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 A32: Applied Computational Fluid Dynamics I |
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Chair: Omar Matar, Imperial College London Room: Georgia World Congress Center B404 |
Sunday, November 18, 2018 8:00AM - 8:13AM |
A32.00001: Three-dimensional study of gas-centered, liquid-swirl coaxial injector flow dynamics at supercritical condition Xingjian Wang, Yanxing Wang, Vigor Yang Supercritical fluid flow dynamics of a gas-centered, liquid-swirl coaxial injector are numerically investigated under conditions typical of contemporary oxidizer-rich staged-combustion cycle engines. Gaseous oxygen is injected into the center tube while kerosene is tangentially introduced into the coaxial annulus at pressure of 253 bar. Previous studies on axisymmetric configurations revealed distinctive flow characteristics and identified the importance of recess length to the mixing process. The axisymmetric assumption, however, leads to the neglect of flow variations in the azimuthal direction and the exclusion of the vortex-stretching mechanism responsible for turbulent energy transfer from large to small eddies. The present three-dimensional work includes these features and employs a large-eddy-simulation technique. Instead of a slit entry, kerosene is injected through 12 tangential orifices. Complex vortical structures and flow dynamics are explored in detail. Various underlying mechanisms dictating the flow evolution are analyzed. |
Sunday, November 18, 2018 8:13AM - 8:26AM |
A32.00002: A Parametric Study of Gas-Centered Liquid-Swirl Coaxial Injector under Supercritical Conditions Yixing Li, Xingjian Wang, Liwei Zhang, Vigor Yang Gas-centered, liquid-swirl coaxial injector has been adopted in many modern propulsion engines. In the present work, the flow dynamics of gas-centered, liquid-swirl coaxial injectors are numerically investigated at supercritical conditions using large-eddy-simulation techniques. Gaseous oxygen is injected axially into the center post at a temperature of 687.7K, while kerosene is introduced tangentially into the coaxial annulus at a temperature of 492.2K. The operating pressure is 25.3 MPa, well above the thermodynamic critical points of propellants. Key flow characteristics are identified and analyzed in detail. These key dynamic processes include longitudinal acoustic waves in the center post and recess region, vortex shedding near the injection slit, the Kelvin-Helmholtz instability in the recess region and vortical expansion and amalgamation in the taper region. The influence of the recess length on flow dynamics are also explored in depth. Further details will be presented at the meeting. |
Sunday, November 18, 2018 8:26AM - 8:39AM |
A32.00003: Computational simulation of fiber suspension in single and multiphase flow Dennis E Oztekin, Zixiang Liu, Cyrus K Aidun Particle-level numerical methods have been used (Wu and Aidun, JFM 2010) for direct simulation of flexible fiber suspensions in shear flow based on the lattice-Boltzmann (LB) method with external boundary force (EBF). In this method, the flow is computed on a fixed regular ‘lattice’ using the lattice Boltzmann method, where each solid particle, or fiber in this case, is mapped onto a Lagrangian frame moving continuously through the domain. The LB-EBF method works well as long as the fiber length scale is comparable to the LB unit scale. In many industrial applications, such as paper forming, this is not the case. Also, the suspension could include fine particles and capsules that are freely suspended and may interact with the fibers. A more computationally efficient method is developed based on analyzing the motion of fiber by Langevin Dynamics (LD) simulation of beads connected by a FENE spring. In this study, we have coupled the LD analysis of each fiber with the LB fluid. This method allows analysis of fiber suspension in practical industrial applications with laminar or turbulent flow. Furthermore, it is now possible to include particles and capsules in the fluid. We show that this approach provides a practical tool for analysis of many industrial applications. |
Sunday, November 18, 2018 8:39AM - 8:52AM |
A32.00004: Simulation of turbulent mixing of confined co-axial jets with disparate viscosity Vincent Lee, Dennis E. Oztekin, Mustafa Usta, Devesh Ranjan, Cyrus K Aidun, Irfan Khan Viscosity variations have shown to affect the mixing behavior and chemical yield in industrial processes. This study investigates the mixing of two miscible liquids of different viscosity in a co-axial jet mixer. The computational approach is based on large-eddy simulation (LES) using the opensource software OpenFOAM. The computational domain is decomposed with a structured grid and optimized for parallel performance. Theoretical turbulent flow profile is imposed at the inlet boundary. Three different LES sub-grid scale (SGS) models, namely the regular Smagorinsky (SM), dynamic (DM) and dynamic mixed (DMM) models have been compared. It appears that at moderate Reynolds number considered here, both DM and DMM results compare well with experiments at viscosity ratio of one. The time-averaged mixture fractions, velocity, and RMS values for mixing fluids with uniform viscosity are compared with literature and experimental data. The numerical results for viscosity ratios from 1 to 1000 will be discussed. |
Sunday, November 18, 2018 8:52AM - 9:05AM |
