Vortex Lens: Interactive Vortex Core Line Extraction using Observed Line Integral Convolution

Area of Science:

• Fluid Dynamics
• Computational Science
• Scientific Visualization

Background:

• Detecting and visualizing vortex structures in unsteady 2D fluid flows is crucial for understanding complex fluid phenomena.
• Existing methods may lack accuracy or interactivity in identifying and tracking vortex core lines.

Purpose of the Study:

• To develop and present a novel, interactive method for detecting and visualizing vortex structures in unsteady 2D fluid flows.
• To enable accurate extraction of Lagrangian vortex core lines with user-steered control and controllable numerical error.

Main Methods:

• Employs interactive local reference frame estimation to minimize the time derivative of the flow field.
• Utilizes a user-steered 'vortex lens' for focused visualization via Observed Line Integral Convolution (LIC).
• Seeds vortex core lines from critical points (where flow field equals reference frame) and solves an ODE with strict error bounds.

Main Results:

• The method successfully identifies and visualizes vortex structures in unsteady 2D flows.
• Lagrangian vortex core lines are extracted as simultaneous solutions to two ODEs, with error controllable by integration step size.
• Experimental verification confirms the relationship between step size and extraction error.

Conclusions:

• The proposed interactive method provides an effective and user-friendly approach for vortex structure detection and visualization.
• It offers accurate extraction of Lagrangian vortex core lines with controllable numerical precision, outperforming state-of-the-art methods.
• The system's usability is demonstrated through an interactive lens metaphor.