Based on the author’s previous research, a novel hybrid grid generation technique is developed by introducing an Artificial Neural Network(ANN) approach for realistic viscous flow simulations. An initial hybrid grid ...Based on the author’s previous research, a novel hybrid grid generation technique is developed by introducing an Artificial Neural Network(ANN) approach for realistic viscous flow simulations. An initial hybrid grid over a typical geometry with anisotropic quadrilaterals in the boundary layer and isotropic triangles in the off-body region is generated by the classical mesh generation method to train two ANNs on how to predict the advancing direction of the new point and to control the grid size. After inputting the initial discretized fronts, the ANN-based Advancing Layer Method(ALM) is adopted to generate the anisotropic quadrilaterals in boundary layers. When the high aspect ratio of the anisotropic grid reaches a specified value, the ANN-based Advancing Front Method(AFM) is adopted to generate isotropic triangles in the off-body computational domain.The initial isotropic triangles are smoothed to further improve the grid quality. Three typical cases are tested and compared with experimental data to validate the effectiveness of grids generated by the ANN-based hybrid grid generation method. The experimental results show that the two ANNs can predict the advancing direction and the grid size very well, and improve the adaptability of the isotropic/anisotropic hybrid grid generation for viscous flow simulations.展开更多
The foundation of modern Digital Earth frameworks is the Discrete Global Grid System(DGGS).To standardize the DGGS model,the Open Geospatial Consortium(OGC)recently created the DGGS Abstract Specification,which also a...The foundation of modern Digital Earth frameworks is the Discrete Global Grid System(DGGS).To standardize the DGGS model,the Open Geospatial Consortium(OGC)recently created the DGGS Abstract Specification,which also aims to increase usability and interoperability between DGGSs.To support these demands and aid future research,open implementations are necessary.However,several OGC conformant DGGSs are not available for researchers to use.This has motivated us to develop an open-source web service that allows users to create quadrilateral grids based on the rHEALPix DGGS.In this paper,we describe the implementation of the web service,including issues and limitations,and demonstrate how discrete global grids and regional grids can be created.Lastly,we present examples that show how vector data sets can be modeled and integrated at different levels of resolution–a key benefit of the DGGS model.展开更多
A new finite volume difference method for solving 2-D diffusion equation isconstructcd in this paper. The choice of computational nodes is studied on thegross distortion concave quadrilateral grid. We choose the midpo...A new finite volume difference method for solving 2-D diffusion equation isconstructcd in this paper. The choice of computational nodes is studied on thegross distortion concave quadrilateral grid. We choose the midpoint of a diagonalline of the mesh cells as the calculation nodes because it can assure the cells con-tain the calculation nodes and reduce the total calculation. In order to keep theconservation, we use the conditions of flux conservation to compute the values ofthe central of the boundary. Lagrange multiplier method is used to get the valuesof grid points. With the consideration of the relative position of the grid points,the method is more suitable for nonorthogonal grids. We make experiments onconcave grids and "Z" grids. The numerical results show that the new arithmeticis feasible and effective, especially for highly distortional meshes.展开更多
基金supported by the National Key Re-search and Development Program of China(No.2016YFB0200701)the National Natural Science Foundation of China(Nos.11532016 and 11672324)the National Key Project(No.GJXM92579)。
文摘Based on the author’s previous research, a novel hybrid grid generation technique is developed by introducing an Artificial Neural Network(ANN) approach for realistic viscous flow simulations. An initial hybrid grid over a typical geometry with anisotropic quadrilaterals in the boundary layer and isotropic triangles in the off-body region is generated by the classical mesh generation method to train two ANNs on how to predict the advancing direction of the new point and to control the grid size. After inputting the initial discretized fronts, the ANN-based Advancing Layer Method(ALM) is adopted to generate the anisotropic quadrilaterals in boundary layers. When the high aspect ratio of the anisotropic grid reaches a specified value, the ANN-based Advancing Front Method(AFM) is adopted to generate isotropic triangles in the off-body computational domain.The initial isotropic triangles are smoothed to further improve the grid quality. Three typical cases are tested and compared with experimental data to validate the effectiveness of grids generated by the ANN-based hybrid grid generation method. The experimental results show that the two ANNs can predict the advancing direction and the grid size very well, and improve the adaptability of the isotropic/anisotropic hybrid grid generation for viscous flow simulations.
基金the Natural Sciences and Engineering Research Council of Canada (NSERC-DG).
文摘The foundation of modern Digital Earth frameworks is the Discrete Global Grid System(DGGS).To standardize the DGGS model,the Open Geospatial Consortium(OGC)recently created the DGGS Abstract Specification,which also aims to increase usability and interoperability between DGGSs.To support these demands and aid future research,open implementations are necessary.However,several OGC conformant DGGSs are not available for researchers to use.This has motivated us to develop an open-source web service that allows users to create quadrilateral grids based on the rHEALPix DGGS.In this paper,we describe the implementation of the web service,including issues and limitations,and demonstrate how discrete global grids and regional grids can be created.Lastly,we present examples that show how vector data sets can be modeled and integrated at different levels of resolution–a key benefit of the DGGS model.
文摘A new finite volume difference method for solving 2-D diffusion equation isconstructcd in this paper. The choice of computational nodes is studied on thegross distortion concave quadrilateral grid. We choose the midpoint of a diagonalline of the mesh cells as the calculation nodes because it can assure the cells con-tain the calculation nodes and reduce the total calculation. In order to keep theconservation, we use the conditions of flux conservation to compute the values ofthe central of the boundary. Lagrange multiplier method is used to get the valuesof grid points. With the consideration of the relative position of the grid points,the method is more suitable for nonorthogonal grids. We make experiments onconcave grids and "Z" grids. The numerical results show that the new arithmeticis feasible and effective, especially for highly distortional meshes.
