Experimental investigation on the cavity evolution and dynamics with special emphasis on the development stage of ventilated partial cavitating flow
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2019 Elsevier Ltd Ventilated cavitating flows involve complex features and dynamic characteristics due to the strong interactions between gas and liquid. In the present work, we especially focus on the experimental investigation of the development stage of ventilated partial cavitating flow in a closed-loop water tunnel at Harbin Institute of Technology. In the experiments, a conical axisymmetric test body made of aluminum alloy with a ventilation slot at the nose is placed at the middle of the test section. A high-speed camera is used to capture the flow patterns. Five pressure transducers are installed in the test model to measure the unsteady dynamic pressure. A multi-field synchronous measurement system for cavitating flow is established to address the relationship between cavity evolution and instantaneous pressure. The effect of gas ventilation rate on cavity evolution and dynamic pressure are investigated. Three unsteady flow patterns are observed namely foamy cavity (FC), continuous transparent and foamy cavity (CTFC), continuous transparent and asymmetric cavity (CTAC) respectively. In addition, three distinct cavity regimes are also observed based on the dynamic cavity topology, referred to as gas-filled cavity region (GFCR), re-entrant jet region (REJR) and wake region (WR). The gas entrainment mechanism determined by the re-entrant flow model of a partial ventilated cavity is analyzed. A phenomenon we observed is that the increase in ventilation rate can improve the dynamic stability inside the cavity and can help reduce the load on the test body. Moreover, we find that there are location gaps in space between the pressure peaks and the foamy cavity closure position due to the effect of re-entrant flow.
