摘要:

The solution of large sets of equations is required when discrete methods are used to solve fluid flow and heat transfer problems. The cost of the solution often becomes prohibitive when the coefficients of the algebraic equations become strongly anisotropic or when the number of equations in the set becomes large. The present paper demonstrates how the additive correction method of Settari and Aziz can be used and extended to improve the convergence rate for two- and three-dimensional problems when the coefficients are anisotropic. Such methods are interpreted as simple multigrid methods. With this as the basis a new general multigrid method is developed that has attractive properties. The efficiency of the new method is compared to that of a conventional multigrid method, and its performance is demonstrated on other problems.

ISSN:0149-5720    

DOI:10.1080/10407788608913491

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A computational methodology is presented for the problem of melting of a pure metal from an isothermal vertical wall. The governing conservation equations of mass, momentum, and energy are solved with a control volume-based discretization scheme adapted for irregular geometries. The moving boundary is immobilized by employing the quasi-steady assumption with an algebraically generated nonorthogonal grid. All terms in the governing equations arising from the nonorthogonatity of the computational grid are retained in the solution algorithm. The model is validated by comparison with available experimental data for the effect of natural convection on melting heat transfer in a pure metal system. The influence of Rayleigh number on velocity and temperature fields is investigated, and sample results are presented for overall heat transfer and melting rate. The predictions indicate that buoyancy-induced fluid motion may have a less dominant role in energy transport in the transition to quasi-steady melting in the liquid metal system than in high Prandtl number melting processes studied previously. However, the influence of Prandtl number on natural-convection heat transfer in the quasi-steady melting regime appears to be weak.

ISSN:0149-5720    

DOI:10.1080/10407788608913492

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A study of the computation of recirculating flows using body-fitted coordinates has been conducted with a numerical algorithm developed previously. Both the consistent treatment of the continuity equation and the effects of the grid skewness on the calculated flow field have been investigated. A more consilient method has been developed that formally satisfies the conservation laws more closely, allowing the mass residual to be driven to lower levels on highly irregular grids. The new method can also be more effective in numerically damping out disturbances in the flow field as the solution progresses. Since the computed flow fields arc found to be quite insensitive to the final level of the residuals, the residuals are not a good indicator of the level of convergence; the kinetic energy of the flow field serves as a useful alternative. It is found that the effects of the excessive local mesh skewness on the overall ac~ curacy of the calculated solution are quite tolerable. This finding demonstrates the desirable robustness of the present numerical algorithm.

ISSN:0149-5720    

DOI:10.1080/10407788608913493

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The problem of mixed convection flow about a vertical plate fin embedded in a porous medium, taking into consideration the interaction between conduction in the fin and convection in the surrounding fluid, has been analyzed. It was found that the governing parameters for the problem are the Prandtl number Pr, the mixed convection parameter ω, and the convection-conduction parameter Ncc. The results of the analysis were found to be similar to those of the classical fluids. In particular, at a high value of the convection-conduction parameter Ncc, the local heat transfer coefficient is found to decrease first, attain a minimum value, and then increase in the stream-wise direction. This behavior can be attributed to the enhanced buoyancy force resulting from an increase in the wall-to-fluid temperature difference along the stream-wise direction. The total heat transfer rate was found to decrease with increasing Ncc.

ISSN:0149-5720    

DOI:10.1080/10407788608913494

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Numerical analysis is performed for two-dimensional mixed convection in the annulus between horizontal concentric cylinders with a heated rotating inner cylinder. The ratio of the annulus gap width to the inner cylinder radius is held fixed at 1.6. The Grashof number range is taken from 1.39 × 102to 1.39 × 105and the rotational parameter σ ( = Gr/Re2) varies from ∞ ( pure natural convection) to 1. The flow and temperature fields and heat transfer characteristics are presented over this parameter range where effects of both buoyancy and centrifugal force due to rotation are significant. A relatively novel formulation of the Navier-Stokes equations is employed in the present study. A vorticity transport equation, two Poisson equations for the velocity components, and the energy equation are solved by a finite-difference scheme. A direct method is used to solve simultaneously for the dependent variables along a grid line via a block tridiagonal matrix algorithm. The formulation is found to be stable over the entire range of σ studied and appropriate for investigating fluid flow and heat transfer problems in multiply connected domains where the net flow rate is not known a priori.

ISSN:0149-5720    

DOI:10.1080/10407788608913495

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A numerical investigation is made of laminar mixed convection of air in a vertical channel. The thermal boundary conditions considered are symmetric heating, where both plates are heated, and asymmetric heating, where one plate is heated and the other is adiabatic. Results are obtained for Rayleigh numbers of 103, 105, and 106and Gr/Re2values of 0.1, 1, 3, and 5. The temperatures are observed to increase with increasing Gr/Re2and decreasing Rayleigh number. The velocity profile peaks near the hot plates and exhibits a concavity, which, in the symmetric heating case, occurs around the centerline. With increasing Gr/Re2the velocity near the hot wall increases while the velocity near the centerline decreases. The Nusselt number attains its maximum value near the inlet of the channel and increases with decreasing Gr/Re2values.

ISSN:0149-5720    

DOI:10.1080/10407788608913496

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A second-order accurate finite-difference scheme based on a modification of the upwind method for the classical wave equation is proposed for transient forced convection in laminar channel flow. Stability analysis is performed, and the modified equation is established. The problem involving a step change in inlet temperature is studied for both slug and parabolic flow inside a parallel-plate duct. The accuracy of the numerical scheme is examined by comparing the results to the exact solutions available for the case of slug flow. Numerical results are presented for the average flow temperature and local Nusselt number as a function of position along the channel at different times, and the thermal wave propagation phenomena are physically interpreted.

ISSN:0149-5720    

DOI:10.1080/10407788608913497

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0149-5720    

DOI:10.1080/10407788608913498

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor