Conjugate Natural Convection in a Porous Enclosure with Non-Uniform Heat Generation

Effects of a conductive wall on natural convection in a square porous enclosure having internal heating at a rate proportional to a power of temperature difference is studied numerically in this article. The horizontal heating is considered, where the vertical walls heated isothermally at different temperatures while the horizontal walls are kept adiabatic. The Darcy model is used in the mathematical formulation for the porous layer and finite difference method is applied to solve the dimensionless governing equations. The governing parameters considered are the Rayleigh number (0 ???Ra ???1000), the internal heating and the local exponent parameters (0 ????? ???5), (1 ????? ???3), the wall to porous thermal conductivity ratio (0.44 ???Kr ???9.9) and the ratio of wall thickness to its width (0.02 ???D ???0.5). The results are presented to show the effect of these parameters on the fluid flow and heat transfer characteristics. It is found a strong internal heating can generate significant maximum fluid temperature more than the conductive solid wall. Increasing value thermal conductivity ratio and/or decreasing the thickness of solid wall can increase the maximum fluid temperature. It is also found that at very low Rayleigh number, the heat transfer across the porous enclosure remain stable for any values of the thermal conductivity ratio.     

Thermally stratified flow of hybrid nanofluids with radiative heat transport and slip mechanism: multiple solutions

Research on flow and heat transfer of hybrid nanofluids has gained great significance due to their efficient heat transfer capabilities.In fact,hybrid nanofluids are a novel type of fluid designed to enhance heat transfer rate and have a wide range of engineering and industrial applications.Motivated by this evolution,a theoretical analysis is performed to explore the flow and heat transport characteristics of Cu/Al₂O₃ hybrid nanofluids driven by a stretching/shrinking geometry.Further,this work focuses on the physical impacts of thermal stratification as well as thermal radiation during hybrid nanofluid flow in the presence of a velocity slip mechanism.The mathematical modelling incorporates the basic conservation laws and Boussinesq approximations.This formulation gives a system of governing partial differential equations which are later reduced into ordinary differential equations via dimensionless variables.An efficient numerical solver,known as bvp4c in MATLAB,is utilized to acquire multiple(upper and lower)numerical solutions in the case of shrinking flow.The computed results are presented in the form of flow and temperature fields.The most significant findings acquired from the current study suggest that multiple solutions exist only in the case of a shrinking surface until a critical/turning point.Moreover,solutions are unavailable beyond this turning point,indicating flow separation.It is found that the fluid temperature has been impressively enhanced by a higher nanoparticle volume fraction for both solutions.On the other hand,the outcomes disclose that the wall shear stress is reduced with higher magnetic field in the case of the second solution.The simulation outcomes are in excellent agreement with earlier research,with a relative error of less than 1%.     

Synthesis,optimization, characterization,and potential agricultural application of polymer hydrogel composites based on cotton microfiber

The optimum content of cotton microfiber, initiator, cross-linker, and sodium hydroxide were determined using the central composite design method. Polymer hydrogels (PHGs) were characterized using Fourier-transform infrared (FT-IR), scanning electron microscopy, and thermal gravimetric analysis. A comparison between plain PHG and the polymer hydrogel composite (PHGC) in terms of biodegradation, swelling rate, and re-swelling capacity was carried out. The effect of PHGC on the sandy soil holding capacity, urea leaching loss rate (ULLR), and okra plant growth were evaluated. The highest water absorption capacity was obtained at 1.30 mass %, 0.15 mass %, 13.00 mass %, and 13.50 mass % of the initiator, cross-linker, sodium hydroxide, and cotton microfiber, respectively. Cotton microfiber has a prominent effect on the swelling rate, re-swelling capacity, and biodegradability of PHG. Okra plant growth and ULLR were positively affected by PHGC and the best leaching loss rate of 33.3 mass % was observed for the lowest urea loaded sample.     

The optical properties of trivalent rare earth ions (Er3+) doped borotellurite glass

Erbium doped borotellurite glass has been fabricated by using conventional melting method. The density and molar volume have been calculated and analyzed while their optical properties were studied by measuring the optical absorption and luminescence spectra at room temperature. From the XRD results, since the patterns do not exhibit any diffraction line thus it confirms their amorphous nature. It is found that the density of the glass samples increased and the molar volume decreased with respect to Er ions content. Meanwhile, the upconversion emissions centered at 487, 523, 558, 642, 695 and 782 nm have been observed under the 650 nm excitation in the ⁴ F _9/2 level. Some other results will be analysed and discussed in details.     

Interacting Entropy-Corrected New Agegraphic K-essence, Tachyon and Dilaton Scalar Field Models in?Non-flat Universe

We consider the new agegraphic dark energy model with the help of the quantum corrections to the entropy-area relation in the setup of loop quantum gravity. Employing this new form of dark energy so called entropy-corrected new agegraphic dark energy (ECNADE), we investigate the model of interacting dark energy and derive its equation of state (EoS). We study the correspondence between the K-essence, tachyon and dilaton scalar fields with the interacting (ECNADE)in the non-flat FRW universe. Moreover, we reconstruct the corresponding scalar potentials which describe the dynamics of the scalar field.     

Approximate analytical solution for MHD stagnation-point flow in porous media

In this paper, the steady two-dimensional laminar forced MHD Hiemenz flow against a flat plate with variable wall temperature in a porous medium which was solved numerically using the implicit finite-difference of Keller-box method [Yih KA. The effect of uniform suction/blowing on heat transfer of magnetohydrodynamic Hiemenz flow through porous media. Acta Mech 1998;130:147–58] is revisited. A simple analytic approach of the Adomian decomposition method (ADM) is employed to obtain an approximate analytical solution of the problem. The skin friction coefficient and the rate of heat transfer given by the ADM are in good agreement with the numerical solutions of the Keller-box method.