The Finite Element Immersed Boundary Method with Distributed Lagrange   multiplier
  We introduce a new formulation for the finite element immersed boundary method which makes use of a distributed Lagrange multiplier. We prove that a full discretization of our model, based on a semi-implicit time advancing scheme, is unconditionally stable with respect to the time step size. 
Daniele Boffi, Nicola Cavallini, Lucia Gastaldi
math.NA