determining stagnation line on a surface
 

I am modelling flow through the intake of a turbine engine. At some point on the engine intake wall, the flow splits and either goes into the engine or around the engine. As this is a cylindrical intake, there is some, generally circular, line on the intake wall exactly where the split occurs. I would call this line a stagnation line, as the flow would be brought to rest here all the way around the intake wall. I want to, somehow, create a line-surface in FLUENT for use in other postprocessing endeavors.

I've tried looking for zero wall shear stress. No luck. I've tried to look at minimum dynamic pressure. No luck again. The problem is, as I go around the circumference of the intake wall, the local minimum changes. So I cannot adjust my scale to one value for the minimum and see my line.

Any helpful suggestions?