Interpreting CFD Visualizations
 

Hi, I am doing a project on the aerodynamics of bicycle race wheels. I am having trouble interpreting the flow visualizations around various race wheels. On page 23 and 24 of this document:http://www.acusim.com/papers/AIAA10_...431_MNGodo.pdf, it discusses zones of recirculation. I'm confused as to what zones of recirculation are, and if they are a 'good' or a 'bad' thing when trying to create an aerodynamic object.

Also, on page 24, there are flow visualizations for increasing rim-depth wheels. The deeper the rim depth, the more aerodynamic the wheel is. I want to describe how the flow visualizations for the various wheels show that they are more aerodynamic, but I don't know what indicators to look for.

Thanks in advance! Sara