Modelling The Transitional Boundary Layer

Modelling the Transitional Boundary Layer

Recent developments in the modelling of the transition zone in the boundary layer are reviewed (the zone being defined as extending from the station where intermittency begins to depart from zero to that where it is nearly unity). The value of using a new non-dimensional spot formation rate parameter, and the importance of allowing for so-called subtransitions within the transition zone, are both stressed. Models do reasonably well in constant pressure 2-dimensional flows, but in the presence of strong pressure gradients further improvements are needed. The linear combination approach works surprisingly well in most cases, but would not be so successful in situations where a purely laminar boundary layer would separate but a transitional one would not. Intermittency-weighted eddy viscosity methods do not predict peak surface parameters well without the introduction of an overshooting transition function whose connection with the spot theory of transition is obscure. Suggestions are made for further work that now appears necessary for developing improved models of the transition zone. Narasimha, R. Unspecified Center NAS1-18605...

Elements of Transitional Boundary-Layer Flowlements

Second Enhanced Edition Suitable for advanced-level courses or an independent study in fluid mechanics, this text by an expert in the field provides the basic aspects of laminar-to-turbulent flow transition in boundary layers. Logically organized into three major parts, the book covers pre- and post-transitional flow, transitional flow, and several advanced topics in periodically disturbed transitional flow. Some of the subjects covered within the book include high-frequency unsteady laminar flow, turbulent flow, natural transition, bypass transition, turbulent spot theory, turbulent spot kinematics and production, correlations for the onset and rate of transition, global and conditional averaging, transitional flow models, wakeinduced transition, multimode transition, and separated-flow transition. Containing some 202 figures (all drawn by the author), 28 tables, 12 appendices, a supplement on tensors, and an extensive bibliography, the 415 page book provides a wealth of data and information about the subject.

Modelling the Transitional Boundary Layer