Newtonian Behavior Research Articles

Formulation and Characteristics of Edible Oil Nanoemulsions Modified with Polymeric Surfactant for Encapsulating Curcumin.

Curcumin (Cur) is a beneficial phytochemical with numerous health advantages. However, its limited solubility in oil and poor stability hinder its potential for biomedical applications. In this study, we employed a mixture of food-grade Tween 60, a polymeric surfactant, and Span 60 to adjust the hydrophilic lipophilic balance number (HLBt) and prepared nanoemulsions (NEs) of coconut oil (Cc oil) as carriers for Cur. The effects of HLBt values, surfactant-to-oil ratio, and oil ratio on the physicochemical characteristics of the food-grade oil-NEs were investigated using dynamic light scattering, transmission electron microscopy, differential scanning calorimetry, fluorescence polarization spectroscopy, and viscometry. Increasing the addition ratio of Tween 60 in the NEs, thereby increasing the HLBt, resulted in a reduction in NE size and an improvement in their storage stability. The temperature and size of the phase transition region of the NEs decreased with increasing HLBt. NEs with higher HLBt exhibited a disordering effect on the intra-NE molecular packing of Cc oil. NEs with high HLBt displayed low viscosity and demonstrated nearly Newtonian fluid behavior, while those with lower HLBt exhibited pseudoplastic fluid behavior. Cur was effectively encapsulated into the Cc oil-NEs, with higher encapsulation efficiency observed in NEs with higher HLBt values. Furthermore, the Cur remaining activity was significantly enhanced through encapsulation within stable NEs. The biocompatibility of the Cc oil-NEs was also demonstrated in vitro. In summary, this study highlights the preparation of stable NEs of Cc oil by adjusting the HLBt using Tween 60, facilitating effective encapsulation of Cur. These findings provide valuable insights for the development of Cur carriers with improved solubility, stability, and bioavailability.

Effect of 3-Carene and the Micellar Formulation on Leishmania (Leishmania) amazonensis.

Leishmaniases are neglected tropical diseases caused by obligate intracellular protozoa of the genus Leishmania. The drugs used in treatment have a high financial cost, a long treatment time, high toxicity, and variable efficacy. 3-Carene (3CR) is a hydrocarbon monoterpene that has shown in vitro activity against some Leishmania species; however, it has low water solubility and high volatility. This study aimed to develop Poloxamer 407 micelles capable of delivering 3CR (P407-3CR) to improve antileishmanial activity. The micelles formulated presented nanometric size, medium or low polydispersity, and Newtonian fluid rheological behavior. 3CR and P407-3CR inhibited the growth of L. (L.) amazonensis promastigote with IC50/48h of 488.1 ± 3.7 and 419.9 ±1.5 mM, respectively. Transmission electron microscopy analysis showed that 3CR induces multiple nuclei and kinetoplast phenotypes and the formation of numerous cytosolic invaginations. Additionally, the micelles were not cytotoxic to L929 cells or murine peritoneal macrophages, presenting activity on intracellular amastigotes. P407-3CR micelles (IC50/72 h = 0.7 ± 0.1 mM) increased the monoterpene activity by at least twice (3CR: IC50/72 h >1.5 mM). These results showed that P407 micelles are an effective nanosystem for delivering 3CR and potentiating antileishmanial activity. More studies are needed to evaluate this system as a potential therapeutic option for leishmaniases.

