The vertical water-entry experiments of hydrophilic and super-hydrophobic hot spheres within the temperature range of 28°C-350°C were conducted and recorded with a high-speed video camera. The effects of surface wettability,water temperature,sphere body temperature and water-entry velocity on characteristics of cavitation morphology in water were analyzed. The results showed that in high temperature water,bubble disturbance in nucleate boiling stage can cause a hydrophilic sphere to form a complete rough cavitation at a lower water-entry rate,and a super-hydrophobic sphere affected by coupling of nucleate boiling and hydrophobicity can produce a smooth cavitation with folds,a super-hydrophobic sphere can enter a film boiling stage under a lower sphere temperature to form a smooth cavitation in water,the cavitation wall surface is not easy to be disturbed with increase in water-entry velocity compared with a hydrophilic sphere; in low temperature water,stable vapor film is not easy to keep when sphere temperature is higher,a super-hydrophobic sphere can produce a more complete cavitation than a hydrophilic one can.
Key words
hot sphere /
water-entry cavity /
superhydrophobicity /
boiling
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