Computer-aided visualization of simulated turbulent channel flow

Iso-surfaces are used as a visualization method to study turbulent phenomena, especially the turbulent burst process. A database of numerical simulations of turbulent channel flow has been investigated. Organized motions observed in the turbulent flow visualization experiments can be recognized from numerical simulation results.;An iso-surface construction algorithm has been developed which can handle all cases of iso-surface geometry. The algorithm is robust and gives correct results by treating the ambiguous cases properly. The algorithm has been devised after a thorough study of possible iso-surface construction methods. Since iso-surfaces can be applied only to scalar fields, a color-coding scheme for the iso-surface representation has been developed which allows the visualization of a vector field. The iso-surface is created for the magnitude of the given vector information and is subsequently color-coded according to the directional information derived from the vector field.;For the wireframe representation of an iso-surface, a fast algorithm for 2-D contour construction has been developed. Significant performance improvement was gained based on an indexed search method instead of a sequential search as used in existing algorithms. The goal of real-time response in the iso-surface generation and the view manipulation process has been achieved.;The developed algorithms have been used to visualize well-known flow structures and to study near-wall turbulent structures. The design of effective data structures and the proper integration of the algorithms with an efficient user interface allows a thorough study of large scalar and vector fields in a reduced amount of time. The new algorithms and tools are helpful in gaining a better understanding of the complex phenomena found in turbulent flows.