Assessment of Immerded Boundary Method (IBM) A validation tool is used to investigate the numerical errors associated with IBM. The goal is to suggest new strategies to increase the accuracy of IBM in the context of finite difference and finite volume schemes used on a structured mesh. The benefit offered by the cut-cell technique [1] which use a second-order Marker and Cell method [2] is shown. The assessment procedure is based on a reference solution for the classical problem of the flow over a circular cylinder at Reynolds number Re = 40. [1] F. Bouchon, T. Dubois, N. James, A second order cut-cell method for the numerical simulation of 2D flows past obstacles, Computers and Fluids (2012) [2] F. Harlow, J.E. Welch, "Numerical Calculation of Time-dependent Viscous Incompressible Flow of Fluid with Free Surface". Phys. Fluids (1965)