Multidisciplinary Design Optimization For Flying Wing Aircraft Preliminary Design

Flying wing is a kind of unconventional configuration aircraft. The preliminary design of flying wing configuration aircraft involves aerodynamics, stealth, structure, weight, center of gravity, and performance disciplines which have coupling relationships. There is little historical data (or statistical data) for the flying wing configuration aircraft design. The multidisciplinary design optimization is an effective approach to solve the problem of preliminary design for flying wing configuration aircraft. The research work in this dissertation focuses on the application of multidisciplinary design optimiza-tion on preliminary design of flying wing configuration aircraft. The major contents are summarized as follows.1) An optimization strategy is proposed for preliminary multidisciplinary design optimization of flying wing configuration flight vehicle. The strategy divides this complex integrated design into two levels, i.e. system level optimization and sub-system level optimization (or analysis). The task of sys-tem level optimization is to obtain optimal system objective or multi-objective through the adjustment of global design variables. The sub-system optimization (or analysis) consists of the aerody-namic/stealthy integrated design, the structure optimization, weight and center of gravity analysis and performance evaluation. The aerodynamic/stealthy integrated design is aim to obtain the maximum lift to drag ratio under constraints of stealthy performance through the adjustment of local shape de-sign variables. The task of the structure optimization is to minimize the structural weight by adjusting the size of structural components. The task of weight and center of gravity analysis is to find out the weight of fuel and the variation range of center of gravity with different loading and fuel consumption. The aircraft takeoff distance, landing distance, maximum climb rate at sea-level, flight radius and maximum range are evaluated in performance analysis. In order to reduce computational complexity during optimization procedure, a surrogate-based two-level optimization is applied.2) A parametric geometric modeling approach for flying wing configuration is proposed. The geometric model of the flying wing consists of three elements: contour parametric, section parametric and transition parametric model. Based on this model, a Microsoft Visual Basic routine for the para-metric geometric modeling of the flying wing is implemented by the VB-CATIA scripts. A three-di-mensional shape of the flying wing can be automatically generated by running the routine.3) To implement the automation of multidisciplinary design optimization procedure, an approach for the multidisciplinary model generator implementation is proposed by using API of CAD software CATIA, script file of mesh generation software Gridgen and Patran Command Language. This mul-tidisciplinary model generator can automatically generate the analysis models for different disciplines based on a unified CAD model. The seamless connection between CAD model and aerodynamic, stealthy, structural, weight and center of gravity, performance analysis models is accomplished, which solves one of the key issues for the multidisciplinary design optimization of the aircraft preliminary design with the flying wing configuration.4) According to the surrogate-based two-level optimization, a detail flowchart for the imple-mentation of multidisciplinary design optimization of the flying wing configuration aircraft is setup. All steps are integrated into the software iSIGHT-FD to construct the computing environment for the multidisciplinary design optimization. The process of the optimization is executed automatically.5) Two flying wing configuration aircraft with single-engine and multi-engine are used to illus-trate the detail process of the multidisciplinary design optimization. The application results indicate that the method and computing environment proposed in the dissertation can effectively solve the multidisciplinary design optimization problem of preliminary design for the flying wing configuration aircraft.