Advanced flow visualization
Han‐Wei Shen, Liya Li · 2007
Flow visualization has been playing a substantial role in many engineering and scientific applications, such as automotive industry, computational fluid dynamics, chemical processing, and weather simulation and climate modelling. Many methods have been proposed in the past decade to visualize steady and time-varying flow fields, in which textures-based and geometry-based visualization are widely used to explore the underlying fluid dynamics. This dissertation presents a view-dependent flow texture algorithm, an illustrative streamline placement algorithm on two-dimensional vector fields, and an image-based streamline placement algorithm on three-dimensional vector fields. Flow texture, generated through convolution and filtering of texture values according to the local flow vectors, is a dense representation of the vector field to provide global information of the flow structure. A view-dependent algorithm for multi-resolution flow texture advection on two-dimensional structured rectilinear and curvilinear grid is presented. By using an intermediate representation of the under-lying flow fields, the algorithm can adjust the resolutions of the output texture on the fly as the user zooms in and out of the field, which can avoid aliasing as well as ensure enough detail. Geometry-based methods use geometries, such as lines, tubes, or balls, to represent the motion paths advected from the vector fields. It provides a sparse representation and an intuitive visualization of flow trajectory. For two-dimensional vector fields, a streamline placement strategy is presented to generate representative and illustrative streamlines, which can effectively prevent the visual overload by emphasizing the essential and deemphasizing the trivial or repetitive flow patterns. A user study is performed to quantify the effectiveness of this visualization algorithm, and the results are provided. For three-dimensional vector fields, an image-based streamline seeding algorithm is introduced to better display the streamlines and reduce visual cluttering in the output images. Various effects can be achieved to enhance the visual understanding of three-dimensional flow lines.