摘要:

A study of the use of a multilevel (multigrid) technique for the solution of Poisson and Navier-Stokes equations was conducted. Solutions were obtained using Gauss-Seidel, line-by-line, and strongly implicit relaxation schemes for the Poisson equation and Gauss-Seidel and strongly implicit schemes for the Navier-Stokes equations. In all test problems substantial improvement in the rate of convergence was found when using a multilevel ( multigrid) technique to reduce the low wave number errors with a Gauss-Seidel relaxation method. The rate of convergence improves, but less dramatically, when using a strongly implicit relaxation scheme. This is attributed to the fact that the strongly implicit scheme is itself quite efficient in reducing low wave number errors. It was also found that benefits from the use of multilevel ( multigrid) techniques are greater when the flow being predicted has strong pressure-momentum coupling.

ISSN:0149-5720    

DOI:10.1080/10407788808913601

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The fluid flow, mass transfer, and heat transfer associated with the evaporation of a liquid from a partially filled rectangular cavity have been modeled both rigorously and approximately and then evaluated numerically. A uniform tangential velocity was prescribed at the top of the cavity, and the side and bottom walls of the cavity were adiabatic. All of the numerical results were for the evaporation of water into an air ambient having various degrees of humidity. The modeling studies demonstrated that results of high accuracy for the evaporation rate and for the temperature at the gas-liquid interface could be obtained without having to solve the conservation equations for the liquid zone. The interface temperatures corresponding to convection-driven evaporation deviated only slightly from those for diffusion-driven evaporation ( i.e., no convection). Furthermore, the variation of the evaporation rate with the ambient temperature and relative humidity was found to be very similar for the convection-driven and diffusion-driven cases.

ISSN:0149-5720    

DOI:10.1080/10407788808913602

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The characteristics of combined buoyancy and thermocapillary flow for liquid metals in a rectangular cavity have been studied numerically. Results show that, for augmenting buoyancy and surface tension forces, qualitative flow patterns and isotherms are unchanged, but enhanced fluid velocities and heat transfer rates occur. In contrast, for counteracting buoyancy and surface tension forces, three different flow regimes are identified, with minimum heat transfer rates occurring when buoyancy and surface tension forces are of equal importance. The flow and temperature fields, as well as heat transfer rates, have been studied for aspect ratios of 0.5, 1.0, and 2.0.

ISSN:0149-5720    

DOI:10.1080/10407788808913603

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Combined forced and free convection around horizontal cylinders as well as spheres has been numerically investigated, with the emphasis placed on the pressure solutions. The stream function (ψ)-vorticity (ω) formulation is adopted in conjunction with hybrid (central and upwind) difference and nonuniform grids. For recovery of the pressure distribution, which seems unavailable in the literature, the pressure Poisson's equation is solved after convergence of ψ and at solutions has been achieved. Computed results of Nusselt numbers are compared with several reported literature values. Good agreement has been found between these values.

ISSN:0149-5720    

DOI:10.1080/10407788808913604

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Natural convection flow induced by localized heating from below in a horizontal porous layer is investigated numerically. The geometry considered is a two-dimensional rectangular cavity whose portion of the bottom surface is isothermally heated, the upper surface is cooled at a constant temperature, and all other surfaces are adiabatic. Parameters of the problem are the cavity aspect ratio A, dimensionless length of heat source B, dimensionless position of heat source ε with respect to the vertical line of symmetry of the cavity, and Rayleigh number R based on cavity width. Three main convective modes are studied—conduction and single- and double-cell convection—and their features are described in detail. Maximum stream function and global Nussett numbers are presented as functions of the external parameters. Multiplicity of solutions is explored for an aspect ratio of unity. The existence of two steady-state solutions for a given set of the governing parameters is demonstrated.

ISSN:0149-5720    

DOI:10.1080/10407788808913605

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Subject to many simplifying assumptions, the motion of a square particle in a two-dimensional channel flow is studied in order to estimate (1) the influence of the particle on the convection heat transfer to the channel wall and (2) the conduction heat transfer associated with particle collision with the wall. Particles with low and high thermal diffusivities are considered. The results show that for the high thermal diffusivity particles, the conduction heat transfer is dominant and the particles attain near local thermal equilibrium with the fluid. Therefore, these particles quickly recover the heat loss due to impact. For glass particles the convection and conduction contributions are nearly the same.

ISSN:0149-5720    

DOI:10.1080/10407788808913606

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0149-5720    

DOI:10.1080/10407788808913607

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor