Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Fluid Dynamics
Volume 56, Number 18
Sunday–Tuesday, November 20–22, 2011; Baltimore, Maryland
Session H13: Multiphase Flow IV: Numerical I |
Hide Abstracts |
Chair: Olivier Desjardins, Cornell University Room: 316 |
Monday, November 21, 2011 10:30AM - 10:43AM |
H13.00001: Numerical simulation of a round liquid jet using the refined level set grid method with subgrid Lagrangian drop breakup model Dokyun Kim, Parviz Moin An accurate and robust numerical method has been developed to simulate the breakup of a round liquid jet surrounded by a coaxial flow of gas. A Refined Level Set Grid (RLSG) method coupled to a Lagrangian drop breakup model is used to capture the breakup process of the liquid jet. The phase interface is tracked by the level-set method, while small subgrid droplets produced from resolved ligaments are transferred from the level-set representation to the Lagrangian drops. The further secondary atomization is handled by a stochastic breakup model. When thin ligaments are not resolved on the level-set grid, a capillary breakup model is used to predict the drop size distribution from the pinching off process and inserted as Lagrangian drops. This method improves the mass conservation error as well as reducing the computational cost. The numerical results are consistent with the observed breakup mechanisms in the experiment and the stability analysis. The drop size distribution of the resulting spray is also compared with the experimental data. These numerical results demonstrate the applicability and feasibility of our method for simulation of the atomization process of liquid jets. [Preview Abstract] |
Monday, November 21, 2011 10:43AM - 10:56AM |
H13.00002: A multilevel simulation approach to derive the slip boundary condition of the solid phase in two-fluid models Zhi-Gang Feng, Efstathios Michaelides, Shaolin Mao The simulation of particulate flows for industrial applications often requires the use of a two-fluid model (TFM), where the solid particles are considered as a separate continuous phase. One of the underlining uncertainties in the use of aTFM in multiphase computations comes from the boundary condition of the solid phase. The no-slip condition at a solid boundary is not a valid assumption for the solid phase. Instead, several researchers advocate a slip condition as a more appropriate boundary condition. However, the question on the selection of an exact slip length or a slip velocity coefficient is still unanswered. In the present work we propose a multilevel simulation approach to compute the slip length that is applicable to a TFM. We investigate the motion of a number of particles near a vertical solid wall, while the particles are in fluidization using a direct numerical simulation (DNS); the positions and velocities of the particles are being tracked and analyzed at each time step. It is found that the time- and vertical-space averaged values of the particle velocities converge, yielding velocity profiles that can be used to deduce the particle slip length close to a solid wall. [Preview Abstract] |
Monday, November 21, 2011 10:56AM - 11:09AM |
H13.00003: ABSTRACT WITHDRAWN |
Monday, November 21, 2011 11:09AM - 11:22AM |
H13.00004: Numerical investigation of a turbulent hydraulic jump: Interface statistics and air entrainment Milad Mortazavi, Dokyun Kim, Ali Mani, Parviz Moin The objective of this study is to develop an understanding of formation of bubbles due to turbulence/interface interactions and nonlinear surface wave phenomena. As a model problem a statistically stationary turbulent hydraulic jump has been considered. Turbulent hydraulic jump with an inflow Froude number of 2 and Reynolds number of 88000--based on inflow height--has been numerically simulated. Based on typical air- water systems, a density ratio of 831 has been selected for our calculations. A refined level-set method is employed to track the detailed dynamics of the interface evolution. Comparison of flow statistics with experimental results of Murzyn et al. (Int. J. Multiphase Flow, 2005) will be presented. The probability density function of principal curvatures of the air- water interface and curvature distribution patterns in the chaotic regions are investigated. The importance of liquid impact events in bubble generation will be discussed. [Preview Abstract] |
Monday, November 21, 2011 11:22AM - 11:35AM |
H13.00005: Multiscale modeling of blood-plasma separation in bifurcations Xuejin Li, Aleksander Popel, George Karniadakis Motion of a suspension of red blood cells (RBCs) flowing in a Y-shaped bifurcating microfluidic channel is investigated using a low-dimensional RBC validated 3D model based on dissipative particle dynamics. No-slip wall boundary and adaptive boundary conditions were implemented to model hydrodynamic flow within a specific wall structure of diverging microfluidic channels. Plasma skimming and the all-or-nothing phenomenon of RBCs in a bifurcating microfluidic channel have been investigated in our simulations, including the size of cell-free layer on the daughter channels. The results show that the flowrate ratio of the daughter channels and the feed hematocrit level have considerable influence on blood-plasma separation. Compared with the particle recovery efficiencies of healthy RBCs, malaria-infected RBCs ($i$RBCs) have a tendency to travel into the low flowrate daughter channels because of the increased stiffness of $i$RBCs. The simulation results are consistent with previous experimental results and theoretical predictions. [Preview Abstract] |
Monday, November 21, 2011 11:35AM - 11:48AM |
H13.00006: Direct numerical simulations of gas-liquid annular flows in horizontal pipes: predictions of film height and mechanisms for film sustainment Jeremy McCaslin, Olivier Desjardins Direct Steam Generation (DSG), a technology that uses parabolic solar reflectors to generate steam from water flowing through horizontal pipes located at the focal points of the reflectors, often requires an annular pipe flow in which the liquid is distributed as a thin film around the circumference of the pipe. The distribution of the gas-liquid interface for such flows (i.e. the thickness of the liquid film and the measure of liquid droplets entrained in the gas core) can have ramifications for both the optimized operation and economical design of DSG loops. In this work, a conservative finite difference scheme is used in conjunction with a state-of-the-art discontinuous Galerkin conservative level set methodology to simulate periodic sections of such flows. Under the assumption of a gas core-dominated flow, dimensional analysis suggests a theoretical basis that is presented for the prediction of flow ``annularity'' (i.e. contiguousness of the liquid film). Mechanisms for film sustainment such as wave propagation up the pipe walls and droplet entrainment and deposition are also numerically investigated for a variety of annular flows. [Preview Abstract] |
Monday, November 21, 2011 11:48AM - 12:01PM |
H13.00007: High order discretization of interfacial jump conditions for the Poisson equation on Cartesian grids Amir Riaz, Keegan Delaney, Elias Balaras A robust, 2$^{nd}$ order accurate discretization method for both Dirichlet and Neumann jump conditions at sharp discontinuities in space is developed for the Poisson equation with spatially varying, discontinuous coefficients. The method advances previous approaches that are based on either 1$^{st}$ order treatment of jumps across discontinuities or employ implementations that are not robust for 2-D and 3-D applications with moving interfaces. This particularly simple and robust approach to higher order discretization is based on the volume-fraction weighted average of the solution variables at cell centers. The resulting coefficient matrix for the Poisson equation remains symmetric and can be inverted by the available fast solver algorithms. Examples and algorithmic details will be discussed. [Preview Abstract] |
Monday, November 21, 2011 12:01PM - 12:14PM |
H13.00008: Numerical modeling of the early interaction of a planar shock with a dense particle field Jonathan Regele, Guillaume Blanquart Dense compressible multiphase flows are of interest for multiphase turbomachinary and energetic material detonations. Still, there is little understanding of the detailed interaction mechanisms between shock waves and dense (particle volume fraction $\alpha_d>0.001$) particle fields. A recent experimental study [Wagner et al, AIAA Aero. Sci., Orlando, 2011-188] has focused on the impingement of a planar shock wave on a dense particle curtain. In the present work, numerical solutions of the Euler equations in one and two dimensions are performed for a planar shock wave impinging on a fixed particle curtain and are compared to the experimental data for early times. Comparison of the one- and two-dimensional results demonstrate that the one-dimensional description captures the large scale flow behavior, but is inadequate to capture all the details observed in the experiments. The two-dimensional solutions are shown to reproduce the experimentally observed flow structures and provide insight into how these details originate. [Preview Abstract] |
Monday, November 21, 2011 12:14PM - 12:27PM |
H13.00009: High Fidelity Simulation of Liquid Jet in Cross-flow Using High Performance Computing Marios Soteriou, Xiaoyi Li High fidelity, first principles simulation of atomization of a liquid jet by a fast cross-flowing gas can help reveal the controlling physics of this complicated two-phase flow of engineering interest. The turn-around execution time of such a simulation is prohibitively long using typically available computational resources today (i.e. parallel systems with $\sim $O(100) CPUs). This is due to multiscale nature of the problem which requires the use of fine grids and time steps. In this work we present results from such a simulation performed on a state of the art massively parallel system available at Oakridge Leadership Computing Facility (OLCF). Scalability of the computational algorithm to $\sim $2000 CPUs is demonstrated on grids of up to 200 million nodes. As a result, a simulation at intermediate Weber number becomes possible on this system. Results are in agreement with detailed experiment measurements of liquid column trajectory, breakup location, surface wavelength, onset of surface stripping as well as droplet size and velocity after primary breakup. Moreover, this uniform grid simulation is used as a base case for further code enhancement by evaluating the feasibility of employing Adaptive Mesh Refinement (AMR) near the liquid-gas interface as a means of mitigating computational cost. [Preview Abstract] |
Monday, November 21, 2011 12:27PM - 12:40PM |
H13.00010: Towards direct numerical simulation of pressure swirl injectors with realistic geometries Mark Czajkowski, Olivier Desjardins Atomization of hydrocarbon fuels is of critical importance to the transportation sector, in particular for aircraft gas turbine engines. In this work, simulations of a Delevan pressure swirl injector with realistic geometry was investigated. Results were compared with simulations performed by Fuster et al. (Int J Multiphase Flow, 2009) of a swirl jet at lower density ratios. The pressure swirl injector is used for many applications and is a component within air-blast injectors commonly found in gas turbines and aeroengines. Direct numerical simulation of the pressure swirl injection process has the potential to provide much-needed information about the complex physics of atomization in swirling flows, but has yet to be used due to the interaction of a complex turbulent multiphase flow with complicated injector geometries. A variety of novel numerical methods are used to facilitate the numerical simulations including a conservative implementation of immersed boundaries used to represent the injector geometry, an accurate interface transport scheme with mass conservation properties based on a discontinuous Galerkin discretization of the conservative level set method, and a novel discretization of the Navier-Stokes convective term allowing for robust simulations at high density ratios. Simulations were conducted by combining the methods with a fully parallelized computational code called NGA. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2022 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
1 Research Road, Ridge, NY 11961-2701
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700