A32.00005: A Comparative Analysis of the Air Entrainment through Different Infrared Suppression (IRS) Devices: A Numerical Investigation Viplove Ranjan Ganguly, Sukanta Kumar Dash Present investigation compares different infrared suppression (IRS) devices which are used in naval warships to cool the hot exhaust gases coming out of the gas turbine plant. These IRS devices work passively by mixing the hot exhaust gases coming out of the gas turbine plant with the cold ambient air which is entrained inside these devices on account of pressure difference. The IRS devices considered here are single-cylinder, multi-cylinder and multi-conical IRS device. The analysis of these IRS devices is based on data related to real scale gas turbine installations, which is typically seen in warships like LM 2500 gas turbine from GE. A numerical analysis of these IRS devices has been undertaken by solving the conservation equations of mass, momentum and energy in 3-D using the k-epsilon turbulence model. The comparison is made on the basis of equal volume. The maximum air entrainment is observed when four nozzles are used at the exit of each IRS device. The maximum air entrainment is achieved for the single-cylinder IRS device whereas the multi-cylinder IRS device gives the lowest possible IRS exit temperature. The air entrainment can be maximized by maintaining a higher Reynolds number at the nozzle exit along with a nozzle protruding height of about 0.2m. |
Sunday, November 18, 2018 9:05AM - 9:18AM |
A32.00006: Two-dimensional numerical simulation of thin film flow on a rotating disk Mohsen Lahooti, Daegyu Lim, Kyungmin Nam, Seouk-Hoon Woo, Daegyoum Kim The flow of a thin liquid film on a solid surface is the phenomenon encountered commonly in industries, particularly in the manufacturing of semiconductors. Numerical simulation of the film flow, however, is challenging due to multi-phase effects and especially the large difference in length scales between film domain size and film height. In this study, to evaluate the development process of photolithography, we use a finite-volume based solver for the two-dimensional simulation of liquid film flow over a rotating disk. Governing equations are averaged over the height of the film, which results in a set of equations for evolving film height as well as radial and tangential velocities. In our work, to simulate the development process, development liquid is injected over a rotating wafer through a nozzle that moves independently from the wafer. The impinging region is modeled using prescribed height and momentum source term, whose values are determined using a simple analytical approach. Our numerical results show excellent agreement with three-dimensional VOF simulations and experiments. |
Sunday, November 18, 2018 9:18AM - 9:31AM |
A32.00007: Direct numerical simulation of three-dimensional liquid jet breakup with surfactant Cristian Ricardo Constante Amores, Lyes Kahouadji, Assen Batchvarov, Damir Juric, Jalel Chergui, Seungwon Shin, Richard V Craster, Omar K Matar Surfactant-laden jet flows are studied using a massively-parallelised, direct numerical simulation code, which uses a hybrid technique based on the front-tracking and the level-set methods. We focus on isolating the effect of surfactant-induced Marangoni stresses on the complex interfacial dynamics. The interface-tracking nature of the numerical method employed facilitates the faithful modelling and simulation of the spatio-temporal evolution of the surfactant concentration field for both soluble and insoluble surfactant species. This type of jet flow features (i) the formation of a ‘mushroom’-like shape exhibiting ‘roll-up’ that are driven by the density contrasts between the two phases; (ii) Kelvin-Helmholtz instability due to the velocity contrast between the phases; (iii) atomization inside and outside the liquid jet preceded by the formation of holes, ligaments, and droplets pinch-off events. The addition of surfactant slows down the breakup process, which is due to the presence of surfactant-induced Marangoni stresses. A full parametric study is presented, and the relevant mechanisms underlying the flow phenomena are elucidated. |
Sunday, November 18, 2018 9:31AM - 9:44AM |
A32.00008: Development of 1-D model for swirl decay rate inside annular swirl injectors Jaehoon Choi, Eunbeom Jung, Seongwon Kang, Hyungrok Do Many gas turbine combustors use swirls to generate a central toroid recirculation zone (CTRZ) for flame stabilization. The characteristics of CTRZ can be predicted using the swirl number at the nozzle. We propose a new ODE-based model to predict the axially varying swirl number inside an annular swirl injector with varying cross-sectional area. Wall shear stress and turbulent viscosity are modeled by applying empirical correlations to include viscous diffusion and turbulent dispersion effects. An approach to apply the proposed model to a flat-vane axial vortex generator was developed for practical applications. The proposed model was verified by 3-D simulations for various vortex injectors. The results of the proposed model show good agreement with the simulation results. For a swirl-stabilized burner, the predicted swirl number and CTRZ are validated, which confirms the importance of the swirl number and accuracy of the proposed model. A comparison is made with an inviscid model to identify conditions where the proposed model is relativey more useful. |
Sunday, November 18, 2018 9:44AM - 9:57AM |
A32.00009: Direct numerical simulations of elongated bubbles in the presence of surfactants Assen Batchvarov, Mirco Magnini, Lyes Kahouadji, Omar K Matar The effect of surfactants on elongated bubbles in creeping flows (Re<<1) has been studied in the past both analytically and numerically (Ratulowski and Chang, 1990; Park, 1992; Stebe and Barthes-Biesel, 1995; Olgac and Muradoglu, 2013). These studies showed that surfactants tend to accumulate at the bubble tail and modify its shape. At much higher Reynolds numbers (Re>>1), studies for surfactants-free configurations show that the tail of the elongated bubble exhibits undulations along the liquid film (Magnini, 2017). The present work investigates the impact of surfactants on tail undulations. Numerical investigations are carried out using 3D DNS simulations of elongated bubbles in pipes in the presence of soluble and insoluble surfactants, using the hybrid front-tracking code BLUE (Shin et al., J. Comp. Phys. 2018). |
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