayed in tabular form as well as graphical form along with the velocity and temperature profiles. Multiple solutions are observed in the shrinking sheet as well as the buoyancy assisting flow. The findings demonstrate that when volume concentration increases, the Nusselt number rises noticeably. In addition, the permeability parameter expands the boundary layer thickness in the lower solution, while the contrary behavior is observed in the upper solution.

Effect of a nonwoven geotextile on nano-TiO2 transport and retention in aggregated porous media under saturated flow conditions

In this experimental work, the transport and retention of TiO2 nanoparticles (nano-TiO2) through a geotextile-aggregated porous media filtration system at two distinct flow velocities and three ionic strengths (ISs) were investigated. Experimental results showed higher nano-TiO2 recovery in the effluent and less retention when increasing the flow velocities under unfavorable conditions. The surface roughness morphology of the porous media may have a meaningful impact on the attachment of nano-TiO2. The nano-TiO2 deposition increased with IS increasing, which are qualitatively in line with the prediction calculated by the extended Derjaguin−Landau−Verwey−Overbeek (XDLVO) theory. Specially, under unfavorable physicochemical conditions (i.e. 0.1 and 5 mM), nano-TiO2 can be retained on the porous media surface at secondary minima and primary minima. While more deposition of nano-TiO2 may occur at primary minima at the IS of 25 mM (refers to favorable physicochemical conditions). And nano-TiO2 transport pathways became less dispersive and more uniform under high flow rate in the porous media with geotextile. The geotextiles can improve flow homogeneity leading to an enhancement in nano-TiO2 particles removal. Our study showed for the first time that geotextile can be served as an efficient barrier to remove the nano-TiO2 through aggregated porous media. The fitted parameters derived from HYDRUS-1D simulations indicated that both mechanisms of physicochemical attachment and straining occur under the current conditions of this work and they have the same importance in nano-TiO2 retention at column scale.

Effect of salt types on salt precipitation and water transport in saline sandy soil

AbstractSalt precipitation on the surface of porous media significantly affects water transport processes. Most studies on salt precipitation mainly focused on single salts, but in nature, salt precipitation usually occurs as mixtures. Consequently, information on the crystallization of salt mixtures and its effect on water transport remains scarce. This study investigated the precipitation of mixtures (the mass ratios of NaCl:Na2SO4 were 3:7, 5:5, and 7:3, respectively) of NaCl (typical efflorescence) and Na2SO4 (typical subflorescence) in the initially saturated sandy soil columns and its effect on evaporation and compared it with the cases of the two salts individually. The results showed that salt mixtures exhibited a mixed pattern of crystals including both efflorescence and subflorescence, and the efflorescence showed granular aggregation, unlike the mono‐salts. The crystallization coverage of the salt mixtures was smaller than that of NaCl mono‐salt; high (7:3) and low (5:5 and 3:7) proportions of NaCl led to larger and smaller crystallization coverage than that of Na2SO4 mono‐salt, respectively. While the salt mixtures had less crystallization coverage than the mono‐salts, they showed lower evaporation because the salt mixtures formed a denser crystallization structure of efflorescence‐subflorescence‐soil layer, this crystallization structure exhibited greater inhibition of water vapour diffusion, thus reducing evaporation. In addition, the crystallization of the salt mixtures with higher NaCl proportion afforded greater resistance of evaporation. The mixed crystallization pattern formed by the salt mixtures significantly enhances the crystallization resistance to evaporation.

Entropy optimization on magnetized radiative bioconvective flow of Carreau-Yasuda hybrid CNTs through a spherical surface in a non-Darcian porous medium with activation energy

This work inspects entropy generation and heat transfer induced by a bioconvection slip flow of nonlinear radiative Carreau-Yasuda hybrid nanofluid (NF) over a convectively heated sphere. Activation energy for microbes is contemplated in order to comprehend its contribution toward flow features. The original partial differential equations (PDEs) are rendered non-dimensional through appropriate conversions, and the resulting PDEs are solved using the overlapping grid spectral collocation algorithm. The impact of diverse flow factors on flow profiles, entropy generation, skin friction, heat, mass, and motile microbes transport rates is analyzed. Key outcomes reveal that hybrid NF flow demonstrates a supplementary indispensable feature in the operation of heat transport compared to mono NF flow. More entropy is generated in the system by using the hybrid NF model along with magnetic field, heat source, convective heating, nonlinear radiation, and viscous dissipation. Thermal fields and rate of heat transport are improved by including nonlinear radiative heat flux in the system. Mass and motile microbes transport rates are respectively enhanced by chemical and microbial reactions, but both quantities are reduced by activation energy. The effects of microbial reactions on flow quantities substantiate the significance of these features for the dynamics of microorganisms. The findings of this study can be useful in the upsurge of thermal performance of the working fluid and contribute toward the improvement of microbial fuel cell performance.

