A. A. Siddiqui

Bio: A. A. Siddiqui is an academic researcher from Bahauddin Zakariya University. The author has contributed to research in topics: Tensor & Nusselt number. The author has an hindex of 2, co-authored 2 publications receiving 20 citations.

TiO2-water nanofluid in a porous channel under the effects of an inclined magnetic field and variable thermal conductivity

Abstract: The TiO2-water based nanofluid flow in a channel bounded by two porous plates under an oblique magnetic field and variable thermal conductivity is formulated as a boundary-value problem (BVP). The BVP is analytically solved with the homotopy analysis method (HAM). The result shows that the concentration of the nanoparticles is independent of the volume fraction of TiO2 nanoparticles, the magnetic field intensity, and the angle. It is inversely proportional to the mass diffusivity. The fluid speed decreases whereas the temperature increases when the volume fraction of the TiO2 nanoparticles increases. This confirms the fact that the occurrence of the TiO2 nanoparticles results in the increase in the thermal transfer rate. The fluid speed decreases and the temperature increases for both the pure water and the nanofluid when the magnetic field intensity and angle increase. The maximum velocity does not exist at the middle of the symmetric channel, which is in contrast to the plane-Poiseuille flow, but it deviates a little bit towards the lower plate, which absorbs the fluid with a very low suction velocity. If this suction velocity is increased, the temperature in the vicinity of the lower plate will be increased. An explicit expression for the friction factor-Reynolds number is then developed. It is shown that the Hartmann number of the nanofluid is smaller than that of pure water, while the Nusselt number of the nanofluid is larger than that of pure water. However, both the parameters increase if the magnetic field intensity increases.

Debye-Hückel solution for steady electro-osmotic flow of micropolar fluid in cylindrical microcapillary

Abstract: Analytic expressions for speed, flux, microrotation, stress, and couple stress in a micropolar fluid exhibiting a steady, symmetric, and one-dimensional electro-osmotic flow in a uniform cylindrical microcapillary were derived under the constraint of the Debye-Huckel approximation, which is applicable when the cross-sectional radius of the microcapillary exceeds the Debye length, provided that the zeta potential is sufficiently small in magnitude. Since the aciculate particles in a micropolar fluid can rotate without translation, micropolarity affects the fluid speed, fluid flux, and one of the two non-zero components of the stress tensor. The axial speed in a micropolar fluid intensifies when the radius increases. The stress tensor is confined to the region near the wall of the microcapillary, while the couple stress tensor is uniform across the cross-section.

Recent advances on the fundamental physical phenomena behind stability, dynamic motion, thermophysical properties, heat transport, applications, and challenges of nanofluids