Generalized-Newtonian fluid transport by an instability-driven filament

Cilia are micro-scale hair-like organelles. They can exhibit self-sustained oscillations which play crucial roles in flow transport or locomotion. Recent studies have shown that these oscillations can spontaneously emerge from dynamic instability triggered by internal stresses via a Hopf bifurcation. However, the flow transport induced by an instability-driven cilium still remains unclear, especially when the fluid is non-Newtonian. This study aims at bridging these gaps. Specifically, the cilium is modelled as an elastic filament, and its internal actuation is represented by a constant follower force imposed at its tip. Three generalized Newtonian behaviours are considered, i.e. the shear-thinning, Newtonian and shear-thickening behaviours. Effects of four key factors, including the filament zero-stress shape, Reynolds number ( $Re$ ), follower-force magnitude and fluid rheology, on the filament dynamics, fluid dynamics and flow transport are explored through direct numerical simulation at $Re$ of 0.04 to 5 and through a scaling analysis at $Re \approx 0$ . The results reveal that even though it is expected that inertia vanishes at $Re \ll 1$ , inertial forces do alter the filament dynamics and deteriorate the flow transport at $Re\ge 0.04$ . Regardless of $Re$ , the flow transport can be improved when the flow is shear thinning or when the follower force increases. Furthermore, a linear stability analysis is performed, and the variation of the filament beating frequency, which is closely correlated with the filament dynamics and flow transport, can be predicted.

Rheological, Physical, and Spectroscopical Characterization of Gamma-Irradiated Albumin Nanoparticles Loaded with Anthocyanin.

Anthocyanins are the main active compounds in blueberry. However, they have poor oxidation stability. If anthocyanins are encapsulated in protein nanoparticles, their oxidation resistance could be increased as a result of the slowing down of the oxidation process. This work describes the advantages of using a γ-irradiated bovine serum albumin nanoparticle bound to anthocyanins. The interaction was characterized biophysically, mainly by rheology. By computational calculation and simulation based on model nanoparticles, we estimated the number of molecules forming the albumin nanoparticles, which allowed us to infer the ratio of anthocyanin/nanoparticles. Measurements by UV-vis spectroscopy, FTIR spectroscopy, fluorescence spectroscopy, dynamic light scattering (DLS), ζ potential, electron transmission microscopy, and rheology at room (25 °C) and physiological (37 °C) temperatures were performed. The spectroscopy measurements allowed identifying additional hydrophobic sites created during the irradiation process of the nanoparticle. On the basis of the rheological studies, it was observed that the BSA-NP trend is a Newtonian flow behavior type for all the temperatures selected, and there is a direct correlation between dynamic viscosity and temperature values. Furthermore, when anthocyanins are added, the system increases its resistance to the flow as reflected in the morphological changes observed by TEM, thus confirming the relationship between viscosity values and aggregate formation.

Effect of nanodispersed zinc oxide concentrations on the structural, optical, dielectric, viscous, and acoustic properties of ethylene glycol– glycerol mixture based nanofluids

Nanofluids (NFs) are green-formulated innovative soft materials, enormously used for thermal management medium in energy harvesting/ storage and heat transport, as high breakdown voltage insulators/ nanodielectrics in electrical and energy storage systems, and in the advances of soft condensed matter device technologies. In this study, NFs consisting of ethylene glycol (EG) and glycerol (Gly) mixture in equal volumes as the base fluid and semiconductive zinc oxide (ZnO) nanoparticles with increasing concentrations from 0.005 to 1.00 wt% are prepared and characterized by employing different advanced techniques. X-ray diffraction (XRD) patterns recorded directly on these NFs confirmed the homogeneity and nanosuspension stability of ZnO particles in the hydrogen-bonded supramolecular 3D structure of viscous EG–Gly base fluid. The UV-Vis absorbance spectra explained the ZnO concentration tunable photo sensing and UV blocking properties of these semiconductive nanofluids. The 20 Hz to 1 MHz range dielectric spectra revealed high static dielectric permittivity of these NFs, at 298.15 K, confirming them as promising nanodielectric for electric energy storage devices. The dielectric dissipation factor, electric modulus, and impedance spectra confirmed that these EG–Gly/ZnO NFs have electrode polarization and conductivity relaxation processes around 200 Hz and 20 kHz, respectively. The electrical conductivity is observed in the range of 0.32– 0.65 μS/cm with a noticeable increase at the higher ZnO concentration which infers appreciable insulation performance of these NFs. The rheological measurements demonstrated Newtonian behavior of these NFs with a dynamic viscosity of about 69 mPa.s, at 298.15 K. Ultrasound velocity and various acoustic parameters of these NF materials are marginally altered with varying the ZnO concentration and revealed appreciable thermal conductivity of 0.31 W·m–1·K–1, at ambient temperature. The temperature dependent viscosity measurements of EG–Gly/1.00 wt% ZnO sample demonstrated its Arrhenius behavior with high activation energies for both the viscous and relaxation processes. These experimental results establish the EG–Gly/ZnO nanofluids as multifunctional materials for highlighting current applications and also in futuristic soft condensed matter technologies.

