Bulletin of the American Physical Society
67th Annual Meeting of the APS Division of Fluid Dynamics
Volume 59, Number 20
Sunday–Tuesday, November 23–25, 2014; San Francisco, California
Session R35: Multiphase Flow Applications |
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Chair: Chris White, University of New Hampshire Room: 2001A |
Tuesday, November 25, 2014 1:05PM - 1:18PM |
R35.00001: Improvement on Gas-Solid Two-phase Flow Separation in U-beam Separator by Inlet Fins Xiaoying Zhou, Xiaoping Chen, Hua-Shu Dou Inertia separation is widely used in gas-solid separation and dusting technology due to advantages such as low resistance, high abrasion resistance and low manufacturing cost. In order to achieve high separation efficiency and low pressure drop, a traditional U-beam is altered with inlet fins. The fin angle of the separator is from 30 to 60 dregree. Then, numerical simulation is carried out for gas-solid two-phase flow in the traditional U-beam separator and the inlet fined U-beam separator, and their performances are compared. It is assumed that the gas phase is continuous and the solid particle phase is discrete for low volume fraction. The governing equation for gas phase is the Reynolds-averaged Navier-Stokes equation with the k-epsilon turbulent model, while the discrete phase model (DPM) and the stochastic tracking model are used for the solid phase. Results show that the maximum separation efficiency is obtained at the fin angle of 35 degree, but there is no obvious increase in the pressure drop. It is found that fin induces generation of a stagnation region which could collect particles and lead to change of vortical structures. The fin induced flow also causes the turbulent intensity inside the baffle to decrease which helps separation. [Preview Abstract] |
Tuesday, November 25, 2014 1:18PM - 1:31PM |
R35.00002: Numerical simulations of crude-oil fouling Junfeng Yang, Omar Matar Crude-oil fouling proceeds via several individual steps: initiation, transportation, attachment, removal and ageing. At initiation, two foulant formation routes have been identified: chemical reaction and asphaltene precipitation. Current fouling models either focus on the kinetics of each route individually, or simply lumps the routes together. Very few studies address the issue of interaction of the two routes. The sparingly-soluble foulant precursor could either form larger insoluble fouling particles, or precipitate out of the crude-oil phase directly. Clearly, these two routes compete with each other, e.g. higher chemical reaction fouling rates lead to greater consumption of the sparingly-soluble foulant, and lower precipitation rate. Accounting for the mechanism of interaction between reaction- and precipitation-driven fouling is critical for accurate prediction of the overall fouling formation rate, and the development of fouling mitigation strategies. We develop CFD tools that account for the individual steps that accompany fouling in circular tubes, and use large eddy simulations to simulate turbulence. We use our simulations to elucidate the interaction between the different deposition routes. [Preview Abstract] |
Tuesday, November 25, 2014 1:31PM - 1:44PM |
R35.00003: ABSTRACT WITHDRAWN |
Tuesday, November 25, 2014 1:44PM - 1:57PM |
R35.00004: Modeling of wall-induced force for wall-bounded bubbly flow Dongjoo Kim, Jungwoo Kim, Hyungmin Park, Jun Ho Lee The two-fluid model based on Eulerian-Eulerian approach has been widely used for simulating two-phase flow in industrial applications due to much less CPU time compared with interface tracking methods. However, the two-fluid approach requires accurate modeling of mass and momentum transfers between phases. The interfacial momentum exchange terms include drag, shear-induced lift, and wall-induced force. The last one is particularly important in order to correctly predict ``wall peaking'' and ``core peaking'' phenomena observed in bubbly pipe flows. However, the wall-induced force is not fully understood yet and the wall force coefficient used in previous studies has a wide range of values, probably tuned to match experiment. Therefore, we propose a new wall-induced force model in the present study. To verify the accuracy of present model, numerical simulations are performed for several laminar bubbly flows available in the literature. The spatial distributions of void fraction, liquid velocity, and bubble velocity are compared with those with previous models as well as experimental results. [Preview Abstract] |
Tuesday, November 25, 2014 1:57PM - 2:10PM |
R35.00005: Experimental and numerical study of viscosity effects on the dynamics of the Benjamin bubble Alessandro Mariotti, Paolo Andreussi, Maria Vittoria Salvetti The ``Benjamin bubble'' is a gas bubble, which, due to gravity, forms and moves in a horizontal pipe, initially filled with stagnant liquid, once one end of the pipe is opened. In water this bubble moves with a constant velocity, which can be predicted by a non-viscous model. The Benjamin bubble velocity is also the base of state-of the-art predictions of the bubble drift velocity in the slug flow regime occurring e.g. in oil transport pipelines. Thus, it is interesting to investigate the dynamics of the Benjamin bubble in highly viscous oils. The findings of experiments and numerical simulations aimed at characterizing the effects of viscosity on the dynamics of the Benjamin bubble are presented. Experiments and simulations were carried out for a large range of fluid viscosities. The results show that two different flow regimes can be defined according to the Reynolds number. For high Reynolds, the bubble velocity and shape do not change in time, as for the classical Benjamin model. Conversely, for low Reynolds (heavy oils) the bubble velocity decreases along the pipe and the height of the bubble front is progressively reduced. We also show that the two different flow regimes are due to the critical or subcritical flow conditions of the liquid phase under the bubble. [Preview Abstract] |
Tuesday, November 25, 2014 2:10PM - 2:23PM |
