Modelling of turbulent flow in gas-turbine blading: achievements and prospects

Some of the problems associated with applying currently available viscous flow calculation schemes to turbulent flow in gas-turbine blading and passages are reviewed. These flows pose severe difficulties in both numerics and turbulence modelling, although the main emphasis here is on the latter aspect. Since complex strain fields and strong body forces are an intrinsic part of flow in turbomachinery, it is preferable that the turbulence modelling of these flows be based on an approximation of the Reynolds stress transport equations themselves. Some current views on closure approximations for these equations are discussed. Applications considered include the effects of free stream turbulence and streamline curvature, the mixing of blade wakes, and the three-dimensional flows that arise in a 90° bend and in the corner boundary layer near a blade root