Abstract: For more than two decades, nanotechnology’s rapid development have created quite a lot of prospects for scientists and engineers. Nanofluid is one of the remarkable consequences of such progression. Nanofluids are engineered by suspending nanoparticles with average sizes below 100 nm in traditional heat transfer fluids such as water, oil, and ethylene glycol. Nanofluids are considered to offer substantial advantages over conventional heat transfer fluids. When dispersed uniformly and suspended stably in base fluids, a minimal amount of nanoparticles can significantly improves the thermal properties of host fluids. Present work attempts to address this challenge considering state-of-the-art advances in understanding, characterizing, and mitigating issues about nanofluids’ stability. Stable and highly conductive nanofluids are produced generally by, one step and two step production methods. Both approaches of creating nanoparticle suspensions suffer from nanoparticles’ agglomeration, which is a critical issue in all technologies involving nanopowder. Therefore, numerous numerical models and the principal physical phenomena affecting the stability (fundamental physical principles that govern the interparticle interactions, clustering and deposition kinetics, and colloidal stability theories) have been analyzed. Concerning the particles’ dynamic motion, the importance of different forces in nanofluid flows that exist in particulate flows such as drag, lift (Magnus and Saffman), Brownian, thermophoretic, van der Waals, and electrostatic double-layer forces is considered. Moreover, an overview of nanofluids’ thermophysical properties, physical models, and heat transfer models is​ included in this work. To understand the unexpected discoveries and overcome classical models’ limitations, several investigators have proposed new physical concepts and mechanisms and developed new models to enhance the transport properties. In the present work, the wide-ranging structural evolution of nanofluids has been discoursed thoroughly by sketching out a gargantuan depiction of the diminutive biosphere of nanofluids through a brief review of some foremost chronological milestone such as the concepts of nanofluids, the preparations and performances of nanofluids, conductivity, viscosity, and density correlations of nanofluids, and potential applications and benefits of nanofluids. Also, different kinds of modeling and essential slip mechanisms of constructing heat transfer modeling of nanofluids have been discussed comprehensively in this study. Potential novel 2D materials as nanofluids have also been discussed and reported. A brief overview of the potential applications utilizing nanofluids has been reviewed, and future research gaps have been reported. Furthermore, recommendations were drawn regarding current knowledge gaps and future research directions to overcome the physical phenomenon, stability, thermophysical properties, overview of some applications, and the limitations hindering these nanofluids’ deployment. The review is presumed to be valuable for scholars and researchers working in the area of numerical simulations of nanofluids and experimental aspects and helps them understand the fundamental physical phenomena taking place during these numerical simulations and experiments and explores the potential of nanofluids both in academia and industry.

Recent advances on the fundamental physical phenomena behind stability, dynamic motion, thermophysical properties, heat transport, applications, and challenges of nanofluids

Abstract: In the past decade, nanotechnology’s rapid developments have created quite a lot of prospects for researchers and engineers to check up on. And nanofluids are important consequences of this progression. Nanofluids are created by suspending nanoparticles with average diameters below 100 nm in conventional heat transfer carriers such as water, oil, ethylene glycol, etc. Nanofluids are considered to offer substantial advantages over usual heat transfer fluids. When dispersed in a uniform way and suspended stably in the base fluids, a minimal amount of nanoparticles can significantly improve the thermal properties of host fluids. Present work attempts to address this challenge considering state-of-the-art advances in understanding, discussing, and mitigating problems about nanofluids’ stability. Stable and highly conductive nanofluids are produced by generally, one-step and two-step production methods. Both approaches suffer from problems with the nanoparticles’ agglomeration to be an important one. Thus, numerous numerical models and the principal physical phenomena affecting the stability (fundamental physical principles that govern the interparticle interactions, clustering and deposition kinetics, and colloidal stability theories) have been analyzed. Concerning the particles’ dynamic motion, the significance of different forces in nanofluid in particulate flows such as drag, lift (Magnus and Saffman), Brownian, thermophoretic, Van der Waals, electrostatic double-layer forces are investigated. Furthermore, an overview of nanofluids’ thermophysical properties, physical models, and heat transfer models is​ included in this work. In order to realize the unexpected discoveries and overcome classical models’ limitations, several researchers have suggested new physical concepts and mechanisms, and they have created new models to enhance the transport properties. This review study includes numerous aspects of the nanofluids’ science by investigating applications, thermal properties and giving critical chronological milestones about the nanofluids’ evolution. Also, the present review discusses in detail various modeling and slip mechanisms for the heat transfer of nanofluids. Potential novel 2D materials as nanofluids have also been discussed and reported. A brief overview of the potential applications utilizing nanofluids has been reviewed, and future research gaps have been reported. Furthermore, recommendations were extracted regarding current scientific gaps and future research directions to cover the physical phenomenon, stability, thermophysical properties, overview of some applications, and the limitations hindering these nanofluids’ deployment. The review is presumed to be valuable for scholars and researchers working in the area of numerical simulations of nanofluids and experimental aspects and help them understand the fundamental physical phenomena taking place during these numerical simulations and experiments and explore the potential of nanofluids both in academia and industry.