R35.00006: Echo Particle Image Velocimetry in Pipeflow of Liquefied Lignocellulosic Biomass Nicholas DeMarchi, Chris White Echo particle image velocimetry (EPIV) is used to acquire planar fields of velocity in pipeflow of liquefied biomass. The biomass used is acid washed corn stover liquefied by enzymatic hydrolysis. The liquefaction process produces a complex multiphase fluid suspension with a microstructure consisting of insoluble solid particles dispersed within a continuous liquid phase. The solid particles are generally heavier than the liquid phase, non-spherical, and distributed over a wide size range. Batches of liquefied biomass are produced at various mass loadings from 1.5\% to 20\%, from which samples are withdrawn and used to evaluate the rheology, microstructure, and solid particle settling velocities. Next, EPIV measurements are used to evaluate how the suspension rheology, microstructure, and particle sedimentation affects the flow of liquefied biomass under laminar pipeflow conditions. [Preview Abstract] |
Tuesday, November 25, 2014 2:23PM - 2:36PM |
R35.00007: Constitutive modeling of calcium carbonate supersaturated seawater mixtures Martina Reis, Maria de F\'{a}tima Sousa, Celso Bertran, Adalberto Bassi Calcium carbonate supersaturated seawater mixtures have attracted attention of many researchers since the deposition of CaCO$_{3}$(s) from such solutions can lead to scaling problems in oil fields. However, despite their evident practical importance in petroleum engineering, the hydro and thermodynamic behaviors of these mixtures have not been well-understood yet. In this work, a constitutive model based on the foundations of the constitutive theory of continuum mechanics, and the M\"{u}ller-Liu entropy principle is proposed. The calcium carbonate supersaturated seawater mixture is regarded as a reactive viscous fluid with heat and electrical conductions. The obtained results indicate that the thermodynamic behavior of CaCO$_{3}$ supersaturated seawater mixtures is closely related to the individual dynamics of each constituent of the mixture, particularly to the linear momentum, and mass exchanges. Furthermore, the results show that, unlike classical continuum mixtures, the extra entropy flux is not null, and higher-order gradients of deformation contribute to the residual entropy production of the class of mixtures under study. The results of this work may be relevant for the prevention of the mineral scale formation in oil fields. [Preview Abstract] |
Tuesday, November 25, 2014 2:36PM - 2:49PM |
R35.00008: Thermal conductivity and heat capacity of n-decane and n-hexadecane through molecular simulations John Shelton Atomistic molecular dynamics simulations were carried out at equilibrium to calculate the constant pressure heat capacity and thermal conductivity of n-decane and n-hexadecane within the range of ambient to extreme temperature and pressure conditions (i.e. up to 500 $^{\circ}$F and 35,000 psi). Both a computationally efficient united-atom force field and an all-atom force field were employed in this investigation. A quantitative comparison of the results was performed against experimental values and values predicted from a high temperature - high pressure perturbed chain - statistically associated fluid theory (HPHT PC-SAFT) model. Analysis of the intra- and inter-molecular structure of the fluid as well as its dynamical characteristics were performed. [Preview Abstract] |
Tuesday, November 25, 2014 2:49PM - 3:02PM |
R35.00009: Optimisation of sensor locations for falling film problems based on importance maps Fangxin Fang, Zhizhao Che, James Percival, Chris Pain, Michael Navon, Omar Matar In studying complex flow problems, it is essential to simulate or measure key parameters accurately and place sensors at the locations with high ``importance.'' This study attempts to build a systematic linkage between experimental measurements and numerical simulations through sensitivity analysis, sensor optimisation, and data assimilation. An ensemble method is used to optimise sensor locations for falling film problems based on an ``importance'' map. This map can identify the important regions in the time-space domain according to a ``target'' function. The sensor locations are selected based on the importance map, the variation of the variables, and the costs of performing the measurements. The results of the data assimilation study show that assimilating data from optimised sensor locations can significantly reduce model uncertainty and more accurately reproduce the true system. The required number of sensors can be reduced significantly by using optimised sensors. This method can be used not only in falling film problems, but also in other complex flow problems in numerous applications. [Preview Abstract] |
Tuesday, November 25, 2014 3:02PM - 3:15PM |
R35.00010: Equations and simulations for multiphase compressible gas-dust flows Elaine Oran, Ryan Houim Dust-gas multiphase flows are important in physical scenarios such as dust explosions in coal mines, asteroid impact disturbing lunar regolith, and soft aircraft landings dispersing desert or beach sand. In these cases, the gas flow regime can range from highly subsonic and nearly incompressible to supersonic and shock-laden flow, the grain packing can range from fully packed to completely dispersed, and both the gas and the dust can range from chemically inert to highly exothermic. To cover the necessary parameter range in a single model, we solve coupled sets of Navier-Stokes equations describing the background gas and the dust. As an example, a reactive-dust explosion that results in a type of shock-flame complex is described and discussed. [Preview Abstract] |
Tuesday, November 25, 2014 3:15PM - 3:28PM |
R35.00011: Controlling phase change: Drying-up under water or staying wet during boiling Paul Jones, Adrian Kirn, Dennis Rich, Ashley Elliot, Neelesh Patankar Rough textured surfaces may be used to manipulate the phase of water. Textured surfaces that are hydrophobic are capable of keeping surfaces dry when submerged under water. In particular, surfaces with conical geometry may be used to de-wet while under water. These surfaces, with nanometer-scale roughness spacing, act to stabilize the vapor phase of water, even when liquid is the thermodynamically favorable phase. Textured surfaces that are hydrophilic are useful for the reverse phenomenon of keeping surfaces wet under conditions for boiling. Here, the presence of vapor is expected, which is contrary to our results. This approach for stabilizing the liquid phase of water may be generalized to other phase transformations of water. We use molecular dynamics simulations to demonstrate stabilizing the vapor and liquid phases of water adjacent to textured surfaces that do not rely upon trapped air. This work aims to help organize the types of geometries that will wet, and those that will de-wet once ambient pressure subsides. [Preview Abstract] |
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