A detailed analysis of the flow around a rotating rotor hub of a four bladed helicopter configuration was conducted. Two wind tunnel models were used for the experimental part of the work, a fuselage - rotor hub configuration and an isolated rotor hub. Force, pressure and velocity field measurements were used to investigate the rotor hub - fuselage interaction. Additionally to the experiments, a numerical simulation for the isolated rotor hub was made and compared with velocity field and force measurements. The comparison shows a good agreement of the velocity field and also the predicted drag of the simulation. Based on the combination of experimental and numerical results a detailed view on the occurring flow phenomena could be made. The drag breakdown of the rotor hub shows that most of the drag is produced by the blade attachments. A vortex pair in the wake of the rotor hub was detected. These vortices can be related with spots of higher turbulence in the wake, which can cause fluid structure interaction like the tail shake phenomenon at the fin of the tailboom. Based on the numerical simulation the origin of the vortex structures were detected.
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