Numerical Simulation of Oscillating Wings Using a Moving Grid Technique

Abstract

Steady flow in nature is a simplified version of the more realistic unsteady flow. A stationary airfoil, by itself, may have to contend with the unsteadiness of the turbulent flow separation, which results in time dependent vortices structures. With increasing emphasis on emerging UAV technologies, there is a renewed interest in being able to model the lowReynolds-number viscous effects in the incompressible flow regimes as well as to account for moving components in small aircraft. The current work makes use of the moving grid technique to investigate the unsteady incompressible flows past three-dimensional (3-D) wings with oscillations in pitch. The modified SIMPLE method is used to solve the unsteady 3-D Navier-Stokes equations with a RNG k-ε turbulence model. As an initial step of LES research, the Smagorinsky sub-grid-scale (SGS) model is implemented and some preliminary LES calculations are performed. In order to preserve the grid conservative property, a space conservation law is implemented in the moving grid calculation. The cell-centered finite volume method is used in the spatial discretisation. A fully implicit temporal differencing scheme permits an unconditional stability in time marching. With the predictive capability demonstrated in the validation using a wing based on the NACA 0012 airfoil, the current code is then applied to simulate the flows past oscillating wings based on the ONERA 209 and 213 airfoil profiles. The results in the current investigation are qualitatively compared with the data reported by other authors.