So-called Immersed Boundary Methods (IBM) are gaining an ever increasing popularity in
the CFD community. In these methods, an obstacle is represented on a non-conforming
grid, often by adding extra momentum sources in the momentum equations. Ease of
application and economy in use are reasons for using these methods.

This colloquium is a follow-up of the very successful colloquium 507 on Immersed Boundaries in 2009.
Many open problems were observed at this colloquium, and many exciting developments have taken place since, for instance with respect to the application of IBM with higher order numerical methods, the application to ever larger scale problems, problems which require a very careful treatment of the boundaries, such as acoustic problems, and the so-called grid-locking problem which is experienced by solid bodies moving moving over a fixed grid.
This colloquium aims to address the new developments and applications since the last colloquium.