A Velocity Potential Based Finite State Modeling Of Ground Effect

Abstract

A recent development in the Velocity Potential Based Finite State Model (VPBFSM) has introduced an approach to study rotors in ground effect. This approach represents the ground as mass source distributions in the flow field and uses optimization to impose the non-penetration flow boundary condition at the ground. However, it has shown high sensitivity to several parameters, such as the initial guess for optimization and the selection of the ground rotor size. To address these challenges, this paper proposes an alternative approach to impose the flow boundary condition at the ground. The new approach formulates an equation to estimate the strengths of ground mass sources in terms of rotor loading. Additionally, systematic processes are developed to impose the boundary condition for studying an isolated rotor in full, inclined, and partial ground effect cases. This approach is applied to the R-50 helicopter rotor using geometric and aerodynamic data from the literature. The results for the full ground effect show good correlation with the Hayden model and exhibit a rotor inflow trend similar to that of the Pressure Potential Based Finite State Model (PPBFSM). Inclined and partial ground effect cases demonstrate distinct inflow trends compared to the PPBFSM, primarily due to the boundary condition imposed in the current approach, which is not accounted for in the PPBFSM.