Natural convection in the ferrofluid enclosed in a porous and permeable cavity

Abstract: The thermal transfer in the water-based ferrofluid enclosed porous cavity attached with a novel permeable (suction/injection) chamber is investigated within this research. The mathematical analysis of the problem is fulfilled with the modified Rosensweig-model (mRm) accounting for the Darcy porous medium in cooperation with the energy equation. The relevant governing equations are numerically treated via the successive-over-relaxation method (SOR) based on a special finite difference scheme. The pertinent effects of physical parameters on the convection and heat transfer of the ferrofluid inside the cavity are examined in detail. It is determined that the Nusselt number enhances at the left wall but it is reduced at the right wall if one increases either (i) the concentration of the ferroparticles or (ii) the Lorentz force. But the effect of Kelvin force is different from the effect of the Lorentz force on the Nusselt number in the sense that; the Nusselt number decays at the left wall but it intensifies at the right wall if we increase the Lorentz force or its representative the Hartmann number. In addition, the Nusselt number at the left wall of the cavity rises about 1.4 times if the Hartmann number increases from 0 to 50. The problem setup in the current work may be useful in the applications regarding bio-medical, pharmaceutical and engineering industries. The generated results from the present work quantitatively as well as qualitatively match with the existing literature.

Significance of variability in magnetic field strength and heat source on the radiative-convective motion of sodium alginate-based nanofluid within a Darcy-Brinkman porous structure bounded vertically by an irregular slender surface

Abstract: The dynamical behavior and thermal transportation feature of an enhanced MHD convective Casson bi-phasic flows of sodium alginate-based nanofluids are examined numerically in a Darcy-Brinkman medium bounded by a vertical elongating slender concave-shaped surface. The mathematical framework of the present flow model is developed properly by adopting the single-phase approach, whose solid phase is selected to be metallic or metallic oxide nanoparticles. Besides, the influence of thermal radiation is taken into consideration in the presence of an internal variable heat generation. A set of feasible similarity transformations are applied for the conversion of the governing PDEs into a nonlinear differential structure of coupled ODEs. An advanced differential quadrature algorithm is employed herein to acquire accurate numerical solutions for momentum and energy equations. For validating the obtained numerical findings, extensive comparison tests are carried out in this sense. The results of the current exploration show that the wall heat transfer rate and the frictional effect are strengthened with the loading of nanoparticles and weakened with the mounting values of the heat source parameters. However, the magnetic parameter exhibits a reverse trend concerning those engineering quantities. Statistically, the slope linear regression method (SLRM) proves that the aurum-sodium alginate nanofluid presents the higher frictional factor, whereas the copper oxide-sodium alginate is the more thermal performant nanofluid.

Electroosmotic flow of biorheological micropolar fluids through microfluidic channels

Abstract: An analysis is presented in this work to assess the influence of micropolar nature of fluids in fully developed flow induced by electrokinetically driven peristaltic pumping through a parallel plate microchannel. The walls of the channel are assumed as sinusoidal wavy to analyze the peristaltic flow nature. We consider that the wavelength of the wall motion is much larger as compared to the channel width to validate the lubrication theory. To simplify the Poisson Boltzmann equation, we also use the Debye-Huckel linearization (i.e. wall zeta potential ≤ 25mV). We consider governing equation for micropolar fluid in absence of body force and couple effects however external electric field is employed. The solutions for axial velocity, spin velocity, flow rate, pressure rise and stream functions subjected to given physical boundary conditions are computed. The effects of pertinent parameters like Debye length and Helmholtz-Smoluchowski velocity which characterize the EDL phenomenon and external electric field, coupling number and micropolar parameter which characterize the micropolar fluid behavior, on peristaltic pumping are discussed through the illustrations. The results show that peristaltic pumping may alter by applying external electric fields. This model can be used to design and engineer the peristalsis-lab-on-chip and micro peristaltic syringe pumps for biomedical applications.