Study On Post-processing Algorithms For The Boundary Face Method And Their Implementation

In the newly developed boundary face method (BFM), both boundary integration and variable approximation are performed in the 2-D parametric space of the boundary surface of solid represented by the boundary. The proposed approach can not only provide much more accurate results than the boundary element method (BEM), but also avoid geometric error in the BFM. Visualization in post-processing plays an important role in the application of the BFM. Although there are already abundant of matured post-processing tools existing for the finite element method (FEM), these codes can not be directly applied to the BFM. Therefore, it is necessary to investigate new algorithms that are especially suitable for the BFM post-processing.In this paper, the algorithms of the data preparation and isoline generation in the BFM post-processing were studied in detail. Our work involves four aspects as follows:(1) For instance of solving a potential problem by the BFM, according to the speciality of the BFM, an adaptive tree structure for calculating the value of variable at any point is proposed.(2) Based on the theory of isoline generation, the traditional rectangular grid method has been improved. For the shortage that broken line would be created when the linear interpolation was taken, based on the rectangular grid method, some self-adaptive algorithm using grid subdividing was presented. Furthermore, the traditional irregular triangular grid method was analyzed; and the isoline tracking was limited in the traditional element to avoid the problem of distinction between the boundary isoline and internal isoline.(3)Based on the theory of the contour generation, two contour filling algorithms were discussed respectively, one of which is based on the topological relation and the other one of which is based on triangular cell. The formation of the topological relation for isolines is crucial to the contour filling algorithm based on the topology relationship. The contour filling algorithm which is based on the triangular cell has been improved, and patches were directly generates in the cell to fulfill contour filling in the patch. Comparison of two methods showed that the latter algorithm is better than the former in the program implemented and adaptability.(4) After the study on the theory of secondary development of UG and its related technology, the project of post-processing of BFM which is UG-NX oriented has been developed. Numerical examples showed that excellent visualization can be obtained by proposed methods.