Finite State Modeling of Ground Effect Using Mass Source Distribution at the Ground Plane

Ground effect analytical models in the literature, such as the Pressure Potential Based Finite State Model (PPBFSM) or Velocity Potential Based Finite State Model (VPBFSM) have been developed to study an isolated rotor in full ground effect. These models use the mass source distributions to account for the ground plane. Also, these models consider that the exit pressure of those distributions is equal to the pressure exerted from the rotor at the ground plane. However, PPBFSM and VPBFSM do not satisfy the non-penetration of flow boundary condition at the ground plane. This paper develops a new ground effect model using the VPBFSM that considers the non-penetration of flow boundary condition at the ground plane by varying ground rotor size and using optimization to find the strength of the mass source distributions. Additionally, it captures the flow at any point below the disk which is missing in the previous study of ground effect using VPBFSM. The developed model is applied to the R-50 unmanned helicopter rotor using its geometric and aerodynamic data from the literature. The results show a good correlation compared to the Hayden model. Additionally, the present model exhibits a similar trend of rotor inflow in ground effect at different rotor heights above ground compared to the PPBFSM.