Techniques for Assistance in Streamline and Stream Surface Visualizations
Ross Vasko · The Knowledge Bank (The Ohio State University) · 2017
Flow fields provide a mathematical model of fluid flows and arise in various fields of science and engineering. Fluid flows are often visualized with streamlines and stream surfaces. A streamline is a curve that is tangent everywhere to the flow field and a stream surface is a surface that is tangent everywhere to the flow field. These geometric techniques can provide the user with a clear, intuitive visualization if applied effectively. Visualizations with either technique are not trivial to create. Streamline visualizations often suffer from sampling or occlusion issues while the construction of stream surfaces themselves is difficult and time consuming. Here we provide methods to automatically place streamlines in the flow field and to automatically create a stream surface seeding curve. Streamline visualizations should not be created with arbitrary seedings. An arbitrary seeding can very easily miss features in the flow field or create an unhelpful visualization due to clutter. We describe a method of measuring the complexity of streamlines based on fractal dimension in order to assist the user in creating a seeding of streamlines. A scalar grid is also made from the complexity measurements and can be visualized to further assist the user in locating interesting regions of the flow field. Stream surfaces are difficult to generate because of the challenge of creating a "good" seeding curve for the surface. A streamline is integrated from a single point, while a curve to integrate is required to create a stream surface. This curve is not inherently determined by the flow field and must be created by the user. We describe desirable properties to have in a seeding curve and then provide an algorithm that generates seeding curves based on these properties. We also provide a technique based on similarity measurements to filter stream surfaces from the visualization to reduce clutter.