Renewable energy production units, such as wind turbines, involve geometrically complex bodies (rigid or flexible) in contact with fluids. State of the art computations in wind energy are based on Large-Eddy simulations (LES) coupled with actuator line methods (ALM). This framework requires the geometry and the airfoil aerodynamic coefficients of the turbine’s blades to model the influence of the structure to the fluid. Although valid in a wide range of configurations, its specific assumptions render it irrelevant in some cases like with yaw misalignment. Therefore we propose the use of another numerical tool, namely the immersed boundary methods (IBM). These methods allow to avoid body-fitted meshes by representing the geometry of the immersed body in the mesh via ‘solid nodes’ with imposed velocity. Due to the lack of body conforming nodes, the computation of forces acting on the body is not trivial. This work aims to compare two force computation approaches for IB methods. The first one is based on the pressure integral over a locally reconstructed fictive body surface (local approach). The second one is based on the formulation of Noca et al. [1], where, thanks to the velocity and vorticity fields in a finite region enclosing the body, we are able to compute the instantaneous forces acting on it (global approach). These methods will be evaluated for two types of penalization IB methods for unstructured grids: i) a sharp-interface IBM where the penalization terms are located in a narrow band around the solid/gas interface, ii) a smoothed-interface IBM where the added forces are regularized in the vicinity of the interface. [2]. Both methods will be examined and validated against resolved body-fitted simulations of well-documented academic cases with stationary and moving bodies. Mesh-dependancy of the methods will also be investigated. The simulations will be performed by the low Mach-number massively-parallel finite-volume unstructured LES flow solver YALES2 [3, 4].