Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session C01: Turbulent and Chemically-reacting Flow Modeling I |
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Chair: Peyman Givi, University of Pittsburgh Room: 2A |
Sunday, November 24, 2019 8:00AM - 8:13AM |
C01.00001: Edward E. O'Brien's Seminal Contributions to Turbulence Theory Foluso Ladeinde, Cesar Dopazo, Peyman Givi A brief overview will be presented of the influential contributions of Edward E. (Ted) O'Brien to the theory of turbulence, with an emphasis on scalar mixing and reaction.~While perhaps best known for his work on the transported PDF methods, Ted's contributions are very diverse and consider a broad range of theoretical and computational approaches.~~In the 1960s, he made some very fundamental contributions to the spectral theory of reactive scalars, analyzed the consequences of passive scalar tagging using Corsin's ``backward Lagrangian diffusion'' concept, and contributed to the interpretation of Kraichnan's ``direct interaction approximation'' (DIA) for turbulent mixing.~~~In the 1970s-1980s, he focused on scalar PD Functional and Function methods. In fact, he is widely recognized for introducing and popularizing single- and multi-point PDF closures, as well as the scalar-gradient PDF within the reactive turbulent flow community.~In the 1990s, he focused on applying the EDQNM and the ``amplitude mapping closure'' (AMC) models, respectively~to reactive turbulent scalars and mixing.~~With wider availability of supercomputers in the late 1990's-2000's, Ted utilized DNS for the development and appraisal of modern turbulence closures.~~He is also credited with introducing the ``filtered density function'' (FDF) transport equation for LES of turbulent reactive flows.~~In fact, he is the first to develop a transported scalar-FDF equation for multi-species turbulent reactive flows.~~Professor O'Brien's publications continue to be highly cited within the turbulence research community. [Preview Abstract] |
Sunday, November 24, 2019 8:13AM - 8:26AM |
C01.00002: Numerical Simulation of Colorless Distributed Combustion with LES/FMDF Husam Abdulrahman, Farhad Jaberi, Abdoulahad Validi, Ashwani Gupta \textbf{Honoring Ted O'Brien. }Turbulent mixing and combustion in non-premixed and premixed Colorless Distributed Combustion (CDC) systems are studied with the hybrid large eddy simulation/filtered mass density function (LES/FMDF) methodology and its Eulerian--Lagrangian computational solver. The CDC has shown to significantly reduce NOx and hydrocarbon emissions while improving the reaction pattern factor and stability with low pressure drop and noise. The combustion in CDC is distributed and is characterized by wide fluctuations in flow variables. In addition to non-conventional distributed turbulent reaction, mixing between fuel, oxidizer, and combustion products in CDC is unique and complex. The LES/FMDF model is shown to be able to capture all the unique features of turbulent mixing and combustion in CDC. The consistency of the Eulerian and Lagrangian parts of LES/FMDF is established for both non-reacting and reacting conditions. The LES/FMDF results are shown to be in good agreement with the available experimental data. The numerical results indicate that the variations in the inflow air temperature, jet velocity and composition and premixing have a significant effect on the flow, mixing and combustion in the CDC. They also indicate the importance of jets setup in the combustor. [Preview Abstract] |
Sunday, November 24, 2019 8:26AM - 8:39AM |
C01.00003: Filtered Mass Density Function for Large-Eddy Simulations of Multiphase Turbulent Reacting Flows Farhad Jaberi, Zhaorui Li, Araz Banaeizadeh, Abolfazl Irannejad Honoring Ted O'Brien. The filtered mass density function (FMDF) methodology is further extended and employed for large-eddy simulations (LES) of multiphase turbulent reacting flows. The two-phase LES/FMDF model is implemented with a unique Lagrangian-Eulerian-Lagrangian mathematical/computational methodology. In this methodology, the filtered carrier gas velocity field is obtained by solving the filtered form of the compressible Navier-Stokes equations while the gas scalar (e.g. temperature and species mass fractions) field and the liquid (spray) phase are obtained by solving two different sets of Lagrangian equations. The two-way interactions between the phases and all the Eulerian and Lagrangian fields are included in the two-phase LES/FMDF methodology. The accuracy and reliability of the model is demonstrated by comparing the two-phase LES/FMDF results with those obtained from the direct numerical simulation (DNS) and experimental data for a range of fundamental and practical multiphase flows including a spatially developing turbulent mixing layer with evaporating and reacting droplets and spray combustion in a preheated high-pressure closed chamber, a dump combustor, a double-swirl burner, and an internal combustion engine. [Preview Abstract] |
