Numerical Analysis of Aerodynamic Characteristics of the HALE Diamond Joined-Wing Configuration UAV

The investigation on the aerodynamic characteristics of the high-attitude long-endurance (HALE) Diamond Joined-Wing configuration unmanned aerial vehicle ( UAV) was carried out by the theoretical analysis method and numerical simulation. Research indicates that as the wing of the UAV is composed of the front wing and the after wing, the after wing has the ability to transmit the front wing's boundary layer to the after wing root which can inhibit the front wing's flow separation. Although the front wing was affected by the retardation of the after wing, the aerodynamic performance of the front wing was better than that of alone front wing in most cases. The after wing was also affected by the wake and downwash of the front wing, and its aerodynamic performance was greatly decreased. The characteristic curve of the pitching moment of the UAV had nonlinear characteristics. The flow field structure of the after wing changed by the front wing wake direct sweep and flow separation at the after wing root were the main reasons that non-linear ′rise′phenomenon occurred in two segments ( α = 0° and α = 8° ) of the characteristic curve of pitching moment. Moreover, coupling of the flow separation characteristic of the front wing and the after wing resulted in the pitching moment ′pitchup′ phenomenon. The lateral-directional static stability of the flat layout was weak. The HALE Diamond Joined-Wing configuration UAV ' s aerodynamic performance can be improved and the problems in engineering applications can be effectively alleviated by adjusting the overall layout parameters.

Aero-structural design of joined-wing aircraft based on high-fidelity model

The joined-wing configuration reduces induced drag and structural weight by connecting the rear wing to the front wing.In addition,the rear wing can replace the role of the horizontal tail of a conventional aircraft,thus eliminating the aerodynamic drag and weight associated with the horizontal tail.This particular shape creates a highly coupled relationship between aerodynamics and structure,which must be fully considered during the overall design process to enhance aircraft performance.In this research,an aero-structural design model of the joined-wing aircraft is constructed based on high-fidelity computational fluid dynamics and structural finite element methods.The model is able to obtain accurate aerodynamic loads for the non-planar wing and to simulate the statically indeterminate structure of the closed wing configuration.The influence of the joined-wing shape parameters on the aerodynamic and structural disciplines,as well as the influence of geometric nonlinear characteristics,deformation constraints and buckling constraints on the structural weight are all taken into consideration.The model is applied to complete the aero-structural design optimization of a high-altitude long-endurance joined-wing aircraft,and wind tunnel tests are conducted.The test results verify the credibility of the design model proposed and the validity of the design environment.