Bulletin of the American Physical Society
75th Annual Meeting of the Division of Fluid Dynamics
Volume 67, Number 19
Sunday–Tuesday, November 20–22, 2022; Indiana Convention Center, Indianapolis, Indiana.
Session L25: Reacting Flows: Detonations, Explosions and DDT |
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Chair: Sai Sandeep Dammati, Texas A&M University; Praveen Ramaprabhu, University of North Carolina at Charlott Room: 233 |
Monday, November 21, 2022 8:00AM - 8:13AM |
L25.00001: Simulating detonations with tabulated chemistry Alexandra Baumgart, Matthew X Yao, Guillaume Blanquart The presence of both shocks and chemical reactions in detonations poses a challenge for simulation efficiency. Detailed chemical kinetic models require one equation per chemical species. To model hydrogen combustion, nine species are needed; for hydrocarbon fuels, there may be hundreds or even thousands of species to consider. The cost of chemistry has been addressed for subsonic reacting flow simulations using the tabulated chemistry method, in which one (or a combination of) species mass fraction tracks the progress of reactions in a system. However, reaction rates and mixture properties also depend on the thermodynamic state. In compressible flows, the temperature and the progress variable are used to describe the enthalpy and specific heat capacity of the mixture, which are used along with the equation of state to compute the pressure. The progress variable, pressure, and enthalpy are then used to obtain the progress variable source term and transport properties. This work extends the methodology that has been implemented for turbulent flames to include one- and two-dimensional detonations. The reduced-order chemical model is validated against simulation data obtained with detailed chemistry. |
Monday, November 21, 2022 8:13AM - 8:26AM |
L25.00002: Droplet Dynamics Characterization in Spray Detonations of Hydrocarbon Fuels Sai Sandeep Dammati, Yoram Kozak, Alexei Y Poludnenko Detonations have long held promise of significant efficiency gains in propulsion and energy conversion devices. Despite significant progress over the years in studies of gas-phase detonations, liquid-fuel detonations remain largely unexplored. Presence of a liquid spray brings in a multitude of complexities such as droplet-flow and droplet-droplet interactions, spray atomization, evaporation, and mixing, which all pose significant challenges for modelling. Here, we present results of the spray detonation simulations in dodecane/air mixtures using an Eulerian-Lagrangian formulation with complex chemistry and detailed multi-species transport. We contrast the obtained detonation properties with those of a purely gas-phase detonation. Furthermore, we discuss the flow regimes encountered by the liquid spray in a freely propagating detonation in order to determine the fidelity and limitations of the existing droplet drag, atomization, and evaporation models. In particular, we analyze the thermodynamic conditions encountered by liquid droplets along with droplet Reynolds, Mach, Weber, and Ohnesorge numbers. We conclude by discussing future extensions of the physical models necessary for the accurate and predictive modelling of liquid spray detonations. |
Monday, November 21, 2022 8:26AM - 8:39AM Author not Attending |
L25.00003: Assessment of non-thermal termolecular reactions on H2/air detonation cell size Swapnil Desai, Yujie Tao, Raghu Sivaramakrishnan, Jacqueline H Chen Previous numerical studies by Taylor et al. (Proc. Combust. Inst. 34 (2013) 2009-2016) have shown that thermally equilibrium chemical kinetic models may be insufficient for modeling detonation. The computed detonation cell sizes and cell regularity differ from experimental observations, indicating that the chemical kinetic model overestimates both the rate of energy release and its sensitivity to temperature behind detonation shocks. To resolve this discrepancy between the numerical detonation cell size and experimental observations, numerical simulations were conducted in this work on a two-dimensional adaptive grid with a detailed thermochemical reaction model for a premixed nitrogen-diluted hydrogen-oxygen mixture. Following the procedure described by Tao et al. (Proc. Combust. Inst. 38 (2021) 515–522), non-thermal reactions were included in the macroscopic kinetic model as chemically termolecular reactions facilitated by the H + OH radical-radical recombination and H + O2 radical-molecule association reactions. Comparison of the simulated detonation cell widths between the different cases suggests that non-thermal reactivity can lead to a noticeable increase in gaseous detonation cell-size. As such, it is important to properly account for non-thermal reactions in simulations of H2/air detonations. |
Monday, November 21, 2022 8:39AM - 8:52AM |
L25.00004: Numerical Simulation of Chemical Freeze-Out in Explosive Post-Detonation Flows Anthony A Egeln Jr, Ryan W Houim A numerical simulation study was performed to examine the post-detonation reaction processes produced by the detonation of a 12 mm-diameter hemispherical PETN explosive charge. The simulations used a finite rate detailed chemical reaction model consisting of 59 species and 368 reactions to capture post-detonation reaction processes. The BKW real-gas equation of state is used for the gas phase to allow for the mixing of reactive species. A recent simplified reactive burn model is used to propagate the detonation through the charge and allow for detailed post-detonation reaction processes. The computed blast, shock structures, and mole fractions of detonation product species agree well with experimental measurements. A comparison of the simulation results to equilibrium calculations indicates that the assumption of a local equilibrium is fairly accurate until the detonation products rapidly cool to temperatures below 1500 to 1800 K by expansion waves. Below this range, the computed results show mole fractions that are nearly chemically frozen within the detonation products for a significant portion of expansion. These results are consistent with the freeze-out approximation used in the blast modeling community. |
