High Quality Content by WIKIPEDIA articles! The immersed boundary method is an approach – in computational fluid dynamics – to model and simulate mechanical systems in which elastic structures (or membranes) interact with fluid flows. Treating the coupling (the elastic boundary changes the flow of the fluid and the fluid moves the elastic boundary simultaneously) of the structure deformations and the fluid flow poses a number of challenging problems for numerical simulations. In the immersed boundary method approach the fluid is represented in an Eulerian coordinate frame and the structures in a Lagrangian coordinate frame. For Newtonian fluids governed by the Navier–Stokes equations the immersed boundary method fluid equations are