Bulletin of the American Physical Society
75th Annual Meeting of the Division of Fluid Dynamics
Volume 67, Number 19
Sunday–Tuesday, November 20–22, 2022; Indiana Convention Center, Indianapolis, Indiana.
Session A10: Particle-Turbulence Interactions I |
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Chair: Tim Berk, Utah State University Room: 138 |
Sunday, November 20, 2022 8:00AM - 8:13AM |
A10.00001: Direct numerical simulation of hydrosol dynamics in turbulent channel flow Sanaz Abbasi, Amirfarhang Mehdizadeh, Pedro Costa Deposition of Asphaltene particles in crude oil during production/process poses a serious challenge in petroleum industry and has gone unaddressed yet. More specifically, dispersion and deposition of hydrosol (solid particles in a liquid such as asphaltene particles in crude oil) have not been studied extensively, and may have different dynamics compared to widely studied aerosol (solid particles in a gas) dynamics due to different properties of the carrier (fluid) phase such as density. Here we aim to take a foundational step to unveil the major underlying mechanisms of asphaltene particle (hydrosol) deposition process using high fidelity data obtained from Point-Particle Direct Numerical Simulations (PP-DNS). In particular, dispersion and deposition dynamics (e.g., deposition velocity) of hydrosol will be assessed and compared to aerosol when small particles are considered. |
Sunday, November 20, 2022 8:13AM - 8:26AM |
A10.00002: Physics-informed neural networks for synthesizing preferential concentration of particles in turbulent flows Thibault OUJIA, Suhas S Jain, Keigo Matsuda, Kai Schneider, Jacob R West, Kazuki Maeda Cluster and void formation are key processes in the dynamics of particle-laden turbulence. Here we consider direct numerical simulation (DNS) of inertial point particles in homogeneous isotropic turbulence at high Reynolds numbers as the database. We propose different data driven and physics-informed machine learning techniques for synthesizing preferential concentration fields. For training, we are using the enstrophy fields computed by DNS and compare the accuracy using the enstrophy either in the physical space or a sparse wavelet space representation of vorticity. We propose to use and compare autoencoder, U-net, and generative adversarial network (GAN) approaches. We assess the statistical properties of the generated fields, and we find that the best results, showing clusters and voids, are obtained with GANs. This yields interesting perspectives for reducing the computational cost of expensive DNS computations by avoiding the tracking of billions of particles. We also explore the inverse problem of synthesizing the enstrophy fields using the particle density distribution, at different Stokes numbers, as the input. Our study thus provides perspectives to use neural networks to predict the enstrophy field using particle data in experimental PIV measurements. |
Sunday, November 20, 2022 8:26AM - 8:39AM |
A10.00003: Coupling of anisotropic fiber tracking with instantaneous volumetric flow field in turbulent channel flows. Giuseppe Caridi, Vlad Giurgiu, Mobin Alipour, Marco De Paoli, Alfredo Soldati Time-resolved and instantaneous volumetric measurements are coupled with Lagragian tracking of anisotropic curved fibers in the TU Wien Turbulent Water Channel. The experiments are conducted at friction Reynolds number ranging from 180 to 720 in the viscous wall region and in the channel center. The length of the fiber (1.2mm) and the spatial resolution of the velocity vector field (0.5mm) are comparable to the Kolmogorov length scales (0.3-0.8 mm). Full rotation rate tensor of small slender fibers is simultaneously captured with instantaneous velocity gradient tensor of the flow, which allows the determination of statistical and instantaneous velocity and rotational slip between the fiber and the flow structures (laden). |
Sunday, November 20, 2022 8:39AM - 8:52AM |
A10.00004: Effect of low clay concentration on nearly isotropic turbulence Shyuan Cheng, Shaelynn Kaufman, Vaibhav Tipnis, Jim Best, Leonardo Chamorro An experimental investigation was conducted to investigate and quantify the effect of low clay concentrations on nearly isotropic turbulence created in a customized cubic mixing box. A novel approach using Laponite RD, a synthetic clay, produced a nearly transparent water-clay mixture suspension. This clay-laden flow allowed full optical access for high-speed particle image velocimetry (PIV) to characterize the spatio-temporal dynamics around the center of the mixing box. We investigated mass concentrations of C(%) = 0, 1, 1.5, and 2, which minimized non-Newtonian behavior. Clay particles significantly modulated the turbulence structure even at low concentrations of laponite with a monotonic reduction of turbulence kinetic energy, mean dissipation rate, and an increase of the Taylor microscale, λ, as clay concentration increased. Velocity spectra demonstrated a clear dependence on clay concentration and the Taylor microscale Reynolds number scaling correction, p, of the power law in the inertial subrange. The Taylor microscale estimation by p-factor agrees well with those obtained from structure function and direct PIV measurements. The energy budget suggests that the reduction in TKE and increase in λ are likely associated with the presence of clay particle aggregation. |
Sunday, November 20, 2022 8:52AM - 9:05AM |
A10.00005: Transport of Inertial Droplets in a Turbulent Boundary Layer Martin A Erinin, Luc Deike The transport of highly inertial droplets in the presence of a turbulent boundary layer is studied experimentally inside a wind tunnel. Water droplets are injected into the boundary layer at free-stream velocities ranging from U_{∞} = 2.4 to 6.6 m/s with a boundary layer thickness ranging from δ = 11.4 to 12.5 cm. The size, speed, and acceleration of droplets are measured using a high-speed cinematic in-line holographic system positioned 162 cm downstream from the nozzle and at many wall-normal streamwise locations spanning the full thickness of the boundary layer. Water droplets with diameters ranging from 30 to 1000 μm are measured with corresponding Stokes numbers ranging from St_{η} = 0.11 to 160. Wall-normal droplet concentration and velocity profiles are reported. Droplet statistics like velocity and acceleration are discussed as a function of droplet size and wall-normal location. The importance of turbulence on the motion of highly inertial droplets is discussed and compared to similar statistics obtained from inertial droplets produced by breaking wind-forced waves. |
Sunday, November 20, 2022 9:05AM - 9:18AM |
A10.00006: On the suspended microplastic dispersion in turbulent shallow flows under progressive gravity waves Aman G. G Kidanemariam, Marco Mazzuoli, Jason Monty, Ivan Marusic When wind waves approach the coast over a relatively shallow water, the wave-induced orbital motion promotes the development of a turbulent boundary layer at the bottom, enhancing the transport and dispersion of suspended microplastics. Furthermore, the strong wave-bed interaction results in a net non-periodic shoreward Longuett-Higgins current close to the bottom superimposed to the wave orbital motion [1]. Via direct numerical simulation, we analyse the effect of the wave orbital motion, the steady current and the near-wall turbulence on the dispersion and vertical distribution of microplastics both inside and outside the bottom boundary layer. For performing the simulations, we utilise a boundary-fitted hybrid pseudo-spectral/finite-difference code which implicitly solves the Navier-Stokes equations together with the dynamic and kinematic boundary conditions at the free-surface. The motion of the suspended microplastics is treated by a Lagrangian particle tracking algorithm in the framework of the point-particle approach. The aim of this work is to understand the physical mechanisms behind the microplastic transport processes under shallow progressive waves. This has important implication in parameterising the mechanistic behaviour of suspended microplastics and assessing existing predictive microplastic transport models. |
Sunday, November 20, 2022 9:18AM - 9:31AM |
A10.00007: Modelling precipitation-driven flows in planetary interiors: effects of particle inertia and dissolution Quentin Kriaa, Eliot Subra, Benjamin Favier, Michael Le Bars As an analog of settling snow flakes in planetary interiors which may drive large scale motions in liquid metal, we instantaneously release clouds of glass spheres in a water tank, which quickly evolve as turbulent thermals. Synchronous cameras analyse the two-way coupling between the settling spheres and the fluid : one camera performs a Lagrangian tracking of particles while the other one analyses turbulence with PIV or LIF. The size of particles is systematically varied in the range 5µm-1mm. We notably show that due to particle-turbulence interactions, particle clouds entrain more than salt water clouds of identical mass excess, with an optimum of entrainment for a finite inertia, as confirmed by our 3D DNS of the same clouds using Basilisk. |
Sunday, November 20, 2022 9:31AM - 9:44AM |
A10.00008: Surfacing of gyrotactic swimmers in stratified/unstratified free-surface turbulence Cristian Marchioli, Francesco Zonta, Alfredo Soldati The surfacing of gyrotactic swimmers in free-surface turbulence mimics the dynamic behavior of several phytoplankton species in water bodies in the absence of large surface waves and ripples. We examine the surfacing dynamics via direct numerical simulation of open-channel turbulence at varying shear Reynolds number (from 170 to 1018 based on the channel height) coupled with Lagrangian tracking of inertialess swimmers with stability number covering 2 orders of magnitude, which orient themselves according to Jeffery equation. We consider both spherical and elongated swimmers, the latter being modeled as prolate ellipsoids with aspect ratio up to 10. We show that the vertical migration of the swimmers, which are initially distributed randomly throughout the flow, depends on both their re-orientation ability and shape. Once at the surface, swimmers tend to stay there and organize themselves into filamentary clusters, which are in direct correlation with the topology of surface turbulence. The surfacing process is found to depend strongly on the level of thermal stratification within the water body, which we examine at varying Richardson number (from 0, corresponding to the unstartified case, to 510, corresponding to a stratfied flow characterized by the occurrence of a thermocline below the free-surface). Our results indicate that free-surface turbulence and thermal stratification have a strong influence on the swimmers' spatial distribution and, in turn, on the carbon-dioxide exchange cycle across the water/atmosphere interface. |
Sunday, November 20, 2022 9:44AM - 9:57AM |
A10.00009: Effect of particle size on characteristics of transitional particle-laden pipe flow Sagnik Paul, Ellen K Longmire Neutrally buoyant particles in laminar pipe flow exhibit a phenomenon called the tubular pinch effect, where they accumulate at a certain radius near the wall. Particles also promote or hinder the transition to turbulence. The transitional regime is marked by intermittent turbulent structures called puffs. These phenomena are characterized by the particle-to-pipe diameter ratio(D/d), the particle volume fraction (ϕ), and Reynolds Number (Re). In the current study, we examine the interaction between polystyrene beads in a 20% glycerol-water solution (ρ=1046 kg-m^{-3}) and puffs using PTV. Even at small loadings (ϕ=0.2%), larger particles (D/d=43) lead to transition at lower Re than single-phase flow while smaller particles (D/d=86) delay the transition to higher Re. In the laminar regime, the particle concentration was found to peak near 0.88R. Puffs disrupt this accumulation, with the particles migrating radially inwards. The radial velocities of the particles are significant over a distance of 10D near the trailing edge of the puff, and the disruption persists for more than 100D. We examine the radial trends of particle velocity, concentration, and recovery with respect to particle size and volume fraction. |
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