Change search
Refine search result
1 - 6 of 6
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. De Marchis, M.
    et al.
    Milici, B.
    Sardina, Gaetano
    Stockholm University, Faculty of Science, Department of Meteorology .
    Napoli, E.
    Interaction between turbulent structures and particles in roughened channel2016In: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 78, p. 117-131Article in journal (Refereed)
    Abstract [en]

    The distribution of inertial particles in turbulent flows is highly non-uniform and is driven by the local dynamics of the turbulent structures of the underlying carrier flow field. In the specific context of dilute particle-laden wall-bounded flows, deposition and resuspension mechanisms are dominated by the interaction between inertial particles and coherent turbulent structures characteristic of the wall region. The macroscopic behavior of these two-phase systems is influenced by particle inertia, which plays a role at the microscale of a single dispersed element. These turbulent structures, which control the turbulent regeneration cycles, are strongly affected by the wall roughness. The effect of the roughness on turbulent transport in dilute suspension has been still poorly investigated. The issue is discussed here by addressing direct numerical simulation (DNS), at friction Reynolds number Re-tau = 180, of a dilute dispersion of heavy particles in a turbulent channel flow, spanning two orders of magnitude of particle inertia. The irregular wall roughness is obtained through the superimposition of four sinusoidal functions of different wavelengths and random amplitudes. We use DNS combined with Lagrangian particle tracking to characterize the effect of inertia on particle preferential accumulation, looking at the effect of roughness on particle distribution, by comparing the statistics computed for fluid and particles of different size and observing differences in terms of distribution patterns and preferential sampling.

  • 2. Gualtieri, P.
    et al.
    Picano, F.
    Sardina, Gaetano
    Stockholm University, Faculty of Science, Department of Meteorology .
    Casciola, C. M.
    Exact regularized point particle method for multiphase fows in the two-way coupling regime2015In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 773, p. 520-561Article in journal (Refereed)
    Abstract [en]

    Particulate flows have mainly been studied under the simplifying assumption of a one-way coupling regime where the disperse phase does not modify the carrier fluid. A more complete view of multiphase flows can be gained calling into play two-way coupling effects, i.e. by accounting for the inter-phase momentum exchange, which is certainly relevant at increasing mass loading. In this paper we present a new methodology rigorously designed to capture the inter-phase momentum exchange for particles smaller than the smallest hydrodynamical scale, e.g. the Kolmogorov scale in a turbulent flow. The momentum coupling mechanism exploits the unsteady Stokes flow around a small rigid sphere, where the transient disturbance produced by each particle is evaluated in a closed form. The particles are described as lumped point masses, which would lead to the appearance of singularities. A rigorous regularization procedure is conceived to extract the physically relevant interactions between the particles and the fluid which avoids any 'ad hoc' assumption. The approach is suited for high-efficiency implementation on massively parallel machines since the transient disturbance produced by the particles is strongly localized in space. We will show that hundreds of thousands of particles can be handled at an affordable computational cost, as demonstrated by a preliminary application to a particle-laden turbulent shear flow.

  • 3. Noorani, Azad
    et al.
    Sardina, Gaetano
    Stockholm University, Faculty of Science, Department of Meteorology .
    Brandt, Luca
    Schlatter, Philipp
    Particle Velocity and Acceleration in Turbulent Bent Pipe Flows2015In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 95, no 2-3, p. 539-559Article in journal (Refereed)
    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.

  • 4. Nowbahar, Arash
    et al.
    Sardina, Gaetano
    KTH Mech, SeRC Swedish E Sci Res Ctr, Stockholm, Sweden.
    Picano, Francesco
    KTH Mech, SeRC Swedish E Sci Res Ctr, Stockholm, Sweden.
    Brandt, Luca
    KTH Mech, SeRC Swedish E Sci Res Ctr, Stockholm, Sweden.
    Turbophoresis attenuation in a turbulent channel flow with polymer additives2013In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 732, p. 706-719Article in journal (Refereed)
  • 5. Olivieri, S.
    et al.
    Picano, F.
    Sardina, Gaetano
    Stockholm University, Faculty of Science, Department of Meteorology . Royal Institute of Technology .
    Iudicone, D.
    Brandt, L.
    The effect of the Basset history force on particle clustering in homogeneous and isotropic turbulence2014In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 26, no 4, p. 041704-Article in journal (Refereed)
    Abstract [en]

    We study the effect of the Basset history force on the dynamics of small particles transported in homogeneous and isotropic turbulence and show that this term, often neglected in previous numerical studies, reduces the small-scale clustering typical of inertial particles. The contribution of this force to the total particle acceleration is, on average, responsible for about 10% of the total acceleration and particularly relevant during rare strong events. At moderate density ratios, i.e., sand or metal powder in water, its presence alters the balance of forces determining the particle acceleration.

  • 6.
    Sardina, Gaetano
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Picano, Francesco
    Brandt, Luca
    Caballero, Rodrigo
    Stockholm University, Faculty of Science, Department of Meteorology .
    Continuous Growth of Droplet Size Variance due to Condensation in Turbulent Clouds2015In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 115, no 18, article id 184501Article in journal (Refereed)
    Abstract [en]

    We use a stochastic model and direct numerical simulation to study the impact of turbulence on cloud droplet growth by condensation. We show that the variance of the droplet size distribution increases in time as t(1/2), with growth rate proportional to the large-to-small turbulent scale separation and to the turbulence integral scales but independent of the mean turbulent dissipation. Direct numerical simulations confirm this result and produce realistically broad droplet size spectra over time intervals of 20 min, comparable with the time of rain formation.

1 - 6 of 6
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf