Recent Developments in Particle Tracking Diagnostics for Turbulence Research

Abstract

Flow velocity measurements based on the analysis of the motion of particles imaged with digital cameras have become the most commonly used measurement technique in contemporary fluid mechanics research [1, 2]. Particle image velocimetry (PIV) and particle tracking velocimetry (PTV) are two widely used methods that enable the characterisation of a flow based on the motion of particles, from Eulerian (PIV) or Lagrangian (PTV) points of view. Several aspects influence the accuracy and reliability of the measurements obtained with these techniques [2]: resolution (temporal and spatial), dynamical range, the capacity to measure 2D or 3D components of velocity in a 2D or 3D fluid domain, statistical convergence, etc. These imaging and analysis considerations depend on the hardware (camera resolution, repetition rate, on-board memory, optical system, etc.) but also on the software (optical calibration relating real-world coordinates to pixel coordinates, particle identification and tracking algorithms, image correlation, dynamical postprocessing, etc.) used in the measurements. In this context, particle tracking velocimetry can provide highly resolved, spatially and temporally, measurements of the flow velocity (if the particles are flow tracers) or of particle velocities (if the particles immersed in the flow have their own dynamics) in experimental

3D Lagrangian Particle Tracking in Fluid Mechanics

“…In contrast to PIV methods, particle tracking methods have been developed with 3D PTV schemes that enable relatively sparse particle track reconstructions (e.g., Nishino et al 1989, Maas et al 1993, Malik et al 1993, Guezennec et al 1994, Virant & Dracos 1997, Ouellette et al 2006, Machicoane et al 2019, Dabiri & Pecora 2020 at particle image densities between ∼0.005 and 0.02 ppp. Increased particle track densities in the measurement volume can be achieved with scanning 3D PTV techniques (Hoyer et al 2005, Kozul et al 2019, reaching higher ppv values for relatively low flow velocities.…”

“…Tomo-PIV and 3D LPT/PTV techniques, as well as various similar volumetric velocimetry techniques for fluid flows, have been extensively presented and discussed in recent reviews (e.g., Scarano 2013, Westerweel et al 2013, Discetti & Coletti 2018, Machicoane et al 2019) and textbooks (Schröder & Willert 2008, Adrian & Westerweel 2011, Raffel et al 2018, Dabiri & Pecora 2020. Furthermore, with the recent development of high-speed lasers and cameras, the range of flow velocities in which time-resolved velocity field information can be gained via PIV and LPT has been widened significantly in spatial and temporal resolution (Beresh 2021).…”

Single inertial particle statistics in turbulent flows from Lagrangian velocity models

“…Transport processes of particles in turbulent flows play an important role in turbulence theory [1][2][3] and are intimately related to the problems of turbulent mixing and turbulent diffusion. Recent advances in particle tracking [4,5] allow for the accurate quantification of single-particle statistics and yield important insights into the behavior of marked fluid particles (so-called Lagrangian tracers) as well as heavier particles, i.e., particles with finite inertia [6,7]. For such inertial particles, for instance, numerical and experimental evidence suggests the segregation of particles into clusters [8][9][10][11].…”