This paper provides some of the last results obtained by the CFD group of the Department of Mechanics, Mathematics and Management at the Polytechnic of Bari in the development of Immersed Boundary (IB) methods. In particular, two main issues will be addressed about developing and testing two IB methods, using an advanced data structure, a very efficient solver, and an MPI parallelization for solving: i) the three-dimensional compressible Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations, coupled with the heat conduction equation, as a predictive tool for conjugate heat transfer problems, such as the refrigeration of the first stage blades of a gas turbine by film cooling; ii) fluid-body interaction problems in incompressible laminar flows. Both methods allow one to solve complex three-dimensional problems within reasonable computer time. Results obtained by the former method are presented for a two-dimensional unsteady conjugate heat transfer problem, already considered using the original scalar 2D code, whereas several problems involving rigid as well as deforming bodies within a fluid are solved using the latter method. All of these results demonstrate the merits of both solvers. Ongoing work concerns: applications of the compressible URANS solver to three-dimensional conjugate heat transfer problems characterized by subsonic, transonic and supersonic external flow; and extension of the incompressible flow solver to the URANS and large eddy simulations so as to tackle fluid-body interaction problems at higher values of the Reynolds number