Reduction of water entry impact force by a gas jet

作者：Jiang, Yunhua^*; Zou, Zhihui; Yang, Lele; Shen, Le; Liu, Yun; Zhang, Mengqi^*

来源：Physical Review Fluids, 2023, 8(6): 064005.

DOI：10.1103/PhysRevFluids.8.064005

• LIQUID SURFACE
• SLAMMING LOADS
• INITIAL-STAGE
• SPHERE
• INSTABILITY
• PENETRATION
• DYNAMICS
• MODEL

The violent hydrodynamic impact in water entry is a well-known phenomenon. Various methods have been applied to mitigate this "destructive force." We experimentally investigate a method for reducing the impact force of water entry, which uses a gas jet to impinge on the liquid surface prior to the object entry. The blowing of the gas jet flow forms a cavity in the water and the penetration of the object into the water is thus less impactful. This method also significantly alters the flow field structure in the impact region, resulting in a reduction of the added fluid mass, the counterthrust of the gas jet that can further attenuate the impact intensity. We reported four cavity regimes and six impact modes formed in the gas-liquid interaction for a range of the modified Froude numbers. In particular, the regime of jet cavity only has a jet-assisted water entry with almost no impact event, and the maximum reduction in impact acceleration can reach nearly 90% with the reduction in entry velocity being about 10% relative to the impact without gas jet. The impact force reduction mechanism is considered to be a combination of the reduction of the added fluid mass and the presence of gas jet momentum.

• 单位
  1; 中山大学; 上海交通大学