Predictive Simulation of Underwater Implosion: Coupling Multi-Material Compressible Fluids With Cracking Structures

Abstract

The implosive collapse of a gas-filled underwater structure can lead to strong pressure pulses and high-speed fragments that form a potential threat to adjacent structures. In this work, a high-fidelity, fluid-structure coupled computational approach is developed to simulate such an event. It allows quantitative prediction of the dynamics of acoustic and shock waves in water and the initiation and propagation of cracks in the structure. This computational approach features an extended finite element method (XFEM) for the highly-nonlinear structural dynamics characterized by large plastic deformation and fracture. It also features a finite volume method with exact two-phase Riemann solvers (FIVER) for the solution of the multi-material flow problem arising from the contact of gas and water after the structure fractures. The Eulerian computational fluid dynamics (CFD) solver and the Lagrangian computational structural dynamics (CSD) solver are coupled by means of an embedded boundary method of second-order accuracy in space. The capabilities and performance of this computational approach are explored and discussed in the full-scale simulations of a laboratory implosion experiment with hydrostatic loading and a three-dimensional manufactured implosion problem with explosion loading.

A Fluid-Structure Coupled Computational Framework for Fluid-Induced Failure and Fracture

“…In [1], a high-fidelity, fluid-structure coupled computational framework is presented for fluid-structure interaction with dynamic, fluid-induced failure and fracture. This computational framework couples a novel finite volume compressible flow solver, FIVER, with a finite element nonlinear structural solver using an embedded boundary method.…”

“…In this work, we generalize the fluid-structure coupled computational framework presented in [1] to allow the use of many finite element based fracture models and methods, including the extended finite element method (XFEM), element deletion (ED), and various cohesive element methods. In particular, a generic interface tracking algorithm is proposed to track the fractured fluid-structure interface with respect to the non body-fitted fluid computational mesh.…”

“…The remainder of this paper is organized as follows. The fluid-structure coupled computational framework presented in [1] is outlined in Section 2. Several popular, finite element based computational fracture models and methods are introduced in Section 3.…”

High-Fidelity Fluid Structure Coupled Simulations for Underwater Propulsion Using Flexible Biomimetic Fins

“…In this work, a high-fidelity, fluid-structure coupled computational framework proposed in [14][15][16][17][18][19][20] is applied to simulate a series of experiments reported in [11]. The objective is twofold: (1) to verify the conclusion of [11] that the inaccurate prediction of thrust magnitude is caused by the 2D panel method; and (2) to demonstrate that the high-fidelity computational framework is capable of accurately predicting the propulsive performance of flexible biomimetic fins, therefore is a powerful tool for designing new fins.…”

“…Key components include: (1) an embedded boundary method based on local, one-dimensional multi-material Riemann solvers [15,17]; (2) robust and efficient algorithms for tracking the fluid-structure interface with respect to the non body-fitted CFD mesh [16,19]; (3) conservative methods for transferring the fluid-load to the finite element structural model [15,19]; (4) a low-Mach preconditioner to efficiently solve low-speed flows near the incompressibility limit using a finite volume compressible flow solver [20]; and (5) high-order and numerically stable fluid-structure coupled timeintegrators [14]. This computational framework has been successfully validated for several engineering applications including underwater implosion [18,22], pipeline explosion [19], and the flight of flapping wing micro aerial vehicles [21].…”