Arbitrary Lagrangian-Eulerian Method for Transient Fluid-Structure Interactions

An arbitrary Lagrangian-Eulerian method used to describe the fluid motion together with a Lagrangian method used to analyze the structural response for solving fluid-structure interaction problems are presented. A two-dimensional computer code, ALICE, based on these methods is developed for analyzing transient phenomena generated in a reactor-containment system during a hypothetical core disruptive accident. The finite difference equations that are used to approximate the governing equations for the motion of the fluid can be solved with either an explicit or implicit scheme; the finite element equations that are used to approximate the governing equations for the structure can be performed only in the explicit scheme. Thus, the ALICE code can perform two types of coupling calculations for the fluid and structure (explicit-explicit and implicit-explicit). The arbitrary Lagrangian-Eulerian method used to describe the fluid motion allows the vertices of the fluid computing mesh to

1. move with the fluid
2. remain stationary
3. move in a prescribed way, for example, to coincide with the movement of the adjacent structure or to minimize excessive mesh distortion.

Due to the flexibility of the arbitrary Lagrangian-Eulerian method, reactor safety problems can be more realistically simulated and the computational procedure is significantly simplified.