Feature Extraction in Flow Simulations

Abstract

The flow of water, air and other liquid or gaseous substances is commonly described in 2D or 3D vector fields changing over time.

Research groups from several fields derive such data through data collection or simulation in order so answer specific questions. These usually boil down to the identification, tracking or quantification of certain features of interest. We will work closely together with these domain experts and assist by extracting and visualizing the required features.

In a joint work with statisticians at the King Abdullah University of Science and Technology (KAUST), we have extracted the shapes of irregular eddies in Red Sea simulations [1]. An eddy is a mass-coherent water vortex that transports large quantities of water both horizontally between coasts as well as vertically between ocean surface and floor. We have employed an integration-based approach to automatically extract their shape, even when it is highly irregular as in the Red Sea.

In collaboration with the fluid mechanics group at KTH, we are investigating properties of turbulence [2]. To validate a uniform random distribution of certain derived scalar fields, we employ percolation theory: As one observes the number of connected components for a rising threshold, a single, "percolating" cluster will rapidly emerge at a certain point. We have significantly sped up this analysis by two orders of magnitude, which allows us to quickly compare different parameters and fields.

Future collaborations in both the field of turbulence/percolation and climate/cycloe tracking are planned.

[1] A Lagrangian Method for Extracting Eddy Boundaries in the Red Sea and the Gulf of Aden, Friederici, A. and Kele, H. T. M. and Weinkauf, T. and Theisel, H. and Hadwiger, M., Proceedings IEEE Scientific Visualization Short Papers 2018.

[2] An efficient algorithm for percolation analysis and its application to turbulent duct flow, Friederici, A. and Atzori, M. and Vinuesa, R. and Schlatter, P. and Weinkauf, T., Euromech Colloquium 598: Coherent structures in wall-bounded turbulence, 2018.