Study of flow of Buongiorno nanofluid in a conical gap between a cone and a disk

The cone–disk apparatus consists of a cone that touches the disk at its apex and is used in medical evices, viscosimeters, conical diffusers, etc. Theoretically, a three-dimensional flow of a nanofluid in a conical gap of a cone–disk apparatus is studied for four different physical configurations. Buongiorno nanofluid model, consisting of thermophoresis and Brownian diffusion mechanisms, is used to describe the convective heat transport of the nanofluid. The continuity equation, the Navier–Stokes momentum equation, the heat equation, and the conservation of nanoparticle volume fraction equation constitute the governing system for the flow of nanofluids. The Lie group approach is used to obtain self-similar equations. Solutions are computed for an appropriate rotational Reynolds number and four different gap angles to examine flow, mass, and heat transport features. The skin friction coefficients and torque are computed and analyzed. Multivariate nonlinear regression analysis is also performed. A co-rotating disk and cone configuration has been shown to produce less torque due to the increased centrifugal force. Of the four cone–disk apparatus configurations, the maximum heat/mass transport occurs for a rotating disk with a static cone for all selected gap angles, and the least drag in the radial direction is attained for a rotating cone with a static disk. In addition, there is a minimal drag along the tangential direction for the counter-rotating disk and cone configuration. Brownian diffusion and thermophoresis of the nanoparticles lead to a higher fluid temperature and, thus, lower Nusselt numbers are obtained

Study of Multilayer Flow of a Bi-Viscous Bingham Fluid Sandwiched Between Hybrid Nanofluid in a Vertical Slab with Nonlinear Boussinesq Approximation

Bi-Viscosity Bingham plastic fluids are used to understand the rheological characteristics of pigment-oil suspensions, polymeric gels, emulsions, heavy oil, etc. High-temperature applications in many industrial and engineering problems, linear density-temperature variation is inadequate to describe convective heat transport. Therefore, the characteristics of the nonlinear convective flow of a Bi-Viscosity Bingham Fluid (BVBF) through three layers in a vertical slab are studied. The two outer layers of the oil-based hybrid nanofluid and the intermediate layer of BVBF are considered. The thermal buoyancy force is governed by the nonlinear Boussinesq approximation. Continuity of heat flux, velocity, shear stress, and temperature are imposed on the interfaces. The governing equations are derived from the Navier-Stokes equation, conservation of energy, and conservation of mass for three layers. The nonlinear multipoint (four-point) boundary value problem (NMBVP) is solved using the differential transform method (DTM). Converging DTM solutions are obtained, and they are validated. The entropy equation and Bejan number were also derived and analyzed. It is established that the nonlinear density-temperature variation leads to a significant improvement in the magnitude of the velocity and temperature profiles due to the increased buoyancy force and as a result, the drag force on the walls is reduced. The drag force on the slab gets reduced by decreasing the volume of nanoparticles. Furthermore, nonlinear convection and mixed convection give rise to an advanced rate of heat transport on the walls and thereby to an enhanced heat transport situation

PHARMACOGNOSTICAL EVALUATION AND ANTICONVULSANT ACTIVITY OF STEM OF ABUTILON INDICUM LINN SWEET

Objective: To investigate the pharmacognostical characteristics and in vivo anticonvulsant activity of chloroform, ethanol (90%) and aqueous extracts of Abutilon indicum Linn sweet stem.Methods: The Abutilon indicum Linn sweet stem were successively extracted using chloroform, ethanol and aqueous solvent (water). The extracts were screened for phytochemicals using HPTLC and GC-MS techniques. The extracts were also screened for acute toxicity and anticonvulsant activity, against MES and PTZ induced convulsions, using Wistar albino rats.Results: The phytochemical screening study reveals the presence of more chemical constituents in chloroform extract followed by ethanol and aqueous extract. We found no significant changes in average body weight of animals, up to tested oral dose of 3000 mg/kg, during acute toxicity study. The in vivo study reveals the anticonvulsant activity of chloroform and ethanol extract against MES and PTZ induced convulsions. The chloroform extract is found to be more potent, similar to Phenytoin, in controlling both MES and PTZ induced convulsions than ethanol and aqueous extracts.Conclusion: The results obtained suggest that the chloroform extract of Abutilon indicum stem has remarkable anticonvulsant activity. Also, our study indicates the potential application of Abutilon indicum stems in the treatment of convulsive disorders as a need of modern health science. However, the further studies are needed to screen the active constituent having an anticonvulsant effect.Â

Hall Effect on Two-Phase Laminar Boundary Layer flow of Dusty Liquid due to Stretching of an Elastic Flat Sheet

The present investigation is concerned with the effect of Hall current on boundary layer two-phase flow of an electrically conducting dusty fluid over a permeable stretching sheet in the presence of a strong magnetic field. The boundary layer approximation is employed for mathematical modeling. The governing partial differential equations are reduced to a set of ordinary differential equations using suitable similarity transformations. Subsequent equations are solved numerically by using Runge-Kutta-Fehlberg fourth-fifth order method. A comprehensive parametric study is conducted to reveal the tendency of solutions. It is found that the mass concentration of dust particles can be used as a control parameter to control the friction factor at the sheet. The influence of suction and injection are opposite on the momentum boundary layer growth