STUDY OF THE RHEOLOGICAL AND PHYSICOCHEMICAL PROPERTIES OF FRUCTAN FRACTIONS OF Agave tequilana cv. cenizo

The physico-mechanical properties of fructan fractions in different agave species without Tequila Denomination of Origin (DOT) need to be studied to identify and expand industrial applications. The rheological and physicochemical characterization of three fractions of Agave tequilana cv. cenizo fructans without DOT, with different degree of polymerization (DP) was carried out to propose their use as an additive in the food industry. Fractions were obtained by apparent DP enrichment (DPa) by stepwise ultradiafiltration with 10, 5 and 1 kilodalton (kDa) membranes and classified on the basis of the enriched fraction evidenced by HPLC profiling with amperometric detector. The ultradiafiltrate of the membrane with 10 kDa, called High Degree of Polymerization (HDP), showed enrichment of fructans with high DPa ≥ 30, the one with 5 kDa called Intermediate Degree of Polymerization (IDP), presents enrichment in DPa between 10 to 30, these fractions dried by spray, showed a modal particle size distribution (D [4,3] < 20 µm). In the ultradiafiltrate of the 1 kDa membrane, called Low Polymerization Grade (LDP), fructo-oligosaccharides (FOS) and fructans with maximum DPa of 15 were enriched; this sample was concentrated to 72 °Brix. The glass transition (Tg) showed a DPa-dependent increase (LDP = 152.17 °C, IDP = 216.12 °C and HDP = 227.5 °C). Viscosity was dependent on the degree of polymerization, exhibiting thermo-mechanically stable flow behavior. The reconstituted powders exhibited Newtonian and flow-stable behavior in a concentration range of 2-50 %, temperature of 5-45 °C and pH of 2-9. The macro and micro structural properties identified in the respective fractions of agave fructans, diversify possible applications with potential interest as encapsulating material, stabilizer and prebiotic sweetener, among others that agave fructans have in the food and nutraceutical industry.

Experimental study of the flow of viscous Newtonian fluids in a centrifugal pump

This paper analyzes the influence of viscosity and impeller rotation speed in the calculation of the flow and in the theoretical prediction of the performance of a centrifugal pump impeller. The evaluation of the viscous effects allows the prediction of the frictional losses of the impeller and a more correct evaluation of the operating characteristics than can be obtained with a perfect fluid. The viscosity modifies the values of the velocity distribution in the channels of the impeller and the deviation of the flow at the exit of the blade. The experiments were carried out with mineral oils of different viscosities varying between 96.10-3 Pa.s and 520.10-3 Pa.s and which are represented by a perfectly newtonian behavior.

Investigating the impact of zinc ion substitution on the rheological properties and hyperthermia potential of cobalt ferrite-based ferrofluids

