Investigation of 3D Flow Structures in a Linear Blade Cascade with Stereo Particle Image Velocimetry

Abstract

In most experiments and numerical calculations of flow through blade cascades, there is a tendency to reduce the problem to 2D. This is understandable due to the design of the experimental rigs and measurement methods, as well as the very long computation times of 3D numerical flow simulations. In reality, however, 3D flow structures such as streamwise vortices begin to appear in wakes behind profiles even for 2D geometry even at low Reynolds nubers. They can create force variations acting along the blade span, which can be represented on average by the 2D measurement and simulation and give a correct result, e.g. for the total lift and drag of the profile. However, when investigating dynamic aeroelastic instabilities such as flutter, local variations in aerodynamic forces can greatly influence the overall behaviour, e.g. by inducing stall flutter.