Learning Forum

[rhiannon.elliott]

I am using Fluent to investigate the centroid location and radius of wing tip vortices that are generated by the flow over a wing. I have used the SpalartAllmaras viscosity model, and the Q-criterion to identify the location of the tip vortex.
In the Graphics section in Results, I created a plane that bisected the vortex, 3 chord lengths away from the trailing edge. Within this plane, I want to display the either the vorticity magnitude, or lamda-2 criterion to identify the vortex centroid. When i did this, I was surprised to see that the velocity magnitude (and lamda 2 crit) across the whole fluid domain cross section was constant and there was no region where the vortex core was really visible, despite the plane clearly intersecting with the vortex from what I can see based on the q-criterion contour. I have verified that the vortex should be present in this region, when I have produced contours of the vertical velocity component, it is clear there is some elemt of flow in the region where I would anticipate a tip vortex. 
Does anyone have any ideas as to why I am struggling to view a cross section of the vortex core? I am relatively new to Fluent, any pointers would be really appreciated.
All the best!