Experimental Investigation on Cavity Characteristics during Water Entry of Disc-Headed Vehicle Assisted by Gas Jet Flow

Abstract

The trans-medium vehicle is expected to quickly and stably break the free liquid surface. In addition, there are some problems in the trans-medium process, such as the damage to structures and instruments caused by the high impact load, cavity collapse, and ballistic trajectory instability caused by complex unsteady multiphase flow. To address these issues, a forward jet flow was provided at the head of the vehicle to make the vehicle quickly and stably break the free liquid surface. The jet flow penetrated and changed the flow field structure of the free liquid surface to reduce the high impact load. To investigate the multiphase flow characteristics of the cavity during water entry of the disc-headed vehicle assisted by gas jet, the water entry experiment of the disc-headed vehicle assisted by forward jet flow was carried out. The cavity morphology formed during water entry was analyzed, as well as the formation and evolution process of the broken cavity in the case of a gas jet flow impinging on the liquid surface. The effects of different ventilation nozzle diameters and ventilation flow rates on the cavity diameter and jet flow length were discussed. The experimental results indicate that the formation process of the broken cavity includes four stages, namely liquid surface depression, liquid surface oscillation, liquid flow, and cavity formation. The diameter and depth of the broken cavity decrease with the increase in ventilation nozzle diameter and increase with the increase in ventilation flow rate.

Keywords

• trans-medium vehicle
• water entry
• gas jet
• cavity