Zn-substituted cobalt ferrite-based ferrofluids (FFs) were successfully synthesized using a modified co-precipitation method. In this study, we aimed to investigate the heating performance of the synthesized FFs using a resonance coil-based magnetic hyperthermia setup and characterize their viscoelastic behaviour using a magneto rheometer. The crystalline spinel phase with Fd3m (227) symmetry was confirmed through Powder X-ray Diffraction (PXRD. Additionally, Vibrating Sample Magnetometer (VSM) measurements allowed us to analyze the effect of Zn substitution on the room temperature magnetic properties of the FFs. To gain insights into the viscoelastic properties, steady-state rheological measurements were performed. The FFs exhibited non-Newtonian behaviour at low shear rates (<100 s−1) and transitioned to Newtonian fluid behaviour at higher shear rates. Furthermore, we investigated the magneto-viscoelastic behaviour of the FFs across a range of magnetic field strengths (0 to 1 T) using three different fluids. It was observed that the viscosity increased as the field strength increased, which can be attributed to the formation of chain-like structures. The heating efficiency of the FFs was evaluated in terms of Specific Absorption Rate (SAR) using the Initial Slope Method (ISM) and Box Lucas Method (BLM). The SAR values for the FFs exhibited a significant increase with Zn substitution, with the maximum values recorded as 188 ± 8 W/g (ISM) and 212 ± 9 W/g (BLM) for Zn0.4Co0.6Fe2O4, surpassing the SAR value of CoFe2O4 (72 ± 8 W/g, ISM; 92 ± 5 W/g, BLM). To assess biocompatibility, we conducted a cell viability assay using HEK-293 cell lines. The results demonstrated high cell viability (>75%) for Zn0.4Co0.6Fe2O4 at a concentration of 100 µg/ml after a 48-hour incubation period.

Experimental Investigations of Forced Convection of Nanofluids in Smooth, Horizontal, Round Tubes: A Review

A comprehensive review of published works dealing with experimental studies of forced convection heat transfer of nanofluids is presented. The survey is limited to straight, smooth, and round tubes. Moreover, only mono nanofluids exhibiting Newtonian behaviour are considered. Works on experimental research of forced convection in tubes are presented in a chronological order in the first part of the article. In this part, attention was paid to the influence of nanoparticles on the intensification of heat transfer. Information on the tested nanofluids, the measurement technique used, and the measurement range are presented in tabular form. Correlation equations proposed by individual researchers are also presented. In order to explain the controversy regarding the different influences of nanoparticles on the intensity of heat transfer during forced convection of nanofluids, the second part of the paper presents a comparison of the test results obtained by different researchers for the same nanofluid, possibly under the same thermal and flow conditions. Finally, the main conclusions are discussed.

Tribological evaluation of PEG-based nanolubricants modified with graphene and copper oxide

Nanolubricants are dispersions of nanomaterials in a lubricating base. In this work, polyethylene glycol (PEG) was modified with graphene (G) and copper oxide (CuO) to obtain a nanolubricant (NL). The nanolubricants were prepared and their physicochemical and tribological properties were evaluated. The base and the nanomaterials were evaluated using Fourier-transform infrared spectrometry (FTIR), field-emission scanning electron microscopy coupled with energy dispersive spectroscopy (FE-SEM-EDS), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and Raman spectroscopy (Raman). Rheology and Tribology tests were also performed using a four-ball tester according to ASTM 2783. The results showed that nanolubricants have a Newtonian behavior and the viscosity was not significantly modified with the additives. The weld point obtained for the nanolubricants was 160 kgf. In addition, when compared to the PEG, the size of the wear scars was reduced by 9.6% (PEG with 0.01% w/w of CuO) and 35.3% (PEG with 0.05% w/w of CuO and G). The wear protection provided by G is higher than the protection provided by CuO. When the two additives were added, the wear protection increased, and a synergistic effect was observed. Two protection mechanisms were observed in the SEM: rolling bearing/ball effect (CuO) and deposition of G at valleys and peaks of the surface roughness. This article shows novel results related to a laboratory evaluation of nanolubricants in a typical tribological test (four-ball). A novel result was observed in the synergistic effect between the two additives (graphene and CuO) determined by the wear mechanism observed in the tests.

Optimized Chitosan-Based Nanoemulsion Improves Luteolin Release.

