Some comments on C. S. Wallace's random number generators

We outline some of Chris Wallace's contributions to pseudo-random number generation. In particular, we consider his idea for generating normally distributed variates without relying on a source of uniform random numbers, and compare it with more conventional methods for generating normal random numbers. Implementations of Wallace's idea can be very fast (approximately as fast as good uniform generators). We discuss the statistical quality of the output, and mention how certain pitfalls can be avoided.Comment: 13 pages. For further information, see http://wwwmaths.anu.edu.au/~brent/pub/pub213.htm

Relevance of accurate Monte Carlo modeling in nuclear medical imaging

Monte Carlo techniques have become popular in different areas of medical physics with advantage of powerful computing systems. In particular, they have been extensively applied to simulate processes involving random behavior and to quantify physical parameters that are difficult or even impossible to calculate by experimental measurements. Recent nuclear medical imaging innovations such as single-photon emission computed tomography (SPECT), positron emission tomography (PET), and multiple emission tomography (MET) are ideal for Monte Carlo modeling techniques because of the stochastic nature of radiation emission, transport and detection processes. Factors which have contributed to the wider use include improved models of radiation transport processes, the practicality of application with the development of acceleration schemes and the improved speed of computers. This paper presents derivation and methodological basis for this approach and critically reviews their areas of application in nuclear imaging. An overview of existing simulation programs is provided and illustrated with examples of some useful features of such sophisticated tools in connection with common computing facilities and more powerful multiple-processor parallel processing systems. Current and future trends in the field are also discussed

Supercomputing in Aerospace

Topics addressed include: numerical aerodynamic simulation; computational mechanics; supercomputers; aerospace propulsion systems; computational modeling in ballistics; turbulence modeling; computational chemistry; computational fluid dynamics; and computational astrophysics

Numerical solution of three-dimensional incompressible unsteady viscous flows

Issued as Semi-annual progress reports [nos. 1-7], and Final report, Project E-16-61

Transonic Symposium: Theory, Application, and Experiment, Volume 1, Part 1

Topics addressed include: wind tunnel and flight experiments; computational fluid dynamics (CFD) applications, industry overviews; and inviscid methods and grid generations

Aeronautical engineering: A continuing bibliography with indexes (supplement 258)

This bibliography lists 536 reports, articles, and other documents introduced into the NASA scientific and technical information system in October 1990. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Combined convection and other effects in heat transfer in horizontal flows

For many internal flow situations the effect of buoyancy is to cause significant modifications of the internal flow field and heat transfer rate. The present study focuses on combined forced and free convection under laminar flow conditions in horizontal cylindrical ducts. There, the superposition of secondary, buoyancy induced circulations to the basic forced flow, and the presence of peripheral and axial conduction in the duct wall, give rise to a three-dimensional conjugate heat transfer problem. Such a combined convection feature had not been investigated previously. A novel parallel predictive and experimental study of combined convection for laminar flow in cylindrical ducts is carried out here. The finite volume code FLOW3D from Harwell is used to treat the fully elliptic three-dimensional thermal-flow problem. The choice derives from a complete and detailed survey of the numerical techniques used in the context of combined convection. The predictive work relates specifically to a new experimental study, which has the object of obtaining fresh data for combined convection in horizontal duct flow. A 3 m long, 16 mm I.D. copper pipe is used, with uniform peripheral electrical heating. Wall temperature measurements are taken at twelve axial positions. The experiment covers the range of stable mixed convection and strictly laminar flow conditions, with the Reynolds number ranging from 500 to 1000, and the modified Rayleigh number, Raq, from 1x10⁵ to 5x10⁶. The scope of the experiment is to provide data for comparison with numerical predictions. These, in turn, are designed to model the experimental conditions very accurately, including, in particular, the effects of peripheral and axial wall conduction. The study is complemented with various analyses intended to understanding properly both pure forced and natural convection modes. These are investigated separately in the first part of the work. Overall, this work provides fresh experimental and predictive evidence on various features relevant to the onset and the development of buoyancy induced secondary flows in round ducts under heating conditions. More specifically, the effects, of conduction in the duct wall are highlighted, and demonstrated to have a definite influence on wall temperature, and Nusselt number distributions, even in the case of long, thin-walled ducts

Aeronautical Engineering, A Continuing Bibliography With Indexes

This bibliography lists 693 reports, articles and other documents introduced into the NASA scientific and technical information system in September 1984

HPCCP/CAS Workshop Proceedings 1998

This publication is a collection of extended abstracts of presentations given at the HPCCP/CAS (High Performance Computing and Communications Program/Computational Aerosciences Project) Workshop held on August 24-26, 1998, at NASA Ames Research Center, Moffett Field, California. The objective of the Workshop was to bring together the aerospace high performance computing community, consisting of airframe and propulsion companies, independent software vendors, university researchers, and government scientists and engineers. The Workshop was sponsored by the HPCCP Office at NASA Ames Research Center. The Workshop consisted of over 40 presentations, including an overview of NASA's High Performance Computing and Communications Program and the Computational Aerosciences Project; ten sessions of papers representative of the high performance computing research conducted within the Program by the aerospace industry, academia, NASA, and other government laboratories; two panel sessions; and a special presentation by Mr. James Bailey