Sunday, November 24, 2019 8:39AM - 8:52AM |
C01.00004: A High-Order FDF Large Eddy Simulator of Complex Flows Shervin Sammak, Aidyn Aitzhan, Arash Nouri, Peyman Givi Honoring Ted O'Brien. The flow solvers in most previous LES-FDF are based either on high-order discretization schemes in simple flows, or low-order (finite-volume) methods in complex flows. In this work, we develop a new computational methodology which allows LES of complex flows via the use of a high-order spectral-hp element scheme. The high order accuracy of the spectral discretization and the versatility of the finite element domain decomposition, facilitate high-fidelity simulation of flows within complex geometries. This CFD solver is combined with a Lagrangian Monte Carlo scheme for LES of a bluff-body reacting flow via the FDF subgrid scale closure [1]. Demonstrations are made of the consistency and the overall superior performance of this high order hybrid scheme. [1] Gao, F. and O'Brien, E. E., ``A Large-Eddy Simulation Scheme for Turbulent Reacting Flows,'' Phys. Fluids A, vol. 5(6), pp. 1282-1284 (1993). [Preview Abstract] |
Sunday, November 24, 2019 8:52AM - 9:05AM |
C01.00005: On Large Eddy Simulation/Filtered Density Function based Modeling of Circular Bluff Body Configurations. Cesar Celis, Ricardo Franco Honoring Ted O'Brien. Large eddy simulation/filtered density function (LES/FDF) numerical results of inert and reacting flows characterizing the near wake of bluff body configurations are discussed in this work. Circular bluff body configurations are studied because they feature strong interactions between turbulence and chemical reaction, as well as pollutants formation. All numerical results obtained here are compared to experimental data gathered previously. Parameters particularly analyzed include velocity profiles, turbulent kinetic energy, Reynolds stress and strain rate tensors. A strong anisotropic flow is observed from the obtained results along with a flow recirculation zone consisting of a toroidal vortex. At inert conditions, large turbulent fluctuations are found at the stagnation point region. The observed flow anisotropy is associated with the stagnation point flow. The results discussed here correspond to on-going work involving both bluff body burner configurations and numerical predictions of rather complex phenomena such as soot formation. [Preview Abstract] |
Sunday, November 24, 2019 9:05AM - 9:18AM |
C01.00006: Molecular mixing in highly turbulent premixed flames Xinyu Zhao, Patrick Meagher Honoring Ted O’Brien: The molecular mixing rules and rates in premixed flames subject to intense turbulence are investigated in this study. Direct numerical simulation (DNS) of a spherical product kernel is conducted in a homogeneous isotropic turbulence box. The triply periodic computational domain outside the product kernel is comprised of fresh mixtures. The transient flame kernel undergoes flame propagation, local extinction, and eventually global extinction. During the transition, the compositional space evolves from a low-dimensional manifold to increasingly higher dimensions. The DNS data are subsequently explicitly filtered to study the subgrid-scale behavior of the scalars. The Euclidean minimum spanning trees are constructed to understand the change of localness during the extinction process. Conditional statistics of major and minor species are collected, according to the mixing rules of various mixing models. A scalar gradient based mixing frequency model is constructed and assessed for its suitability to represent the mixing rates of critical species during all phases of the flame kernel evolution. [Preview Abstract] |
Sunday, November 24, 2019 9:18AM - 9:31AM |
C01.00007: Uniform mean scalar gradient in grid turbulence: Asymptotic probability distribution of a paasive scalar Xiaodan Cai Honoring Ted O'Brien. Dr. Edward E. O'Brien was my Ph.D advisor in mechanical engineering at Stony Brook University. It was he who introduced me to study flow turbulence in the United States after we met at a Fluid Dynamics confererence in Beijing. He was an extremely humble, patient and optimistic person, and was an inspiration to all. Dr. O'Brien stressed the importance of understanding the fundamentals and was rigorous in applying them to solve important problems. I am one of Professor O'Brien's students who has benifited immensely from his approaches and values. I will now present our work on asymptotic behaviors of probability distribution function for a passive scale in grid turbulence, which highlights Professor O'Brien's legacy. [Preview Abstract] |
Sunday, November 24, 2019 9:31AM - 9:44AM |
C01.00008: Modeling Radiative Heat Transfer and Turbulence-Radiation Interactions Using PDF and FDF Methods Daniel Haworth Honoring Ted O’Brien. In 1974, Dopazo and O’Brien proposed using a modeled equation for the probability density function of a set of scalar variables that describe the thermochemical state of a reacting medium (a transported composition joint PDF) to model mixing and reaction in chemically reacting turbulent flows. Since then, the benefits of PDF methods, including subsequent extension to large-eddy simulations (filtered density function -- FDF) methods, for modeling turbulence-chemistry interactions have been well established. Those benefits are a consequence of the ability of PDF/FDF methods to represent the influences of unresolved turbulent fluctuations on one-point physical processes (such as chemical reactions) in a natural way. For the same reason, PDF/FDF methods have an advantage in dealing with the influences of unresolved turbulent fluctuations on radiative emission. And when coupled with a stochastic radiation solver, the benefits can be extended to radiative absorption, thereby capturing both emission and absorption turbulence-radiation interactions. A model that combines stochastic Lagrangian particle PDF/FDF methods and a photon Monte Carlo method for radiative transfer is presented. Results are presented for laboratory flames and high-pressure combustion systems. [Preview Abstract] |
Sunday, November 24, 2019 9:44AM - 9:57AM |
C01.00009: Deep Learning of Single-Point PDF Closure for Turbulent Scalar Mixing Peyman Givi, Hessam Babaee, Maziar Raissi Honoring Ted O'Brien. O'Brien and Jiang [1] have shown that a useful means of characterizing the single-point PDF of a scalar field, is to consider its corresponding rate of the conditional expected dissipation. They demonstrate it by implementing the amplitude mapping closure (AMC) as applied to the classical problem of the binary scalar mixing. Based on recent developments in physics-informed deep learning and deep hidden physics models, we put forth a framework for discovering turbulent scalar mixing models from scattered and potentially noisy spatio-temporal measurements of the PDF. Our discovered model is appraised via comparison with the exact solution obtained by O'Brien and Jiang [1]. [1] O'Brien, E. E. and Jiang, T.-L., ``The Conditional Dissipation Rate of an Initially Binary Scalar in Homogeneous Turbulence,'' Phys. Fluids A, vol. 3(12), pp. 3121-3123 (1991). [Preview Abstract] |
Sunday, November 24, 2019 9:57AM - 10:10AM |
C01.00010: Investigation of scalar-scalar-gradient filtered joint density function for large eddy simulation of turbulent combustion Chenning Tong Honoring Ted O'Brien. The scalar-scalar-gradient filtered joint density function (FJDF) is studied experimentally. Measurements are made in the fully developed region of an axisymmetric turbulent jet (with a jet Reynolds number of 40000) using an array consisting of three X-wires and three resistance-wire temperature probes. Filtering in the cross-stream and streamwise directions are realized by using the array and by invoking Taylor's hypothesis, respectively. The measured mean FJDF conditional on the (subgrid-scale) SGS scalar variance is unimodal when the SGS scalar variance is small compared to its mean. The scalar gradient depends weakly on the SGS scalar. For large SGS variance the FJDF is bimodal and the gradient depends strongly on the SGS scalar. The SGS scalar under such a condition contains diffusion layer structures and the SGS mixing is similar to the early stages of binary mixing. The iso-scalar surface in the diffusion layer has a lower surface-to-volume ratio than those in a well mixed scalar. The conditionally filtered diffusion of the scalar gradient has a S-shaped dependence on the scalar gradient, which is expected to be qualitatively different from that of a reacting scalar under fast chemistry conditions. However, because modeling is performed at a higher level and because the scalar-scalar-gradient FJDF contains the information about the scalar dissipation and the surface-to-volume ratio, the FJDF approach is expected to be more accurate than scalar filtered density function approaches and has the potential to model turbulent combustion over a wide range of Damkohler numbers. [Preview Abstract] |
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