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Laminar Natural Convection In A Discretely Heated Cavity: I—Assessment Of Three-Dimensional Effects, Theodore J. Heindel, S. Ramadhyani, F. P. Incropera
Laminar Natural Convection In A Discretely Heated Cavity: I—Assessment Of Three-Dimensional Effects, Theodore J. Heindel, S. Ramadhyani, F. P. Incropera
Theodore J. Heindel
Two and three-dimensional calculations have been performed for laminar natural convection induced by a 3 × 3 array of discrete heat sources flush-mounted to one vertical wall of a rectangular cavity whose opposite wall was isothermally cooled. Edge effects predicted by the three-dimensional model yielded local and average Nusselt numbers that exceeded those obtained from the two-dimensional model, as well as average surface temperatures that were smaller than the two-dimensional predictions. For heater aspect ratios Ahtr ≲ 3, average Nusselt numbers increased with decreasing Ahtr . However, for Ahtr ≳ 3, the two and three-dimensional predictions were within 5 percent …
Laminar Natural Convection In A Discretely Heated Cavity: Ii—Comparisons Of Experimental And Theoretical Results, Theodore J. Heindel, F. P. Incropera, S. Ramadhyani
Laminar Natural Convection In A Discretely Heated Cavity: Ii—Comparisons Of Experimental And Theoretical Results, Theodore J. Heindel, F. P. Incropera, S. Ramadhyani
Theodore J. Heindel
Three-dimensional numerical predictions and experimental data have been obtained for natural convection from a 3 × 3 array of discrete heat sources flush-mounted on one vertical wall of a rectangular cavity and cooled by the opposing wall. Predictions performed in a companion paper (Heindel et al., 1995a) revealed that three-dimensional edge effects are significant and that, with increasing Rayleigh number, flow and heat transfer become more uniform across each heater face. The three-dimensional predictions are in excellent agreement with the data of this study, whereas a two-dimensional model of the experimental geometry underpredicts average heat transfer by as much as …
Dynamic Simulation Of Crack Propagation With Dislocation Emission And Migration, N. Zacharopoulos, D. J. Rolovitz, Richard Alan Lesar
Dynamic Simulation Of Crack Propagation With Dislocation Emission And Migration, N. Zacharopoulos, D. J. Rolovitz, Richard Alan Lesar
Richard Alan Lesar
We present a simulation procedure for fracture that self-consistently accounts for dislocation emission, dislocation migration and crack growth. We find that the dislocation microstructure in front of the crack tip is highly organized and shows a complex temporal-spatial evolution. The final dislocation microstructure and the number of emitted dislocations immediately proceeding fracture varies rapidly with the loading rate. For high loading rates, fracture occurs at smaller loads with increasing loading rate. However, the load at fracture shows a maximum with respect to loading rates.
Modeling Multiple Reactive Scalar Mixing With The Generalized Iem Model, Kuochen Tsai, Rodney O. Fox
Modeling Multiple Reactive Scalar Mixing With The Generalized Iem Model, Kuochen Tsai, Rodney O. Fox
Rodney O. Fox
An outstanding feature of the amplitude mapping closure is its ability to relax an arbitrary initial probability density function (PDF) to a Gaussian PDF asymptotically. Due to the difficulties in computing either the analytical or numerical solution, the mapping closure has never been applied to multiple scalars with finite reaction rates. In this work, the generalized IEM (GIEM) model is combined with the mapping closure to model the molecular mixing terms in the PDF balance equation. The GIEM model assumes a linear relationship between the rates of change of the reactive scalars and an inert scalar (shadow scalar) during the …
Origin Of The 〈11/20〉 Atomic Short-Range Order In Au-Rich Au-Fe Alloys, M. F. Ling, J. B. Staunton, Duane D. Johnson, F. J. Pinski
Origin Of The 〈11/20〉 Atomic Short-Range Order In Au-Rich Au-Fe Alloys, M. F. Ling, J. B. Staunton, Duane D. Johnson, F. J. Pinski
Duane D. Johnson
We have calculated the atomic short-range order (ASRO) and paramagnetic susceptibility in high-temperature, chemically disordered Au75Fe25 and Au90Fe10, using a density-functional-based, electronic-structure method. For both alloys, we obtain 〈11/20〉-type ASRO, in excellent agreement with experiments performed on samples that have been fast quenched from high temperature. We also identify the underlying electronic mechanism responsible for this unusual ordering behavior. During annealing at high temperatures, we suggest that aligning local moments via an external magnetic field will produce interesting AuFe alloys with 〈100〉-type ASRO.
