Visualization of Complex Unsteady 3D Flow: Flowing Seed Points and Dynamically Evolving Seed Curves with Applications to Vortex Visualization in CFD Simulations of Ultra Low Reynolds Number Insect Flight
Haibo Dong (Committee Member), Arthur Goshtasby (Committee Member), Joerg Meyer (Committee Member), Yong Pei (Committee Member), Thomas Wischgoll (Advisor)
Doctor of Philosophy (PhD)
Three dimensional integration-based geometric visualization is a very powerful tool for analyzing flow phenomena in time dependent vector fields. Streamlines in particular have many perceptual benefits due to their ability to provide a snapshot of the vectors near key features of complex 3D flows at any instant in time. However, streamlines do not lend themselves well to animation. Subtle changes in the vector field at each time step lead to increasingly large changes between streamlines with the same seed point the longer they are integrated. Path lines, which show particle trajectories over time suffer from similar problems when attempting to animate them.
Dynamic deformable objects in the flow domain also complicate the use of integration-based visualization. Current methods such as streamlines, path lines, streak lines, particle advection and their many conceptual and higher dimensional variants produce undesirable results for this kind of data when the most important flow phenomena occurs near and moves with the objects.
In this work I present methods to handle both of these problems. First, the flowing seed point algorithm is introduced, which visually captures the perceptual benefits of smoothly animated streamlines and path lines by generating a series of seed points that travel through space and time on streak lines and timelines. Next, a novel dynamic seeding strategy for both streamlines and generalized streak lines is introduced to handle deformable moving objects in the flow domain in situations where static seeding objects fail for most time steps.
These two methods are then combined in order to visualize the instantaneous direction and orientation of a flow which results from flapping objects in a fluid. Initial tests are performed with a single rigid flapping disk. Further tests were performed on a more complex biologically inspired CFD simulation of the deformable flapping wings of a dragonfly as it takes off and begins to maneuver. For this test, seeds are automatically chosen such that the formation, evolution and breakdown of the leading edge vortex is highlighted as well as the wing wake interactions that occur between the forewings and hind wings.
Department or Program
Department of Computer Science and Engineering
Year Degree Awarded
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