THE ROLE OF LAMINAR TURBULENT TRANSITION IN GAS-TURBINE ENGINES - A DISCUSSION

An extended discussion of Mayle's (1991) critical study of transition phenomena in gas turbine engines is presented. Attention is focused on transition in decelerating flow regions, which are the major sources of loss production for axial turbomachine blades. The following points are examined in detail: (a) the physics of transition and its implica tions for the correlation of various transition phenomena; (b) the rel ative importance of pressure gradient and free-stream turbulence in co ntrolling transition; (c) the influence of pressure gradient on period ic-unsteady transition; (d) the correlation of transition length under conditions of arbitrary pressure gradient and free-stream turbulence level, and (e) transition behavior in laminar separation bubbles. The discussion examines various differences in philosophy concerning the a bove phenomena and makes further suggestions for transition research, which may assist in resolving the issues raised.