Transport of graphene oxide in the capillary fringe: Insights from sandbox experiments and numerical simulation

Studying contaminant transport in the capillary fringe (CF), a crucial part of the vadose zone, offers insights into the mechanisms controlling pollution in soils and groundwater aquifers. This paper investigated contaminant transport in the CF by continuously injecting a conservative tracer (NaCl) and graphene oxide nanoparticle (GONP), an adsorptive contaminant, into a sandbox. After entering the CF from the unsaturated zone, both NaCl and GONP underwent lateral transport. The breakthrough curves (BTCs) for NaCl and GONP were derived from water samples collected at predetermined sampling holes. Subsequently, contaminant transport in the CF was modeled using a one-dimensional–two-dimensional (1D-2D) coupled hydrodynamic model. This model incorporated lateral dispersivity (αL = 1.198 cm) and longitudinal dispersivity (αT = 0.286 cm), calculated using a point-by-point method. The hydrodynamic dispersion coefficients obtained were then applied to the Brooks and Corey (BC) and the van Genuchten (VG) parametric models. The BC model more accurately simulated the NaCl migration compared to the VG model, leading to its application in simulating GONP transport in the CF. However, the simulated BTCs for GONP showed a lag behind the measured data, especially at high ionic strengths. This discrepancy was attributed to the variable adsorption partition coefficient of GONP under different ionic conditions. During the experiment, GONP adsorption onto the porous media's surface altered the capillary dynamics, notably increasing capillary rise height, decreasing seepage velocity, and reducing GONP dispersion. Therefore, it is necessary to consider the adsorption capacity of the contaminants in order to accurately assess their transport within the vadose zone.

Magnetophoresis of paramagnetic metal ions in porous media.

We report a numerical investigation of the magnetophoresis of solutions containing paramagnetic metal ions. Using a simulated magnetic field of a superconducting magnet and the convection-diffusion model, we study the transport of transition metal salts through a porous medium domain. In particular, through a detailed comparison of the numerical results of magnetophoretic velocity and ion concentration profiles with prior published experiments, we validate the model. Subsequent to model validation, we perform a systematic analysis of the model parameters on the magnetophoresis of metal ions. Magnetophoresis is quantified with a magnetic Péclet number Pem. Under a non-uniform magnetic field, Pem initially rises, exhibiting a local maximum, and subsequently declines towards a quasi-steady value. Our results show that both the initial and maximum Pem values increase with increasing magnetic susceptibility, initial concentration of metal solutes, and ion cluster size. Conversely, Pem decreases as the porosity of the medium increases. Finally, the adsorption of metal salts onto the porous media surface is modeled through a dimensionless Damkohler number Daad. Our results suggest that the adsorption significantly slows the magnetophoresis and self-diffusion of the paramagnetic metal salts, with a net magnetophoresis velocity dependent on the kinetics and equilibrium adsorption properties of the metal salts. The latter result underscores the crucial role of adsorption in future magnetophoresis research.

Numerical Technique for a Darcy-Forchheimer Casson CuO-MgO/Methanol Hybrid Nanofluid Flow due to an Elongated Curved Surface with Chemical Reaction

The insight of the present work is for analyzing the Darcy-Forchheimer model on energy and mass transfer fluid flow with the impact of CuO and MgO metallic nanoparticles with methanol as base fluid due to an elongated curved surface in uniform porous media numerically. For the two-dimensional physical model, the governing nonlinear coupled partial differential equations are derived with suitable boundary conditions and in turn, using appropriate similarity transformation transferred to nonlinear coupled ordinary differential equations. Runge-Kutta Felhberg (RKF) computational results are carried out using Maple software to understand the characteristics variations of momentum fluid flow, heat and mass transfer on various control non-dimensional parameters of the model viz local Reynolds number, Schmidt number, porosity and curvature parameters. The findings are shown numerically and graphically to demonstrate the performance of flow-related physical parameters on energy, velocity, and concentration patterns. Furthermore, the Nusselt number, skin friction coefficient and Sherwood number for the currently stated system are numerically computed. The Prandtl number denotes the deterioration of the temperature profile's performance. It is believed that increasing the Casson parameter value lowers the velocity field. Moreover, the concentration field declines as the Schmidt number grows. The findings are compared to previous studies which turn out to be in good accord.

