This article provides a summarizing account of the results obtained in the current collaborative work of four research institutes concerning near-wall flow in turbomachinery. Specific questions regarding the influences of boundary layer development on blades and endwalls as well as loss mechanisms due to secondary flow are investigated. These address skewness, periodical distortion, wake interaction and heat transfer, among others. Several test rigs with modifiable configurations are used for the experimental investigations including an axial low speed compressor, an axial high-speed wind tunnel, and an axial low-speed turbine. Approved stationary and time resolving measurements techniques are applied in combination with custom hot-film sensor-arrays. The experiments are complemented by URANS simulations, and one group focusses on turbulence-resolving simulations to elucidate the specific impact of rotation. Juxtaposing and interlacing their results the four groups provide a broad picture of the underlying phenomena, ranging from compressors to turbines, from isothermal to non-adiabatic, and from incompressible to compressible flows.

This paper transfers findings from linear cascade studies to the annular system. Experimental studies have been conducted on the newly designed 1.5 stage full annular rotating axial turbine rig at Chair of Thermal Turbomachinery, Ruhr-Universität Bochum. Therefore, an existing large scale low speed test rig was retrofitted with newly designed T106^RUB low pressure turbine (LPT) blading, state-of-the-art measurement technologies and multi-dimensional traversing devices to allow for highly resolved measurements of unsteady wake stator flow interaction in both space and time. Incoming wakes are generated by a variable-speed driven rotor disk equipped with cylindrical bars. The measuring concept for an in-depth analysis of unsteady flow phenomena is presented and results from highly resolved time-averaged and time-resolved flow field traverses are discussed and compared. In detail the time-dependent interaction of periodically passing bar wakes with the boundary layers and secondary flow structures of the T106^RUB stator row is investigated. Special emphasis is put on time-varying dilatation and location of individual components of the vortex system and on potential flow separation along the blade suction surface. It is evaluated how these factors can contribute to a time-dependent homogenization of stator exit flow and a consequent loss reduction in the present configuration.

In this work we present the results of the numerical investigations concerning interaction effects between periodically incoming wakes, secondary flow development and boundary layer flow inside a low pressure turbine (LPT) equipped with modified T106-profile blades. The numerical predictions obtained using 3D Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations are compared against stationary and time resolved experimental results conducted in the same configuration and discussed in part 1 of this 2-part work. For the investigation of the spatial topologies and the dynamics of the coherent flow structures under periodical wake impact, a frequency domain analysis as well as proper orthogonal decomposition (POD) of the unsteady data is proposed and discussed.