Luteolin (LUT) is a flavonoid found in several edible and medicinal plants. It is recognized for its biological activities such as antioxidant, anti-inflammatory, neuroprotective, and antitumor effects. However, the limited water solubility of LUT leads to poor absorption after oral administration. Nanoencapsulation may improve the solubility of LUT. Nanoemulsions (NE) were selected for the encapsulation of LUT due to their biodegradability, stability, and ability to control drug release. In this work, chitosan (Ch)-based NE was developed to encapsulate luteolin (NECh-LUT). A 23 factorial design was built to obtain a formulation with optimized amounts of oil, water, and surfactants. NECh-LUT showed a mean diameter of 67.5 nm, polydispersity index 0.174, zeta potential of +12.8 mV, and encapsulation efficiency of 85.49%. Transmission electron microscopy revealed spherical shape and rheological analysis verified the Newtonian behavior of NECh-LUT. SAXS technique confirmed the bimodal characteristic of NECh-LUT, while stability analysis confirmed NECh-LUT stability when stored at room temperature for up to 30 days. Finally, in vitro release studies showed LUT controlled release up to 72 h, indicating the promising potential of NECh-LUT to be used as novel therapeutic option to treat several disorders.

Newtonian Fractional-Dimension Gravity and Galaxies without Dark Matter

We apply Newtonian fractional-dimension gravity (NFDG), an alternative gravitational model, to some notable cases of galaxies with little or no dark matter. In the case of the ultra-diffuse galaxy AGC 114905, we show that NFDG methods can effectively reproduce the observed rotation curve using a variable fractional dimension DR, as was performed for other galaxies in previous studies. For AGC 114905, we obtain a variable dimension in the range D≈ 2.2–3.2, but our fixed D = 3 curve can still fit all the experimental data within their error bars. This confirms other studies indicating that the dynamics of this galaxy can be described almost entirely by the baryonic mass distribution alone. In the case of NGC 1052-DF2, we use an argument based on the NFDG extension of the virial theorem applied to the velocity dispersion of globular clusters showing that, in general, discrepancies between observed and predicted velocity dispersions can be attributed to an overall fractal dimension D&lt;3 of the astrophysical structure considered, and not to the presence of dark matter. For NGC 1052-DF2, we estimate D≈2.9, thus confirming that this galaxy almost follows standard Newtonian behavior. We also consider the case of the Bullet Cluster merger (1E0657-56), assumed to be one of the strongest proofs of dark matter existence. A simplified but effective NFDG model of the collision shows that the observed infall velocity of this merger can be explained by a fractional dimension of the system in the range D≃ 2.4–2.5, again, without using any dark matter.

Hempseed polysaccharide (Cannabis sativa L.): Physicochemical characterization and comparison with flaxseed polysaccharide

The whole hempseed contains about 27.6% of fiber, of which 5.4% and 22.2% are soluble and insoluble fiber, respectively. The defatted hempseed meal contains about 42.6% of total fiber. Despite the abundant amount of fiber in the hempseed, the application of hempseed polysaccharides (HSP) is currently limited in the food industry. It is necessary to understand their physicochemical properties to extend their food applications. Hence, the objective of the current study is to investigate the physicochemical properties of soluble hempseed polysaccharides in comparison with flaxseed polysaccharides. The physicochemical properties, including molecular weight distribution, shape conformation, total sugar content, uronic acid content, rheological properties, and emulsification properties, were evaluated. The results indicated that the HSP contains about 33% uronic acids, 53% total sugars, and possesses an oblate ellipsoidal shape (Rg = 23.07 nm, Rh = 22.61 nm). Compared to flaxseed polysaccharides and pectin, the HSP showed a high surface active behavior at concentrations above 0.5% (w/v). The dynamic flow curves demonstrated the shear thinning behavior of HSP at the low shear rate range (0.01–10 s−1), followed by a Newtonian behavior at the high shear rate range. The HSP exhibited a weak gel property and an elastic nature. The emulsion stability of HSP and flax polysaccharide did not show a significant difference. The effects of pH and heat treatment on HSP stabilized emulsion were insignificant compared to flax polysaccharides. Finally, the freeze-thaw stability of HSP was inferior compared to flaxseed polysaccharides and pectin. The study has revealed that the HSP could be a potential emulsifying agent in the food system.

