Implicit second-order immersed boundary methods with boundary mass

The immersed boundary method is a computational framework for problems involving the interaction of a fluid and immersed elastic structures. Immersed boundary computations typically evaluate the elastic forces explicitly in the configuration of the immersed elastic structure. In many applications this results in a severe restriction on the time step. We present a semi-implicit and a fully implicit second-order accurate immersed boundary method. The methods provide a natural way to handle mass on the immersed elastic structures. We demonstrate their performance for a prototypical fluid-structure interaction problem. The methods are shown to possess superior stability properties that significantly alleviate the typically severe time step restriction of explicit computations.