3D Lagrangian Particle Tracking and Data Assimilation in Fluid Mechanics – Resolving a wide range of flow scales by STB and FlowFit

Abstract

Dense 3D Particle Tracking allows characterizing unsteady and turbulent flows within the Lagrangian and Eulerian frame of reference at high spatial and temporal resolution. The 3D Lagrangian Particle Tracking (LPT) method “Shake-The-Box” (STB) has been continuously developed during the past couple of years and is able to reliably and efficiently extract particle trajectories from volumetric flow measurements at unprecedented numbers. STB delivers accurate data on particles position, velocity and acceleration (material derivative) along densely distributed tracks. The STB method can be applied as well to short recording sequences, acquired with a multi- or two-pulse technique, allowing investigating high-speed flows at Reynolds numbers relevant for research in aerospace engineering. Subsequently, the FlowFit (FF) data assimilation or PINN methods can be applied, which use Navier-Stokes-constraints for a linear or non-linear optimization process resulting in a continuous or grid-based interpolation of the flow field including pressure with minimized deviation to the measurement data. In the keynote presentation examples of STB and FlowFit applications for flow analyses and turbulence characterization based on experimental data will be presented.