The advent of fast scalar computers in the 1970s led to explosive activity in computational physics of fluid mechanics and heat transfer. The current decade of parallel (such as vector) computers and supercomputers promises to be even more exciting. These computers will permit, through their enormous speed and size, the solution of numerous problems that have previously been considered intractable. These rapid developments have led to an ever-growing body of literature devoted to numerical fluid mechanics and heat transfer. However, because of the many and varied applications of fluid mechanics and heat transfer in science and technology, the literature is spread throughout numerous journals and conference proceedings covering diverse themes and subject matter. Clearly, there exists a compelling need to devote a series exclusively to expository, comprehensive, state-of-the-art reviews by specialists in various fields of applications. With this as the objective, coverage in the series Annual Review of Numerical Fluid Mechanics and Heat Transfer will encompass a wide spectrum of engineering fluid mechanics and heat transfer, including high-speed gas dynamics, turbulence, multiphase flows, rheology, meteorology, tribology, oceanography, hydrology, combustion, chemical and metallurgical processes, energy conversion and power, pollution, biomedicine, noise and acoustics, nuclear and fusion engineering, low-gravity space manufacturing processes, and arctic and cryogenic heat transfer. This series is intended to serve not only researchers, scholars, and graduate students in academic institutions but also practicing engineers. Review articles are written with a view to reaching nonspecialists. The articles begin with well-understood basic principles underlying the physics and computational aspects of applications and then proceed to the present state of knowledge. The series will publish papers that deal with the development of computational methods (finite difference, finite element, perturbation, boundary element integral, and other innovative techniques), with applications to physical problems, with numerical solutions that aid the development of physical models, or with physical modeling that facilitates the numerical solutions. Papers are published by invitation or submission by specialists in their areas of expertise and are evaluated through a critical peer review process to assure uniform standards and high quality. The present volume contains eight papers written by invitation by leading experts in the field. Three deal with physical modeling and five with numerical methods. The launching of a new series always requires considerable preparation and planning. Without the cooperation and very close association of Ms. Florence Padgett, Senior Acquisitions Editor of Hemisphere Publishing Corporation, the series would not have materialized. The guiding spirit behind the series is Mr. William Begell, President of Hemisphere, whose support and encouragement made this undertaking possible. The status and prestige provided to the series by the acceptance of Professor Brian Spalding to serve as Chairman of the Editorial Advisory Board represents an immeasurable contribution to the successful launching of the series. I am deeply grateful for all the suggestions, cooperation, and encouragement I have received from Professor Spalding. I would be severely remiss if I did not also thank Mrs. Marsha Mehaffey for her excellent secretarial skills and cooperation. I greatly appreciate the assistance and cooperation she afforded to my wife Carolyn, who, during my protracted illness, literally took over the majority of my duties as editor. I am eternally grateful to her. The assistance and cooperation provided by my division−Reactor Analysis and Safety−under the directorship of Dr. Robert Avery and subsequently Mr. John Marchaterre and Dr. Dean Pedersen, Program Manager, are also greatly appreciated. Last, but not least, I express my sincere thanks to the members of the Editorial Advisory Board for their cooperation and support.