Laminar boundary layer separation in BZT fluids

Research project P 14362 Laminar boundary layer separation in BZT fluids Alfred KLUWICK 06.03.2000 In the past fifteen years there has been a rapidly growing interest in flows of gases and vapours consisting of complex molecules thus having high specific heats. Studies concentrating on gasdynamic aspects of such media (now commonly termed BZT fluids), i.e. neglecting the influence of internal friction and heat conduction, have revealed a number of new and even anti intuitive phenomena which are not possible in classical gasdynamics. These include the occurrence of rarefaction shocks and shocks which 9plit into combinations of weaker shocks and wave fans. Furthermore, it is found that the lower critical Mach number associated with transonic flows past airfoils which are of relevance, for example, for the operation of turbomachines can be significantly higher than in the case of perfect gases leading in turn to a substantial reduction of drag. These and other results indicate that the technical use of BZT fluids, in particular as working fluids in turbomachines, may be beneficial. However before a final conclusion can be drawn it will be necessary to investigate thermoviscous effects which have received scant attention so far only in more detail. This is the aim of the present proposal which deals with high Reynolds number flows where these effects are confined to thin boundary layers. In addition, the proposed research focuses on questions related to boundary layer separation which is of considerable practical importance.