Extraction of limit streamlines in 2D flow field using virtual boundary

To describe the structure of a flow field and understand the flow field image, limit streamlines must be extracted. In this paper, we propose a new intelligent method to extract them automatically. This method is also based on topological analysis, but has the ability to extract open limit streamlines that are not captured by conventional topology-based methods. Given a 2D flow field, we extend it firstly by vector mirroring around its boundary, and then detect and classify the critical points in the extended field. All saddles among the critical points are selected to compute limit streamlines. Contributing to the boundary extending, open limit streamlines, if any one exists, are included in the resulting lines as well as the closed ones. Furthermore, our method can find out limit cycles at the same time without any modification. Test results show that our method significantly improves the extraction of limit streamlines.