Unsteady flow computations around moving airfoils by overset unstructured grid method

The study presents a computational method for unsteady flows around moving multiple objects using overset unstructured grid method. To capture unsteady flow characteristics, the dual time-stepping method coupled with the LU-SGS implicit scheme is applied to the time integration. Two or more moving boundaries can be treated easily by the overset unstructured grid method. In this study, Chimera-hole cutting is performed automatically along with movement of the objects. For validation, the numerical results for inviscid and Viscous flow and the experimental results are compared using the lift coefficient and pressure coefficient distribution of a pitching NACA0012 airfoil. Both results show the tendency of the experimental data, confirming the validity of this method. Furthermore, the flow around several objects is examined and the generality of the overset grid method is verified. Two demonstrations of the unsteady computation flapping airfoil, and a section of a vertical-axis wind turbine with three rotors are also described.