Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Fluid Dynamics
Volume 58, Number 18
Sunday–Tuesday, November 24–26, 2013; Pittsburgh, Pennsylvania
Session H23: DFD Minisymposium: Frontiers in Combustion Physics I |
Hide Abstracts |
Chair: Forman Williams, University of California - San Diego Room: 318 |
Monday, November 25, 2013 10:30AM - 10:56AM |
H23.00001: Direct Numerical Simulation of Turbulent Premixed Hydrogen/Air Flames in Sheared Turbulence and in Counterflow with Product Stratification Invited Speaker: J.H. Chen Petascale direct numerical simulations (DNS) have been performed of canonical turbulent configurations to glean physical insight into turbulence-chemistry interactions in combustion and to provide validation data for the development of coarse-grained models for engineering CFD. The role of DNS is illustrated through two examples. In the first example, DNS of turbulent hydrogen/air premixed flames interacting with intense shear driven turbulence in the thin reaction zones regime at turbulent Reynolds numbers approaching 1000 (Hawkes et al. 2012) are performed over a range of Damk\"{o}hler numbers. The DNS data are used to study inter-scale energy transfer through one-dimensional spectra of turbulent kinetic energy and reactive scalars from the turbulent premixed flames. Balance equations for the density weighted turbulent kinetic energy and scalar fluctuation spectra for reacting flows are derived and used to understand the physical processes unique to reacting flows. In the second example, DNS of highly turbulent lean premixed hydrogen-air flames stabilized against counterflowing non-adiabatic stoichiometric combustion products in chemical equilibrium are performed. The influence of product stratification on the mechanisms associated with local extinction and re-ignition in turbulent stratified combustion is studied.\\[4pt] In collaboration with H. Kolla, Sandia National Labs; A. Kerstein, 72 Lomitas Road Danville, CA 94526; N. Swaminathan, Cambridge University; E.R. Hawkes, University of New South Wales; S. Lyra, B. Coriton, J.H. Frank, Sandia National Labs; and A. Gomez, Yale University. [Preview Abstract] |
Monday, November 25, 2013 10:56AM - 11:22AM |
H23.00002: The know unknowns: Detailed simulations and low-order modeling to characterize facility-induced non-idealities in chemical-kinetics experiments Invited Speaker: Matthias Ihme Experimental investigations to study chemical-kinetics processes, reaction-rates or ignition properties are frequently accompanied by facility-induced non-idealities. Examples are turbulence and thermo-viscous boundary layers in rapid compression machines, temperature fluctuations and mixture inhomogeneities in flow-reactors, or shock-bifurcations and pressure drifts in shock-tubes. Although experimental investigations are carefully conducted to mitigate these effects, they are difficult to quantify experimentally. Simulations can assist in identifying these non-idealities and in guiding experimental instrumentation to improve measurement accuracies. This presentation discusses three different modeling approaches to characterize facility-effects in rapid compression machines, flow reactors, and shock-tubes. After providing an overview about these facilities and describing the underlying models, examples are presented to illustrate effects of turbulence, mixture-inhomogeneities, heat-losses, and thermal stratification on the ignition dynamics in these facilities. Diagnostics is developed to assess the sensitivity of the induction chemistry and to quantify reliable operating regimes that are not contaminated by these non-ideal processes. [Preview Abstract] |
Monday, November 25, 2013 11:22AM - 11:48AM |
H23.00003: Spray combustion: scales, regimes, and formulations Invited Speaker: Antonio L. S\'anchez This talk will cover some recent results relevant to the modeling of spray flames. Controlling parameters and combustion regimes will be reviewed. Conditions will be identified under which analyses of laminar mixing layers can shed light on aspects of turbulent spray combustion. Conservation equations will be derived for dilute sprays, including separate equations for the gas and liquid phases. Linear combinations of the gas-phase conservation equations for the species and energy will be used to formulate the problem in terms of chemistry-free coupling functions, including the relevant mixture fraction and the total enthalpy, which are not conserved scalars, because their conservation equations include source terms associated with the vaporizing droplets. Implications for spray-flamelet modeling, associated with the multivalued spatial dependence of the mixture fraction, will be explained. Applications of the coupling-function formulation to the computation of spray flames in the limit of infinitely fast reaction rate will be discussed, including the high-order corrections needed to account for the presence of droplets on the air side of the flame. Recent work on ignition of spray flames will also be presened.