Unsteady Lift and Drag Characteristics of Cavitating Clark Y-11.7% Hydrofoil

27th IAHR Symposium on Hydraulic Machinery and Systems

Watanabe, S.^1 ; Yamaoka, W.^2 ; Furukawa, A.^3

Department of Mechanical Engineering, Kyushu University, 744 Motooka, Nishi-ku Fukuoka

819-0395, Japan^1

Graduate School of Engineering, Kyushu University, Fukuoka

819-0395, Japan^2

Oita National College of Technology, 1666 Maki, Oita

870-0152, Japan^3

关键词: Cavitating flow;    Cavitation instability;    Cavity oscillations;    High speed video cameras;    Instantaneous frequency;    Lift coefficient;    Time-averaged;    Unsteady cavitating flows;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/22/5/052009/pdf
DOI  :  10.1088/1755-1315/22/5/052009

来源: IOP

【 摘 要 】

Unsteady cavitating flow and lift/drag characteristics of a two-dimensional Clark Y- 11.7% hydrofoil are experimentally investigated in order to clarify the relation between the lift drop mechanism and the unsteady cavity behavior. Unsteady lift and drag forces are measured by strain gauges attached on the cantilever supporting the hydrofoil, assuming the negligible bending moment. In combination with the above force measurements, the cavitating flow is filmed from both top and side simultaneously using two high speed video cameras. It is clearly observed that, in larger attack angle conditions (4-10 degrees), the time-averaged lift coefficient slightly increases from that in the non-cavitating condition. After the slight increase, the lift gradually decreases then its steep decrease starts to occur. On the other hand, in a small attack angle case (2 degrees), little increase of the lift is observed, and just after that the sudden lift drop occurs. From the instantaneous frequency spectra of the lift, the followings are found; during the slight increase of the lift, the cavity is being a partial cavity in almost steady state, but during the subsequent gradual lift decrease, the partial cavity oscillates with cloud cavity shedding, in other word, the partial cavity oscillation occurs, whose frequency decreases with the growth of the cavity. During the sudden lift drop, the low frequency transitional cavity oscillation occurs, in which the cavity dramatically changes between partial and super cavities. The typical events of cavity behavior during the cavitation instabilities are found to be able to be related with the behavior of instantaneous lift force and pressure.