PREDICTION OF THE UNSTEADY TURBINE TRAILING EDGE WAKE FLOW CHARACTERISTICS AND COMPARISON WITH EXPERIMENTAL DATA

The trailing edge base pressure is known to play a significant role in the profile losses of turbine blades in particular at transonic outlet Mach numbers. Recent tests have shown that the assumption of an isobaric near wake region is wrong because of the highly unsteady character of the near wake flow which affects directly the trailing edge base pressure. New experimental data show the evolution of the trailing edge base pressure in function of the downstream Mach number from a uniform base pressure at moderate subsonic Mach numbers to an increasingly strong non-uniform distribution up into the transonic range followed by a sudden return to an isobaric base trailing edge pressure. To get more insight into the unsteady flow features, numerical simulations are carried out. A LES approach is validated and employed in this work to analyze three different operating conditions for the profile, representing three configurations of the flow and the trailing edge shock system.