Unsteady squeezing flow of a magnetized nano-lubricant between parallel disks with Robin boundary conditions

The aim of the present work is to examine the impact of magnetized nanoparticles (NPs) in enhancement of heat transport in a tribological system subjected to convective type heating (Robin) boundary conditions. The regime examined comprises the squeezing transition of a magnetic (smart) Newtonian nanolubricant between two analogous disks under an axial magnetism. The lower disk is permeable whereas the upper disk is solid. The mechanisms of haphazard motion of NPs and thermophoresis are simulated. The non-dimensional problem is solved numerically using a finite difference method in the MATLAB bvp4c solver based on Lobotto quadrature, to scrutinize the significance of thermophoresis parameter, squeezing number, Hartmann number, Prandtl number and Brownian motion parameter on velocity, temperature, nanoparticle concentration, Nusselt number, factor of friction and Sherwood number distributions. The obtained results for the friction factor are validated against previously published results. It is found that friction factor at the disk increases with intensity in applied magnetic field. The haphazard (Brownian) motion of nanoparticles causes an enhancement in thermal field. Suction and injection are found to induce different effects on transport characteristics depending on the specification of equal or unequal Biot numbers at the disks. The main quantitative outcome is that, unequal Biot numbers produce significant cooling of the regime for both cases of disk suction or injection, indicating that Robin boundary conditions yield substantial deviation from conventional thermal boundary conditions. Higher thermophoretic parameter also elevates temperatures in the regime. The nanoparticles concentration at the disk is boosted with higher values of Brownian motion parameter. The response of temperature is similar in both suction and injection cases; however, this tendency is quite opposite for nanoparticle concentrations. In the core zone, the resistive magnetic body force dominates and this manifests in a significant reduction in velocity i.e. damping. The heat buildup in squeeze films (which can lead to corrosion and degradation of surfaces) can be successfully removed with magnetic nanoparticles leading to prolonged serviceability of lubrication systems and the need for less maintenance

Influence of variable viscosity and thermal conductivity, hydrodynamic and thermal slips on magnetohydrodynamic micropolar flow: a numerical study

Thermophysical and wall slip effects arise in many areas of nuclear technology. Motivated by such applications, in this article the collective influence ofvariable viscosity, thermal conductivity, velocity and thermal slipseffects on a steady two-dimensional magnetohydrodynamic microplar fluid over a stretching sheet are analyzednumerically. The governing nonlinear partial differential equations have been converted into a system of non-linear ordinary differential equations using suitable coordinate transformations. The numerical solutions of the problem are expressed in the form of non-dimensional velocityand temperature profiles and discussed from their graphical representations. Nachtsheim-Swigert shooting iteration technique together withthesixth order Runge-Kutta integration scheme has been applied for the numerical solution.A comparison with the existing results has been done and an excellent agreement is found.Further validation with adomian decomposition method is included for the general model. Interesting features in the heat and momentum characteristics are explored. It is found that greater thermal slip and thermal conductivity elevate thermal boundary layer thickness. Increasing Prandtl number enhances Nusselt number at the wall but reduces wall couple stress (micro-rotation gradient). Temperatures are enhanced with both magnetic field and viscosity parameter. Increasing momentum (hydrodynamic) slip is found to accelerate the flow and elevate temperatures

Heat Transfer of Nanomaterial over an Infinite Disk with Marangoni Convection: A Modified Fourier’s Heat Flux Model for Solar Thermal System Applications

The demand for energy due to the population boom, together with the harmful consequences of fossil fuels, makes it essential to explore renewable thermal energy. Solar Thermal Systems (STS’s) are important alternatives to conventional fossil fuels, owing to their ability to convert solar thermal energy into heat and electricity. However, improving the efficiency of solar thermal systems is the biggest challenge for researchers. Nanomaterial is an effective technique for improving the efficiency of STS’s by using nanomaterials as working fluids. Therefore, the present theoretical study aims to explore the thermal energy characteristics of the flow of nanomaterials generated by the surface gradient (Marangoni convection) on a disk surface subjected to two different thermal energy modulations. Instead of the conventional Fourier heat flux law to examine heat transfer characteristics, the Cattaneo–Christov heat flux (Fourier’s heat flux model) law is accounted for. The inhomogeneous nanomaterial model is used in mathematical modeling. The exponential form of thermal energy modulations is incorporated. The finite-difference technique along with Richardson extrapolation is used to treat the governing problem. The effects of the key parameters on flow distributions were analyzed in detail. Numerical calculations were performed to obtain correlations giving the reduced Nusselt number and the reduced Sherwood number in terms of relevant key parameters. The heat transfer rate of solar collectors increases due to the Marangoni convection. The thermophoresis phenomenon and chaotic movement of nanoparticles in a working fluid of solar collectors enhance the temperature distribution of the system. Furthermore, the thermal field is enhanced due to the thermal energy modulations. The results find applications in solar thermal exchanger manufacturing processes