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Applied Computational Fluid Dynamics Techniques - Wiley Episode 2 Part 7

Tham khảo tài liệu 'applied computational fluid dynamics techniques - wiley episode 2 part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 396 APPLIED COMPUTATIONAL FLUID DYNAMICS TECHNIQUES Figure 18.12. Deactive point points are added using an advancing-front nearest-neighbour layer algorithm and flagged as inactive. The procedure stops once points that are attached to crossed edges have been reached. b Automatic seed points. For external aerodynamics problems one can define seed points on the farfield boundaries. At the beginning all points are marked as deactive. Starting from the external boundaries points are activated using an advancing front technique into the domain. The procedure only activates neighbour points if at least one of the edges is active and attached to an active point. All unmarked points and edges are then deactivated. c Automatic deactivation. For complex geometries with moving surfaces the manual specification of seed points becomes impractical. An automatic way of determining which regions correspond to the flowfield region one is trying to compute and which regions correspond to solid objects immersed in it is then required. The algorithm starts from the edges crossed by embedded surfaces. For the endpoints of these edges an in outside determination is attempted. This is non-trivial particularly for thin or folded surfaces Figure 18.13 . A more reliable way Figure 18.13. Edges with multiple crossing faces to determine whether a point is in outside the flowfield is obtained by storing for the crossed edges the faces closest to the endpoints of the edge. Once this in outside determination has been done for the endpoints of crossed edges the remaining points are marked using an advancing front algorithm. It is important to remark that in this case both the inside active and outside deactive points are marked at the same time. In the case of a conflict preference is always given to mark the points as inside the flow domain active . Once the points have been marked as active inactive the element and edge groups required to avoid memory contention i.e. to allow vectorization are