Experimental Study of Disappearance Phenomenon of Unsteady Cavitation on NACA16-012
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In the previous study which was conducted by J. P. Franc et al., it was reported that on NACA16-012 hydrofoil at the angle of attack 4 degree, partial cavitation disappears although cavitation number is decreasing. We call this phenomenon “Disappearance phenomenon” and aim to clarify this mechanism. In the same previous study, it was also reported that at around 4 degree, reattachment of laminar separation leads transition to turbulence boundary layer and cavity cannot occur. In this study, in order to investigate the detail of boundary layer characteristic at the angle of attack where disappearance phenomenon occurred, we measured the pressure distribution on NACA16-012 hydrofoil and made boundary layer visible by oil flow method. In addition, fluid force was measured under the conditions from non-cavitation to super cavitation in order to estimate boundary layer characteristics during disappearance phenomenon. As the result, although the position of reattachment was different, reattachment of laminar separation described in previous study was confirmed and the lift during disappearance phenomenon was the almost same value as that of non-cavitation condition. From this result, it could be inferred that pressure distribution i.e. boundary layer characteristic during disappearance phenomenon was greatly different from that of non-cavitation condition.