Underwater shock‐free surface–structure interaction

Abstract

SUMMARYA recently developed numerical method has been employed to evaluate the in uence of free surface on shock loading in a cylindrical underwater explosion carried out near to both a free surface and a cylindrical rigid structure. In the usual simulation of underwater shock-structure interaction, the shock loading tends to accelerate=move the (rigid) structure only in the resultant force direction. The presence of a free surface and explosion bubble suggests the existence of a reverse loading and provides an additional torque (rotational moment) on the loaded structure. The numerical results also demonstrate the possible existence of a cavitation zone=region in the immediate vicinity of the free surface due to the near-surface underwater explosion.

Isentropic one-fluid modelling of unsteady cavitating flow

“…One example is the flow generated by an underwater explosion near a structure and a free surface [19], where (bulk) cavitation just below the free surface and (hull) cavitation nearby the structure surface are usually created and collapse very violently. The dominant difficulties for simulating such kinds of cavitating flows are dynamical phase creation, dynamical interface creation, and treatment of the cavitating flow and cavitation collapse.…”

The simulation of cavitating flows induced by underwater shock and free surface interaction

“…The works listed in [1,26] focused on the cavitation generated from the shock-structure interaction where the cavitation region or extent is relatively small compared to the (possible) cavitation region generated from the shock and free surface interaction. On the recent works relating to underwater shock and free surface interaction, Liu et al [13,15] studied in-depth the wave propagation and refraction at the free surface. The possible presence of induced cavitation near the free surface, however, is not modeled and analyzed although Liu et al [15] have explicitly mentioned the likely effect of the free surface and cavitation on the submerged structure.…”

“…On the recent works relating to underwater shock and free surface interaction, Liu et al [13,15] studied in-depth the wave propagation and refraction at the free surface. The possible presence of induced cavitation near the free surface, however, is not modeled and analyzed although Liu et al [15] have explicitly mentioned the likely effect of the free surface and cavitation on the submerged structure. On the other hand, Kedrinskii [10] has discussed that the negative pressure may be predicted at the region just below the free surface (i.e.…”

A high-resolution mapped grid algorithm for compressible multiphase flow problems

“…Our next example for problems in more general geometries is an underwater explosion flow with circular obstacles, see [24] for a similar computation but with a square obstacle. In this test, the physical domain is a rectangular region of size ([À2, 2]  [À1.5, 1]) m 2 in which inside the domain there are two circular obstacles, denoted by D 1 and D 2 , with the centers ð x D 1 1 ; x D 1 2 Þ ¼ ðÀ0:6; À0:8Þ m and ð x D 2 1 ; x D 2 2 Þ ¼ ð0:6; À0:4Þ m, respectively, and of the same radius r D 1 ¼ r D 2 ¼ 0:2 m. The initial condition we consider is composed of a horizontal air-water interface at x 2 = 0 and a circular gas bubble in water that lies below the interface.…”

“…; M f . Then based on the fact that all the material quantities c i ; B i , and q 0,i will be kept as a constant in each phase of the domain at all time, from (22) or (24), it is easy to find the transport equation for the volume-fraction a i as…”