This work deals with the numerical simulation of interaction of fluid and vapor structures on NACA 2412 hydrofoil during the partial cavitation oscillation. This interaction is supposed to be the most important reason...This work deals with the numerical simulation of interaction of fluid and vapor structures on NACA 2412 hydrofoil during the partial cavitation oscillation. This interaction is supposed to be the most important reason for the cavity shedding when, in a certain range of the cavitation numbers, some “resonance” effect can be reached. The incidence angle is 8? and the Reynolds number is 1.56 × 106. The hydrofoil with the span/chord ratio of 1.25 corresponds to the experiments carried out in the cavitation tunnel. The Detached Eddy Simulation (DES) is used on full 3D geometry of the straight NACA 2412 hydrofoil to capture the strong influence of side-wall effects. Real properties of water including estimated content of undissolved air are con-sidered to affect the compressibility of the mixture and its speed of sound. The link between strong pressure pulses during the cavity cycles and the interaction of fluid and vapor structures is discussed in detail.展开更多
A method is presented to determine significant frequencies of oscillations of cavitation structures from high-speed camera recordings of a flow around a 2-D hydrofoil. The top view of the suction side of an NACA 2412 ...A method is presented to determine significant frequencies of oscillations of cavitation structures from high-speed camera recordings of a flow around a 2-D hydrofoil. The top view of the suction side of an NACA 2412 hydrofoil is studied in a transparent test section of a cavitation tunnel for selected cloud cavitation regimes with strong oscillations induced by the leading-edge cavity shedding. The ability of the method to accurately determine the dominant oscillation frequencies is confirmed by pressure measure- ments. The method can resolve subtle flow characteristics that are not visible to the naked eye. The method can be used for non- invasive experimental studies of oscillations in cavitating flows with adequate visual access when pressure measurements are not available or when such measurements would disturb the flow.展开更多
文摘This work deals with the numerical simulation of interaction of fluid and vapor structures on NACA 2412 hydrofoil during the partial cavitation oscillation. This interaction is supposed to be the most important reason for the cavity shedding when, in a certain range of the cavitation numbers, some “resonance” effect can be reached. The incidence angle is 8? and the Reynolds number is 1.56 × 106. The hydrofoil with the span/chord ratio of 1.25 corresponds to the experiments carried out in the cavitation tunnel. The Detached Eddy Simulation (DES) is used on full 3D geometry of the straight NACA 2412 hydrofoil to capture the strong influence of side-wall effects. Real properties of water including estimated content of undissolved air are con-sidered to affect the compressibility of the mixture and its speed of sound. The link between strong pressure pulses during the cavity cycles and the interaction of fluid and vapor structures is discussed in detail.
基金supported by the Czech Science Foundation(Grant No.13-23550S)the institutional support RVO:61388998 of the Institute of Thermome-chanics of the CAS,v.v.i
文摘A method is presented to determine significant frequencies of oscillations of cavitation structures from high-speed camera recordings of a flow around a 2-D hydrofoil. The top view of the suction side of an NACA 2412 hydrofoil is studied in a transparent test section of a cavitation tunnel for selected cloud cavitation regimes with strong oscillations induced by the leading-edge cavity shedding. The ability of the method to accurately determine the dominant oscillation frequencies is confirmed by pressure measure- ments. The method can resolve subtle flow characteristics that are not visible to the naked eye. The method can be used for non- invasive experimental studies of oscillations in cavitating flows with adequate visual access when pressure measurements are not available or when such measurements would disturb the flow.
