摘要:

Buoyancy force and surface tension are two important sources of bulk flow motion in a thermal-driven cavity with a free surface. In this paper, the interaction between these two forces has been studied by the semi-implicit scheme based on the operator-splitting finite-element method. Time-dependent momentum, energy, and continuity equations have been solved for both augmenting and counteracting convection in normal gravity and low-gravity environments. Numerical results show that the Marangoni number strongly affects the flow field as well as the heal transfer phenomena, and low aspect ratio and Prandtl number enhance the thermocapillary flow development. The cases investigated here include Ra = 1, 104; |Ma| < 104; pr = 5, 0.71, 0.01; and Ar= 2, 1, 0.5.

ISSN:1040-7782    

DOI:10.1080/10407789208944774

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A numerical study has been conducted on natural convection in a vertical slot with a narrow upper section. The fluid (air) in the slot is initially at a uniform temperature and is motionless. The top and bottom are insulated. The left walls are subjected to a step change in temperature, while the right walls are kept at the initial temperature. The resulting flow patterns and heat transfer for different Rayleigh numbers are numerically studied by a projection method involving a Godunov-type discretization for connective terms.

ISSN:1040-7782    

DOI:10.1080/10407789208944775

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Laminar mixed convective flow across a block-mounted plate in a vertical channel is studied numerically. One plate with blocks is elevated to a constant temperature different from the inlet air and the other is adiabatic. The results show that the local Nusselt number is significantly affected by secondary flows induced by buoyancy and channel geometry. It is also noted that the heat transfer is mainly a function of the three geometric ratios and the Reynolds number. The average Nusselt numbers decrease with increasing Gr/Re2values in the blocks and increase with Gr/Re2at high Grashof numbers in the recirculation zones.

ISSN:1040-7782    

DOI:10.1080/10407789208944776

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A two-dimensional numerical study that models solidification of a pure metal in a horizontal crucible by using a finite-volume-enthalpy method has been carried out. The primary goals of the investigation are to assess the influence of phase change on the known transition to time-periodic convection and to predict the critical parameters associated with this phenomenon. Numerical simulations reveal the influence of the dimensionless solidification temperature Ts, on the critical value of the Grashof number Grcrit. The influence is found to be directly related to an effective aspect ratio of the liquid part of the cavity. When Tsis increased, it is found that oscillatory convection takes place at a higher Grashof number and with slightly higher frequency. However, varying the Stefan number Ste has small influence on the critical parameters. The critical value of Gr for the onset of the oscillation is determined by carrying out a series of time-dependant calculations.

ISSN:1040-7782    

DOI:10.1080/10407789208944777

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The thermal impact of the convective inertia term, which resembles the term used in the Navier-Stokes equation for pure fluids, is investigated numerically considering Bénard convection in a fluid-saturated porous medium. There has been some theoretical discussion in the archival literature about the correctness of including an inertia term in the form of a velocity divergent. The present study shows numerically that this convective term (inertia) is negligible for most cases and has a negligible effect on the overall heat transfer. The relative importance of the inertia and Forchheimer terms bated on scale analysis is found to agree with the numerical results. This evidence adds strength to the theoretical assessment found in the literature.

ISSN:1040-7782    

DOI:10.1080/10407789208944778

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This work presents a numerical study of natural convection in a two-dimensional, rectangular, porous medium, differentially heated from its vertical walls. A finite-volume procedure is used to solve the Darcy-Brinkman-Forchheimer model with one energy equation. The purpose of the study is to analyze the effect of thermal dispersion, considering that the effective thermal conductivity of the porous medium depends on the local filtration velocity. The introduction of thermal dispersion in the classical Darcy-Brinkman-Forchheimer model leads to a significant increase in the overall heat transfer and to better agreement with the experimental data, particularly when the thermal conductivities of the fluid and the solid matrix are similar.

ISSN:1040-7782    

DOI:10.1080/10407789208944779

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor