Geometry Discretisation and Mesh Generation

The constituent subprocesses of discretisation consist of mesh generation (determining the types of mesh elements), space discretisation and time discretisation. 

For CFD discretisation, some methods are available in commercial systems. These common methods include finite difference (FD), finite volume (FV) and finite element (FE) methods. Each of them takes a different approach in approximating the differential equations essentially based on the Navie-Stokes equation. Their underlying approaches are similar and they all approximate differential equations by a system of algebraic equations for the variables in some set of discrete locations in space and time. 

With an accurate flow space or domain defined in terms of its geometry and a strategy for discretisation determined, it is necessary to select a suitable specific discretisation method before a problem can be solved. Having studied the field of 

In an FV method, the whole solution domain is subdivided into a finite number of contiguous control volumes. The computational node is located at the centroid of each control volume, whereas the node is located at the grid in the FD method. The FV method uses the integral form of the conservation equation 

The FE approaches used in CFD originate from structural mechanics and is similar to the FV method. A domain is divided into many discrete control volumes or finite elements. These elements are generally unstructured meshes. The most commonly used 2-D elements are triangles or quadrilaterals, whereas for 3-D 

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