Von Karman rotating nanofluid flow with modified Fourier law and variable characteristics in liquid and gas scenarios

This investigation aims to explore the temperature-dependent variable characteristics of viscosity, and thermal conductivity with modified Fourier law in a nanofluid flow over a rotating disk. The uniqueness of the envisioned mathematical model is improved with the additional impacts of the chemical reaction, non-uniform source/sink, and convective boundaries. The salient feature of the existing problem is to discuss the whole scenario with liquid and gas thermo-physical characteristics. The graphical depiction is attained for arising pertinent parameter is attained by using Bvp4c a built-in MATLAB function. The visco-thermal conduct of the gases and liquids is examined by observing the mean flow and thermal distributions for the convectively heated disk. It is followed that liquid behaves more viscous with an increase in temperature in of the gas, but an opposing tendency can be seen for the liquid. The attained results are verified when compared with a published result.

Impact of convective boundary mixing on the TP-AGB

ABSTRACT The treatment of convective boundaries remains an important source of uncertainty within stellar evolution, with drastic implications for the thermally pulsing stars on the asymptotic giant branch (AGB). Various sources are taken as motivation for the incorporation of convective boundary mixing (CBM) during this phase, from s-process nucleosynthesis to hydrodynamical models. In spite of the considerable evidence in favour of the existence of CBM on the pre-AGB evolution, this mixing is not universally included in models of TP-AGB stars. The aim of this investigation is to ascertain the extent of CBM, which is compatible with observations when considering full evolutionary models. Additionally, we investigate a theoretical argument that has been made that momentum-driven overshooting at the base of the pulse-driven convection zone should be negligible. We show that, while the argument holds, it would similarly limit mixing from the base of the convective envelope. On the other hand, estimations based on the picture of turbulent entrainment suggest that mixing is possible at both convective boundaries. We demonstrate that additional mixing at convective boundaries during core-burning phases prior to the thermally pulsing AGB has an impact on the later evolution, changing the mass range at which the third dredge-up and hot-bottom burning occur, and thus also the final surface composition. In addition, an effort has been made to constrain the efficiency of CBM at the different convective boundaries, using observational constraints. Our study suggests a strong tension between different constraints that makes it impossible to reproduce all observables simultaneously within the framework of an exponentially decaying overshooting. This result calls for a reassessment of both the models of CBM and the observational constraints.

Influence of cross diffusions on natural convection flow through annulus region with Navier slip and convective boundaries

In this manuscript we present the influence of cross diffusions on incompressible natural convection laminar flow between concentric cylinders with slip and convective boundaries. In addition, the first order chemical reaction is also considered. The governing equations with boundary conditions are transformed to a non - dimensional form with suitable transformations. Homotopy Analysis Method (HAM) is used to solve the system of equations. The influence of the various parameters like Slip, Dufour, Soret, chemical reaction parameters and the Biot number on velocity, temperature and concentration are investigated and presented through plots. It is found from this study that the influence of slip parameter and Biot number, the velocity and temperature profiles increase, while there is a reverse tendency under the effect of chemical reaction parameter.

Keller-Box Analysis of Buongiorno Model with Brownian and Thermophoretic Diffusion for Casson Nanofluid over an Inclined Surface

The key objective of the study under concern is to probe the impacts of Brownian motion and thermophoresis diffusion on Casson nanofluid boundary layer flow over a nonlinear inclined stretching sheet, with the effect of convective boundaries and thermal radiations. Nonlinear ordinary differential equations are obtained from governing nonlinear partial differential equations by using compatible similarity transformations. The quantities associated with engineering aspects, such as skin friction, Sherwood number, and heat exchange along with various impacts of material factors on the momentum, temperature, and concentration, are elucidated and clarified with diagrams. The numerical solution of the present study is obtained via the Keller-box technique and in limiting sense are reduced to the published results for accuracy purpose.

Construction of Roller Compacted Concrete Dams in Hot Arid Regions

Roller compacted concrete (RCC) dams are attractive to many water and energy corporations around the world due to their ease in construction and low construction cost. The hydration of cement and the climatic changes on the convective boundaries are the two main heat sources for the temperature rise in the roller compacted concrete dams. Thus, changing the RCC placement schedule according to climate conditions might eliminate the problem of thermal cracks. In this research, the RCC dam method was applied in an arid region; the Bisha state in Saudi Arabia was chosen as a case study. We found that RCC dam technology can be applied safely with an alternative solution, like selecting a suitable placement schedule and reducing the placing temperature of facing at upstream and downstream sides to overcome the risk of thermal cracks.

Significant uncertainties from calibrating overshooting with eclipsing binary systems

The precise measurement of the masses and radii of stars in eclipsing binary systems provides a window into uncertain processes in stellar evolution, especially mixing at convective boundaries. Recently, these data have been used to calibrate models of convective overshooting in the cores of main sequence stars. In this study we have used a small representative sample of eclipsing binary stars with 1.25 ≤ M/M⊙ < 4.2 to test how precisely this method can constrain the overshooting and whether the data support a universal stellar mass–overshooting relation. We do not recover the previously reported stellar mass dependence for the extent of overshooting and in each case we find there is a substantial amount of uncertainty, that is, the same binary pair can be matched by models with different amounts of overshooting. Models with a moderate overshooting parameter 0.013 ≤ fos ≤ 0.014 (using the scheme from Herwig et al. 1997, A&A, 324, L81) are consistent with all eight systems studied. Generally, a much larger range of f is suitable for individual systems. In the case of main sequence and early post-main sequence stars, large changes in the amount of overshooting have little effect on the radius and effective temperature, and therefore the method is of extremely limited utility.