Structural uncertainty assessment for fire-engulfed objects in crosswind: Establishing credibility for a multiphysics wall-modeled large-eddy simulation paradigm

Journal Article · Wed May 07 00:00:00 EDT 2025 · Physical Review Fluids

DOI:https://doi.org/10.1103/PhysRevFluids.10.054604· OSTI ID:2585632

Domino, Stefan Paul ^[1]; Scott, Sarah Nicole ^[2]; Hubbard, Joshua Allen ^[1]

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1. Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
2. Sandia National Laboratories (SNL-CA), Livermore, CA (United States)

A structural uncertainty validation study for a large-scale, fire-engulfed, elevated object subjected to crosswind is presented to establish the credibility of a high-fidelity, low-Mach, turbulent reacting flow wall-modeled large-eddy simulation (WMLES) approach that includes multiphysics coupling to participating media radiation and conjugate heat transfer. To establish that WMLES can accurately predict surface quantities including drag and pressure coefficient in the low-Mach crosswind regime, a foundational elevated isothermal cylinder validation case is presented at a similar gap-to-diameter ratio of 0.25, spanning the subcritical to supercritical drag regime (Re_𝐷 = 1.1 × 10⁵ and 4.3 × 10⁵, respectively). Here, this study exercised both static and dynamic coefficient LES (Smagorinsky and 𝑘_sgs) with both local and exchange-based velocity sampling. Results showcase that the drag crisis (or the sudden drop in drag coefficient at increased Re_𝐷) is well captured when using an exchange-based dynamic coefficient WMLES methodology, while noting lack of mesh convergence and overall drag and pressure coefficient predictively when using a static coefficient, local velocity sampling WMLES. For the 𝒪⁡(10) m JP-8 liquid pool fire crosswind validation study presented, two experimental crosswind configurations (2 m/s and 9.5 m/s) are showcased for a fire-engulfed mock fuselage roughly 4 m in diameter. Using the best model-form practices identified in the isothermal study, dynamic coefficient 𝑘_sgs exchange-based WMLES fire validation findings demonstrate accurate peak irradiation and skin temperature predictions as a function of crosswind magnitude. Excessive yaw in the low-crosswind fuselage configuration, consistent with experimental findings, captured a significant predicted asymmetry in flame attachment and heat flux toward the downwind cylindrical cap—indicative of axial vortex structures transporting the flame along the upper and lower fuselage leeward surface. All fire mesh resolution simulations captured the experimental finding that as crosswind increased, predicted flame shape and peak irradiation magnitude onto the fuselage transitioned from a windward to a leeward cylinder location due to the migration of the upper- to lower-shear fuel/air mixing layer thereby demonstrating the novelty, significance, and credibility of this high-fidelity WMLES reacting flow framework.

• Research Organization: Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Office of Defense Programs (DP)
• Grant/Contract Number: NA0003525
• OSTI ID: 2585632
• Report Number(s): SAND--2025-06128J; 1770068
• Journal Information: Physical Review Fluids, Journal Name: Physical Review Fluids Journal Issue: 5 Vol. 10; ISSN 2469-990X
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English