tailieunhanh - KUNDU Fluid Mechanics 2 Episode 10

Tham khảo tài liệu 'kundu fluid mechanics 2 episode 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | . Introduction 379 During the past four decades different types of numerical methods have been developed to simulate fluid Hows involving a wide range of applications. These methods include finite difference finite element finite volume and spectral methods. Some of them will be discussed in this chapter. The CFD predictions are never completely exact. Because many sources of error arc involved in the predictions one has to be very careful in interpreting the results produced by CFD techniques. The most common sources of error are Discretization error. This is intrinsic to all numerical methods. This error is incurred whenever a continous system is approximated by a discrete one where a finite number of locations in space grids or instants of time may have been used to resolve the flow field. Different numerical schemes may have different orders of magnitude of the discretization error. Even with the same method die discretization error will be different depending upon the distribution of the grids used in a simulation. In most applications one needs to properly select a numerical method and choose a grid to control this error to an acceptable level. input data error. This is due to the fact that both flow geometry and fluid properties may be known only in an approximated way. initial and boundary condition error. It is common that the initial and boundary conditions of a flow field may represent the real situation too crudely. For example flow information is needed at locations where fluid enters and leaves the flow geometry. Flow properties generally are not known exactly and are thus only approximate. Modeling error. More complicated flows may involve physical phenomena that are not perfectly described by current scientific theories. Models used to solve these problems certainly contain errors for example turbulence modeling atmospheric modeling problems in multiphase flows etc. As a research and design tool CFD normally complements experimental and theoretical