Bulletin of the American Physical Society
68th Annual Meeting of the APS Division of Fluid Dynamics
Volume 60, Number 21
Sunday–Tuesday, November 22–24, 2015; Boston, Massachusetts
Session R4: CFD: Applications II |
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Chair: Chris Pain, Imperial College London Room: 103 |
Tuesday, November 24, 2015 12:50PM - 1:03PM |
R4.00001: Three-dimensional numerical simulations of falling films using an adaptive unstructured mesh Chris Pain, Zhihua Xie, Omar Matar Falling liquid films have rich wave dynamics, often occurring in many industrial applications, such as condensers, evaporators and chemical reactors. A number of numerical studies featuring falling liquid films are available in the literature; the majority of them, however, have focused on two-dimensional falling films. Far fewer studies have considered three-dimensional falling films, and those that have only studied the flow in a periodic domain. The objective of this study is to investigate flow dynamics of developing three-dimensional falling films using the Navier-Stokes equations coupled with interface capturing approach over extended domains. An adaptive, unstructured mesh modelling framework is employed here to study this problem, which can modify and adapt three-dimensional meshes to better represent the underlying physics of multiphase problems and reduce computational effort without sacrificing accuracy. Numerical examples of three-dimensional falling films in a long domain are presented and discussed. [Preview Abstract] |
Tuesday, November 24, 2015 1:03PM - 1:16PM |
R4.00002: Simulation of bubble growth and coalescence in reacting polymer foams Daniele Marchisio, Mohsen Karimi This work concerns with the simulation of reacting polymer foams with computational fluid dynamics (CFD). In these systems upon mixing of different ingredients polymerization starts and some gaseous compounds are produced, resulting in the formation of bubbles that growth and coalesce. As the foam expands, the polymerization proceeds resulting in an increase of the apparent viscosity. The evolution of the collective behavior of the bubbles within the polymer foam is tracked by solving a master kinetic equation, formulated in terms of the bubble size distribution. The rate with which individual bubbles grow is instead calculated by resolving the momentum and concentration boundary layers around the bubbles. Moreover, since it is useful to track the evolution of the interface between the foam and the surrounding air, a volume-of-fluid (VOF) model is adopted. The final computational model is implemented in the open-source CFD code openFOAM by making use of the compressibleInterFoam solver. The master kinetic equation is solved with a quadrature-based moment method (QBMM) directly implemented in openFOAM, whereas the bubble growth model is solved independently and "called" from the CFD code by using an unstructured database. Model predictions are validated against experimental data. [Preview Abstract] |
Tuesday, November 24, 2015 1:16PM - 1:29PM |
R4.00003: A compressible real gas eulerian model for LES of fuel sprays Edward Knudsen, Eric Doran A compressible solver for eulerian multiphase spray simulations is presented. This large eddy simulation solver employs a Peng-Robinson (PR) equation of state to describe mixtures of two species such as liquid dodecane and gaseous nitrogen. Modeling challenges associated with the use of PR are discussed, as are the resource requirements associated with using a compressible formulation to describe liquids when full fuel injector applications are considered. The solver is analyzed using canonical cases and the Spray A experiment from the Engine Combustion Network. [Preview Abstract] |
Tuesday, November 24, 2015 1:29PM - 1:42PM |
R4.00004: ABSTRACT WITHDRAWN |
Tuesday, November 24, 2015 1:42PM - 1:55PM |
R4.00005: Computational Fluid Dynamics Analysis of Canadian Supercritical Water Reactor (SCWR) Mohammad Movassat, Joanne Bailey, Metin Yetisir A Computational Fluid Dynamics (CFD) simulation was performed on the proposed design for the Canadian SuperCritical Water Reactor (SCWR). The proposed Canadian SCWR is a 1200 MW(e) supercritical light-water cooled nuclear reactor with pressurized fuel channels. The reactor concept uses an inlet plenum that all fuel channels are attached to and an outlet header nested inside the inlet plenum. The coolant enters the inlet plenum at 350 C and exits the outlet header at 625 C. The operating pressure is approximately 26 MPa. The high pressure and high temperature outlet conditions result in a higher electric conversion efficiency as compared to existing light water reactors. In this work, CFD simulations were performed to model fluid flow and heat transfer in the inlet plenum, outlet header, and various parts of the fuel assembly. The ANSYS Fluent solver was used for simulations. Results showed that mass flow rate distribution in fuel channels varies radially and the inner channels achieve higher outlet temperatures. At the outlet header, zones with rotational flow were formed as the fluid from 336 fuel channels merged. Results also suggested that insulation of the outlet header should be considered to reduce the thermal stresses caused by the large temperature gradients. [Preview Abstract] |
Tuesday, November 24, 2015 1:55PM - 2:08PM |
R4.00006: Numerics of surface acoustic wave (SAW) driven acoustic streaming and radiation force Nitesh Nama, Rune Barnkob, Christian Kahler, Francesco Costanzo, Tony Jun Huang Recently, surface acoustic wave (SAW) based systems have shown great potential for various lab-on-a-chip applications. However, the physical understanding of the precise acoustic fields and associated acoustophoresis is rather limited. In this work, we present a numerical study of the acoustophoretic particle motion inside a SAW-actuated, liquid-filled polydimethylsiloxane (PDMS) microchannel. We utilize a perturbation approach to divide the flow variables into first- and second-order components. The first-order fields result in a time-averaged acoustic radiation force on suspended particles, as well as the time-averaged body force terms that drive the second-order fields. We model the SAW actuation by a displacement function while we utilize impedance boundary conditions to model the PDMS walls. We identify the precise acoustic fields generated inside the microchannel and investigate a range of particle sizes to characterize the transition from streaming-dominated acoustophoresis to radiation-force-dominated acoustophoresis. Lastly, we demonstrate the ability of SAW devices to tune the position of vertical pressure node inside the microchannel by tuning the phase difference between the two incoming surface acoustic waves. [Preview Abstract] |
