The flow field between a rotating and a stationary disk at high-positioned air inflow condition was investigated by Particle Image Velocimetry(PIV) technology.The experiments indicate that PIV technology could be used on the flow measurement of the rotating cavity.The flow in the most area became turbulence in the range of experiments.Batchelor-type flow was observed in the experiments.Separate boundary layers were formed on the rotor and stator.Between the boundary layers there was an inviscid core rotating in the same direction as the rotor at a lower speed.The experimental data of the relative rotational speed β in the core was lower than 0.43

the value in the closure system with large clearance.β did not show obvious changes with the change of flow rate coefficient or rotational Reynolds number

but the axial clearance between the rotor and stator affected β much obviously.