Search results for "Convection"

Measurement of Local Hot-Wall Heat Transfer in High-Rayleigh Number Free Convection Flow

1999

Influence of Rayleigh Number and End Wall Boundary Conditions on Free Convection Heat Transfer in a Rectangular Enclosure

2000

Determination of the electroactive area of graphite+polyethylene composite electrodes. Uncompensated resistance effects and convolution analysis of c…

1998

In this work, it is shown how the convolution analysis of chronoamperograms permits the observation of the uncompensated resistance and the natural convection effects on the electrochemical response of potassium ferrocyanide. The uncompensated resistance causes the current intensity to follow the Cottrell equation only after a certain critical time. The convolution of chronoamperograms worked out at different integration times shows a maximum when this time is long enough. The classical diffusion equations cannot explain this phenomenon themselves. The development of this maximum associated with the natural convection is discussed. If both these factors, the ohmic drop and the natural conve…

Constraining the Equation of State of Neutron Stars with Genral Relativity

2005

When a radio pulsar breakes down by virtue of magnetodipole emission, its gravitational mass decreases accordingly. If the pulsar in hosted in a binary system, this mass loss will increase the orbital period of the system. We show that this relativistic effect can be indeed observable if the NS is fast and magnetized enough and that, if observed, it will help to put tight constraints on the equation of state of ultradense matter.

A NEW SOLVER FOR NON-ISOTHERMAL FLOWS IN NATURAL AND MIXED CONVECTION

2022

Most thermal fluid flow of real-life practical problems fall in the category of low Mach-number or incompressible flow (e.g., industrial flows inside ducts, or around stationary/moving objects, flows in biological/biomedical problems, or atmospheric flows). Several numerical techniques have been proposed for simulation of thermal flows, Finite Difference (FDM), Finite Element (FEM), Finite Volume (FVM) and Lattice Boltzmann (LBM) methods. Unlike the FVMs and FEMs, the classical FDMs show some difficulties in handling irregular geometries. Conventional formulation of FEMs (e.g., Galerkin FEMs) suffers from the lack of local mass balance, recovered by modified formulations (Narasimhan & W…

SOLAR MODELS WITH ACCRETION. I. APPLICATION TO THE SOLAR ABUNDANCE PROBLEM

2011

We generate new standard solar models using newly analyzed nuclear fusion cross sections and present results for helioseismic quantities and solar neutrino fluxes. We discuss the status of the solar abundance problem and investigate whether nonstandard solar models with accretion from the protoplanetary disk might alleviate the problem. We examine a broad range of possibilities, analyzing both metal-enriched and metal-depleted accretion models and exploring three scenarios for the timing of the accretion. Only partial solutions are found: one can bring either the depth of the convective zone or the surface helium abundance into agreement with helioseismic results, but not both simultaneousl…

Effects of WIMP DM transport in the Sun

2011

We study the effect of dark matter (DM) particles in the Sun, focusing in particular on the possible reduction of the solar neutrinos flux due to the energy carrie d away by DM particles from the innermost regions of the Sun, and to the consequent reduction of the temperature of the solar core. We find that in the very low-mass range between 4 and 10 Ge V, recently advocated to explain the findings of the DAMA and CoGent experiments, the e ffects on neutrino fluxes are detectable only for DM models with very small, or vanishing, self-annihilation cross section, such as the so-called asymmetric DM models, and we study the combination of DM masses and Spin Dependent cross sections which can b…

Laminar flow through fractal porous materials: the fractional-order transport equation

2015

Abstract The anomalous transport of a viscous fluid across a porous media with power-law scaling of the geometrical features of the pores is dealt with in the paper. It has been shown that, assuming a linear force–flux relation for the motion in a porous solid, then a generalized version of the Hagen–Poiseuille equation has been obtained with the aid of Riemann–Liouville fractional derivative. The order of the derivative is related to the scaling property of the considered media yielding an appropriate mechanical picture for the use of generalized fractional-order relations, as recently used in scientific literature.

The MAST FV/FE scheme for the simulation of two-dimensional thermohaline processes in variable-density saturated porous media

2009

A novel methodology for the simulation of 2D thermohaline double diffusive processes, driven by heterogeneous temperature and concentration fields in variable-density saturated porous media, is presented. The stream function is used to describe the flow field and it is defined in terms of mass flux. The partial differential equations governing system is given by the mass conservation equation of the fluid phase written in terms of the mass-based stream function, as well as by the advection-diffusion transport equations of the contaminant concentration and of the heat. The unknown variables are the stream function, the contaminant concentration and the temperature. The governing equations sy…

Well-posedness of the boundary layer equations

2004

We consider the mild solutions of the Prandtl equations on the half space. Requiring analyticity only with respect to the tangential variable, we prove the short time existence and the uniqueness of the solution in the proper function space. Theproof is achieved applying the abstract Cauchy--Kowalewski theorem to the boundary layer equations once the convection-diffusion operator is explicitly inverted. This improves the result of [M. Sammartino and R. E. Caflisch, Comm. Math. Phys., 192 (1998), pp. 433--461], as we do not require analyticity of the data with respect to the normal variable.