Research on the Adsorption Law of HFAD Agents on the Surface of Porous Media during Hydraulic Fracturing-Assisted Oil Displacement in Low-Permeability Reservoirs.

Adsorption loss of surfactants in porous media is one of the key factors affecting their application in low-permeability reservoirs. The hydraulic fracturing-assisted oil displacement (HFAD) technology can effectively reduce the adsorption loss of surfactants in porous media. However, the adsorption laws of HFAD agents (surfactants) during the HFAD process are still unclear. It was studied based on physical simulation experiments in this paper. The results showed that 0.3% SY-D as the HAFD agent achieved the best effect, which could reduce the oil-water interfacial tension to 0.0239 mN/m and increase the wettability index to 0.7492. In the high-pressure injection process of HFAD technology, the injection pressure and core permeability are positively correlated with the dynamic saturation adsorption capacity of the HFAD agent on the surface of porous media and the ambient temperature is negatively correlated with it. The higher the injection pressure and the larger the core permeability, the lower the dynamic saturation adsorption capacity of the HFAD agent on the porous media surface. In addition, since adsorption is an exothermic process, increasing the temperature has an inhibitory effect on adsorption. The higher the temperature, the slower the adsorption process of the HFAD agent on porous media. Among the three influencing factors, permeability has the greatest influence on the dynamic saturation adsorption capacity of the HFAD agent on the surface of core porous media, followed by injection pressure, and temperature has the least influence on it. Therefore, when implementing HFAD technology for the reservoir with low permeability, it can be considered to increase the injection pressure of HFAD technology to reduce the dynamic saturation adsorption capacity so as to increase the effective concentration of the agent. The research results have certain guiding significance for the application of HFAD technology in the field.

A gel system with long‐term high‐temperature stability for deep profile modification of high‐temperature oil and gas reservoirs

AbstractProfile modification is the key for efficient development of oil and gas reservoirs, especially high‐temperature reservoirs, which requires the system to have good high‐temperature resistance. According to the characteristics of high‐temperature reservoir, a high temperature gel composed of terpolymer, modified phenolic resin, aromatic amine curing agent and thiourea was developed. The effects of different components on the properties of the gel system were clarified. Then, the long‐term thermal stability under high‐temperature conditions was studied. In addition, the plugging performance of gel system under different permeability and injection volume was studied. Finally, the gelation properties and plugging properties of gel system with the flow distance were studied by simulating the flow of porous media. The results show that the gel system has high strength and suitable gelation time, and it can be adjusted in real time according to different oilfield requirements. In the range of 75–150°C, the gel system had excellent long‐term stability. When the temperature was 75°C, no free water after 120 days, and the viscosity only decreased from 13,131 to 11,254 mPa·s. Even at 150°C, the viscosity was as high as 8350 mPa·s after 120 days, and the free water was only 5.5%. The gel system had good adhesion ability on the porous media surface and strong anti‐flooding properties. When the injection volume was 0.1 pore volume (PV in short), the plugging rate to the sand packed tube was 72.7%. When the injection volume was 0.5 PV, the plugging rate was as high as 97.6%. The plugging rate of the gel system for the sand packed tube with permeability of 500 mD was 98.7% when the injection volume was 0.5 PV. When the permeability increased to 3000 mD, the plugging rate still reached 92.3%. The gel system also had an excellent deep profile control ability, and the viscosity retention of at 60 cm was as high as 96%. When the flow distance was 2 m, the viscosity retention also reached 75%. The rheological properties also shown that the gel system had excellent shearing resistance and adsorption resistance. Finally, combined with the state of the gel system on the surface of the porous media, there was no cementation between the formation sand before the injection, and the sand particles did not stick to each other. After the gel was injected, the adhesion of gel system on the porous media surface was very strong. The 3D network structure was also very dense, the sand particles could have good cementation effect under the adhesion of gel system.

