Validation of immersed boundary method for the numerical simulation of flapping wing flight

The two classes (continuous and discrete forcing) of the immersed boundary method (IBM) is tested for its suitability as a simulation tool for the analysis of the moving wings of the flapping micro aerial vehicles (FMAVs), for flows at Re = 5000-10,000. Comparison is made between numerical and experimental results of moving airfoils/wings from literature. Results obtained with body-conforming grid flow solvers are included for comparison. We show that both the continuous and discrete forcing IBM solvers give reasonably accurate results in terms of thrust coefficient, although the discrete forcing IBM solver gives smoother results at a lower grid resolution. This indicates that it is indeed able to capture the thin boundary layer better. From visual comparison, flow field patterns as represented by vorticity contours plots of both IBM solvers show good agreement compared to the referenced results. In one test case, there is a disagreement in the lift coefficient with respect to the experimental results, but it applies to all the numerical solvers. This could be due to turbulent effects in the experiment. Finally, the discrete forcing IBM solver is able to simulate a 3D NACA0012 and fruitfly wing undergoing plunging and complex flapping motion respectively at a Re of 10,000. The results compare well, which shows that the IBM solvers are suitable for 3D flapping wing simulations.