Identification Of Mechanical Parameters And Optimal Design Of Inlet Shape Based On Gradient Algorithms

Back analysis and optimization design are widely used in various fields of aerospace,especially in the evaluation of complex mechanical properties of composite materials in aircraft structure and the design of scramjet inlet structure.In this paper,based on the gradient optimization algorithms,the spatial heterogeneity mechanical parameters of composite materials and the optimal design of inlet shape are analyzed and studied,the details are as follows:In the problem of non-homogeneous elasticity,the boundary element method(BEM)is used to discretize two-dimensional and three-dimensional numerical models,and the radial integral method(RIM)is used to evaluate the geometric deformation and displacement fields with spatial non-homogeneous elasticity.Compared with the finite element method and the finite difference method,the radial integral boundary element method(RIBEM)only discretizes the geometry boundary,which significantly reduces the computational degree of freedom.In the back analysis of elasticity problem,the objective function including actual displacement fields and the calculated displacement fields is constructed,and the objective function is minimized based on the Levenberg-Marquardt algorithm(LMA).In the process of solving the gradient,the complex variable derivative method(CVDM)is introduced into the LMM.Compared with the finite difference scheme,the numerical displacement fields are solved in the complex domain rather than the real domain,and the derivative of the objective function is calculated accurately and stably.Finally,the results of two-dimensional and three-dimensional back analysis prove that the proposed method can identify the non-homogeneous mechanical parameters efficiently and accurately,and the proposed method still has good robustness in the presence of up to 5% measurement error.In the optimal design work based on the gradient method,the optimization design is carried out for the shape of the scramjet intake port,the multi-objective collaborative optimization function including the total pressure recovery coefficient and the flow capture coefficient is constructed,and the actual intake port geometric model is combined with multi-parameters optimization design of grid distribution design,and spectral gradient algorithm is used to build an optimization design platform based on Fortran programming language and CFD commercial simulation software,which automatically completes the optimal design of the cross-sectional shape of the scramjet intake port.The research work of this paper provides some new ideas for the improvement of calculation accuracy and efficiency in the back analysis method and optimization design in the aerospace field.