A Numerical Analysis Of The Aerodynamic Performance Of The Ducted-fan UAV

Ducted-fan UAV has the advantages of VTOL, excellent maneuver ability and hovering reconnaissance ability, so the perspective of their application is wide. There is no adult studying method for the ducted-fan system when it flies with a small angle because it is now placed in the complicated air current coming from toward and the stream caused by the screw propeller.This work has studied the aerodynamic performance of the ducted-fan UAV. Firstly we introduced the basic mathematic and physics model used in this work, which includes the basic equations that are suitable for liquid's flow, the semi-implicit method for pressure-linked equations and some turbulence models; secondly, we studied the aerodynamic performance of a certain airfoil and listed the results that have been contrasted with the results got from experiments; thirdly, we studied the structure of the flow field inside the duct and analyzed the fashion how the angle of attack affects the aerodynamic force acted on the duct; at last we established the method how to analyze the aerodynamic performance of the whole ducted-fan UAV with CFD method and respectively analyzed the aerodynamic performance of two ducted-fan UAV which are different from their structures and got the particular results of aerodynamic force and the detailed structure of the flow fields separately from modeling the different flying states.From this work we can draw these main conclusions: the well designed duct can restrain the whorl near the tine of the propeller and now the propeller should be placed at the top of the inside wall of the duct and the distance between the tine and the wall should be as short as possible. The shape of the duct above the propeller should be designed as streamline shape and as broad as possible. When the stream acted by the propeller flows into the ducted-UAV, it creates a circuitous flow accreting the tip of the duct, which makes the fact that the pressure debases along the duct. A pitch moment will be produced for the distribution of the pressure along the duct. To improve the controlling performance of the UAV, the rudders should be placed under the wings inside the duct so as to make full use of the symmetrical stream.This work can sustain the designing and research of the ducted-fan UAV.