# Particle capture by turbulent recirculation zones measured using long-time Lagrangian particle tracking

Particle capture by turbulent recirculation zones measured using long-time Lagrangian particle... We have measured the trajectories of particles into, and around, the recirculation zone formed in water flowing through a sudden pipe expansion with radius ratio 1:3.7, at Reynolds numbers between 5,960 and 41,700 over a range of particle Stokes number (here defined as $$St = {\frac{{T_{\text{f}} }}{{\tau_{\text{p}} }}}$$ , where T f is an appropriate mean or turbulent timescale of the fluid flow and a particle relaxation time, τp,) between 6.2 and 51 and drift parameter between 0.3 and 2.8. The particles were thus weakly inertial but nevertheless heavy with a diameter about an order of magnitude larger than the Kolmogorov scale. Trajectories of particles, released individually into the flow, were taken in a Lagrangian framework by a three-dimensional particle tracking velocimeter using a single 25 Hz framing rate intensified CCD camera. Trajectories are quantified by the axial distribution of the locations of particle axial velocity component reversal and the probability distributions of trajectory angle and curvature. The effect of increasing the drift parameter was to reduce the tendency for particles to enter the recirculation zone. For centreline release, the proportion of particles entering the recirculation zone and acquiring a negative velocity decreased from about 80% to none and from about 66% to none, respectively, as the drift parameter increased from 0.3 to 2.8. Almost half of the particles experienced a relatively large change of direction corresponding to a radius of curvature of their trajectory comparable to, or smaller than, the radius of the downstream pipe. This was due to the interaction between these particles and eddies of this size in the downstream pipe and provides experimental evidence that particles are swept by large eddies into the recirculation zone over 1.0 <  $$Z^{*}$$  < 2.5, where $$Z^{*}$$ is axial distance from the expansion plane normalized by the downstream pipe diameter, which was well upstream of the reattachment point at the wall ( $$Z^{*} \approx 3. 5$$ ). Once inside the recirculation zone, the particle motion was governed more by the drift parameter than by the Stokes number. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

# Particle capture by turbulent recirculation zones measured using long-time Lagrangian particle tracking

, Volume 51 (1) – Jan 5, 2011
27 pages

/lp/springer_journal/particle-capture-by-turbulent-recirculation-zones-measured-using-long-sTfFFCTCnd
Publisher
Springer-Verlag
Subject
Engineering; Fluid- and Aerodynamics; Engineering Fluid Dynamics; Engineering Thermodynamics, Heat and Mass Transfer
ISSN
0723-4864
eISSN
1432-1114
D.O.I.
10.1007/s00348-010-0913-1
Publisher site
See Article on Publisher Site

### Abstract

We have measured the trajectories of particles into, and around, the recirculation zone formed in water flowing through a sudden pipe expansion with radius ratio 1:3.7, at Reynolds numbers between 5,960 and 41,700 over a range of particle Stokes number (here defined as $$St = {\frac{{T_{\text{f}} }}{{\tau_{\text{p}} }}}$$ , where T f is an appropriate mean or turbulent timescale of the fluid flow and a particle relaxation time, τp,) between 6.2 and 51 and drift parameter between 0.3 and 2.8. The particles were thus weakly inertial but nevertheless heavy with a diameter about an order of magnitude larger than the Kolmogorov scale. Trajectories of particles, released individually into the flow, were taken in a Lagrangian framework by a three-dimensional particle tracking velocimeter using a single 25 Hz framing rate intensified CCD camera. Trajectories are quantified by the axial distribution of the locations of particle axial velocity component reversal and the probability distributions of trajectory angle and curvature. The effect of increasing the drift parameter was to reduce the tendency for particles to enter the recirculation zone. For centreline release, the proportion of particles entering the recirculation zone and acquiring a negative velocity decreased from about 80% to none and from about 66% to none, respectively, as the drift parameter increased from 0.3 to 2.8. Almost half of the particles experienced a relatively large change of direction corresponding to a radius of curvature of their trajectory comparable to, or smaller than, the radius of the downstream pipe. This was due to the interaction between these particles and eddies of this size in the downstream pipe and provides experimental evidence that particles are swept by large eddies into the recirculation zone over 1.0 <  $$Z^{*}$$  < 2.5, where $$Z^{*}$$ is axial distance from the expansion plane normalized by the downstream pipe diameter, which was well upstream of the reattachment point at the wall ( $$Z^{*} \approx 3. 5$$ ). Once inside the recirculation zone, the particle motion was governed more by the drift parameter than by the Stokes number.

### Journal

Experiments in FluidsSpringer Journals

Published: Jan 5, 2011

## You’re reading a free preview. Subscribe to read the entire article.

### DeepDyve is your personal research library

It’s your single place to instantly
that matters to you.

over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month ### Explore the DeepDyve Library ### Search Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly ### Organize Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place. ### Access Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals. ### Your journals are on DeepDyve Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more. All the latest content is available, no embargo periods. DeepDyve ### Freelancer DeepDyve ### Pro Price FREE$49/month
\$360/year

Save searches from
PubMed

Create lists to

Export lists, citations