Investigation of a turbulent spot using multi-plane stereo particle image velocimetry

The multi-plane stereo particle image velocimetry (MSPIV) technique has been applied to an investigation of the spatial and temporal development of turbulent spots in a laminar flat-plate boundary-layer flow with a slight adverse pressure gradient. On the basis of a large number of evaluated instantaneous 3- and 2-component velocity-vector fields, measured synchronously and separated in space, or with different time separations in one or two planes, the technique enabled the determination of several statistical quantities of fluid mechanical significance. The shape and role of coherent substructures for the growth and turbulent mixing of the spot were the focus of this investigation.