Three phases fluid-structure interactive simulations of the deepsea ceramic sphere's failure and underwater implosion

Abstract

Ceramic spherical shell may implode under high hydrostatic pressure, which causes enormous damage to the surrounding equipment or the vehicle. A numerical model was developed to simulate the underwater implosion with actual structure failures. With the weak coupling of the fracture with the water/air fluids, the resultant asymmetrical pressure pulse was obtained and in good agreement with the typical experiments. The implosions of the ceramic initiated by a strike and a squeeze or due to a surface defect under hydrostatic pressure of 7 MPa and 114 MPa were investigated. Simulations showed that the released pressure pulse is closely related to the structural failure process. A shift of the implosion core was activated by the asymmetrical fracture and the asymmetrically inflowed stream(s). However, under hydrostatic pressure of 114 MPa, the sphere fracture completes in ∼μs, and inactivates any core movement. The pressure pulse decays exponentially with respect to the radial distance, where the pressure pulse relates to the total energy of the implosion, and the exponent represents the mechanical energy decays with time/distance. The bias pressure pulse may be used as a circumstantial evidence for cause of failure analysis.