An unsteady numerical simulation for a high-loaded transonic fan was performed.And

BVF(boundary vorticity flux) diagnosis method was employed to study the rotor/stator interaction under unsteady conditions.The results show BVF could capture clearly the influence of rotor/stator interaction upon the flow field

indicating that rotor wake interference was the primary cause of unsteady characteristic in downstream flow.According to the detailed BVF distribution by combining the static pressure and entropy analysis methods

the problems in the rotor tip and stator root for rotor/stator matching were found out.So

BVF diagnosis is a new method that could help reflect the state of rotor/stator matching

and also find out the root of negative factors to the flow field and the solution for flow field improvement.