The Spectral Relaxation Model Of The Scalar Dissipation Rate In Homogeneous Turbulence, Rodney O. Fox
The Spectral Relaxation Model Of The Scalar Dissipation Rate In Homogeneous Turbulence, Rodney O. Fox
Rodney O. Fox
A model for the effect of scalar spectral relaxation on the scalar dissipation rate of an inert, passive scalar (Sc>1) in fully developed homogeneous turbulence is presented. In the model, wave-number space is divided into a finite number [the total number depending on the turbulence Reynolds number Re, and the Schmidt number (SC)] of intermediate stages whose time constants are determined from the velocity spectrum. The model accounts for the evolution of the scalar spectrum from an arbitrary initial shape to its fully developed form and its effect on the scalar dissipation rate for finite Re, and Sc>1. …
Van Hove Singularity Induced L11 Ordering In Cupt, J. F. Clark, F. J. Pinski, Duane D. Johnson, P. A. Sterne, J. B. Staunton, B. Ginatempo
Van Hove Singularity Induced L11 Ordering In Cupt, J. F. Clark, F. J. Pinski, Duane D. Johnson, P. A. Sterne, J. B. Staunton, B. Ginatempo
Duane D. Johnson
We describe an ordering mechanism that arises due to coupling between electronic states at van Hove singularities. This novel mechanism, which naturally leads to ordered structures with small unit cells, couples states near the Fermi energy which are localized at high-symmetry points in k space, in contrast to the conventional mechanism which relies on large parallel sheets of Fermi surface. Using first-principles calculations of the electronic structure of ordered and disordered alloys, we show that this mechanism drives the unusual short- and long-range order found in fcc CuPt.
Three-Dimensional Location Estimation Of Trajectories Of Point Targets Using A Projection-Based Transformation Method, Jae-Ho Choi, Sarah A. Rajala
Three-Dimensional Location Estimation Of Trajectories Of Point Targets Using A Projection-Based Transformation Method, Jae-Ho Choi, Sarah A. Rajala
Sarah A. Rajala
A new computational approach for determining the parameters that characterize the locations of trajectories of point targets in a 3-D space is described. The targets of concern are dim, unresolved point targets moving along straight paths across the same field of view. Since the target's signal-to-noise ratio is low and the spatial extent of the target is less than a pixel, one must rely on integration over a target track that spans many image frames. The proposed method estimates these parameters by transforming the entire set of time-sequential images of a constant field of view into the projection space by …
Commensurate And Incommensurate Ordering Tendencies In The Ternary Fcc Cu-Ni-Zn System, J. D. Althoff, Duane D. Johnson, F. J. Pinski
Commensurate And Incommensurate Ordering Tendencies In The Ternary Fcc Cu-Ni-Zn System, J. D. Althoff, Duane D. Johnson, F. J. Pinski
Duane D. Johnson
We show that Fermi-surface (FS) nesting drives both the incommensurate and commensurate ordering tendencies of the fcc ternary Cu-Ni-Zn system. Surprisingly, commensurate order persists over a wide range of composition, despite its origins. For Cu2NiZn, we discuss how FS nesting and the other effects of alloying lead to ordering tendencies consistent with the experimentally observed order-disorder transformations. All calculations are based on a first-principles theory of the atomic short-range order in alloys with an arbitrary number of components.
Crop Yield Mapping: Comparison Of Yield Monitors And Mapping Techniques, Stuart J. Birrell, Steven C. Borgelt, Kenneth A. Sudduth
Crop Yield Mapping: Comparison Of Yield Monitors And Mapping Techniques, Stuart J. Birrell, Steven C. Borgelt, Kenneth A. Sudduth
Stuart J. Birrell
Although the variability in soil nutrients and crop yields has been well documented since the turn of the century (Robinson & Lloyd, 1915; Fairfield Smith, 1938), the mechanization of agriculture and the trend to larger implements has led to larger areas being treated as a single unit. Recent advances, however, in machine technology and improvements in data management have made it possible to reverse this trend by implementing site specific crop management (Goering, 1993).
Comparison Of Variable Rate To Single Rate Nitrogen Fertilizer Application: Corn Production And Residual Soil No3-N, N. R. Kitchen, D. F. Hughes, K. A. Sudduth, Stuart J. Birrell
Comparison Of Variable Rate To Single Rate Nitrogen Fertilizer Application: Corn Production And Residual Soil No3-N, N. R. Kitchen, D. F. Hughes, K. A. Sudduth, Stuart J. Birrell
Stuart J. Birrell
The questions most often asked by farmers when discussing variable rate (VR) fertilizer inputs are "How much will it cost?" and "How will it affect my yields?" Many farmers and custom application services share a reluctance to invest in the time and technology required for variable fertilizer application since studies to answer these questions are few and results have been inconsistent.
Technical Notes: Bidirectional Serial-To-Parallel Converter For Data Acquisition And Control, Stuart J. Birrell, Scott T. Drummond, Kenneth A. Sudduth
Technical Notes: Bidirectional Serial-To-Parallel Converter For Data Acquisition And Control, Stuart J. Birrell, Scott T. Drummond, Kenneth A. Sudduth
Stuart J. Birrell
A bidirectional serial-to-parallel converter was created to allow collection of serial data through the parallel port on a portable laptop computer. The converter consisted of both hardware conversion circuitry and control software. The converter supported both input and output at a variety of transmission formats and adjustable transmission rates. The control software made use of the various I/O registers of the parallel port to collect data and control the hardware circuitry.