Title: Identifying Characteristics of Wildfire Towers and Troughs

Abstract

Wildfire behavior is dictated by the complex interaction of numerous physical phenomena including dynamic ambient and fire-induced winds, heat transfer, aerodynamic drag on the wind by the fuel and combustion. These phenomena create complex feedback effects between the fire and its surroundings. In this study, we aim to study the mechanisms by which buoyant flame dynamics along with vortical motions and instabilities control wildfire propagation. Specifically, this study employs a suite of simulations conducted with the physics-based coupled fire-atmosphere behavior model (FIRETEC). The simulations are initialized with a fire line and the fires are allowed to propagate on a grass bed, where the fuel heights and wind conditions are varied systematically. Flow variables are extracted to identify the characteristics of the alternating counter-rotational vortices, called towers and troughs, that drive convective heat transfer and fire spread. These vortices have previously been observed in wildfires and laboratory fires, and have also been observed to arise spontaneously in FIRETEC due to the fundamental physics incorporated in the model. However, these past observations have been qualitative in nature and no quantitative studies can be found in the literature which connected these coherent structures fundamental to fire behavior with the constitutive flow variables. Tomore » that end, a variety of state variables are examined in the context of these coherent structures under various wind profile and grass height conditions. Identification of various correlated signatures and fire-atmosphere feedbacks in simulations provides a hypothesis that can be tested in future observational or experimental efforts, potentially assisting experimental design, and can aid in the interpretation of data from in situ detectors.« less

Authors:

Banerjee, Tirtha ;

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Holland, Troy; Solander, Kurt; Holmes, Marlin; Linn, Rodman

Publication Date:

Tue Jul 28 00:00:00 EDT 2020

Research Org.:

Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

Sponsoring Org.:

USDOE Laboratory Directed Research and Development (LDRD) Program

OSTI Identifier:

1643970

Alternate Identifier(s):

OSTI ID: 1734718

Report Number(s):

LA-UR-19-30049
Journal ID: ISSN 2073-4433; ATMOCZ; PII: atmos11080796

Grant/Contract Number:  

20180704PRD1; 89233218CNA000001; LFR-20-653572

Resource Type:

Published Article

Journal Name:

Atmosphere (Basel)

Additional Journal Information:

Journal Name: Atmosphere (Basel) Journal Volume: 11 Journal Issue: 8; Journal ID: ISSN 2073-4433

Publisher:

MDPI AG

Country of Publication:

Switzerland

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; Earth Sciences; Energy Sciences; Wildfire Propagation; Coherent Structures; Computational Fluid Dynamics