\\[4pt] In collaboration with Daniel Mart\'{i}nez-Ruiz, Departamento de Ingenier\'{i}a T\'ermica y de Fluidos, Universidad Carlos III de Madrid, Legan\'es 28911, Spain; Javier Urzay, Center for Turbulence Research, Stanford University, Stanford, CA, USA; and Amable Li\~n\'an, ETSI Aeron\'auticos, Pl. Cardenal Cisneros 3, Madrid 28040, Spain. [Preview Abstract] |
Monday, November 25, 2013 11:48AM - 12:14PM |
H23.00004: Modeling Interactions Among Turbulence, Gas-Phase Chemistry, Soot and Radiation Using Transported PDF Methods Invited Speaker: Daniel Haworth The importance of explicitly accounting for the effects of unresolved turbulent fluctuations in Reynolds-averaged and large-eddy simulations of chemically reacting turbulent flows is increasingly recognized. Transported probability density function (PDF) methods have emerged as one of the most promising modeling approaches for this purpose. In particular, PDF methods provide an elegant and effective resolution to the closure problems that arise from averaging or filtering terms that correspond to nonlinear point processes, including chemical reaction source terms and radiative emission. PDF methods traditionally have been associated with studies of turbulence-chemistry interactions in laboratory-scale, atmospheric-pressure, nonluminous, statistically stationary nonpremixed turbulent flames; and Lagrangian particle-based Monte Carlo numerical algorithms have been the predominant method for solving modeled PDF transport equations. Recent advances and trends in PDF methods are reviewed and discussed. These include advances in particle-based algorithms, alternatives to particle-based algorithms (e.g., Eulerian field methods), treatment of combustion regimes beyond low-to-moderate-Damk\"ohler-number nonpremixed systems (e.g., premixed flamelets), extensions to include radiation heat transfer and multiphase systems (e.g., soot and fuel sprays), and the use of PDF methods as the basis for subfilter-scale modeling in large-eddy simulation. Examples are provided that illustrate the utility and effectiveness of PDF methods for physics discovery and for applications to practical combustion systems. These include comparisons of results obtained using the PDF method with those from models that neglect unresolved turbulent fluctuations in composition and temperature in the averaged or filtered chemical source terms and/or the radiation heat transfer source terms. In this way, the effects of turbulence-chemistry-radiation interactions can be isolated and quantified. [Preview Abstract] |
Monday, November 25, 2013 12:14PM - 12:40PM |
H23.00005: Investigation of turbulent spherical flames Invited Speaker: N. Swaminathan The role of turbulence is generally taken to be the main cause for the growth of flame-brush thickness in turbulent spherical flames and Taylor's dispersion theory had been used in past studies to support this. Contrary to this view, this study shows that the differential propagation between the leading and trailing edges of the flame-brush is the predominant cause for the growth of the flame-brush thickness with time in the spherical flames. The leading edge accelerates continuously because of the cumulative effect of flow acceleration resulting from heat release. These insights are derived by analysing URANS computations of 7 spherical and 7 planar flames having combustion conditions in the corrugated flamelets and thin reaction zones regimes. The reaction rate closure is achieved using strained premixed flamelets with scalar dissipation rate as a parameter. Detailed analyses of the results showed that the mean reaction rate does not depend on the flame geometry, planar or spherical. However, the turbulent flame speed which is the leading edge displacement speed showed a flame geometry dependence due to the geometry dependence of turbulent scalar flux. The presentation will highlight these physical insights.\\[4pt] In collaboration with I. Ahmed, Cambridge University Engineering Department. [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. |
© 2024 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
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700