Research On Grid Fin’s Aerodynamic Characteristics Of The Ducted Propeller Roadable Aircraft

Ducted propeller is a compact and innovative lift system for vertical take off and landing(VTOL)aircraft. Modern ducted propeller aircraft request compact layout, high forward flight speed,maneuverability and low noise level, which result in more serious aerodynamic issues.Comparing with the fixed wing, ducted propeller flowfields are more complex, include mainly the following characteristics. Firstly, the flowfields are typically unsteady, under the forward flight condition, the airflow speed relative to the blades of the advancing side increases, following phenomenons of transonic speed such as shock wave,on the other side, the relative speed decreases, the flow angle is comparatively high, usually lead to dynamic stall; Secondly, the duct propeller produces intense tip vortex,which hover around the propeller,and make a strong impact on the aerodynamic characteristics of flight aircraft.After dozens of years＇development, computational fluid dynamics has received practical application in aviation, as a result of the mentioned complexity aerodynamics above, its application to duct propeller is much less than fixed wings. Along with the computer technology development, it’s possible now to resolve the three dimensional time-dependent N-S equations for complex geometry.Considering viscosity effect, the N-S equations have the potential to achieve accurate description of the formation and transportation of vortex, which don’t depend on any wake model. Duct propeller wake can be obtained as a part of solution.The effects of grid fin geometry parameters on the aerodynamic performance of duct propeller were studied by means of computational fluid dynamics. Firstly, the simulation data of lift forces are validated by the experiment;secondly under the working condition of propeller, the simulation models with different chords, attack angles, web thickness and locations of the propeller were established. Based on the analysis of the single parameter influence on duct propeller’s aerodynamic performance, we use the design of testing method to establish the approximation model; Finally, a proper optimization strategy was used to obtain the maximum lift force of the duct propeller. The method about how to choose the grid fin’s geometry parameters that suitable for duct propeller structure is put forward.