Characterization and rheological behavior of vitamin E nanoemulsions prepared by phase inversion composition technique

Many food, pharmaceutical, and cosmetic products are fabricated as nanoemulsions of vitamin E, a vital food micronutrient soluble in oil. Nanoemulsion production, maintenance, and application depend on physicochemical characteristics and rheology. Therefore in this work, we prepared Vitamin E nanoemulsions by the phase inversion composition technique and investigated its physical and rheological characteristics at varied stirring speeds. The nanoemulsions' mean droplet sizes, confined to 5.77 to 11.89 nm, surprisingly showed two different flow behavior regimes: at low-shear rates, Pseudoplastic behavior, and at high-shear rates, Newtonian behavior. Furthermore, their viscosity in high shear rate regimes increased with droplet size. The nanoemulsions exhibited linear viscoelasticity, with storage modulus and loss modulus varying with frequency, and showed concentrated solution behavior, with a storage modulus larger than the loss modulus at higher frequencies. After 30 days of storage, larger droplet-size nanoemulsions showed a more significant viscosity and loss modulus reduction than smaller droplet-size nanoemulsions. This study on Vitamin E nanoemulsions' flow behavior will help develop oil-soluble vitamin delivery applications.

Using transient energy release measurements for the in‐line characterization of non‐Newtonian fluids and fluid state in pipe flow

AbstractAlberini et al. have developed a new technology based on a passive acoustic emission (AE) sensing system that uses only a single sensor, with the goal of providing live and in‐situ measurement of rheology. For this study, three different types of fluids were selected to represent common rheological behaviours: Newtonian behaviour, non‐Newtonian behaviour with power law, and non‐Newtonian behaviour with Herschel–Bulkley relationship. By analyzing the transient energy released during the interaction between the probe and the fluid, distinct acoustic fingerprints were identified in the frequency domain. These acoustic fingerprints were found to be characteristic of the different fluids and their rheology, and were validated in triplicate. Furthermore, the results showed that the intensity of the acoustic emissions increased with higher flow rates (30 to 50 L/min). To test the correlation between flow rate and acoustic response, a neural network regression test was conducted, which demonstrated a direct correlation between AE peaks and flow rate. The neural network used was nonlinear autoregressive network with exogenous inputs (NARX), and the test involved a stepwise regression with 70% training and 30% network validation. The study also introduced the Rheology‐AE quotient, which maps fluid constituents against the acoustic signal. Results showed that this was a reliable means of deriving live rheology from a fluid's frequency domain. Finally, the results obtained from this study were validated using an offline rotational rheometer.

Baru oil (Dipteryx alata vog.) applied in the formation of O/W nanoemulsions: A study of physical-chemical, rheological and interfacial properties

The oil extracted from baru (Dipteryx alata Vog.) seeds is in bioactive compounds and it presents potential to be used in food and cosmetic industries. Therefore, this study aims to provide insights into the stability of baru oil-in-water (O/W) nanoemulsions. For this purpose, the effects of the ionic strength (0, 100 and 200 mM), pH (6, 7 and 8), and storage time (28 days) on the kinetic stability of these colloidal dispersions were evaluated. The nanoemulsions were characterized in terms of interfacial properties, rheology, zeta potential (ζ), average droplet diameter, polydispersity index (PDI), microstructure, and creaming index. In general, for samples, the equilibrium interfacial tension ranged from 1.21 to 3.4 mN.m−1, and the interfacial layer presented an elastic behavior with low dilatational viscoelasticity. Results show that the nanoemulsions present a Newtonian flow behavior, with a viscosity ranging from 1.99 to 2.39 mPa.s. The nanoemulsions presented an average diameter of 237–315 nm with a low polydispersity index (<0.39), and a ζ-potential ranging from 39.4 to 50.3 mV after 28 days of storage at 25 °C. The results obtained for the ζ-potential suggest strong electrostatic repulsions between the droplets, which is an indicative of relative kinetic stability. In fact, macroscopically, all the nanoemulsions were relatively stable after 28 days of storage, except the nanoemulsions added with NaCl. Nanoemulsions produced with baru oil present a great potential to be used in the food, cosmetic, and pharmaceutical industries.

