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Application of Parallel Multigrid Algorithm to Discrete Adjoint Optimization
Received date: 2013-10-18
Revised date: 2014-01-13
Online published: 2014-02-17
The adjoint method is now employed more and more widely for aerodynamic shape optimization. But when used for reducing the drag of a complex aircraft, it still requires a large amount of time-consuming calculation. Based on an unstructured mesh, this paper proposes a parallel multigrid algorithm to solve the discrete adjoint equation for a 3D Reynolds-averaged Navier-Stokes solver, so as to improve the optimization system efficiency. The prolongation operator and the restriction operator are described for the multigrid adjoint solver. By using the V-cycle, the accelerating effect of different layers is compared, and the influence of coarse grid residuals computing methods on the gradient of the objective function is analyzed. Combined with Metis partitioning technology, a simplified parallel-data transfer approach is implemented for the adjoint solver, so that the parallel speedup of the adjoint equation is only 13% lower than the ideal speedup in 300 parallel partitions. The optimization system is successfully demonstrated for a DLR F6 wing-body transonic shape optimization design, in which 112 design variables are selected with the purpose of reducing drag. Shock structure change is presented before and after the optimization, and drag reduction is nine counts. It shows that the efficient optimization system established in this paper has a bright application prospect for three-dimensional complex shape optimization.
LI Bin , TANG Jing , DENG Youqi , ZHANG Yaobing . Application of Parallel Multigrid Algorithm to Discrete Adjoint Optimization[J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2014 , 35(8) : 2091 -2101 . DOI: 10.7527/S1000-6893.2013.0518
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