Research And Optimization On Aerodynamic Characteristics Of Flying-wing With The Tilting Lift Fan

With lift fan of flying wing aircraft has both the advantages of vertical / short take-off and landing(S/VTOL)and flying wing configuration aircraft, but also has he advantages of high thrust-weight ratio, high net rise efficiency and no thermal jets.With the lift fan aircraft to achieve S/VTOL will be an important research subject in the future for a long period of time. But because the lift fan with tilting lift fan is arranged in the central of flying wing. The opening on the wing of the plane will have an important influence on the aerodynamic characteristics of the aircraft. Therefore, it is very important to study the relationship between the aerodynamic characteristics and the shape of the openings.This article did a research on aerodynamic characteristics of the tilting lift-fan UAV’s(unmanned aerial vehicle) openings for the installation of lift fan in flying wing configuration with the method of CFD. The aerodynamic characteristics of the opening wing with different flow velocities and different angles of attack under level flight condition were analyzed.The main content of the article was:1 The two-dimensional model of the maximum longitudinal section of the opening of the opening wing was established. Using ICEM to carry on the structural mesh of the geometric model, then the structure grid was introduced into FLUENT to carry out numerical simulation. Results showed that under the same conditions, the aerodynamic characteristics of the opening wing obviously deteriorated, but the pitch control was better.And vortex appeared at the opening of the opening wing which lost of part of the energy, thus the aerodynamic characteristics of the opening wing were further reduced.2 By comparing the aerodynamic characteristics of the nine optimization models,different forms of modification of wing opening cross section were carried out.Results showed that the opening completely arc optimization and forward proper angle on the front wing surface was the best.3 The three-dimensional geometry model of opening wing was established.Using ICEM to carry on the structural mesh of the geometric model, then the structuregrid was introduced into FLUENT to carry out numerical simulation. Results showed that three dimensional simulation results were similar to the results of two-dimensional simulation. The opening wing losing some of its wings and the vortex loss generated at the opening part of the energy were the two important reasons for the variation of aerodynamic characteristics of the opening wing.4 According to the optimization direction of two-dimensional model, sixteen optimization directions were selected, and the three dimensional numerical simulation was carried out. Results showed that the opening of the front opening wing inscribed circle arc processing of aerodynamic characteristics was the best. See from streamline chart, the optimization of the opening of the openings in the front section of the vortex was very small, and the vortex was negligible compared to the non optimized open wing. After the optimization, the vortex generated by the opening end of the opening wing was also much smaller in the range and the intensity of the vortex.These were the important reasons for the aerodynamic characteristics of the opening wing.In summary,the lift fan with tilting lift fan opening in the central of flying wing reduced the aerodynamic characteristics. But through the reasonable design of the openings, the aerodynamic characteristics could be effectively improved. Two dimensional optimization could represent the direction of optimization to a certain extent, but the result of three-dimensional optimization was more obvious.