Effect of gamma irradiation on structural properties and rheological behavior of binary biopolymer blend: A case study on guar gum-sage seed gum blends

In this study, different gum powders (guar gum (GG), sage seed gum (SSG) and guar-sage seed gums (GG-SSG) were irradiated at 0, 5, and 10 kGy. FTIR analysis revealed some small changes in transmittance of gum samples with gamma irradiation. Flow behavior of the gum solutions (1% w/w) revealed shear thinning behavior with a n value lower than 1. The viscosity of gum solutions (1% w/w) decreased significantly with increase of irradiation dose from 0 to 10 kGy which was in consistent with the effect of irradiation dose on the consistency index (k). Herschel–Bulkley and Sisko models with higher values of determination coefficient (R2) were found to be the best models to explain the steady shear properties of non-irradiated and irradiated gum solutions. Irradiation doses (5 and 10 kGy) changed the flow behavior of guar gum solution (1%) from non-Newtonian shear-thinning to Newtonian behavior. G’ and G’’ in GG, SSG, and GG-SSG were observed to decrease in strain sweep test as the irradiation dose was increased from 0 to 10 kGy. In SSG and GG-SSG, G’ was greater than G’’ with no cross over in all the applied frequency range, while guar gum exhibited a solid-like behavior after cross over point. Frequency sweep rheological parameters of gum solutions (1%) including G’, G’’, and (η*) also affected by gamma irradiation and decreased significantly with increasing irradiation dose from 0 to 10 kGy (p<0.05).

Darcy flow of unsteady Casson fluid subject to thermal radiation and Lorentz force on wavy walls: Case of slip flow for small and large values of plastic dynamic viscosity

This article describes the evolution of the velocity slip and heat transfer effects on the magnetohydrodynamic oscillatory flow of Casson fluid in a wavy channel immersed in a porous medium in the presence of thermal radiation. The Casson fluid model is used to describe non-Newtonian fluid behaviour. Analytical solutions to the dimensionless governing equations are compared to the numerical outcomes produced by MATLAB's built-in numerical solver, bvp4c. The effect of various physical parameters on momentum and energy profiles of the Casson fluid is analysed. This report also examines a parametric analysis illustrating the impact of the Nusselt number and Casson parameter. Increased velocity fields result from higher values of the thermal radiation and Casson-Viscous parameters. When thermal radiation increases, the impact of thermal diffusivity and temperature increases, and the Prandtl number suppresses the temperature distribution. Furthermore, one slip parameter decreases the velocity field while the other increases fluid velocity. For various values of viscous and radiation parameter, the variations for skin friction coefficient and Nusselt number occur periodically because of the asymmetric wavy motion. A comparative study is carried out to characterise Newtonian and non-Newtonian fluid behavior by analyzing the velocity for β – small (non-Newtonian fluid) and β – large (Newtonian fluid) values of plastic dynamic viscosity using linear slope regression analysis.

Characterization of Thermophysical and Electrical Properties of SiC and BN Nanofluids

Experimental data associated with the thermophysical properties (TPPs) of various nanofluids (NFs) are essential for their diverse applications in energy storage and conversion, as well as thermal management. This study experimentally investigated important TPPs such as thermal conductivity (TC), thermal diffusivity, density and viscosity, as well as the electrical conductivity of two new types of NFs, namely silica (SiC) and boron nitride (BN) nanofluids. The NFs are prepared at five low concentrations of nanoparticles from 0.01 to 0.05 vol.% dispersed into a mixture of ethylene glycol (EG) and distilled water (DW). The TPPs are measured, and their enhancements are evaluated in comparison with their base fluids. The results show a good increase in TC and thermal diffusivity for both types of nanofluids with increasing concentrations until reaching the maximum enhancement of about 4.4% for the SiC nanofluid and about 7.0% for the BN nanofluid at the same concentration (0.05 vol.%). On other hand, a Newtonian rheological behaviour is observed, and viscosity and density are also found to increase for both types of NFs, where the maximum increase in viscosity and density at 0.05 vol.% are found to be 5.2% and 0.3%, respectively. The electrical conductivity also increases by up to 3.2 times for SiC nanofluids and 2.8 times for BN nanofluids at the maximum concentration of these nanoparticles (0.05 vol.%) compared with the base fluid (EG/DW). The overall evaluation of the obtained results demonstrates the great potential of these nanofluids in heat transfer applications.