Mathematical modeling of viscoelastic fluid flow across a nonlinear stretching surface in porous media with varying magnetic field

We investigate the cross-diffusion on MHD mixed convective thermo-solutal transport in viscoelastic fluid from a nonlinear stretching sheet. The novelty of the work is the analytical evaluation of the nonlinear stretching sheet in a porous medium with a variable magnetic parameter and radiative flux. Also, thermo-solutal transport of a mixed convective flow is analyzed with Dufour and Soret effects in the presence of the chemical reaction, heat source/sink. The governing PDEs are reduced into ODEs by similarity variables. ODEs were tackled analytically using the homotopy analysis method (HAM). The analysis is carried out up to the 15th order of approximation. HAM contains an h-curve, allowing a flexible method of controlling the series solution convergence area. Graphs and tables are plotted to analyze the influence of different parameters on the fluid. Rates of heat and mass flux are depicted using tables. Our results indicate that the increasing viscoelastic flow enhances the boundary layer, and the thermal boundary layer reduces as radiation enhances. The numerical demonstrations of the wall drag coefficient, Nusselt number and Sherwood number have been tabulated. The growing parameters are taken as [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text]

Falkner-Skan aspects of a radiating (50% ethylene glycol + 50% water)-based hybrid nanofluid when Joule heating as well as Darcy-Forchheimer and Lorentz forces affect significantly

Falkner-Skan aspects are revealed numerically for a non-homogeneous hybrid mixture of 50% ethylene glycol-50% water, silver nanomaterials Ag, and molybdenum disulfide nanoparticles MoS2 during its motion over a static wedge surface in a Darcy-Forchheimer porous medium by employing the modified Buongiorno model. The Brownian and thermophoresis mechanisms are included implicitly along with the thermophysical properties of each phase via the mixture theory and some efficient phenomenological laws. The present simulation also accounts for the impacts of nonlinear radiative heat flux, magnetic forces, and Joule heating. Technically, the generalized differential quadrature method and Newton-Raphson technique are applied successfully for solving the resulting nonlinear boundary layer equations. In a limiting case, the obtained findings are validated accurately with the existing literature outcomes. The behaviors of velocity, temperature, and nanoparticles volume fraction are discussed comprehensively against various governing parameters. As crucial results, it is revealed that the temperature is enhanced due to magnetic field, linear porosity, radiative heat flux, Brownian motion, thermophoresis, and Joule heating effects. Also, it is depicted that the hybrid nanoliquids present a higher heat flux rate than the monotype nanoliquids and liquids cases. Moreover, the surface frictional impact is minimized via the linear porosity factor. Furthermore, the surface heat transfer rate receives a prominent improvement due to the radiative heat flux inclusion.

Chemicals-CO2 mechanisms of inhibiting steam heat transfer and enhancing oil film strip: Steam flow through the wall-adhering oil film surface in porous medium

The CO2 and Sodium Dodecyl Sulfate (SDS) assisted steam flooding technology was an effective approach addressed the persistent issues that have hindered the stable development of high-viscosity cold oil through steam injection. However, in the process of steam flow through porous media, the synergistic influence of the oil film adsorbed in near wellbore porous media, and the CO2-SDS on steam heat transfer has not been investigated. Steam heat transfer is the key factors affecting heavy oil recovery. The primary objective of this study was to research the effect of CO2-SDS on steam heat transfer and oil film stripping by designing experiments. The study results demonstrated that in the initial stage of displacement, the heat transfer resistance between the steam and the porous medium was increased by the oil film adsorbed in near wellbore area. In additional, the condensation mode of the steam was altered from bead condensing to film condensing by the composite thermal fluid flooding, preventing the steam heat dissipation near wellbore area and transferring more thermal to the long-distance area. At the later stage of displacement, the interfacial tension between oil-water and oil-gas was reduced by CO2-SDS, improving the fluidity of oil and providing the seepage channel for steam, and increasing the steam thermal sweep range. Compared to the sandpack experiment of steam flooding, the temperature at the output end of the sandpack model increased from 69.8 °C to 88.7 °C, indicating an expansion of the steam heat sweep range and successful long-distance heat transfer during composite thermal fluid flooding. In the process of composite thermal fluid flooding, the maximum displacement pressure difference increased from 2.28 MPa to 3.07 MPa, and the maximum oil recovery rate increased from 2.48 g/mL to 2.81 g/mL. The peak of the high production period was raised, resulting in a 40.97% to 51.86% increase in recovery rates.

