Introducing OpenLPT: new method of removing ghost particles and high-concentration particle shadow tracking

Lift and drag coefficients of deformable bubbles in intense turbulence determined from bubble rise velocity

“…In addition, in each frame, over 6000 tracer particles were tracked simultaneously using our in-house high-concentration particle tracking code (Tan et al 2019(Tan et al , 2020. A snapshot of our three-dimensional reconstructed results, including both three-dimensional bubble geometry and three-dimensional tracks of surrounding tracers, is shown in figure 1(c).…”

Simultaneous measurements of deforming Hinze-scale bubbles with surrounding turbulence

“…Satisfying both criteria is challenging. For example, many systems that feature a large region of homogeneous and isotropic turbulence tend to have a low energy dissipation rate (Variano, Bodenschatz & Cowen 2004;Mercado et al 2012) ( = O(10 −5 -10 −3 ) m 2 s −3 ), whereas facilities that use water jets to break super-Hinze-scale bubbles can generate a large energy dissipation rate = O(0.1-10 3 ) m 2 s −3 at the cost of having strong flow inhomogeneity and anisotropy (Martínez-Bazán et al 1999b;Vejražka et al 2018).…”

“…Turbulence in the test section was generated using 88 high-speed water jets (with jet velocity up to 12 m s −1 ), each of which has a diameter d j of 5 mm, firing coaxially downward into the test section along with the mean flow. The firing pattern of these momentum jets was randomised in a way similar to the work by Variano et al (2004) in order to ensure that no secondary flow structure would develop in the test section (De Silva & Fernando 1994;Srdic, Fernando & Montenegro 1996;Variano et al 2004). On average, 12.5 % of the jets were kept on at a time as this was found to maximise the turbulence intensity.…”

“…Here ν is the kinematic viscosity of water. We can resolve such a small scale thanks to our in-house high-concentration particle-tracking system (Tan et al 2020) that employs the Shake-the-Box method (Schanz, Gesemann & Schröder 2016).…”

“…In practice, on average, 30-40 particles were used to perform least-squares fit by seeking the minimum value of the squared residuals (Pumir, Bodenschatz & Xu 2013;Ni et al 2015). Although finite-sized bubbles typically come with a large search radius and abundant nearby tracer particles thanks to our tracking method (Tan et al 2020), particles in the vicinity of a bubble are still distributed randomly in space. If nearby particles stay primarily within a quasi-2-D plane, the estimation of the out-of-plane velocity gradient will have large uncertainty.…”