Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session ZC34: Reacting Flows: General |
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Chair: Arpan Sircar, Oak Ridge National Laboratory Room: 255 F |
Tuesday, November 26, 2024 12:50PM - 1:03PM |
ZC34.00001: Flow topology and wind-driven wildfire propagation Siva Viknesh, Ali Tohidi, Fatemeh Afghah, Rob Stoll, Amirhossein Arzani This work investigates the influence of wind flow patterns and topology on wildfire propagation. The Asensio wildfire model (nonlinear reactive flow) is revisited and non-dimensionalized by selecting three distinct time scales, unveiling two non-dimensional numbers, unlike the conventional approach that considers only one time scale. First, scaling analysis is performed to understand the overall wildfire behavior under the identified non-dimensional numbers. Subsequently, a wildfire transport solver is developed within a finite difference method framework, employing compact spatial schemes and an implicit-explicit Runge-Kutta time integrator. We study the characteristics of transient wildfire behavior under steady wind velocity with saddle-type fixed points, emphasizing the importance of the non-dimensional numbers, and consider unsteady wind velocity represented by the double gyre flow, examining various wind oscillation frequencies and amplitudes. This work highlights the complex interactions between wildfire dynamics and wind patterns, providing insights for a better understanding of wind-driven wildfire behavior. |
Tuesday, November 26, 2024 1:03PM - 1:16PM |
ZC34.00002: Investigating the Scalability of Blue Whirl through Numerical Simulations E. Tarik T Balci, Elaine S Oran The blue whirl (BW) is a small, entirely blue, nearly soot-free flame first observed as it emerged from small-scale laboratory experiments of fire whirls (FW) burning liquid hydrocarbons on water (Xiao et al., PNAS, 2016). These BWs were approximately 2–2.5 cm wide and 6–8 cm tall, positioned just above the bottom surface. Recent progress in three-dimensional (3D) numerical simulations (Chung et al., Science Advances, 2020; Zhang et al., Computers and Fluids, 2018) has provided insights into the flame structure of BW. Here, we investigated whether the size of BW can be increased by changing the flame and flow parameters such as gravity, tangential inlet velocity, fuel supply rate, and radial inlet velocity. First, we conducted 3D simulations for these parameters, changing their values and investigating the effects on the BW. Then, according to the results, the limits for the flame regime change were found. Finally, staying within these limits, the four parameters were changed together, and the size of the BW was able to be increased approximately two to three times. |
Tuesday, November 26, 2024 1:16PM - 1:29PM |
ZC34.00003: Heat transfer during fire spread through fine fuels under momentum vs. buoyancy-driven flow. Kelly Clevenson, Daniel Jimenez, Michael J Gollner Understanding and modeling wildfires is essential for protecting the lives of firefighters and mitigating damage to communities located at the wildland-urban interface (WUI). Wildfires become particularly destructive in extreme weather conditions, including low humidity and high wind speeds. Wind-driven flame spread is simulated in a wind tunnel at the US Forest Service Missoula Fire Sciences Laboratory using a bed of fine pine needles as fuel. Pushed by wind speeds of 0.5 m/s and 1 m/s, flames spread along a fuel bed with up to a fuel break where the flame will either jump the gap or extinguish. Wind speed, fuel moisture content (3%-15%), and gap size (0-60cm) are varied in the experiment. In addition to infrared and go-pro videos, high-frequency (1 kHz) total and radiative heat flux data is collected before and after fuel breaks to understand the relationship between radiative and convective heating under different wind, moisture, and fuel break conditions. These experiments show that the flame acts similarly to a buoyancy-driven flow at lower wind speeds while at higher wind speeds it is momentum-driven, resulting in changing profiles of downstream heat transfer. These experiments seek to understand this behavior and its impact on the heating and ignition of small-diameter fuels. |
Tuesday, November 26, 2024 1:29PM - 1:42PM |
ZC34.00004: Fuel-flexible matrix-stabilized combustion of methane/hydrogen mixtures using a non-premixed injection system. Guillaume Vignat, Elinor Tandberg, Matthias Ihme For many industrial and power generation applications, the transition towards low-carbon energy carriers will require adapting burners and combustion systems to operate with a wide range of natural gas and hydrogen mixtures. Matrix-stabilized combustion is an attractive option to stabilize methane/hydrogen flames at very lean conditions. The current work investigates the utilization of an additively manufactured non-premixed fuel injector in conjunction with ceramic foams to mitigate the risk of flashback when operating with a high hydrogen fuel mix. The burner is an axial-flow interface-stabilized design, made of silicon carbide and yttria-stabilized zirconia alumina reticulated foams. The injector was additively manufactured from a nickel alloy and used a coaxial injector setup. This design is optimized to achieve mixing in the near field of the injectors, enabling quasi-premixed combustion within the downstream porous media section. The burner's stability limits and emissions were measured and compared to a fully premixed design. This novel design improves the flashback resistance of the burner while maintaining the beneficial low emission and extinction resistant characteristics of traditional premixed matrix-stabilized combustion. |
Tuesday, November 26, 2024 1:42PM - 1:55PM |
ZC34.00005: Experimental and numerical investigation of aqueous reactive flows in a jet-stirred reactor Jui-Yang Wang, Paul D Ronney Jet-stirred reactors (JSR) have been widely used to study reaction rates for developing detailed chemical kinetic models. However, the prediction and characterization of JSRs unmixedness have received little attention. Our recent modeling results suggest that another JSR geometry based on optimally-positioned sets of inlet jets with concentric outlet ports yields much higher mixing homogeneity than “industry standard” JSR designs. To evaluate the performance of such reactor designs experimentally, in this study we employed aqueous Fenton reagents (combinations of hydrogen peroxide and ferrous ion), visualized with a Planar Laser-Induced Fluorescence (PLIF) technique; the fluorescence signal from a reactive tracer (rhodamine B) is quenched by OH radicals produced therein. The extent and uniformity of reaction is characterized by the spatial distribution of fluorescence intensity. By adjusting the volumetric flow rate and concentrations of reactants, a wide range of Damköhler numbers (ratio of residence time to reaction time scale) were investigated. Reacting-flow computations including the Fenton reactions were performed to enable direct comparisons with the PLIF measurements. |
Tuesday, November 26, 2024 1:55PM - 2:08PM |
ZC34.00006: Stochastic ignition of fuel droplets impacting a hot surface: comparison of alkanes, conventional, and sustainable aviation fuels Guillaume Vignat, Yichi Ma, Jen Zen Ho, Younghwa Cho, Nozomu Hashimoto, Timoteo Dinelli, Taekeun Yoon, Colette Fisher, Matthias Ihme Flammable fluids dripping onto hot surfaces are a major source of fires in aircraft, vehicles, and heavy machinery. The present work investigates experimentally the ignitability of different liquid fuels (linear alkanes, conventional petroleum-derived aviation fuels, and sustainable aviation fuels synthetized from biomass feedstocks) in an idealized scenario in which mm-sized fuel droplets orthogonally impact a flat surface raised to temperatures well-above the Leidenfrost point, in quiescent atmospheric pressure air. These droplets, with Weber number in the order of 250, break up on impact and ignite if the surface temperature is sufficiently elevated. We performed high speed imaging of the droplet break-up and combustion process, and report ignition probabilities and time-to-ignition for the different fuels. In addition, the composition of the fuels was characterized. Evaporation and combustion properties were derived from simulations to interpret our experimental results. |
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