[robo]

Hi all,
I'm working on an incompressible axisymmetric boundary layer code for some bodies of revolution. For some of my results in turbulent flow, I'm getting negative values for the displacement and momentum thicknesses. The rest of the flow field looks correct, and the code appears to be functioning properly in other cases and validated well for flat plate flow and laminar axisymmetric flows. I'm not sure if these negative values are physical, and if they are, how to interpret them. I've done a bit of googling and it seems like they might be indicative of strong streamline convergence leading to an excess of mass and momentum flow in some region or somesuch but I'm not 100% on that. Can these values be negative? What is the best way to interpret that result physically if they can? Finally, are there any good references on this? I'm using Schlichting's and White's books, but haven't been able to find any references in there to negative values for these parameters, at least not so far.
Thanks!