摘要:

This article presents a numerical study of the thermal and fluid flow interaction driven by the sudden contact between saturated liquid water (373 K) and a hot (2300 K) spherical or plane surface. It is shown that under these conditions the sudden contact is characterized initially by single-phase interfacial water and supercritical pressure that decays in time as the water is accelerated away from the interface. The sudden contact generates (high) temperature, pressure, and density waves that propagate away from the surface. The water is modeled as an inviscid single-phase fluid that behaves either as an ideal gas or a real gas with properties taken from steam tables. The ideal-gas results are in good qualitative and quantitative (within a factor of order 1) agreement with the results based on the real-gas model. When the hot object is large (radius ≥ 10 mm), the results are insensitive to the geometry of the model (i.e., spherical versus plane).

ISSN:1040-7782    

DOI:10.1080/10407789608913856

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The nonlinear partial differential equations for the transient free convective heat transfer in a viscous, electrically conducting, and heat-generating fluid past a vertical porous plate in the presence of free stream oscillations are solved by the boundary element method (BEM). Time-dependent fundamental solutions are employed in a time marching scheme to resolve the field variables. Numerical results are compared with previously reported analytical solutions in order to validate the developed BEM algorithm. These previous studies reported results for simpler versions of our problem, in which the convective effects in the momentum and energy equations were neglected in order to obtain analytical numerical solutions. Our BEM results are shown to be in close agreement with the reported data. The effects of convection currents, the temperature-dependent heat sources (or sinks), the magnetic currents, and the viscous dissipation on the flow and heat transfer characteristics are assessed in a parametric study, which considers a variety of the dimensionless parameters Gr, Ec, Pr, M, and γ. It is observed that γ plays an important role in delaying the fluid flow reversal, present in the case of air, and acts to enhance the effect of Gr in augmenting the rate of heat transfer at the wall. The skin friction is observed to be an increasing function of Gr, Ec, and γ and a decreasing function of M and Pr. However, the rate of heat transfer (in an absolute sense) is an increasing function of M, γ, Gr, and Ec and a decreasing function of Pr, Of all the parameters, the Prandtl number has the strongest effect on the flow and heat transfer characteristics.

ISSN:1040-7782    

DOI:10.1080/10407789608913857

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The enthalpy method is one of the most widely used methods for solving phase change problems with a moving boundary. In the application of the enthalpy method, systems of nonlinear equations have to be solved at each time step when implicit time discretization is being used. In this article, we propose to use Broyden 's algorithm as an efficient method for solving these systems of nonlinear equations based on a direct discretization of the enthalpy equation. Numerical experiments are conducted to verify the efficiency of our scheme for a one-dimensional, two-phase solidification problem.

ISSN:1040-7782    

DOI:10.1080/10407789608913858

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The main purpose of this study is to overcome the destabilization problem that usually occurs in turbulent flow calculations using QUICK schemes. The consistently formulated QUICK scheme developed by Hayase et at. is employed in calculations on nonuniform grid meshes. Using the proposed stability-enhancing measure for the source terms, the turbulent flow calculations with the orthodox QUICK scheme are demonstrated to be feasible either with the standard k-ϵ turbulence model or with the low-Reynolds-number k-ϵ turbulence model. This study also demonstrates that a remarkable savings in the number of grid nodes required to yield a grid-independent solution can be obtained through use of the orthodox QUICK scheme, in comparison to the low-order scheme, while the hybrid QUICK/low-order scheme cannot obtain such significant savings.

ISSN:1040-7782    

DOI:10.1080/10407789608913859

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Convective oscillations in porous media are studied numerically. A two-dimensional square, differentially heated cavity, filled with a saturated porous medium, is considered subject to linear harmonic oscillations in the vertical direction. The formulation is based on the Darcy-Boussinesq model. The problem includes three nondimensional parameters: the Rayleigh number for porous media Ra, its vibrational analog Ra, and the nondimensional frequency f. The time-dependent Darcy-Boussinesq equations have been solved using a pseudo-spectral Chebyshev collocation method. The instantaneous fields of the established oscillatory regimes are presented. Also, some instantaneous and mean characteristics are studied and discussed. The distinctions from the case of viscous fluid atone are emphasized.

ISSN:1040-7782    

DOI:10.1080/10407789608913860

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A recursive least squares algorithm (RLSA) is used to estimate a timewise variation plane heat source inside a plate with insulated boundaries, The one-dimensional heat conduction equation with heat source at known location is expressed in continuous-time state equations. By virtue of the Kalman filter adaptor with the input estimation technique, the residual innovation sequence is generated to estimate the strength of a time-varying plane heat source. In order to examine the accuracy of the method, comparison is made with the results of the conjugate gradient method. The RLSA method is found to be more accurate than the conjugate gradient method for these special test cases,

ISSN:1040-7782    

DOI:10.1080/10407789608913861

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor