Transitional Strategy for Annular Lift Fan Aircraft to Lower the Momentum Drag and Pitching Moment

Abstract

The annular lift fan aircraft is a new conceptual vertical takeoff and landing (VTOL) vehicle for which the tremendous momentum drag and pitching moment in transition is a big problem to overcome. In this study, different strut configurations and transitional strategies for the annular lift fan aircraft are numerically investigated using computational fluid dynamics (CFD) software. The results show that the longitudinal struts can significantly reduce the oscillations of lift and drag caused by the interactions between the radial struts and the incoming flow and that the gliding transition strategy reduces the total required thrust by 47% without the need for a skirt. This gliding transition is also faster, taking only about 20 seconds to complete because part of the thrust can be used for the forward acceleration.