Monday, November 21, 2022 8:52AM - 9:05AM |
L25.00005: Droplet Breakup Effects on Liquid Fuel Detonation Manoj Paudel, Benjamin J Musick, Jacob A McFarland, Praveen K Ramaprabhu
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Monday, November 21, 2022 9:05AM - 9:18AM |
L25.00006: Numerical studies of the detonation-bow shock interaction Ashwath Sethu Venkataraman, Elaine S Oran The interaction of a detonation with the bow shock generated by projectiles moving at supersonic speeds has applications in the fields of process and industrial safety. This problem involves a coupling between different compressible and reacting flow phenomena including shock-shock, shock-flame and shock-turbulence interactions. We study the detonation-bow shock interaction problem using AMRFCT, a code that solves the multidimensional, reacting flow conservation equations with a chemical-diffusive model (CDM) for conversion of fuel to products with energy release. The effect of obstacles is incorporated using a flux redistribution cut-cell method and AMRFCT is built on the AMReX framework for black-structured adaptive mesh refinement. First, we present preliminary results for the inviscid interaction of a detonation and a bow shock. Then, we show the effect of obstacles on the flow field and how it affects important detonation properties such as the propagation speed and cellular structure. |
Monday, November 21, 2022 9:18AM - 9:31AM |
L25.00007: Divergent Flow Effects in Gaseous Detonations Stephen J Voelkel, Mark Short Gas detonations have become increasingly relevant due to the development of rotating detonation engines (RDEs), in which a steady detonation propagates around a thin annulus constantly fueled from an inflow at the bottom. In the shock-attached frame, the detonation front attaches to the bottom of the annulus perpendicular to the inflow. Depending on the fuel and RDE dimensions, at some standoff distance from the inflow, the detonation front transitions to a shear layer between the reacting flow and unburned (previously burned) mixture, which effectively acts as an outer boundary for the reacting flow. The standoff distance and angle of this shear layer directly affect the divergence experienced within the reacting flow. Here, we examine these effects directly via a series of hydrogen-air detonations in a 2D planar configuration. A shock-attached frame is imposed onto the flow, and the shear layer is represented as a streamline boundary. This configuration allows us to directly control the standoff distance of the shear layer as well as the flow divergence introduced via the shear angle. A series of studies are performed at varied standoff distances and shear angles to examine how these properties affect detonation propagation and heat release in RDE-like configurations. |
Monday, November 21, 2022 9:31AM - 9:44AM |
L25.00008: Spectral Characterization of Overdriven Irregular Detonations Ramachandran Suryanarayan, Navneeth Srinivasan, Shufan Zou, Suo Yang Rotating Detonation Engines (RDEs) have garnered great interest in recent years due to promising performance efficiencies stemming from compact detonation heat-release rather than deflagration. However, gaps in understanding underlying turbulent irregular detonation processes and the lack of accurate CFD predictions has withheld prototypes from achieving the targeted efficiencies. To inform the development of accurate sub-grid scale (SGS) models for turbulent irregular detonation, we propose a novel spectral description of turbulent irregular detonation, focusing on cell-structure and chemistry spectra. We attempt to quantify and better explain the broad-range of cell-sizes and the influence of the underlying chemical processes from high-quality numerical data generated from Adaptive Mesh Refinement (AMR)-based DNS-like simulations. An overdriven detonation wave composed of a stoichiometric methane-oxygen mixture is studied for which numerical soot foils are generated to obtain cell-size spectrum. A conservative chemical explosive mode analysis (CCEMA) is also conducted to generate chemistry mode spectra which exhibit similar trends indicating tight coupling. |
Monday, November 21, 2022 9:44AM - 9:57AM |
L25.00009: Explorations on Reduced Order Model Development for 2D Detonation Wave Ryan G Camacho, Cheng Huang In recent years, pressure gain combustion systems, specifically rotating detonation engines (RDEs), have exhibited great potential as a viable alternative to traditional combustion in propulsion applications. Though high-fidelity simulations have become accessible for RDE modeling, they remain computationally expensive for practical engineering applications. Recent advancement in reduced-order model (ROM) development provides an avenue to address this challenge. The goal of this study is to develop a reduced-order modelling framework for RDE simulations via model-order reduction (MOR) techniques. However, it is well recognized that the conventional MOR methods exhibit difficulties in capturing problems with convection-dominated physics (e.g., shocks and chemical reactions). Therefore, this work focuses on developing an adaptive ROM method leveraging a recently developed formulation, model-form preserving least-squares projections with variable transformation (MP-LSVT). We will demonstrate the adaptive ROM method on a canonical two-dimensional RDE configuration with imposed periodic boundary conditions. Put simply, this framework will serve to make high-fidelity modeling of rotating detonation engines computationally efficient and aid in the design of future propulsive devices. |
Monday, November 21, 2022 9:57AM - 10:10AM |
L25.00010: On the Heat Flux Components in Supersonic Combustion of a Detonation Engine Foluso Ladeinde, HyeJin Oh, Somnic Jacobs The five components of heat flux in a model of the rotating detonation engine were extensively investigated in this study using numerical simulations that are based on an explicit large-eddy simulation (LES) approach in the presence of multi-step chemical reactions. Some relevant data for thermal management of the engine are provided. |
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