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Particle Velocity and Acceleration in Turbulent Bent Pipe Flows
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre.
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre.ORCID iD: 0000-0002-4346-4732
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre.ORCID iD: 0000-0001-9627-5903
2015 (English)In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 95, no 2-3, 539-559 p.Article in journal (Refereed) Published
Abstract [en]

We study the dynamics of dilute micro-size inertial particles in turbulent curved pipe flows of different curvature by means of direct numerical simulations with one-way coupled Lagrangian particle tracking. The focus of this work is on the first and second order moments of the velocity and acceleration of the particulate phase, relevant statistics for any modelling effort, whereas the particle distribution is analysed in a previous companion paper. The aim is to understand the role of the cross-stream secondary motions (Dean vortices) on the particle dynamics. We identify the mean Dean vortices associated to the motion of the particles and show that these are moved towards the side-walls and, interestingly, more intense than those of the mean flow. Analysis of the streamwise particle flux reveals a substantial increase due to the secondary motions that brings particles towards the pipe core while moving them towards the outer bend. The in-plane particle flux, most intense in the flow viscous sub-layer along the side walls, increases with particle inertia and pipe curvature. The particle reflections at the outer bend, previously observed also in other strongly curved configurations, locally alter the particle axial and wall-normal velocity and increase turbulent kinetic energy.

Place, publisher, year, edition, pages
[Noorani, Azad; Brandt, Luca; Schlatter, Philipp] Royal Inst Technol, Linne FLOW Ctr, KTH Mech, SE-10044 Stockholm, Sweden. [Noorani, Azad; Brandt, Luca; Schlatter, Philipp] Royal Inst Technol, KTH Mech, Swedish E Sci Res Ctr SeRC, SE-10044 Stockholm, Sweden. [Sardina, Gaetano] Univ Stockholm, Dept Meteorol, S-10691 Stockholm, Sweden., 2015. Vol. 95, no 2-3, 539-559 p.
Keyword [en]
Curvature effect, Particulate dispersion, Secondary motion, Gas-solid flow, Bent pipe, Particle transport
National Category
Applied Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-176348DOI: 10.1007/s10494-015-9638-9ISI: 000362364500018Scopus ID: 2-s2.0-84947868160OAI: oai:DiVA.org:kth-176348DiVA: diva2:867879
Note

QC 20151106

Available from: 2015-11-06 Created: 2015-11-03 Last updated: 2017-12-01Bibliographically approved
In thesis
1. Particle-laden Turbulent Wall-bounded Flows in Moderately Complex Geometries
Open this publication in new window or tab >>Particle-laden Turbulent Wall-bounded Flows in Moderately Complex Geometries
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Wall-bounded turbulent dispersed multiphase flows occur in a variety of industrial, biological and environmental applications. The complex nature of the carrier and the particulate phase is elevated to a higher level when introducing geometrical complexities such as curved walls. Realising such flows and dispersed phases poses challenging problems both from computational and also physical point of view. The present thesis addresses some of these issues by studying a coupled Eulerian–Lagrangian computational framework.

The content of the thesis addresses both turbulent wall flows and coupled particle motion. In the first part, turbulent flow in straight pipes is simulated by means of direct numerical simulation (DNS) with the spectrally accurate code nek5000  to examine the Reynolds-number effect on turbulence statistics. The effect of the curvature to these canonical turbulent pipe flows is then added to generate Prandtl’s secondary motion of first kind. These configurations, as primary complex geometries in this study, are examined by means of statistical analysis to unfold the evolution of turbulence characteristics from a straight pipe. A fundamentally different Prandtl’s secondary motion of the second kind is also put to test by adding side-walls to a canonical turbulent channel flow and analysing the evolution of various statistical quantities with varying the duct width-to-height aspect ratios.

Having obtained a characterisation of the turbulent flow in the geometries of bent pipes and ducts, the dispersion of small heavy particles is modelled in these configurations by means of point particles which are one-way coupled to the flow. For this purpose a parallel Lagrangian Particle Tracking (LPT) scheme is implemented in the spectral-element code nek5000 . Its numerical accuracy, parallel scalability and general performance in realistic situations is scrutinised. The analysis of the resulting particle fields shows that even a small amount of secondary motion has a profound impact on the particle phase dynamics and its concentration maps.

For each of the aforementioned turbulent flow cases new and challenging questions have arisen to be addressed in the present research works. The goal of extending understanding of the particle dispersion in turbulent bent pipes and rectangular ducts are also achieved.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xii, 71 p.
Series
TRITA-MEK, ISSN 0348-467X ; 2015:09
Keyword
turbulent, complex geometry, particle
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-177310 (URN)978-91-7595-785-2 (ISBN)
Public defence
2015-12-04, F3, Lindstedtsvägen 26, KTH, Stockholm, 11:01 (English)
Opponent
Supervisors
Funder
Swedish e‐Science Research Center
Note

QC 20151118

Available from: 2015-11-18 Created: 2015-11-18 Last updated: 2015-11-18Bibliographically approved

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