摘要:

A solution algorithm for the Navier-Stokes equations is tested by calculating laminar and turbulent flows over backward facing steps and laminar flow over obstacles. The solution algorithm is based on the finite volume method, curvilinear nonorthogonal coordinates, and a nonstaggered grid arrangement, and the connective fluxes are described by the power law scheme or the second-order upwind scheme. The Rhie and Chow interpolation method is selected for calculating the convective velocities on the cell faces to get good coupling between the velocity and pressure fields. When the flow is turbulent, the k-ϵ turbulence model with wall Junctions is employed. A highly deformed grid generated with an elliptic grid generator is used around the corners of the backward facing steps and obstacles; this represents a severe test of the algorithm. The results are compared with measurements and other calculations.

ISSN:1040-7782    

DOI:10.1080/10407789308902630

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The crystal growth of succinonitrile (SCN) in a horizontal Bridgman apparatus is studied through a three-dimensional numerical simulation. The governing equations considered include the steady state Navier-Stokes and the thermal energy equations. The temperature boundary conditions imposed at the outer surface of the glass ampoule are taken from experimental measurements. To model the phase change inSCN, we use the effective specific heat formulation of the enthalpy method and treat theSCNas a generalized Newtonian fluid. We solve the numerical model using the segregated solution approach provided by a commercial finite element code,FIDAP. The numerical results are compared with data from experiments, and very good agreement has been achieved. The advantages of applying the segregated solution approach in large-scale three-dimensional (3-D) computations are shown through detailed comparisons of efficiency and memory requirements between the segregated and the conventional fully coupled solution approaches. The significant savings of memory requirements by the segregated approach make it possible to solve large-scale3-Dproblems on work stations.

ISSN:1040-7782    

DOI:10.1080/10407789308902631

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A one-dimensional time-dependent heat transfer model is presented for the melting process in a circular scrap melter. The phase change problem is tackled using an enthalpy-based method, and the complex scrap geometry is described with the porosity concept, i.e., the blocking effect of the scrap is represented by a blocking factor that is a function of the scrap porosity. Flame length is represented by a flame damping factor. The numerical procedure is carried out in three stages, from initial heating to complete melting. Some typical cases are simulated. Results show that the flame damping factor can significantly influence the melting process. A lower damping factor gives better uniformity in metal temperature distribution. The melting time can be improved drastically by decreasing this factor. The convective heat transfer coefficient dominates the temperature profile. The higher the convective heat transfer, the faster the temperature increase in the lower part of the furnace. A long flame and good stirring of the melt enhance the melting process.

ISSN:1040-7782    

DOI:10.1080/10407789308902632

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In this paper the main results are reported of a numerical investigation of transient double-diffusive convection in a fluid layer underlying a permeable solid region. Initially, the system is isothermal and possesses a linear distribution of salt in the permeable (porous) region. The system is cooled through its top boundary. The evolution of the transient flow, temperature, and species concentration fields is obtained numerically. In the course of this study the dependence of these fields is determined on the main problem parameters, exemplified by the thermal Rayleigh number, the species Rayleigh number, the Darcy number, the ratio of the height of the porous region to the height of the liquid layer, and the ratio of liquid to solid thermal conductivity. In addition, the above mentioned parameters are investigated in terms of their effect on the heat transfer rate at the top (cold) wall of the system as veil as on the heat and mass transfer rates at the porous-liquid interface.

ISSN:1040-7782    

DOI:10.1080/10407789308902633

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A numerical study for steady laminar double-diffusive natural convection within a vertical closed circular annulus is examined with a constant temperature and mass species (concentration) difference imposed across the vertical walls. The effects of thermal Rayleigh number (5000 ≤ RaT ≤ 100,000) and Lewis number (1 ≤ Le ≤ 10) are investigated for buoyancy ratios of −2, − 1.2, − 1, and 2, representing conditions for mass species dominated opposing, transitional, thermal dominated opposing, and mass species dominated aiding flows, respectively. The relationships between the thermal Rayleigh number and the average Nusselt and Sherwood numbers for − 10 ≤ n ≤ 10 have been obtained for a Lewis number of 5. Also, the relationship between the Lewis number and the average Nussell and Sherwood numbers for the same buoyancy ratio range have been obtained for a constant thermal Rayleigh number of 50,000. The Lewis and thermal Rayleigh numbers are found to influence the buoyancy ratios at which flow transition and flow reversal occur.

ISSN:1040-7782    

DOI:10.1080/10407789308902634

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An inverse analysis utilizing the conjugate gradient method of minimization and the adjoint equation is used to estimate unknown location and timewise-varying strength of a plane heat source placed inside a plate with insulated boundaries. No prior information is used for the functional form of timewise variation of the source strength. Transient temperature recordings computed at the boundaries of the region, modified by adding random errors, served as the simulated experimental data for the inverse analysis. In order to examine the accuracy of the estimation under most strict conditions, timewise variation of the source strength is chosen in the form of rectangular, triangular, and sinusoidal functions. An implicit finite difference scheme is used to solve the resulting inverse problem with a CRAY Y-MP supercomputer.

ISSN:1040-7782    

DOI:10.1080/10407789308902635

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Heat transfer and flow patterns of laminar mixed confection in the developing region of a vertical rectangular duct with one heating wall have been investigated numerically in this study. The parabolic boundary layer model is adopted to predict the three-dimensional buoyancy-assisted flow field. Governing equations art solved by using the SIMPI.KC method coupled with a forward marching, implicit finite difference scheme. The velocity and temperature distributions as well as the stream wise variations of local heat flux and fluid pressure are calculated under various geometric parameters. Results show that the flow characteristics are significantly dependent on the buoyancy effect (Gr / Re), the aspect ratio of cross section of duct (H). and the Prandtl number (Pr). The numerical solutions obtained have been compared and verified with existing studies. Meanwhile, the analytical solutions of fully developed flaw recently reported 181 are found to exactly portray the behavior of flow far downstream.

ISSN:1040-7782    

DOI:10.1080/10407789308902636

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor