Three-layered electro-osmosis modulated blood flow through a micro-channel

Electrokinetic peristaltic multi-layered transport is considered in a micro-channel under the action of an axial electrical field. Three different layers i.e. the core layer, intermediate layer and peripheral layer are simulated with three different viscosities for each fluid layer. The unsteady two-dimensional conservation equations for mass and momentum with electrokinetic body forces, are transformed from the wave frame to the laboratory frame and the electrical field terms are rendered into electrical potential terms via the Poisson-Boltzmann equation, Debye length approximation and ionic Nernst Planck equation. The dimensionless emerging linearized electrokinetic boundary value problem is solved using integral methods. Closed-form expressions are derived for stream functions in the core, intermediate and peripheral layers. Expressions are also derived for the core-intermediate interface shape and the intermediate-peripheral interface shape. Maximum pressures are also computed. To study bolus migration, the range of the trapping limit is also determined in the peripheral layer. It is found that in the core layer larger boluses are computed in the case of lower intermediate layer viscosity relative to peripheral layer viscosity although the number of boluses is greater when the intermediate layer viscosity exceeds the peripheral layer viscosity. Furthermore, in the intermediate layer, stronger concentration of streamlines is computed in the lower half space with positive Helmholtz-Smoluchowski velocity. Also, negative Helmholtz-Smoluchowski velocity reduces the core layer (H1) interface shape whereas it enhances the peripheral layer (H) and intermediate layer (H2) shapes. At lower values of volume flow rate ratio, hydromechanical efficiency is maximum for positive Helmholtz-Smoluchowski velocity whether intermediate layer viscosity is less or greater than peripheral layer viscosity. Finally, greater with greater peristaltic wave amplitude and also for positive Helmholtz-Smoluchowski velocity there is an increase in time-averaged flow rate, whether intermediate layer viscosity is less or greater than peripheral layer viscosity. The analysis is relevant to electro-kinetic hemodynamics and bio-micro-fluidics

Application of Carbon-based Nanofluids in Heat Exchangers: Current Trends

Abstract : The thermal performance of a heat exchanger can be enhanced by adding carbon nanostructured materials such as carbon nanotubes and graphene to the conventional working fluid. When nanomaterials are suspended in the working fluid, the fluid is known as Nanofluid. The enhancement in the thermal and rheological properties of the fluid is responsible for the augmentation in heat transfer performance. The influence of carbon nanomaterial on the thermophysical properties, heat transfer characteristics and flow properties are reviewed. The current trends on the utilization of carbon-based nanofluids in heat exchangers were reported. The study shows that carbon-based nanofluids have the potential to improve the performance of heat exchanger and reduce the cost of fabrication by reducing heat exchange area. The study identifies the scope for future study

Influence of anionic surfactants on the stability of multi-walled carbon nanotubes-based nanofluid

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Electrochemical corrosion behavior of copper in graphene-based thermal fluid with different surfactants

Abstract: This study investigates the effect of different surfactant-dispersed graphene nanofluid on the electrochemical behavior of copper. This study was achieved by measuring the open circuit potential and potentiodynamic polarization of copper in the nanofluids at room temperature. The test media includes surfactant-free graphene nanofluid and graphene nanofluid dispersed using four different surfactants, which are sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, Gum Arabic, and Tween 80. The surface characterization and elemental composition of the copper sample before and after the corrosion tests were determined using a scanning electron microscope coupled with energy-dispersive X-ray spectroscopy. The phase formation after corrosion was also evaluated by measuring X-ray diffraction. The quantity of copper dissolved in the test media was evaluated using an inductively coupled plasma mass spectrometry (ICP-MS). The open-circuit potential measurements revealed that the current free corrosion potential of copper in the different surfactant-aided graphene nanofluids are different. The electrochemical corrosion potential, Tafel slopes, and corrosion rates revealed the better corrosion performance of copper in the nanofluid of different surfactants in the increasing order GA, SDS, Tween 80, and SDBS. Copper in GA-based graphene nanofluid was found to have the lowest corrosion rate while that of SDBS has the highest corrosion rate. However, the ICP-MS result revealed a discrepancy in the corrosion behavior and quantity of copper dissolved in the different test media. This could be attributed to the dissimilar dissolutionredeposition rate of copper in different media

Experimental study and ANFIS modelling of the thermophysical properties and efficacy of GNP‑Al2O3 hybrid nanofuids of different concentrations and temperatures

DATA AVAILABITY STATEMENT: The datasets generated during and/or analysed during the current study are available from the corresponding author upon reasonable request.This study delves into an extensive investigation of the thermophysical properties and heat transfer efficacy of a hybrid nanofluid incorporating graphene nanoplatelets and γ-Al2O3 nanoparticles dispersed in deionised water. The nanofluids were characterised for their viscosity (µ), thermal conductivity (λ), and electrical conductivity (σ) over a 15–40 °C temperature range for varying nanoparticle loading (0.1–0.4 volume%). The experimental results revealed notable enhancements in µ, λ, and σ with increasing nanoparticle concentration, while µ decreased at elevated temperatures as λ and σ increased. At the highest concentration (0.4 vol%), µ increased by 21.74%, while λ and σ exhibited peak enhancements of 17.82% and 393.36% at 40 °C. An Adaptive Neuro-fuzzy Inference System (ANFIS) model was devised to enhance predictive precision by meticulously optimising the number of membership functions (MFs) and input MF type. The ANFIS architecture that exhibited the most remarkable agreement with the experimental data for µ, λ, and σ was found to utilise the Product of Sigmas, Difference of Sigmas, and Generalized Bell MFs, respectively, with corresponding input MF numbers being 2–3, 3–2, and 3–2. The optimal ANFIS model for µ, λ, and σ exhibits a higher prediction accuracy with an R2 value of 0.99965, 0.99424 and 0.99995, respectively. The Figure of Merit analysis using Mouromtseff Number identified an optimal nanoparticle concentration range of 0.1–0.2 volume% for enhanced heat transfer performance with a reasonable µ increase. This range guides practitioners in utilising hybrid nanofluids effectively while managing potential drawbacks.The University Research Council of the University of Johannesburg.https://www.springer.com/journal/42452Mechanical and Aeronautical EngineeringSDG-09: Industry, innovation and infrastructur

Investigation of the thermal conductivity, viscosity, and thermal performance of graphene nanoplatelet-alumina hybrid nanofluid in a differentially heated cavity

This paper investigates the thermophysical properties and heat transfer performance of graphene nanoplatelet (GNP) and alumina hybrid nanofluids at different mixing ratios. The electrical conductivity and viscosity of the nanofluids were obtained at temperatures between 15–55°C. The thermal conductivity was measured at temperatures between 20–40°C. The natural convection properties, including Nusselt number, Rayleigh number, and heat transfer coefficient, were experimentally obtained at different temperature gradients (20, 25, 30, and 35°C) in a rectangular cavity. The Mouromtseff number was used to theoretically estimate all the nanofluids’ forced convective performance at temperatures between 20–40°C. The results indicated that the thermal conductivity and viscosity of water are increased with the hybrid nanomaterial. On the other hand, the viscosity and thermal conductivity of the hybrid nanofluids are lesser than that of mono- GNP nanofluids. Notwithstanding, of all the hybrid nanofluids, GNP-alumina hybrid nanofluid with a mixing ratio of 50:50 and 75:25 were found to have the highest thermal conductivity and viscosity, enhancing thermal conductivity by 4.23% and increasing viscosity by 15.79%, compared to water. Further, the addition of the hybrid nanomaterials improved the natural convective performance of water while it deteriorates with mono-GNP. The maximum augmentation of 6.44 and 10.48% were obtained for Nuaverage and haverage of GNP-Alumina (50:50) hybrid nanofluid compared to water, respectively. This study shows that hybrid nanofluids are more effective for heat transfer than water and mono-GNP nanofluid.http://www.frontiersin.org/Energy_Researcham2022Mechanical and Aeronautical Engineerin

Comparative Effects of Isometric Quadriceps Training, Glucosamine and Chondroitin Sulphate Iontophoresis on Pain Intensity and Physical Functions of Patients with Knee Osteoarthritis

This study was with a view to comparing the effective means of alleviating pain and improving physical functions in patients with knee osteoarthritis using quadriceps strengthening exercises, glucosamine and chondroitin sulphate iontophoresis. Seventy-eight participants with grade II knee OA were purposively selected and randomly assigned to three groups using fish bowl technique. Group one participants received 1g of glucosamine sulphate (GS) through iontophoresis while group two received 1g of chondroitin sulphate (CS) iontophoresis (40mA- min as dosage) using trans-arthral electrode placement technique twice a week, for 12 weeks. Group three participants had intervention in the form of quadriceps muscle strengthening exercise (1RM, 10 reps and 3 sets), which was a baseline treatment for all the groups. Pain intensity, active knee range of motion and physical function were assessed. Descriptive statistics, ANOVA and Kruskal-wallis test were used to analyze the data. Alpha level was set at p ≤ 0.05. The three modes of interventions significantly alleviated pain (p = 0.001), improved the Functional Activity Level and active ranges of motion (p = 0.001) in the groups after 12 weeks. Although, the administration of Quadriceps strengthening exercise alone, significantly improved the Functional Activity Level than Chondroitin sulphate iontophoresis and Glucosamine sulphate (H = 19.89, p = 0.001). However; there was no significant difference in the active range of motion across the 3 groups. In conclusion, Quadriceps strengthening exercise, Glucosamine and Chondroitin sulphate iontophoresis were effective in alleviating pain, enhancing range of motions and improving physical functions. However, Quadriceps strengthening exercise showed higher efficacy compared to others

A photogeological study of the fold structure in okemesi area, Nigeria.

The Okemesi fold, situated in southwestern Nigeria, is one of the most identifiable geological structures in the basement complex. It is a manifestation of Late-Precambrian deformation of metasediments which have been heavily fractured and sheared in places. Aerial photographs covering about 150km2 of the fold belt were selected for the study because of their large scale and good resolution for structural delineation. A total of 175 fractures were extracted with a cumulative length of about 155 kilometers. They are in three main classes of azimuths: 011o-020o, 021o-030o and 101o-110o. Results indicate the existence of a series of faults that offset the fold trend. Field observations also show that schists and schistose quartzites display strong foliation and shearing which are indicated by displacements along sub-parallel planes. Faulting in the area probably post-dated the folding episode as indicated by the Itawure Fault which separates the Okemesi fold into double-plunging halves; one towards the north and the other towards the south. These structures are observed to be the main factor controlling the drainage pattern in the area. The area of study displays a series of folds which were possibly generated by overthrusting of low-dipping rocks and subsequent fracturing that resulted in the plunging of the fold axis. Journal of Mining and Geology Vol. 43 (2) 2007: pp. 125-13

Lithofacies characterization and channel development in the outcrops of cretaceous sedimentary rocks, Dahomey basin, southwestern Nigeria.

Outcrop exposures of Cretaceous sedimentary rocks in Benin Basin southwestern Nigeria, allow the recognition of slope related sediments and slope valleys. Detailed outcrop logging permits the delineation of massive to cross bedded loose sand with lateral facies changes, normally graded sandstone, clay with injected sand, clayey silt with abundant clasts, channel complexes associated with different lithologies, loose sand, very fine to coarse grained sandstone and conglomerate with clasts of sandstone and siltstone. These lithofacies revealed history of erosion and deposition in various proportions. Four sets of channel development were delineated; the initial valley cut, complex reincision and fill, regional erosion and channel abandonment. These four categories of channel development are related to significant erosion and are possibly related to periods of lowstands. The outcrop exposures show that the first set of channel infill probably commenced with deposition of turbidites accompanied by marine transgression associated with contemporaneous slumping. This progress vertically to amalgamated (network of channels) channels filled with diverse lithologic units while the topmost channel is filled with channel lag and conglomerate. Channel infills are composed essentially of sediments derived from turbidites, slumps and debris flows. Two types of architectural elements recognized are single-story channel and multistory channel complex. The different stages of channel development can be considered in terms of low efficiency and high efficiency flows, which are related to slope equilibrium. Keywords: Outcrop, slope, channel development, channel architecture, process model, lowstandJournal of Mining and Geology Vol. 43 (2) 2007: pp. 131-14