# Identifying Characteristics of Wildfire Towers and Troughs

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## Abstract

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## 1. Introduction

- What is the nature of fire—atmosphere interactions in the tower-trough structures?
- What is the impact of controlling factors such as fuel loading, fuel height and wind in modulating the tower trough structures?

## 2. Materials and Methods

#### 2.1. FIRETEC Overview

#### 2.2. Experiment Design

#### 2.3. Identification of Towers and Troughs

## 3. Results and Discussions

#### 3.1. Stationary Tower and Trough Characteristics

#### 3.2. Non-Stationary Tower and Trough Characteristics

#### 3.3. Temporal Evolution of Towers and Trough Structures

## 4. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**Visualization of counter-rotational vortices and tower—trough structures. This is a snapshot of FIRETEC simulation, showing instantaneous vertical (w) velocity. The red structures indicate towers and the blue structures are troughs [3]. The prevailing wind direction is from left to right. A scale is shown for reference.

**Figure 2.**Fire spread and fuel consumption for the idealistic wind case (

**left**) and the realistic wind field (

**right**) 300 s after ignition. The data were collected on a planar test area (vertical plane 80 $\mathrm{m}$ wide in crosswind (y) direction and 9 $\mathrm{m}$ tall located 300 $\mathrm{m}$ downwind (x) of the upwind boundary) and all quantities of interest were recorded (marked on figure). For tower and trough behavior, 4 points each were selected at a line on this plane at 1.5 m height, just above the fuel bed. This line was centered in the cross-stream (or y) direction. The locations of the towers and troughs are marked on the figures with markers—red for towers and blue for troughs. The third panel shows all idealized and realistic wind profiles.

**Figure 3.**(

**Left**) Correlation coefficient between different flow quantities associated with untracked or stationary towers. The y axis shows the two fluctuating quantities (separated by /) between which the correlation coefficients are computed. U,V,W indicate the longitudinal, cross-stream and vertical wind velocities, ${T}_{g}$ indicates gas temperature, ${T}_{S}$ indicates solid or fuel temperature, $RH$ denotes radiative heating, $CH$ indicates convective heating, ${O}_{2}$ denotes oxygen concentration. On the x axis, the different simulation cases are shown. A colormap is used to highlight the correlation coefficient magnitude for ease of comparison. (

**Right**) Same as the left panel but for untracked or stationary troughs.

**Figure 5.**Non-stationary tower plots of oxygen concentration (blue lines) and convective heat flux to the fuels (black lines). Panel titles indicate the simulation cases being depicted. (

**a**) IUx0.5 Tower (

**b**) IU4 Tower (

**c**) IU8 Tower (

**d**) RU8 Tower.

**Figure 6.**Non-stationary tower plots of solid temperature (red lines), horizontal wind velocity (black lines) and vertical wind velocity components (blue lines). Panel titles indicate the simulation cases being depicted. (

**a**) IUx0.5 Tower (

**b**) IU4 Tower (

**c**) IU8 Tower (

**d**) RU8 Tower.

**Figure 7.**Non-stationary trough plots of oxygen concentration (blue lines) and convective heat flux to the fuels (black lines). Panel titles indicate the simulation cases being depicted. (

**a**) IUx0.5 Trough (

**b**) IU4 Trough (

**c**) IU8 Trough (

**d**) RU8 Trough.

**Figure 8.**Non-stationary trough plots of solid temperature (red lines), horizontal wind velocity (black lines) and vertical wind velocity components (blue lines). Panel titles indicate the simulation cases being depicted. (

**a**) IUx0.5 Trough (

**b**) IU4 Trough (

**c**) IU8 Trough (

**d**) RU8 Trough.

Simulation | Wind (${\mathbf{ms}}^{-1}$ at 10 m Height) | Fuel Height ($\mathbf{m}$) | Fuel Load (${\mathbf{kgm}}^{-2}$) |
---|---|---|---|

IU4 | Ideal, 4 | 0.7 | 0.7 |

RU4 | Real, 4 | 0.7 | 0.7 |

IU8 | Ideal, 8 | 0.7 | 0.7 |

RU8 | Real, 8 | 0.7 | 0.7 |

IUx2 | Ideal, 4 | 1.4 | 1.4 |

IUx0.5 | Ideal, 4 | 0.35 | 0.35 |

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**MDPI and ACS Style**

Banerjee, T.; Holland, T.; Solander, K.; Holmes, M.; Linn, R. Identifying Characteristics of Wildfire Towers and Troughs. *Atmosphere* **2020**, *11*, 796.
https://doi.org/10.3390/atmos11080796

**AMA Style**

Banerjee T, Holland T, Solander K, Holmes M, Linn R. Identifying Characteristics of Wildfire Towers and Troughs. *Atmosphere*. 2020; 11(8):796.
https://doi.org/10.3390/atmos11080796

**Chicago/Turabian Style**

Banerjee, Tirtha, Troy Holland, Kurt Solander, Marlin Holmes, and Rodman Linn. 2020. "Identifying Characteristics of Wildfire Towers and Troughs" *Atmosphere* 11, no. 8: 796.
https://doi.org/10.3390/atmos11080796