Bulletin of the American Physical Society
71st Annual Meeting of the APS Division of Fluid Dynamics
Volume 63, Number 13
Sunday–Tuesday, November 18–20, 2018; Atlanta, Georgia
Session D37: Particle-Laden Flows II |
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Chair: Margaret Byron, Pennsylvania State University Room: Georgia World Congress Center B409 |
Sunday, November 18, 2018 2:30PM - 2:43PM |
D37.00001: Volumetric Displacement Effects of the Gaseous Phase on the Euler-Lagrange Prediction of Spray Atomization Pedram Pakseresht, Sourabh V. Apte Accurate prediction of spray atomization process using an Euler-Lagrange (EL) approach is challenging because of the high volume fraction of the liquid phase in dense regimes. This would in reality displace a remarkable portion of the gaseous phase which is commonly ignored in the standard EL approaches. In this work, to capture the volumetric displacement effects using an EL approach, the spatio-temporal changes in the volume fraction of the gaseous phase are taken into account. This leads to zero-Mach number, variable density equations that give rise to a source terms in both momentum and continuity equations. These are typically neglected in the standard EL spray simulations. In this work, the effect of these source terms is quantified on a spray atomization process where the volume fraction of the injecting blob is 52%. A deterministic secondary breakup model together with the standard point-particle forces are coupled with LES of the carrier phase to model the atomization. Spray characteristics are evaluated with and without the volume displacement effects to identify regimes where such effects become important. |
Sunday, November 18, 2018 2:43PM - 2:56PM |
D37.00002: A novel wall-particle collision model for arbitrary-shaped particle Mohsen Daghooghi, Iman Borazjani A numerical scheme based on a discrete model is proposed for the wall-particle collision when a non-spherical particle falls on a wall surface under the gravitational field. In this model, contrary to conventional discrete methods (e.g. discrete element method), no repulsive force (torque) is added to particles during collision procedure. Instead, upon the detection of the collision, particle’s kinematics is modified based on 3D dynamics of a rigid particle such that it reaches to a realistic and physical steady-state. This method is developed to be coupled with the immersed boundary flow solver to simulate the sedimentation of arbitrary-shaped rigid particles in an incompressible Newtonian fluid. However, it also can be used in all discrete models in a various range of Reynolds numbers form high Reynolds number solid-gas to very low Reynolds number solid-liquid applications. |
Sunday, November 18, 2018 2:56PM - 3:09PM |
D37.00003: Influence of electrostatic charges and solid-mass loading on particle dynamics in duct flows Holger Grosshans, Miltiadis V. Papalexandris The modulation of particle-laden flows through electrostatic forces is utilized in various industrial applications, for example powder coating and electrostatic precipitation. However, excessive charge accumulation also results in the formation of deposits on component surfaces and spark discharges which may lead to dust explosions. In order to elucidate the dynamics of charged particles, we performed large-eddy simulations of a fully-developed turbulent gas flow (Re = 10 000) through a generic squared-shaped duct. The flow was seeded by charged monodisperse particles. In our talk we will discuss the influence of the solid-mass loading and the electrostatic charges carried by the particles on the particle concentration over the duct’s cross section. Electrostatic charges of 0 pC, 0.125 pC and 0.25 pC were assigned to the particles whereas solid-gas mass loading ratios between 0.01 and 0.04 were considered. Based on our previous findings we expect an increase of each of these parameters to counteract the turbophoretic drift and smoothen the particle concentration profiles. |
Sunday, November 18, 2018 3:09PM - 3:22PM |
D37.00004: The role of particle properties on powder electrification during pneumatic transport Lise Ceresiat, Holger Grosshans, Miltiadis V. Papalexandris During pneumatic transport, powders often accumulate electrostatic charge due to collisions of the particles with the walls of the pipe, which may cause hazardous spark discharges. For this reason, there is a strong interest in studying various options to constrain the electrification process. In this talk we present results of numerical simulations that we performed in order to evaluate the influence of certain key particle properties to the build-up of charge. In our study, the particle-laden turbulent flow is treated numerically via Large Eddy Simulations (LES), while the motion of each particle is tracked in Langrangian framework, assuming four-way coupling between particles and carrier gas. Further, the governing equations are supplemented with dynamic models accounting for the particle-wall and particle-particle charge exchange. In our presentation we discuss results of the parametric studies with respect to the particle diameter, density and elastic properties of the powder. Our talk concludes with the results of a parametric study with respect to the flow rates of the carrier gas and the powder. |
Sunday, November 18, 2018 3:22PM - 3:35PM |
D37.00005: Effect of flow disturbance around a particle for fluid force estimation in two-way coupling simulation Toshiaki Fukada, Shintaro Takeuchi, Takeo Kajishima In two-way coupling simulations of particle-laden flows, obtained flow field is disturbed by particles and spatially averaged on a grid scale. For estimating the fluid force on particles, the effect of the flow disturbance in the averaged field needs to be considered. In a direct numerical simulation containing particles of comparable size to the minimum length scale of a background flow, the effect of the flow disturbance becomes important because the grid size also becomes comparable. In the present study, a steady viscous force and a pressure gradient force are modelled as functions of averaged velocity and pressure. The effect of the size of the averaging volume is reflected in the models. For the case that the particle is fixed in a uniform flow, the effectiveness of the present estimation model of the steady viscous force is highlighted. The present models are applied to cases of uniform straining flow. The pressure gradient force is reasonably obtained. As the present model is based on the disturbed field, a fluid force contribution due to the local velocity gradient of the undisturbed flow is represented. |
