摘要:

This paper develops a hierarchical least square solution algorithm for highly nonlinear heat transfer problems. The methodology's capability is such that both steady and transient implicit formulations can be handled. This includes problems arising from highly nonlinear heat transfer systems modeled by either finite-element or finite-difference schemes. The overall procedure developed enables localized updating, iteration, and convergence checking as well as constraint application. The localized updating can be performed at a variety of hierarchical levels, i.e., degree of freedom, substructural, material-nonlinear groups, and/or boundary groups. The choice of such partitions can be made via energy partitioning or nonlinearity levels as well as by user selection. Overall, this leads to extremely robust computational characteristics. To demonstrate the methodology, problems are drawn from nonlinear heat conduction. These are used to quantify the robust capabilities of the hierarchical least square scheme.

ISSN:0149-5720    

DOI:10.1080/10407788708913586

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A control volume finite-difference approach for the solution of axisymmetric laminar viscous flow through a converging-diverging pipe is presented. The pipe wall has a sinusoidal shape and constant enthalpy. The physical wavy domain is transformed into a rectangular computational domain to simplify the application of boundary conditions on the solid boundary. The governing equations in primitive variables are discretized on a control volume basis that ensures global as well as local conservation of mass, momentum, and energy. The pseudodiffusive terms that arise from the coordinate transformation are treated as source terms, and the resulting system of equations is solved by a semi-implicit procedure based on line relaxation. Results are obtained for both the developing and the fully developed flow for a Prandtl number of 0.72, ratio of pipe maximum diameter to pitch of 1.0, Reynolds number ranging from 100 to 500, and ratio of wall amplitude to pitch varying from 0.1 to 0.25.

ISSN:0149-5720    

DOI:10.1080/10407788708913587

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A calculation scheme to predict incompressible turbulent flows in arbitrary shapes is presented. The procedure is based on the solution of the primitive-variable formulation of the time-dependent Reynolds-averaged Navier-Stokes equations in general curvilinear coordinates. An ordinary computational cell is used for continuity and transport balances, and all the physical properties are stored at the center of this element. The scheme uses an overlapping mesh along with forward and backward differencing for mass and pressure gradients, respectively. In a manner different from the staggered-grid approach, this procedure prevents the oscillatory behavior of the pressure field. The k-ϵ model is used to describe the turbulent flow process with particular attention to the boundary conditions. Computed results are compared with numerical and experimental data.

ISSN:0149-5720    

DOI:10.1080/10407788708913588

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Hyperbolic heat conduction with radiation is considered in a finite absorbing and emitting slab for the cases of a constant and a pulsed heat flux boundary condition. For small optical thicknesses, the wave nature of hyperbolic heat conduction gives rise to a thermal front propagating from the back surface which results from the heating of the back surface by radiation through the medium. MacCormack's explicit predictor-corrector scheme is used to solve the problem, and the results from the hyperbolic solutions are compared to those obtained from the parabolic equation.

ISSN:0149-5720    

DOI:10.1080/10407788708913589

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

This study concerns the separated laminar forced convection near surface-mounted ribs. Temperature profiles and local heat transfer coefficients were calculated for the entire domain of interest through the well-known SlMPLE/HD numerical scheme. With all walls maintained at a uniform temperature, numerical experiments were performed for a rib aspect ratio (width divided by height of w/s = 1, 2, and 4 at different Reynolds numbers covering the range 63.5 ≤ Re, ≤ 254. Results indicate that the average Nusselt number in the vicinity of the rib is a function of the Reynolds number and aspect ratio and that it can be correlated by an equation of the form

ISSN:0149-5720    

DOI:10.1080/10407788708913590

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

An order-of-magnitude approach is employed to analyze the linear nonparallel wave instability of boundary-layer flows. This analysis removes the restriction imposed by previous investigators on the weak dependence of the streamwise variation of disturbance quantities. A superposition technique along with a modified Thomas trans-formation is employed to solve the resulting nonhomogeneous equation for the amplitude function of the disturbance without the use of an adjoint eigenfunction, which is needed in conventional approaches. All of the eigenfuncrions are treated in their general forms. The growing rate of the disturbance intensity is found to depend on both streamwise and transverse coordinates. At a local observation point × (or Re×), the growing rate of the disturbance intensity has a maximum value near y = Y = Ylpar;U∞/ vX)½ = 3 for Blasiusflow. The neutral stability curve can then be defined by letting the maximum growing rate of the disturbance intensity be zero. Excellent agreement is found between the present results and available experimental data.

ISSN:0149-5720    

DOI:10.1080/10407788708913591

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The problem of natural convection flow of a power-law fluid past a vertical porous wait, taking into consideration the effects of the inertia terms and watt injection or suction on the Nusselt number, has been analyzed. The system of partial differential equations was transformed to a coupled nonlinear set of ordinary differential equations for the isothermal wall and the constant wall heat flux case by using a generalized Rayleigh number that shows the dependence on the power-law index n more explicitly. The resulting two-point boundary-value problem was linearized and solved iteratively using Keller's box method. It was confirmed that inclusion of the inertia terms is more important for flow situations with low to moderate Prandtt numbers than for polymeric liquids with very high Prandtl numbers. The results indicate that both suction and injection at wall Reynolds numbers less than unity have a significant effect on the velocity and temperature profiles and ultimately on the Nussett number.

ISSN:0149-5720    

DOI:10.1080/10407788708913592

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A pragmatic combination of time-integration methods is presented. In particular, the backward difference method is changed into a modified Crank-Nicolson method with a doubling of the time step. This combination is specially effective in the case of linear analysis, since it simplifies the element assembly and the forward elimination process. As compared with the backward difference method, this time integration method has the potential to significantly reduce computation time with improved accuracy.

ISSN:0149-5720    

DOI:10.1080/10407788708913593

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor