Ground/Wall Effects on a Tilting Ducted Fan

Mini-vertical take-off and landing aircraft have a wide range of potential applications in urban areas. In flights in confined spaces, however, the aerodynamics of the lifting devices (e.g., tilted ducted fans) change which significantly affects the flight performance. Therefore, for a successful flight, a model is required to provide the control system with the environmental effects on the lifting devices in real time. This paper presents the study performed on a tilted ducted fan to characterize ground/wall effects and develop a practical model for online flight control. For this, computational fluid dynamic simulations were performed in Fluent, for a ducted fan at different distances from ground/wall and with different tilt angles. The incompressible Reynolds Averaged Navier Stokes (RANS) equations, with the standard k-epsilon model and the non-equilibrium wall function, were solved. To reduce the complexity of meshing, the fan was represented by Virtual Blade Model (VBM). A comprehensive study was performed to show that, by using the method of images and representing the fan as a single potential dipole, the fan performance can be predicted accurately on a practical range of operation. The developed potential flow model highly reduces the computational requirements and is practical to use for online semi-autonomous or autonomous navigation of ducted fan aerial vehicles.