Lawrence Berkeley National Laboratory

Fluid mechanics considers two frames of reference for an observerwatching a flow field: Eulerian and Lagrangian. The former isthe frame of reference traditionally used for flow analysis, and involvesextracting particle trajectories based on a vector field. Withthis work, we explore the opportunities that arise when consideringthese trajectories from the Lagrangian frame of reference. Specifically,we consider a form where flows are extracted in situ and thenused for subsequent post hoc analysis. We believe this alternate,Lagrangian-based form will be increasingly useful, because the Eulerianframe of reference is sensitive to temporal frequency, andarchitectural trends are causing temporal frequency to drop rapidlyon modern supercomputers. We support our viewpoint by running aseries of experiments, which demonstrate the Lagrangian form canbe more accurate, require less I/O, and be faster when compared totraditional advection.