Tuesday, November 24, 2015 2:08PM - 2:21PM |
R4.00007: Streaming Potential and Energy Conversion in Nanochannel Grafted With Poly-Zwitterion Brushes Jahin Patwary, Guang Chen, Siddhartha Das Here we study the streaming potential and electrochemomechanical energy conversion in nanochannels grafted with poly-zwitterion (PZ) brushes. PZs are polymer molecules consisting of negative and positive charge centres simultaneously; depending on the bulk pH, the extent of dissociation differs at each of these charge centres, yielding a particular net charge on the PZ molecule. This PZ charge, therefore, develops a pH dependent electrostatics of the PZ brushes grafted at the naochannel walls. We develop a self-consistent field theory model to calculate this electrostatics by appropriately accounting for the explicit hydrogen ion concentration. Secondly, we use this electrostatics to calculate the streaming potential and the resulting electrochemomechanical energy conversion in nanochannels grafted with poly-zwitterion (PZ) brushes. Our results indicate distinct influences of pH, bulk ion concentration, and the ionization parameters of the PZs in regulating the nanochannel energy conversion. [Preview Abstract] |
Tuesday, November 24, 2015 2:21PM - 2:34PM |
R4.00008: Polarizable water model for Dissipative Particle Dynamics Igor Pivkin, Emanuel Peter Dissipative Particle Dynamics (DPD) is an efficient particle-based method for modeling mesoscopic behavior of fluid systems. DPD forces conserve the momentum resulting in a correct description of hydrodynamic interactions. Polarizability has been introduced into some coarse-grained particle-based simulation methods; however it has not been done with DPD before. We developed a new polarizable coarse-grained water model for DPD, which employs long-range electrostatics and Drude oscillators. In this talk, we will present the model and its applications in simulations of membrane systems, where polarization effects play an essential role. [Preview Abstract] |
Tuesday, November 24, 2015 2:34PM - 2:47PM |
R4.00009: Polarizable protein model for Dissipative Particle Dynamics Emanuel Peter, Kirill Lykov, Igor Pivkin In this talk, we present a novel polarizable protein model for the Dissipative Particle Dynamics (DPD) simulation technique, a coarse-grained particle-based method widely used in modeling of fluid systems at the mesoscale. We employ long-range electrostatics and Drude oscillators in combination with a newly developed polarizable water model. The protein in our model is resembled by a polarizable backbone and a simplified representation of the sidechains. We define the model parameters using the experimental structures of 2 proteins: TrpZip2 and TrpCage. We validate the model on folding of five other proteins and demonstrate that it successfully predicts folding of these proteins into their native conformations. As a perspective of this model, we will give a short outlook on simulations of protein aggregation in the bulk and near a model membrane, a relevant process in several Amyloid diseases, e.g. Alzheimer’s and Diabetes II. [Preview Abstract] |
Tuesday, November 24, 2015 2:47PM - 3:00PM |
R4.00010: Modeling of mesoscopic electrokinetic phenomena using charged dissipative particle dynamics Mingge Deng, Zhen Li, George Karniadakis In this work, we propose a charged dissipative particle dynamics (cDPD) model for investigation of mesoscopic electrokinetic phenomena. In particular, this particle-based method was designed to simulate micro- or nano- flows which governing by Poisson-Nernst-Planck (PNP) equation coupled with Navier-Stokes (NS) equation. For cDPD simulations of wall-bounded fluid systems, a methodology for imposing correct Dirichlet and Neumann boundary conditions for both PNP and NS equations is developed. To validate the present cDPD model and the corresponding boundary method, we perform cDPD simulations of electrostatic double layer (EDL) in the vicinity of a charged wall, and the results show good agreement with the mean-field theoretical solutions. The capacity density of a parallel plate capacitor in salt solution is also investigated with different salt concentration. Moreover, we utilize the proposed methodology to study the electroosmotic and electroosmotic/pressure-driven flow in a micro-channel. In the last, we simulate the dilute polyelectrolyte solution both in bulk and micro-channel, which show the flexibility and capability of this method in studying complex fluids. [Preview Abstract] |
Tuesday, November 24, 2015 3:00PM - 3:13PM |
R4.00011: Modeling of advection-diffusion-reaction processes using transport dissipative particle dynamics Zhen Li, Alireza Yazdani, Alexandre Tartakovsky, George Em Karniadakis We present a transport dissipative particle dynamics (tDPD) model for simulating mesoscopic problems involving advection-diffusion-reaction (ADR) processes, along with a methodology for implementation of the correct Dirichlet and Neumann boundary conditions in tDPD simulations. In particular, the transport of concentration is modeled by a Fickian flux and a random flux between tDPD particles, and the advection is implicitly considered by the movements of Lagrangian particles. To validate the proposed tDPD model and the boundary conditions, three benchmark simulations of one-dimensional diffusion with different boundary conditions are performed, and the results show excellent agreement with the theoretical solutions. Also, two-dimensional simulations of ADR systems are performed and the tDPD simulations agree well with the results obtained by the spectral element method. Finally, an application of tDPD to the spatio-temporal dynamics of blood coagulation involving twenty-five reacting species is performed to demonstrate the promising biological applications of the tDPD model. [Preview Abstract] |
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