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 M5: CFD VI: Combustion |
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Chair: Arnaud Trouve, University of Maryland Room: 308 |
Tuesday, November 22, 2011 8:00AM - 8:13AM |
M5.00001: Turbulence and Combustion in Type Ia Supernovae Aaron Jackson, Dean Townsley, Alan Calder Turbulent combustion plays a critical role in Type Ia supernovae, bright astrophysical explosions that serve as cosmological distance indicators. The most successful scenario for reproducing observations involves a deflagration born in the turbulent core a massive C/O white dwarf that subsequently experiences a deflagration-to-detonation transition (DDT) due to turbulence-flame interaction (TFI), although unconfined DDT is poorly understood. Due to the highly non-linear nature of the explosion, the early flame propagation is critically important for determining the explosion outcome. We present full-star, 3D calculations of the deflagration phase of a SNIa explosion. As the flame evolves, it is subject to the Rayleigh-Taylor and Kelvin-Helmholtz instabilities as well as TFI. We analyze the resolved turbulence at the flame front throughout the evolution of the explosion and consider the necessity of modeling unresolved TFI. Furthermore, we consider whether conditions estimated for DDT are likely to occur given the turbulent intensity at the flame front. [Preview Abstract] |
Tuesday, November 22, 2011 8:13AM - 8:26AM |
M5.00002: A Low-Dissipation Numerical Method for Compressible Multi-component and Reacting Flows Ryan Houim, Kenneth Kuo A low-dissipation for calculating multi-component gas dynamic flows with variable specific heat ratio that is capable of accurately simulating complex flows that contain both high- and low-Mach number features is presented. The numerical method combines features from the quasi-conservative double-flux multi-component model, high-resolution weighted essentially non-oscillatory schemes, and adaptive total variation diminishing slope limiters. Turbulence is implicitly modeled by using a low Mach-number adjustment procedure in conjunction with either AUSM or the HLLC approximate Riemann solver to evaluate numerical fluxes. To avoid spurious oscillations, characteristic variables are interpolated near shock waves and primitive variables are interpolated elsewhere for increased computational efficiency. Success of the method has been demonstrated with a series of numerical experiments including premixed deflagrations, Chapman-Jouget detonations, re-shocked Richtmyer-Meshkov instability, shock-wave and diffusion flame interactions, and multi-dimensional cellular detonations. [Preview Abstract] |
Tuesday, November 22, 2011 8:26AM - 8:39AM |
M5.00003: An Irregularly Portioned FDF Solver Patrick Pisciuneri, S. Levent Yilmaz, Peter Strakey, Peyman Givi The ``Irregularly Portioned Lagrangian Monte Carlo'' (IPLMC) [1] in LES/FDF is extended to include the Eulerian flow solver in a coupled manner. The resulting methodology is for LES of reacting flows on massively parallel platforms, and is intended for LES of turbulent reacting flows described by complex kinetics. The new solver provides much improved scalability over its predecessor for utilization of a higher number of processors. Sample results are presented of LES of non-premixed flames, along with scalability benchmarks. \\[4pt] [1] Yilmaz, S. L., Nik, M. B., Sheikhi, M. R. H., Strakey, P. A., and Givi, P., An Irregularly Portioned Lagrangian Monte Carlo Method for Turbulent Flow Simulation, \textit{J. Sci. Comput.}, \textbf{47}(1):109--125 (2011). [Preview Abstract] |
Tuesday, November 22, 2011 8:39AM - 8:52AM |
M5.00004: Mesh quality metrics for large-eddy simulation of fire dynamics Randall McDermott The Fire Dynamics Simulator (FDS) is a large-eddy simulation code used in fire safety engineering. In this talk, we outline the implementation of three mesh quality metrics in FDS: (1) a measure of turbulence resolution based on a model for the fraction of unresolved kinetic energy (Pope, 2004), (2) a measure of scalar resolution based on a model for the unresolved scalar variance (Vervisch et al., 2010), and (3) a simple wavelet-based error measure. The metrics are examined in grid resolution studies of the McCaffrey fire plume experiments (McCaffrey, 1979), establishing target metric values for fire plume applications. [Preview Abstract] |
Tuesday, November 22, 2011 8:52AM - 9:05AM |
M5.00005: A Parallel Adaptive Wavelet Method for the Simulation of Compressible Reacting Flows Zachary Zikoski, Samuel Paolucci The Wavelet Adaptive Multiresolution Representation (WAMR) method provides a robust method for controlling spatial grid adaption --- fine grid spacing in regions of a solution requiring high resolution (i.e.~near steep gradients, singularities, or near- singularities) and using much coarser grid spacing where the solution is slowly varying. The sparse grids produced using the WAMR method exhibit very high compression ratios compared to uniform grids of equivalent resolution. Subsequently, a wide range of spatial scales often occurring in continuum physics models can be captured efficiently. Furthermore, the wavelet transform provides a direct measure of local error at each grid point, effectively producing automatically verified solutions. The algorithm is parallelized using an MPI-based domain decomposition approach suitable for a wide range of distributed-memory parallel architectures. The method is applied to the solution of the compressible, reactive Navier-Stokes equations and includes multi-component diffusive transport and chemical kinetics models. Results for the method's parallel performance are reported, and its effectiveness on several challenging compressible reacting flow problems is highlighted. [Preview Abstract] |
Tuesday, November 22, 2011 9:05AM - 9:18AM |
M5.00006: Vortex Shedding of Various Bluff Bodies in a Cross Flow and Flame Luminosity Christopher Ruscher, John Dannenhoffer, Mark Glauser, Barry Kiel, Balu Sekar, Robert Kapaku A comparison between flame luminosity and non-combusting flows was made in order to better understand the effects combustion and the flame have on the fluid dynamics of a flow. A large eddy simulation (LES) of a cylinder in a cross flow was done at different Reynolds number in order to make the comparison between flame luminosity and non-combusting flows using OVERSET grid technology. Proper orthogonal decomposition (POD) was done for the different cases in order to compare how much energy is contained in symmetric, asymmetric, and uncorrelated POD modes. Initial results show the modal energies of the non-combusting flow do not match the modal energies of the flame luminosity. [Preview Abstract] |
Tuesday, November 22, 2011 9:18AM - 9:31AM |
M5.00007: Investigation of a subsonic round binary jet release Boris Chernyavsky, Pierre B\'enard We present results of an ongoing study of a binary $H_2$/CO jet/plume release. The original motivation behind this research lies in the need within the fuel cell community to establish safety criteria and the extent of potential danger envelope for unintended $H_2$/CO mixture releases for a variety of possible release conditions, including release velocity (jet versus plume type releases), orientation and release opening diameter, and initial gases fraction ratio, taking into account: a) the extent of flammable concentrations of $H_2$, corrected for the presence of CO; b) the extent of CO concentration exceeding health safety limits; c) the extent of flammable CO concentration. Presented are results of numerical simulations, covering a wide range of release conditions, including release velocity, orientation and gas fraction ratios. Particular attention has been paid to the gas segregation driven by a) buoyancy due to significant difference in gas densities; b) differences in diffusion properties, which could potentially affect jet evolution. It is shown that the observed segregation is small enough so that the concentration of one gas can be estimated from the measured concentration of another with sufficient degree of accuracy, except in the immediate vicinity of the origin of the jet. Subsequent simulations revealed that the primary driver of the segregation appears to be the difference in the diffusion properties between the mixture components. [Preview Abstract] |
Tuesday, November 22, 2011 9:31AM - 9:44AM |
M5.00008: Algebraic decomposition as a seamless multiscale coupling strategy Nicolas Hadjiconstantinou We discuss a new class of approaches for efficiently simulating multiscale kinetic problems, with particular emphasis on applications related to small-scale transport. These approaches, referred to as deviational, are based on a decomposition of the kinetic description into an equilibrium part, that is described deterministically (analytically or numerically), and the remainder, which is described using a particle simulation method. We show that it is possible to derive evolution equations for the two parts from the governing kinetic equation, leading to a decomposition that is dynamically and automatically adaptive, and a multiscale method that seamlessly bridges the two descriptions {\it without introducing any approximation}. Our discussion pays particular attention to stochastic simulation methods that are typically used to simulate kinetic phenomena; in this context, these decomposition approaches can be thought of as control- variate variance reduction formulations, with the nearby equilibrium serving as the control. Such formulations can provide substantial computational benefits in a broad spectrum of applications because a number of transport processes and phenomena of practical interest correspond to perturbations from nearby equilibrium distributions which can be exploited to drastically reduce the number of particles required in the simulation. In many cases the computational cost reduction is sufficiently large to enable otherwise impossible simulations. [Preview Abstract] |
Tuesday, November 22, 2011 9:44AM - 9:57AM |
M5.00009: Modeling of heat transfer and mixing processes for complex geometries with applications to energy conversion systems Nikolaos Prasianakis, Jinfen Kang, Felix Buechi, John Mantzaras The study of advanced small energy conversion systems, such as fuel cells (SOFCs, PEFCs) and microcombustors, requires lattice Boltzmann models that can handle heat transfer and multicomponent species mixing. A new model is developed. The new thermal equilibrium populations are derived following the procedure described in Refs [1,2]. The collision step is split in two BGK-type relaxation processes as described in Ref. [3]. The resulting model has the capability of variable Prandtl and Schmidt numbers. The simplicity of the model allows its implementation to complex geometry flows. For an accurate prediction of the micro flow effects, the diffusive boundary condition is used. Micro-flow simulations of the flow through a SOFC are presented. Preliminary results of flows through three-dimensional complex geometries typically found in PEFCs are shown. \\[4pt] [1] N.I. Prasianakis, I.V. Karlin, PRE 76, 016702 (2007). \\[0pt] [2] N.I. Prasianakis, I.V. Karlin, J. Mantzaras, K. Boulouchos, PRE 79, 066702 (2009). \\[0pt] [3] S. Arcidiacono, I.V. Karlin, J. Mantzaras, C.E. Frouzakis, PRE 76, 046703 (2007). [Preview Abstract] |
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