Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session H28: Particle Laden Flows: Particle Turbulence Interactions |
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Chair: Pedram Pakseresht, Oregon State University Room: 610 |
Monday, November 25, 2019 8:00AM - 8:13AM |
H28.00001: Particle-laden Channel Flow with Strong Radiative Heating Jacob West, Sanjiva Lele In particle-based solar receivers, dense particles in a turbulent flow are radiatively heated, and in turn transfer energy to a carrier fluid via convection. When the particle mass loading and radiative heating are large enough to cause $\mathcal{O}$(1) changes in carrier gas density and viscosity, this coupling introduces additional effects on the turbulence, beyond the turbulence modulation expected in isothermal two-way coupled particle-laden flows. Using a multiphysics code to solve the coupled Navier-Stokes equations, radiative transport equation, and Lagrangian particle trajectories, we perform direct numerical simulation of an irradiated channel flow at low Reynolds number, using the point particle representation. In this study, we present turbulence statistics and the turbulence kinetic energy budget for this flow at various particle mass loading and incident radiation levels. Funding support provided by US Department of Energy (DOE), Predictive Science Academic Alliance Program (PSAAP) II Center at Stanford: DE-NA-0002373 [Preview Abstract] |
Monday, November 25, 2019 8:13AM - 8:26AM |
H28.00002: Interaction between Saltating Particles and Turbulent Structures in Wall Region of Boundary Layer Wei Zhu Interaction between saltating particles and turbulent structures in the wall region of boundary layers was investigated through vertical 4-point measurements of wind fluctuations and sand particle counts synchronously at the Qingtu Lake Observation Array (QLOA) site. The measuring spots were positioned within the sand saltation layer at wall-normal heights of 0.15, 0.2, 0.3 and 0.5m respectively. Based on autocorrelation analysis on the spatial scale of coherent structures, the results show that saltating particles cause the streamwise length scale of coherent structures in the wall region decrease, and the effect introduced by moving particle-phase becomes more obvious as the wall-normal distance decreases. Spectrum analysis on the one-hour wind fluctuations with and without saltating particles shows that saltating particles significantly enhance small-scale turbulent fluctuations while the large-scale motions are weakened in the near wall region. These results indicate that saltating particles destroy the large-scale motions at the bottom of the logarithmic region of the Atmospheric Surface Layer (ASL), which are dissipated into smaller-scale structures. [Preview Abstract] |
Monday, November 25, 2019 8:26AM - 8:39AM |
H28.00003: Comparison of Euler-Lagrange schemes in two-way coupled particle-laden channel flow Jeremy Horwitz, Gianluca Iaccarino, John Eaton, Ali Mani Considerable recent work to advance the state-of-the-art in Euler-Lagrange modelling of particle-laden flows has focused on the development of methods to estimate the undisturbed fluid velocity. This quantity is needed to calculate the drag force, which couples the motion of particles to the fluid. Historically, the undisturbed fluid velocity was estimated as the interpolated fluid velocity at the particle location. However, this estimate can be highly inaccurate when the particle size is not small compared with the mesh size. Promising new approaches have been developed to accurately estimate the undisturbed fluid velocity at particle locations for particle sizes up to and exceeding the grid spacing. One limitation of these methodologies is that they apply strictly in unbounded settings, where the computed disturbance flow can freely decay. In wall-bounded configurations, the disturbance must decay more rapidly---to satisfy no-slip and no-penetration at solid boundaries. Though a number of existing schemes are suitable on anisotropic grid arrangements which are typical of wall-bounded flows, we demonstrate they nevertheless cannot accurately predict the undisturbed fluid velocity at all wall-normal separations. We present an alternative paradigm which can improve undisturbed fluid velocity predictions in wall-bounded environments and apply this methodology to turbulent particle-laden channel flow. [Preview Abstract] |
Monday, November 25, 2019 8:39AM - 8:52AM |
H28.00004: Transport and two-way coupling effect of inertial particles by large-scale and very-large-scale motions in turbulence Guiquan Wang, David Richter Direct numerical simulations two-way coupled with inertial particles are used to investigate the particle distribution and two-way coupling effects associated with the large-scale motions (LSMs) and very-large-scale motions (VLSMs) in an open channel flow at a moderate Reynolds number. One method of filtering the VLSMs from the flow is via artificial domain truncation, which alters the mean particle concentration profile and particle clustering due to the removal of VLSMs from a large domain simulation. In order to exclude possible correlation of the turbulence introduced by a small domain size with periodic boundary conditions, low- and high-pass filtering is performed during the simulation to isolate the particle interaction with different spatial scales. The results show that particle accumulation and turbophoresis are under-predicted without VLSMs, whereas the particle clustering and two-way coupling effects are mainly determined by particle coupling with LSMs. In the inner layer, the elongated streamwise anisotropic particle clustering can be reproduced by particles coupling solely with LSMs for low Stokes number particles. However, we do not observe similar particle clustering behavior in the outer layer as seen in the full simulation. [Preview Abstract] |
Monday, November 25, 2019 8:52AM - 9:05AM |
H28.00005: Characterization of Inertial Particles in Turbulent Axisymmetric Wakes of a Porous Disk Kristin Travis, Sarah E. Smith, Mickaël Bourgoin, Henda Djeridi, Raúl Bayoán Cal, Martin Obligado Previous studies have suggested that dense particles such as dust and precipitation affect wind turbine performance. This study investigates the effects of micrometric inertial particles in the turbulent axisymmetric wake behind a stationary porous disk in a wind tunnel. Recent studies have explored turbulent wakes of stationary porous disks as analogs to the wakes of moving rotors yet inertial particles have not been considered. Phase doppler interferometry and particle image velocimetry were implemented in the near and far wake regions to study the effect of turbulent wakes on the transport of water droplets (with a mean diameter of 60μm). Reynolds numbers and water volume fractions were tested over ranges [$Re_D$ $(17.7 \times 10^3 - 98.6 \times 10^3)$] and [$\phi_v$ $(3.9 \times 10^{-6} - 2.6 \times 10^{-5})$] respectively. Results on the size distribution of particles within the wake, their settling velocity and the preferential concentration are discussed, showing a complex dynamics of such particles, as small particles are entrained and trapped in the near wake. [Preview Abstract] |
Monday, November 25, 2019 9:05AM - 9:18AM |
H28.00006: The role of discrete and carrier phase mechanical coupling in the inertial particles settling velocity Daniel Odens Mora, Martin Obligado, Alberto Aliseda, Alain Cartellier Inertial particles settling velocity plays a non-negligible role in several environmental, and industrial applications, such as, cloud formation and pollutant dispersion. In this study, we have recorded via Laser Doppler Interferometry the vertical and horizontal velocities of sub-kolmogorov particles in a wind tunnel facility. We have explored a wide range of Taylor Reynolds numbers (between 40 and 650) by means of an active (actuated in two different modes), and a classical passive grid. We were able to estimate the turbulence modulation coming from the inertial particles presence with the help of a recent method proposed in the literature. The particle settling velocity data recorded for the different grids tested seems to better collapse when the turbulence modulation by the particles is included into the scalings. [Preview Abstract] |
Monday, November 25, 2019 9:18AM - 9:31AM |
H28.00007: Pair dispersions of particles during turbulence transition Chung-min Lee, Armann Gylfason, Federico Toschi Small passive and inertial particles are present in a variety of natural or engineering flows, and their transportation and mixing by multi-scale turbulence is both of theoretical interest and practical importance. In many natural and industrial environments, however, the turbulent flow is in a transient state. As a prototype system, we investigate the transition from isotropic to anisotropic turbulence by looking at the influence of a transitioning turbulent flow on the statistical representation of the dynamics of particles, and compare with results from homogeneous and isotropic flows. We conduct Direct Numerical Simulations of initially homogeneous turbulence, on which we suddenly impose a mean shear. The flows are initially seeded with passive and inertial particles, assumed of size that is sufficiently small and at sufficiently low seeding density so that their effect on the turbulent flow field can be neglected, and inter-particle dynamics can be ignored. Our interest is on fundamental Lagrangian statistics of the particle motions. In particular we study pair dispersions of passive and inertial particles, and we will discuss approximations to model these behaviors. Relative velocity and covariance of relative velocity and relative acceleration will also be presented. [Preview Abstract] |
Monday, November 25, 2019 9:31AM - 9:44AM |
H28.00008: A correction scheme for two-way coupled Euler-Lagrange wall-bounded flows Pedram Pakseresht, Mahdi Esmaily, Sourabh V. Apte The accuracy of Euler-Lagrange point-particle methods in predicting the drag force reduces when the two phases are two-way coupled owing to the disturbance created by the point-particle force on the background fluid flow. Such disturbance produces an error since the drag closure models often rely on the slip velocity computed based on the {\it undisturbed} fluid velocity, which is not readily available. Recently few approaches have been developed for retrieving the undisturbed fluid velocity for unbounded flows only, where the disturbance field is not influenced by the no-slip boundary condition on walls. In this work, the correction scheme introduced by Esmaily \& Horwitz (JCP, 2018) is extended to wall-bounded flows. It is shown that the newly developed model is generic for all types of flows with and without wall boundaries. The model is tested for a particle settling in a quiescent flow parallel to the wall at different wall distances. It is shown that ignoring the wall effects on correcting the disturbed velocity results in under prediction of settling velocity that is on the same order of magnitude of the uncorrected scheme for particles very close to the wall, underscoring the need for this wall-modified correction for wall-bounded flows. [Preview Abstract] |
Monday, November 25, 2019 9:44AM - 9:57AM |
H28.00009: Feedback Effect of Dispersed Particles on Sustaining Mechanism of Wall Turbulence Yoichi Mito The influence of interaction between particles and fluid turbulence on the latter, which is represented by Lagrangian time scales of the fluid turbulence seen by particles, has been considered using our recent findings on the scales of the fluid motions, that carry particles, in fully-developed turbulent fluid flow through a channel and the Lagrangian measurements, done in a direct numerical simulation of the turbulent fluid flow through a vertical channel where solid particles were ejected from uniformly distributed point sources, of which the latter were presented last APS-DFD meeting. Fluid turbulence is damped by the feedback forces exerted by particles and is damped further with increasing inertia of particles, that is, with increasing scales of particle motions. The increases in the scales of fluid motions in the fluid turbulence, that is being damped by addition of particles, reflect disappearance of small-scale fluid motions and resultant development of non-turbulent fluid motions. These indicate that small-scale fluid motions, such as vortices, are sustained by large-scale fluid motions and that the fluid turbulence is sustained by the multi-directionality and multi-dimensionality of large-scale fluid motions, which are enhanced by small-scale fluid motions. [Preview Abstract] |
Monday, November 25, 2019 9:57AM - 10:10AM |
H28.00010: Particle-turbulence and particle-wall interactions in a turbulent boundary layer Yi Hui Tee, Ellen Longmire The motions of finite-size spheres moving in a turbulent boundary layer are affected by both wall friction and coherent structures. 3D particle tracking experiments conducted at Re$_{\mathrm{\tau }}=$ 700 and 1300 with sphere diameters of 60 and 120 viscous units revealed two distinct sphere behaviors dependent on density ratio. Spheres held stationary on the wall with a density ratio of 1.003 always lifted off once released, translated without rotating, and subsequently fell back toward the wall. After the spheres had accelerated significantly, lift-off events with height larger than those following the initial lift-offs were observed frequently. These subsequent lift-off events are attributed to coherent structures in the flow. By contrast, spheres with a density ratio of 1.15 did not lift off initially, but slid along the wall once released. Further downstream, these spheres developed forward rotation as well as significant rotation about the wall-normal axis, and coincidentally experienced repeated weak lift-offs. Wall friction was crucial in impeding the sphere acceleration as well as in helping initiate rotation. In the talk, PIV results on surrounding flow fields will be used to help explain the various particle-turbulence and particle-wall interactions. [Preview Abstract] |
Monday, November 25, 2019 10:10AM - 10:23AM |
H28.00011: Two-Phase Measurements Of Small Inertial Particles In High-Re Turbulent Boundary Layers Tim Berk, Filippo Coletti The interaction of small inertial particles with a turbulent boundary layer is of importance in a wealth of physical phenomena, e.g., transport of particles in the atmospheric boundary layer as well as industrial and biological applications. Our in-depth understanding is thwarted by the lack of comprehensive experiments. Here we perform two-phase measurements of microscopic inertial particles in high-Re turbulent boundary layers. Particles are injected in the boundary layer in the one-way coupled regime. Flow field measurements (PIV) and tracking of inertial particles (PTV) are performed simultaneously. This enables conditioned evaluation of fluid velocity at and around the inertial particles. The conditionally averaged flow around particles indicates the preferential sampling of specific flow structures by the inertial particles. This preferential sampling can help explain deviation of streamwise particle velocity from the mean fluid velocity and deviation of vertical particle velocity from the Stokes settling velocity. The fluid velocity at the particle location is an important term in, e.g., the advection-diffusion equation. Moreover, using the simultaneous two-phase measurements, widespread assumptions for estimating the concentration profile can be critically evaluated. [Preview Abstract] |
Monday, November 25, 2019 10:23AM - 10:36AM |
H28.00012: On the physical mechanism of the two-way interaction between polymers and near-wall turbulence Junghoon Lee, Changhoon Lee The two-way interaction between polymers and near-wall turbulence was investigated through direct numerical simulations (DNS) of turbulent channel flow coupled with Brownian dynamics simulations. The finitely extensible nonlinear elastic (FENE) dumbbell model was used to describe the motion of polymer molecules. The effect of polymers was included in the Navier-Stokes equations by exerting their reaction forces back on the fluid at the nearby eight grid points via a projection technique. In our simulations, the maximum extension of the FENE dumbbells does not exceed 0.6 in wall units, which is 100 times their equilibrium length. We examine how the polymer feedback forces affect the fluctuating motion of the fluid in coherent near-wall turbulent structures for various polymer relaxation times. Our results are generally consistent with previous DNS studies based on a continuum approach. We provide a more detailed picture of the physical mechanisms for turbulence modification by polymers through investigation on polymer stretch and orientation in the Lagrangian frame. [Preview Abstract] |
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