Sunday, November 18, 2018 3:35PM - 3:48PM |
D37.00006: High-Fidelity Propeller-Ice Interaction Studies using CFD-DEM-MBD Coupling Morteza Heydari, Hamid Sadat, Seifollah Nasrazadani Climate change with ice melting at a quick pace has changed the sea transportation perspective. The possibility of using Northern sea routes, which connects East Asia with Europe, can now cause a sizable reduction in shipping distance and cost. However, one of the major concerns for ships operating in icy water is the extreme loads applied to the propulsion system due to propeller-ice interaction. Due to the limitation of experimental setups and over-simplified numerical studies, the propeller-ice interaction process and resultant loads are not fully understood yet. Hence, a high-fidelity numerical study is conducted in this work to evaluate the loads on propellers in close vicinity of and in contact with an ice block. A coupled CFD, DEM (Discrete Element Method) and MBD (Multibody Dynamics) approach is employed in which the ice block is modeled as a collection of point particles around a dynamic propeller with prescribed rotational speed. The studies are performed for a model of the marine propeller KP505 with the diameter of D=0.093 m operating in various flow conditions. |
Sunday, November 18, 2018 3:48PM - 4:01PM |
D37.00007: Capturing volume fraction effects on turbophoresis with a reduced number of computational particles Perry Johnson, Parviz Moin In turbulent particle-laden flows, turbophoresis leads to enhanced particle concentrations near solid boundaries. However, particle-particle collisions have been shown to significantly attenuate this effect, even at rather low volume fractions. As a result, Lagrangian-Eulerian simulations of wall-bounded particle-laden flows can be very sensitive to the number of Lagrangian particles simulated. In this talk, we explore a method for reducing the number of computational particles below the physical number while maintaining an accurate representation of collisional effects on the near-wall concentration profile. This is done by artificially increasing the size of the particles used for computing particle-particle collisions while leaving the size unaltered for other parts of the computation such as the drag law and particle-wall collisions. Both high and low Stokes number regimes are considered. The results are promising for reducing the cost of Lagrangian-Eulerian simulations of turbulent wall-bounded flows. |
Sunday, November 18, 2018 4:01PM - 4:14PM |
D37.00008: Effect of injection model and turbulent dispersion models on prediction of full-cone nozzle spray in OpenFOAM Ashruf Syed, Amit Kumar Present work simulates a full-cone spray (Delavan CT-1.5–30B) using FireFoam, a solver in OpenFOAM. The solver uses the notion of 'parcels' in forming computational spray cloud. Injection model generates the spray from input parameters provided from experiments viz. particle size and velocity distributions of droplets. For the analysis, point-injection and detailed-profile injection models are considered. Once injected, the droplets are tracked in a Lagrangian manner in an otherwise Eulerian framework for the background air flow field. To model the turbulent fluctuations experienced by particles from surrounding flow, turbulent-dispersion models have been imported from the Lagrangian solver, viz. Stochastic and Gradient-k dispersion models. The predicted sprays with different aforementioned models for injection and dispersion are compared with experimental spray characteristics like Volume Flux, d_{v50} and velocity distribution at near-field and downstream. Detailed-profile injection predicts the spray better compared to point-injection. Stochastic dispersion model gives similar profile compared to no-dispersion, unlike Gradient-k model which shows significant deviation. |
Sunday, November 18, 2018 4:14PM - 4:27PM |
D37.00009: Orientation focusing and stabilization of non-spherical particles in waves Michelle DiBenedetto, Jeffrey R Koseff, Nicholas Ouellette We present results on the dynamics of non-spherical particles in a laboratory wave tank. We vary both the wave strength and particle mass density relative to the fluid. Consistent with our previous numerical and theoretical results, we find that waves tend to focus particle orientation over time. This effect is seen more readily in the neutrally buoyant case, whereas in the heavy particle case there is competition between the wave induced preferred orientation and the orientation which settling particles adopt in quiescent flow. Additionally, contrary to the point-particle inertia-less limit, we find that these finite-sized particles are now stable in the log rolling position in some cases. |
Sunday, November 18, 2018 4:27PM - 4:40PM |
D37.00010: Data-Driven Physical Inquiry: Discovering Relevant Dimensionless Numbers With Physics-Constrained Machine Learning Zachary del Rosario, Andrew Banko, Jeremy A. K. Horwitz, Gianluca Iaccarino Machine learning offers enormously popular methods for interrogating data. However, researchers in the physical sciences remain skeptical of these techniques, as they often produce inscrutable, black-box results. In this work, we present a case study of data-driven physical inquiry -- leveraging machine learning techniques to explore complex data sets, but anchored by physical principles. |
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