Momentum And Heat Transfer Processes In Recirculating Flows

In 1904 Prandtl published the boundary layer equations and, thereby, firmly stamped the direction of research in fluid mechanics for the next sixty-five years. In Aerodynamics especially (a discipline that is intrinsically concerned with non -recirculating flows) the decomposition of the flow into an inviscid region bounded, near rigid surfaces, by thin viscous zones, proved such a powerful stimulus that it sustained decades of outstandingly successful theoretical and experimental work. Yet, in contrast, only a relatively small proportion of the flows in and around Mechanical Engineering equipment are reasonably well described by the thin shear flow equations. Commonly flow recirculations are present, particularly in heat transfer equipment where a judiciously provoked separation is often found to raise substantially the level of heat transfer coefficient. Because the equations describing such flow phenomena are much more difficult to solve than the boundary layer equations, the contributions made by computational fluid mechanics to the design of Mechanical Engineering equipment has been correspondingly less than in Aeronautics. By 1970 the predominance of thin shear flow studies had begun to weaken and the ensuing decade has seen a steady development of computational procedures for recirculating flow and the essential supporting experimental techniques. Although considerable progress has been made, however, it is clear that we are still nearer the beginning than the end in providing the necessary fundamental research basis in this area. Accordingly, to provide both a forum for airing current work and a springboard for further research, the K-8 Committee of the Heat Transfer Division decided to sponsor a session at the 1980 WAM on Momentum and Heat Transfer in Recirculating Flows. In fact, the response to the announcement of the session was so vigorous that two sessions have been scheduled at which the twelve papers contained in the present volume are to be presented. The papers span many of the current areas of work including: both computational and experimental studies; laminar and turbulent flows; and both steady and unsteady flow phenomena.

Computational fluid flow is not an easy subject. Not only is the mathematical representation of physico-chemical hydrodynamics complex, but the accurate numerical solution of the resulting equations has challenged many numerate scientists and engineers over the past two decades. The modelling of physical phenomena and testing of new numerical schemes has been aided in the last 10 years or so by a number of basic fluid flow programs (MAC, TEACH, 2-E-FIX, GENMIX, etc). However, in 1981 a program (perhaps more precisely, a software product) called PHOENICS was released that was then (and still remains) arguably, the most powerful computational tool in the whole area of endeavour surrounding fluid dynamics. The aim of PHOENICS is to provide a framework for the modelling of complex processes involving fluid flow, heat transfer and chemical reactions. PHOENICS has now been is use for four years by a wide range of users across the world. It was thus perceived as useful to provide a forum for PHOENICS users to share their experiences in trying to address a wide range of problems. So it was that the First International PHOENICS Users Conference was conceived and planned for September 1985. The location, at the Dartford Campus of Thames Polytechnic, in the event, proved to be an ideal site, encouraging substantial interaction between the participants.