The instantaneous determination of a transonic stator wake and turbulent burst in a low-speed boundary layer in air using particle image velocimetry (PIV)

PIV (particle image velocimetry) is a technique which can be used to provide an instantaneous description of a velocity field. Two applications of PIV are presented, the first being the determination of a turbulent burst within a low speed boundary layer in air, the second the measurement of a transonic stator wake adjacent to a spinning turbine. The picture of the boundary layer has first been evaluated using a correlation method of processing which effectively provides a local average velocity measurement. Once the local average has been calculated the picture was re-evaluated using a particle tracking algorithm. in this case every particle image pair was identified to provide a complete velocity map of the now without the disadvantage of spatial averaging inherent to the correlation approach. The steady component has been removed from the flow image leaving clear evidence of a turbulent burst. The stator measurements have been processed using the same particle tracking algorithm and have been plotted over an irregular triangular mesh which represents an instantaneous, nonaveraged representation of the flow