Numerical Investigation of the Flow Field around a Rotor above an Obstacle Using a Panel-LBM Hybrid Method

Abstract

The aerodynamic interaction between a rotor and an obstacle results in a complex flow field that can negatively impact rotor performance and handling qualities. To address this issue, a panel–lattice Boltzmann hybrid method is proposed, which tightly couples the rotor panel method and the lattice Boltzmann method (LBM) through a two-way coupling model. In this proposed approach, the rotor panel method is used to predict the distribution of rotor airloads. These airloads are then added into the LBM as an extracted force term. The LBM is used to compute the unsteady flow field, which is taken into consideration in the rotor panel method. The hybrid method was applied to a scenario of a rotor approaching an obstacle and the results were compared with experimental data. The findings indicate that the inflow velocities of the rotor hovering above the obstacle, with and without headwind, are consistent with experimental observations. Additionally, the flow field is predicted more accurately than when using the unsteady panel free-wake method, the vortex particle method, and computational fluid dynamics (CFD). In the case without headwind, the rotor flow is reflected, pushed up by the obstacle, and re-injected into the rotor, resulting in obvious recirculation. Shear flow and separated flow attached to the obstacle, caused by the presence of headwind, are important factors affecting rotor flow. Furthermore, headwind causes the sloped flow stream to be pushed backward, and a clockwise rotating vortex is generated at different positions of the rotor, which is different from the case without headwind.