Biosurfactant-affected mobility of oxytetracycline and its variations with surface chemical heterogeneity in saturated porous media

Herein, the influences of rhamnolipid (a typical biosurfactant) on oxytetracycline (OTC) transport in the porous media and their variations with the surface heterogeneities of the media (uncoated sand, goethite (Goe)-, and humic acid (HA)-coated sands) were explored. Compared to uncoated sand, goethite and HA coatings suppressed OTC mobility by increasing deposition sites. Interestingly, rhamnolipid-affected OTC transport strongly depended on the chemical heterogeneities of aquifers and biosurfactant concentrations. Concretely, adding rhamnolipid (1–3 mg/L) inhibited OTC mobility through sand columns because of the bridging effect of biosurfactant between sand and OTC. Unexpectedly, rhamnolipid of 10 mg/L did not further improve the inhibition of OTC transport owing to the fact that the deposition capacity of rhamnolipid reached its maximum. OTC mobility in Goe-coated sand columns was inhibited by 1 mg/L rhamnolipid. However, the inhibitory effect decreased with the increasing rhamnolipid concentration (3 mg/L) and exhibited a promoted effect at 10 mg/L rhamnolipid. This surprising observation was that the increased rhamnolipid molecules gradually occupied the favorable deposition sites (i.e., the positively charged sites). In comparison, rhamnolipid facilitated OTC transport in the HA-coated sand column. The promotion effects positively correlated with rhamnolipid concentrations because of the high electrostatic repulsion and deposition site competition induced by the deposited rhamnolipid. Another interesting phenomenon was that rhamnolipid's enhanced or inhibitory effects on OTC transport declined with the increasing solution pH because of the decreased rhamnolipid deposition on porous media surfaces. These findings benefit our understanding of the environmental behaviors of antibiotics in complex soil-water systems containing biosurfactants.

Homotopy analysis of mixed convection flow of a magnetized viscoelastic nanofluid from a stretching surface in non-Darcy porous media with revised Fourier and Fickian approaches

This article addresses theoretically the mixed convection hydromagnetic flow of electrically conducting viscoelastic nanofluid from a vertical permeable stretching sheet in a non-Darcy porous medium with Cattaneo–Christov double-diffusion model to evaluate the heat transfer phenomena in steady boundary layer flow on a stretchable surface. In this regard, thermal and solutal hyperbolic wave relaxation effects are included for non-Fourier and non-Fickian models. Heat absorption is also included in the analysis. The Buongiorno two-component nanoscale model is adopted for simulating Brownian motion and thermophoretic body force effects. A non-Darcy drag force model is employed for the porous medium and the Reiner–Rivlin second-grade model for non-Newtonian characteristics. Via appropriate dimensionless similarity variables, the nonlinear dimensional partial differential conservation equations for momentum, energy and concentration with associated boundary conditions are rendered into a nonlinear dimensionless ordinary differential boundary value problem. The homotopy analysis method (HAM) is utilized to solve the boundary value problem and the impact of emerging parameters including thermal relaxation parameters, non-Newtonian material parameter, Darcy permeability parameter, porous inertial parameter and Hartmann magnetic number on the momentum, heat and mass transfer characteristics are visualized graphically and in tables. A 30th-order approximation for HAM is shown to produce sufficient accuracy for the velocity and temperature fields and a 40th-order estimates is adequate for the concentration field. It is observed that increasing the magnitude of thermal and solutal relaxation parameters has the opposite effect on the thermal and concentration distributions. The novelty of the work is the simultaneous inclusion of multiple effects (non-Fourier and non-Fickian thermal relaxation hyperbolic wave models, non-Darcy drag effects and heat generation/absorption) which are relevant to rheological nanomaterials processing and also the deployment of homotopy analysis as an alternative to conventional numerical methods such as finite differences, finite elements and MATLAB solvers. The study is relevant to the manufacture of electro-conductive polymers (ECPs) and smart (functional) magnetic nano-liquids.