Production, optimization, and characterization of Ethiopian variant Prosopis juliflora based biodiesel

Considering the need for biodiesel production from non-edible oil sources and taking into account the fact that Prosopis Juliflora (JF) is identified as a highly invasive species in Ethiopia, this research focuses on biodiesel production from a possible and promising alternative feedstock. The objective of this study is to analyze Ethiopian variant Juliflora based biodiesel (JFB) production through transesterification, carry out optimization by exploring the effects of various process parameters and characterization of functional groups (with GC-MS,FT-IR and NMR) including rheological behavior, not yet been reported earlier. As per ASTM protocol testing, the methyl ester of Juliflora has been found to have the following main fuel properties: kinematic viscosity (mm2/s) 3.395, cetane number 52.9, acid number (mgkoh/g) 0.28, density (gm/ml) 0.880, calorific value (MJ/kg) 44.4, methyl ester content (%) 99.8, and flashpoint (°C) 128, copper strip corrosion value 1a,%FFA (free fatty acid) 0.14. When compared with those of diesel, the viscosity, density, and flash point of JFB are seen to be higher than those of diesel, although it has a similar calorific value but more importantly higher than most of the other biodiesels. Based on an assessment using response surface methodology, methanol concentration together with catalyst loading, temperature, and reaction time are determined to be the most important influencing process parameters. The best molar ratio for methanolysis was observed to be 6:1 with a catalyst concentration of 0.5 wt% at 55 °C for 60 min for biodiesel yield at 65%. The JFB maximum yield of 130 ml at 70 min and the minimum yield of 40 ml at 10 min demonstrate that as mixing time increases, JFB yield tend to increase up to a certain time limit. The maximum raw oil yield rom crushed seed with hexane solvent was observed to be 480 ml within 3 days from 2.5 kg of crushed seed. The Fourier transform infrared analysis (FT-IR) revealed the presence of all desired functional groups necessary for biodiesel on OH radicals at wave numbers of 3314.40 cm−1, Aliphatic methyl C–H at 2942.48 cm− 1 with a functional group (CH-3-,-CH2-), and methylene C–H at 2832.59 cm−1. The gas chromatography-mass spectrometer (GC–MS) study confirmed the higher ester content present in the JFB with a higher unsaturation level of 68.81%. The fatty acid, oleic acid has a lower saturation level of 4.5%, while palmitic acid has a lower threshold level of 2.08%. The Rheometer test showed that shear stress and viscosity reduced with increasing temperature within the range of biodiesel requirements, and the Newtonian behavior was confirmed. The JFB has a fairly high viscosity and shear rate at low temperatures. The 1H NMR (nuclear magnetic resonance) study established that JFB has a necessary ingredient; and aliphatic resonances occur in the chemical shift region of 1.5–3.0 ppm. Significant regions indicate protons bound to heteroaromatics, aldehydes, as shown by 13C NMR spectrum. The findings from the FT-IR, GC-MS, 1H NMR, and 13C NMR are in agreement thus validating the presence of numerous functional groups in JFB as such. Since JFB possesses the requisite biodiesel fuel attributes, Prosopis Juliflora need to be pursued as a promising biodiesel feedstock in Ethiopia for alleviating the burden of imported fuels while also addressing difficulties with emissions released by the combustion of fossil fuels.