FE-Model Reduction for FE-BE Coupling with Large Fluid-Structure Interfaces

For the finite element method model, reduction techniques exist to represent the dynamic behavior of component substructures. Depending on the type of reduction method, the reduction basis contains constraint or attachment modes, which are computed for all structural degrees of freedom on an interface. The interface can either be defined by adjacent substructures or by coupling interfaces to other physical domains, as it is the case for FE-BE coupled systems. A large interface thus leads to an increased size of the reduced order model and limits standard model reduction techniques to applications with small interfaces. In this work, interface reduction methods are investigated. Here, the size of the reduced order model is decreased by reducing the number of retained interface modes, while marginally increasing the reduction error. A direct reduction method based on strain--energy considerations is presented. Additionally, an iterative reduction scheme is proposed which only adds a basis vector to the reduction basis, if the spanned subspace is sufficiently enlarged. The applicability of the proposed methods is shown for an example structure.