Characterization of magnetized CNT-based hybrid nanofluid subjected to convective phenomenon

Hybrid nanofluid gains attention of scientists due to its dynamic properties in various fields, and thus, hybrid nanofluids can be taken as an innovative form of nanofluids. Even though analysts acquire tremendous results in the field of hybrid nanofluids but yet no study has been carried out to predict magnetohydrodynamic effects in such fluid models. In this present analysis, influence of MHD has been investigated for the micro hybrid nanofluid over a stretched surface under convective conditions. Combine boundary layer equations for the flow have been altered into a suitable form via boundary layer approximations. Further, complete nonlinear system of equations has been numerically solved via BVP-4C method. Interesting results have been demonstrated for an exponentially stretched surface and expressed in the form of shear stress and rate of heat transfer. Results have also been visualized in the form of streamlines and isotherms. This study reveals after observing the numeric values of skin friction and Nusselt number that micropolar hybrid nanofluid models have greater heat transfer rate as compared to nanofluids.

Magneto-Convective Analyses of the PbLi Flow for the EU-WCLL Fusion Breeding Blanket

The Water Cooled Lithium Lead (WCLL) breeding blanket is one of the driver blanket concepts under development for the European Demonstration Reactor (DEMO). The majority of the blanket volume is occupied by flowing PbLi at eutectic composition. This liquid metal flow is subdued to high fluxes of particles coming from the plasma which are translated into a high non-homogeneous heat volumetric source inside the fluid. The heat is removed from the PbLi thanks to several water tubes immersed in the metal. The dynamics of the PbLi is heavily affected by the heat source and by the position of the tubes. Moreover, the conducting fluid is electrically coupled with the intense magnetic field used for the plasma confinement. As a result, the PbLi flow is strongly affected by the Magnetohydrodynamics (MHD) forces. In the WCLL, the MHD and convective interactions are expected to be comparable. Therefore, the PbLi dynamics and consequently the heat transfer between the liquid metal and the water coolant will be ruled by the magneto-convective phenomenon. This work presents 3D computational analyses of the PbLi flow in the frontal region of the WCLL design. The simulations include the combined effect of MHD forces caused by the magnetic field and the buoyancy interaction created by the temperature distribution. The latter is determined by the PbLi dynamics, the volumetric heat source and the position of the water tubes. Simulations have allowed computing the heat transfer between the PbLi and the water tubes. Nusselt and Grashof numbers have been obtained in the different regions of the system.

Physical and synoptic predictors and their optimal values leading to the formation of heavy rainfall

The physical and synoptic predictors are presented, which allow refining the automated forecasts of heavy precipitation implemented in the Hydrometeorological Center of Russia on the recommendation of the Roshydromet Central Methodological Forecasting Commission, as well as hydrodynamic forecasts of precipitation and forecasts of weather forecasters. The physical substantiation of the considered predictors is given. Their optimal values for the formation of heavy precipitation are determined. The parameters of convection and the intensity of the convective phenomenon diagnosed on the basis of radar data further expand the possibilities of refining forecasts of heavy and very heavy precipitation and, if necessary, allow issuing a storm warning with a sufficient lead time or refining a storm warning. Keywords: heavy precipitation, physical and synoptic predictors, diagnosed convection parameters, DMRL-C data

Numerical Simulation of the Jovian Wind Band as a Convective Phenomenon

Using a three-dimensional numerical spectral model, we simulate the outermost layer of Jupiter’s convective envelope (two depth cases: 1-23 bars, 1-115 bars). The physical parameters (e.g. internal energy flux, rotation rate) are chosen to be close to those expected, but solar heating as well as dynamical influences from deeper layers are ignored. The model generates a wind field pattern remarkably similar to that observed. There is a narrow, super-rotating jet at the equator, and two prominent humps in temperature also develop in the subtropics. The strength of the jet streams does not change much over depth. The maximum wind speed occasionally reach 100 m/s, but the mean amplitude of the equatorial jet is about a factor of 2-3 lower than the nominal value. The latitudes of the secondary pro-grade jets are higher than those observed, but they are dependent on the depth of the model. Though the quantitative agreement is not quite satisfactory (as might have been caused by neglected physical effects like solar radiation), this model demonstrates, in principle, the feasibility of generating a Jovian type wind pattern through the interaction of fast rotation and convection in a thin shell.

Free Convection in Air-Filled Cavity With a Localized Heater From Below and Cooling Lateral Walls

The paper investigates the development of natural convection in air-filled square enclosure with a heat source flush mounted on the lower horizontal surface; the cavity is symmetrically cooled from the lateral walls. The experimental analysis has been carried out with the real time holographic interferometry that makes possible the investigation of the development of the convective phenomenon, and with the double exposure technique in order to obtain the temperature distribution inside the cavity at the steady-state. The experimental analysis allows the study of a limited range of Rayleigh numbers from about 1.63·104 to 2.8·105. On the contrary the numerical investigation makes possible to enlarge the analysis to a more wide range of Rayleigh numbers; thus the experimental analysis, has been integrated with the numerical results provided by the investigation with the commercial finite volume software Fluent 6.0. for Rayleigh number from 103 to 106. Different convective forms have been obtained depending on Ra, on the heat source length and on its position. The Nusselt number has been evaluated on the heater; graphs with relations between average Nu, Ra, the heat source length and its position are finally presented.

Comments on Solar Convection

This contribution discusses observational aspects of the evolution of individual structures of solar convection.It has been shown, that mesogranulation is a convective phenomenon that fits well into the gap between granulation and supergranulation. Apparently this observation justifies the view that the three members of the granulation family represent sections of a broad continuum of convective motions spanning the range of sizes from a yet unknown fraction of 1 Mm to about 50 Mm. Nevertheless, power spectra of velocity and brightness fluctuations exhibit three maxima, separated by intervals with significantly less power near 3 Mm and 7.5 Mm. Do these gaps give reasons for reconsidering the old idea, that each of the three characteristic scales has its own source layer at a certain depth in the convection zone?Power spectra of the granular energy distribution near the observational limit of spatial resolution suggest a continuous transfer of kinetic energy to smaller eddies by turbulent decay of the larger scale elements. Morphological studies of granular evolution and a comparison of the observed spectral line bisectors with theoretical predictions seem to disprove this idea. These observations imply either that the turbulent cascade, if it exists, is buried in the spatially unresolved part of the power distribution, or that radiative losses ultimately limit the life time of individual granules on all scales.

Depth Dependence of Physical Parameters Associated with Convection in the Solar Atmosphere

It has been often suggested that the solar granulation is essentially a turbulent convective phenomenon. It is then worthwhile to investigate steady state, finite-amplitude convection in the outer layers of the solar convection zone. On the basis that the convection zone is turbulent, we will define an eddy viscosity; and for the present we will consider only the first 300 km of the convection zone. This value is predicted by van der Borght using an asymptotic analysis of convection at high Rayleigh number—provided we assume the horizontal dimension of the cellular pattern to be ˜1000 km.