This image shows longitudinal vortices developed from passing wakes near the pressure surface of a turbine cascade. These newly discovered vortices are neither produced, nor sustained by the usual Gortler instability; rather, they are a consequence of severely straining the passing wakes. The visualization was derived from a numerical simulation, and used the vortex identification method of Jeong and Hussain. For further details, see Wu and Durbin (2001a,b).

References:

[1] J. Jeong and F. Hussain, "On the identification of a vortex", Journal of Fluid Mechanics, 285, 69-94, 1995.

[2] X. Wu and P. A. Durbin, "Wake distortion in a turbine passage",
Physics of Fluids, 13, pp. S9, 2001a, special edition featuring winning entries from the 18th Annual Picture Gallery of Fluid Motion exhibit.

[3] X. Wu and P. A. Durbin, "Evidence of longitudinal vortices evolved
from distorted wakes in a turbine passage", Journal of Fluid Mechanics 446, pp. 199-228, 2001b.

*See http://www-fpc.stanford.edu/Durbin/wu/.