The aerodynamic effect of the secondary flow and its contribution to the additional losses is well known. Secondary flow does not only increase additional total pressure losses, it also interacts with the boundary layer on the suction surface along the blade. Due to the existence of the three-dimensional secondary flow the suppression or distortion of a laminar boundary layer on the suction surface of the blade is likely to occur. A generic sub sonic linear turbine cascade was part of the current investigation. This has been chosen because it can be used to study bypass transition at fairly low Reynolds numbers by extensive pressure measurement techniques. The high speed cascade wind tunnel has been used to achieve the needed operating conditions in order to avoid flow separation on the suction side. Still at these Reynolds numbers, a significant inlet boundary layer will be produced and a well-developed secondary flow can be expected. Experiments were then conducted to better understand the significance of the secondary flow, to assess its influence on the boundary layer on the blade surface and its contribution to total pressure losses for the turbine blade is investigated. These experiments included wake field traverses at different chord lengths downstream of the trailing edge and oil flow visualization of the suction surface. Additional experiments have been carried out, to characterize transition phenomena and their interaction with the particular secondary flow, such as boundary layer traverses and also pressure measurements on the surface at different radial positions. For reference, pressure measurements at midspan position along the blade surface and boundary layers at different axial positions have been carried out. A development of the boundary layer, from laminar to turbulent, in span wise and radial direction is shown.    «

The aerodynamic effect of the secondary flow and its contribution to the additional losses is well known. Secondary flow does not only increase additional total pressure losses, it also interacts with the boundary layer on the suction surface along the blade. Due to the existence of the three-dimensional secondary flow the suppression or distortion of a laminar boundary layer on the suction surface of the blade is likely to occur. A generic sub sonic linear turbine cascade was part of th...    »