Computing mode shapes of fluid-structure systems using subspace iteration methods

The pseudo symmetric subspace iteration method is an efficient technique for computing mode shapes of coupled fluid-structure systems. This approach handles the related unsymmetric eigenvalue problem in a manner that is similar to solving a symmetric eigen-problem. Moreover, it employs a symmetric active column solver in the core of its routines, which makes it very efficient. In the present study, an enhanced and accelerated version of this technique is described, which is ideal especially for extracting a large number of eigen-triplets (e.g. greater than or equal to 40). The accelerated approach is implemented in a special purpose finite element program, and several practical numerical examples are presented herein. Based on these experiences, it is concluded that the accelerated pseudo symmetric subspace iteration method is an extremely efficient approach. This is estimated to be about 3 to 11 times more efficient than its original basic counterpart version.