Multidisciplinary Design Optimization For Preliminary Design Of Unmanned Aerial Vehicle With Blended Wing Body

Blended wing body(BWB)is a kind of new aerodynamic configuration,which has advantages of high aerodynamic efficiency,low structural weight,favorable stealth performance,low noise and emission,and is not only the possible configuration for the future long-range transport aircraft,but also has been adopted by several unmanned aerial vehicles(UAV)at home and abroad.Due to the tight coupling among aerodynamic,stability and controllability,flight performance,structure,stealth,and the lack of historical data,the multidisciplinary design optimization(MDO)method becomes an effective approach for the preliminary design of BWB configuration aircrafts.This dissertation focuses on the application of MDO method to the preliminary design of a BWB reconnaissance and strike integrated UAV,the major contents covered are as follows.1)According to the prescribed tactical and technical performance requirements,a conceptual design is proposed for the BWB reconnaissance and strike integrated UAV.The aerodynamics and stealthy performances analysis for the preliminary design show that it is difficult to realize the longitudinal trim and the lift to drag ratio decreases under trimmed condition.Considering the design features of the BWB UAV,the conceptual design is defined as MDO problems.The coupling relationships between disciplinarians are investigated,and then a flowchart for the implementation of MDO to the conceptual design is established.2)According to the geometrical characteristics,a parametric modeling method for the BWB configuration is proposed.By defining planform parameters,spanwise section parameters,fuselage cross section parameters and deflection parameters of control surfaces,the interface technique of CATIA software in VB environment is utilized to automatically generate the 3D geometry with and without control surface deflections.3)The Gridgen scripts with fault-tolerate capability programmed in Tcl language are used to mesh the geometry with different control surfaces deflection.The aerodynamic analysis model is established based on the combination of the PAN AIR panel method program and engineering methods.The surrogate models are created from the aerodynamic analysis results to calculate the trimmed cruise performances,longitudinal stability,trim capability,flight performances and bending moment at the longitudinal plane of symmetry.The radar cross section(RCS)analysis model is established based on the physical optics method and equivalent current theory.4)According to the execution sequence in the flowchart,a MDO computation environment for the preliminary design of BWB configuration UAV is constructed by integrating all the analysis models in the iSIGHT-FD software.In this computation environment,the automatically execution of multidisciplinary analysis is realized.5)A design of experiment and analysis are implemented.A system level surrogate model is established based on the analysis results of the sample points,and impacts of the major design parameters are evaluated.Optimal designs are obtained through MDO based on the system level surrogate model,and impacts of the different objectives and constraints are investigated.6)The aerodynamic characteristics,stealth performance,stability and controllability are validated by wind tunnel test,RCS numerical analysis with high fidelity and RCS test in the anechoic chamber,and a flight test of the scaled model.The test results indicate that the analysis methods in this study are reliable,and the proposed flowchart and strategy of MDO are also effective for the preliminary design optimization of the unmanned aerial vehicles with BWB configuration.