珠联璧合，相得益彰——景物描写与阅读结合探微

让中学生喜欢并擅长去写景的有效途径是把学习写景与阅读结合起来。在阅读中让学生欣赏美,激发学生的写作兴趣：在阅读中提升学生的观察意识,培养学生观察的品质;在阅读中教会学生写景的技巧,指导学生细致地描写;在阅读中提高学生的想象能力,提升学生作品的主旨：在阅读中鼓励学生积累,扩展学生写作的素材。     

Application of factor difference scheme to solving discrete flow equations based on unstructured grid

A second-order mixing difference scheme with a limiting factor is deduced with the reconstruction gradient method and applied to discretizing the Navier-Stokes equation in an unstructured grid. The transform of nonorthogonal diffusion items generated by the scheme in discrete equations is provided. The Delaunay triangulation method is improved to generate the unstructured grid. The computing program based on the SIMPLE algorithm in an unstructured grid is compiled and used to solve the discrete equations of two types of incompressible viscous flow. The numerical simulation results of the laminar flow driven by lid in cavity and flow behind a cylinder are compared with the theoretical solution and experimental data respectively. In the former case, a good agreement is achieved in the main velocity and drag coefficient curve. In the latter case, the numerical structure and development of vortex under several Reynolds numbers match well with that of the experiment. It is indicated that the factor difference scheme is of higher accuracy, and feasible to be applied to Navier-Stokes equation.