Research On Feature Detection And Visualization Of Sources And Sinks In A Planar Vector Field

The feature structures of the ocean can not only influence it's fine structure and the generation, evolution, power mechanism of large and medium-scale ocean phenomena, but also it has its own special significance to economic, social and military affairs. Sources and Links are instable ocean flow. Therefore, they can make serious damages to marine organisms, fishing and shipping. Accordingly, it is of great significance and scientific value to research the feature of ocean flow field such as sources, sinks, and vortices.When the rotating and diverging movements and ocean flows are very small, they are often covered by the steady-state ocean flows. Accordingly, it is very hard to reflect the important features of ocean flows such as sources and sinks. In order to detect the sources and sinks in such conditions above or to visualize them more clearly under normal condition, this paper decomposes the ocean flow vector field to achieve the divergence field (rotation-free field). The distribution condition of divergence amplitude in rotation-free field is reflected through the vector field decomposition to ocean flow field. Therefore, it is more sensitive to extract the divergent characteristics, and divergence is the parameter of sources and links, thus it is required to focus on the research to decomposed flow field, rotation-free field. This paper focuses on the research of visualizing sources and sinks in divergence field to verify the applicability of vector decomposition algorithm theory to ocean flow field feature detection.Closed streamlines and separatrices are borderlines of two different flow behaviors in the flow field and they are very important topology structure characteristics. Because there are different fluids. Inside and outside the closed streamlines and separatrices, it is acceptable to detect the closed streamlines and separatrices to discern the range of flow field feature(sources and sinks). In order to present more information of sources and sinks to get better visualization effects, it becomes a very important topic to locate closed streamlines and separatrices fast and accurately for flow field feature detection based on feature visualization.Focusing on the detection of closed streamlines and separatrices, this paper proposes a novel method based on the Morse decomposition theory of Conley index in dynamics systems. Through research on the isolated invariant data sets, better visualization effects are obtained after Triangulation and units merger. This method can detect more closed streamlines than Wischgoll algorithm and also improve the efficiency of detection. Furthermore, this method is used to practical ocean data sets and is verify to be efficient.In order to prove that more information of sources and sinks will be presented in ocean flow field feature(sources and sinks)detection after the closed streamlines and separatrices are extracted, this paper uses the method to detect closed streamlines based on the Morse decomposition theory of Conley index for visualizing sources and sinks. The range of different fluid flow behaviors is measured and streamline-based visualization is used to visualize ocean flow with color mapping. The results can clearly reveal the range of sources and sinks so as to enrich the visualization information. The visualization results are more intuitionistic and it is easier for uses to master the flow field information.