Abstract
Aerodynamic interference between forward and back wings of tandem-scheme aircraft significantly affects its pitch and roll moments. The interference increases roll stability in a narrow range of sideslip angles; there is a kink on the dependence of roll moment coefficient versus sideslip angle (that is not observed for conventional-scheme aircraft). Directional stability is decreased by a dihedral angle of forward wings and winglets on them but is increased by the same factors for back wings. If back wings’ bending is significant, then aerodynamic interference may affect directional stability as well. The vortex system of tandem-wings at a sideslip angle was modeled incorrectly by the used CFD method (solving RANS), and further research is needed. The analytical and experimental methods show a good agreement concerning moment characteristics.
Highlights
In the beginning of the XXI century aerodynamic scheme “tandem” became widespread among UAVs and small piloted aircrafts [1,2,3,4].Its aerodynamics has specifics caused by inevitable wing-wing interference
For aerodynamic moments determination the following methods were used: 1) The analytical method developed by the author [5, 6]; 2) The CFD method (RANS solving with Ansys software) [7]; 3) Experimental research
In a narrow range of sideslip angles, the interference increases roll stability that was predicted by the analytical method and was proved in the wind tunnel test
Summary
In the beginning of the XXI century aerodynamic scheme “tandem” (with comparable areas of forward wings and back wings) became widespread among UAVs and small piloted aircrafts (fig. 1) [1,2,3,4]. In the beginning of the XXI century aerodynamic scheme “tandem” (with comparable areas of forward wings and back wings) became widespread among UAVs and small piloted aircrafts Its aerodynamics has specifics caused by inevitable wing-wing interference. The tip vortices of the forward wings affect the flow on the back wings, create upwash and downwash For a small vertical gap, forward wings slow down the flow on the back wings and make it turbulent, but this effect might be low for reasonable parameters of configuration. Downwash and upwash always affect total lift coefficient and moment characteristics that concern the stability of aircraft and is of high importance
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