摘要:

A segregated approach for the prediction of three-dimensional, compressible, subsonic flows is presented. The method uses a collocated finite volume scheme in body-fitted coordinates. For computational expediency and ease of implementation of high-order schemes, the continuity, momentum, and state equations are decoupled and solved sequentially. In order to eliminate potential “checkerboard” pressure distributions due to the decoupling of the pressure-velocity terms in conjunction with a collocated grid, a novel method of nonlinear cell-face interpolation is adopted. The high-order QUICK scheme is implemented for discretizing convective terms, while the central difference scheme is used for discretizing diffusion terms. A four-stage Runge-Kutta explicit scheme is employed to time-march the solution of the governing equations toward steady state. The finite volume code is applied to the prediction of three-dimensional, laminar flows in a straight duct of square cross section, a cubic driven cavity, a strongly curved duct of square cross section and a two-dimensional airfoil. The ability of the method to eliminate checkerboard pressure distribution and achieve convergence is demonstrated. The method yields accurate results, while at the same time utilizing efficiently the architecture of a vector machine. Finally, the ability of the method to perform satisfactorily near the low Mach number limit is demonstrated through comparisons with incompressible flow measurements.

ISSN:1040-7782    

DOI:10.1080/10407789608913818

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Fluid flow and heat transfer in a fixed bed of tube-to-particle-diameter ratio 2.14 is modeled by an arrangement of three staggered spheres in a tube. The problem is solved numerically by a finite element method applied to the three-dimensional incompressible Navier-Stokes equations and the energy equation. Results are obtained for Reynolds numbers in the range 25-101, with a Prandtl number of 0.72 and particle conductivities in the range 0.25-48.0 W/ (m K) Watt heat transfer coefficients obtained from the calculated temperature profiles are in good agreement with values predicted by a model-matching theory using correlations based on experimental measurements,

ISSN:1040-7782    

DOI:10.1080/10407789608913819

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The cause of high operating temperatures experienced by grate blocks in a waste-to-energy power plant is investigated. A three-dimensional numerical analysis is performed to assess convection from the grate to the underfire air supply and conduction within the grate. A number of geometric complexities, including variable solid thickness, extended surfaces, sharp curvatures, and narrow passages, are accounted for via a finite element approach. The grate temperature is found to be very sensitive to the flow characteristics beneath the grates. Analysis of a modified grate structure was performed, showing a 14% reduction in maximum grate temperature.

ISSN:1040-7782    

DOI:10.1080/10407789608913820

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This article reports on the computed flaw characteristics of a slot-ventilated enclosure. The flow was mathematically modeled with an asymptotically consistent low-Reynolds-number k-ϵ model, A comparison of computed and experimental flows reveals that (1) the airflow pattern of the experimental flow was reproduced by computed streamlines, and (2 ) computed velocity profiles were on average within —18% of those measured. Finally, an assessment of the proposed low-Reynolds-number k-ϵ model demonstrates the need for developing damping functions that do not involve the nearest wall distance and the wall shear velocity.

ISSN:1040-7782    

DOI:10.1080/10407789608913821

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This article presents a computational fluid dynamics study of incomplete air mixing in a slot-ventilated enclosure. Two computational rate-of-decay tracer investigations were performed using an asymptotically consistent low-Reynolds-number k-e model. These investigations revealed that (1) incomplete mixing was caused by a quasi-sequential removal of tracer from, simultaneously involved, mixing zones, and (2) these mixing zones resulted from streamwise-convection-dominated mass transfer processes, slightly affected by turbulent diffusion, and turbulent-diffusion-dominated mass transfer processes, little modified by streamwise convection. Underventilated, well-ventilated, and overventilated flaw regions of the enclosure were also defined.

ISSN:1040-7782    

DOI:10.1080/10407789608913822

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Ignition and combustion of a liquid fuel droplet injected into a hot and highly pressurized combustor are investigated numerically, including the effect of internal circulation. Ignition delay times of droplets predicted with internal circulation are almost the same as those from the diffusion limit model insofar as ignition takes near the droplet. Combustion regime maps are drawn to classify the droplet combustion phenomena according to the configuration and location of the flame with respect to initial Reynolds numbers and the surrounding gas temperatures.

ISSN:1040-7782    

DOI:10.1080/10407789608913823

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This article presents comparisons between an analytical and a numerical investigation of porosity formation within the mushy zone during the solidification process. For this purpose, a three-phase model (liquid, solid, and gas) of the mushy zone is utilized. This model takes into account the release of the dissolved gas from the alloy as well as the heat transfer and interdendritic fluid flow in the two-phase region. The main difference between the three-phase model and the two-phase model (only liquid and solid), which is usually used to predict the porosity distribution, is the inclusion of a term describing the porosity formation in Ike continuity equation. The perturbation method is used to obtain an analytical solution describing the porosity formation. Pressure and porosity distributions predicted by these two models are compared for the particular case of aluminum-rich Al-Cu castings.

ISSN:1040-7782    

DOI:10.1080/10407789608913824

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor