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Kozo Sekimoto

Bio: Kozo Sekimoto is an academic researcher from University of Kentucky. The author has contributed to research in topics: Fire whirl & Scale model. The author has an hindex of 4, co-authored 9 publications receiving 159 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, a scaling law that predicts the critical lateral wind velocity was developed and validated by various data including scale-model experiments by other researchers and real urban fire whirls, and a dimensional analysis was conducted to understand the effect of flow circulation on the increase in flame height.

95 citations

Journal ArticleDOI
01 Jan 2013
TL;DR: A fire whirl observed during a wildland fire in Brazil in 2010, occurred over a narrow but long line fire and moved along the line fire at nearly a constant speed.
Abstract: A fire whirl, observed during a wildland fire in Brazil in 2010, occurred over a narrow but long line fire and moved along the line fire at nearly a constant speed. There appeared to be no mountains, tall buildings or trees near the scene, indicating that the fire whirl was generated merely by the interaction between the line fire and background wind. Scale-model experiments having different line fire configurations were designed and performed to reconstruct the above-mentioned Brazil fire whirl. Moving fire whirls were successfully reconstructed during the scale-model experiments, the mechanism and conditions of which are discussed herein.

41 citations

Journal ArticleDOI
Abstract: AEROSPACE LETTERS are brief communications (approximately 2000 words) that describe new and potentially important ideas or results, including critical analytical or experimental observations that justify rapid publication. They are stringently prescreened, and only a few are selected for rapid review by an Editor. They are published as soon as possible electronically and then appear in the print version of the journal.

39 citations

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a scaling law for scale-model experiments on a large-scale wind-aided fire phenomenon, which takes into account the Froude number, defined using the flame height.
Abstract: This short communication proposes a new scaling law, on the basis of which scale-model experiments on a large-scale wind-aided fire phenomenon can be designed. The proposed scaling law takes into account the Froude number, which is defined using the flame height. The results of two different scale-model experiments on the fire whirls observed after the Great Kanto Earthquake are reported. The wind velocities in the scale-model experiments are determined using the proposed scaling law. The scale-model experiments successfully reproduce fire whirls similar to those observed after the Earthquake, thus validating the proposed scaling law.

6 citations


Cited by
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ReportDOI
01 Jan 2011
TL;DR: A summary of existing extreme fire behavior knowledge for use by fire managers, firefighters, and fire researchers can be found in this paper, where the authors focus on the state of the science, but will also consider how that science is currently presented to the fire management community.
Abstract: The National Wildfire Coordinating Group definition of extreme fire behavior (EFB) indicates a level of fire behavior characteristics that ordinarily precludes methods of direct control action. One or more of the following is usually involved: high rate of spread, prolific crowning/spotting, presence of fire whirls, and strong convection column. Predictability is difficult because such fires often exercise some degree of influence on their environment and behave erratically, sometimes dangerously. Alternate terms include “blow up” and “fire storm.” Fire managers examining fires over the last 100 years have come to understand many of the factors necessary for EFB development. This work produced guidelines included in current firefighter training, which presents the current methods of predicting EFB by using the crown fire model, which is based on the environmental influences of weather, fuels, and topography. Current training does not include the full extent of scientific understanding. Material in current training programs is also not the most recent scientific knowledge. National Fire Plan funds have sponsored newer research related to wind profiles’ influence on fire behavior, plume growth, crown fires, fire dynamics in live fuels, and conditions associated with vortex development. Of significant concern is that characteristic features of EFB depend on conditions undetectable on the ground, relying fundamentally on invisible properties such as wind shear or atmospheric stability.Obviously no one completely understands all the factors contributing to EFB because of gaps in our knowledge. These gaps, as well as the limitations as to when various models or indices apply should be noted to avoid application where they are not appropriate or warranted. This synthesis will serve as a summary of existing extreme fire behavior knowledge for use by fire managers, firefighters, and fire researchers.The objective of this project is to synthesize existing EFB knowledge in a way that connects the weather, fuel, and topographic factors that contribute to development of EFB. This synthesis will focus on the state of the science, but will also consider how that science is currently presented to the fire management community, including incident commanders, fire behavior analysts, incident meteorologists, National Weather Service office forecasters, and firefighters. It will seek to clearly delineate the known, the unknown, and areas of research with the greatest potential impact on firefighter protection.

100 citations

Journal ArticleDOI
TL;DR: In this article, a scaling law that predicts the critical lateral wind velocity was developed and validated by various data including scale-model experiments by other researchers and real urban fire whirls, and a dimensional analysis was conducted to understand the effect of flow circulation on the increase in flame height.

95 citations

Journal ArticleDOI
01 Jan 2011
TL;DR: The medium-scale fire whirl was extensively investigated by experimental means, in order to establish correlations of the burning rate, flame height and flame temperature of fire WHR, and to clarify the difference between fire WHRs and general pool fires.
Abstract: The medium-scale fire whirl was extensively investigated by experimental means, in order to establish correlations of the burning rate, flame height and flame temperature of fire whirl, and to clarify the difference between fire whirls and general pool fires. Experimental observations and data confirmed that a free burning fire whirl is a highly stable burning phenomenon with large quasi-steady periods. Burning rates of fire whirls depend on pool diameter similarly to those of general pool fires; however the transition turbulent burning occurs sooner as the pool diameter increases. The lip height seems to have little effect on the burning rate of fire whirls. The correlation H ∗ = K · ( Q ˙ ∗ · Γ ∗ 2 ) m was proposed to couple the height of fire whirl to the fire release rate and ambient circulation. It correlates the data from both this work and the literature. Radial temperature profiles in the continuous region of the fire whirl were confirmed to be hump-type, implying the existence of fuel-rich inner core. The pool diameter and heat release rate do not significantly affect the radial temperature profiles in non-dimensional radial coordinates. It was found that the fire plume of fire whirl involves three distinct zones just like that of pool fire, but with different normalized ranges. Fire whirls maintain a higher ratio of continuous flame height to the overall flame height, and also higher maximum centerline excess temperature in continuous flame region, as compared to general pool fires. It was further demonstrated that the fire whirl plume at its origin behaves like a turbulent jet with moderate swirling, and then tends to become buoyancy dominated downstream, with slight swirling. With an increase in dimensionless height adjusted by the plume origin, the plume centerline excess temperature decays rapidly and approaches the theoretical value of −5/3 for free buoyancy plume.

85 citations

Journal ArticleDOI
TL;DR: The current state of knowledge of the interaction of wildland fire and vortices is examined and reviewed in this paper, where a basic introduction to vorticity is given, and the two common vortex forms in Wildland fire are analyzed: fire whirls and horizontal roll vortice.
Abstract: Vortices are almost always present in the wildland fire environment and can sometimes interact with the fire in unpredictable ways, causing extreme fire behavior and safety concerns. In this paper, the current state of knowledge of the interaction of wildland fire and vortices is examined and reviewed. A basic introduction to vorticity is given, and the two common vortex forms in wildland fire are analyzed: fire whirls and horizontal roll vortices. Attention is given to mechanisms of formation and growth and how this information can be used by firefighters.

76 citations

Journal ArticleDOI
01 Jan 2011
TL;DR: In this paper, the authors discussed why the visibly-determined flame length of a weak fire whirl increases as compared with the corresponding pool fire without spin, which is called weak when the pure aerodynamic effect of flow circulation has a negligible influence on the flame length.
Abstract: This paper discusses why the visibly-determined flame length of a weak fire whirl increases as compared with the corresponding pool fire without spin. Here, a fire whirl is called weak when the pure aerodynamic effect of flow circulation has a negligible influence on the flame length. Split cylinders were used to apply a flow circulation to a 3-cm-diameter methane burner flame and a 3-cm-diameter ethanol pool fire. After applying the flow circulation, the flame length of the ethanol pool fire increased about three times, while little change was observed in the flame length of the methane burner flame. The difference is explained by the fact that the burning rate of the methane burner flame was fixed constant, whereas that of the ethanol pool fire increased due to the increased heat input to the fuel surface caused by a change in flame shape pushed toward the fuel surface. The experimental observations thus demonstrate that the burning-rate effect can significantly increase the flame length even under a weak circulation condition. Computational fluid dynamics (CFD) simulations were conducted to understand the detailed flow structure of a fire whirl. An analytical model was then developed based on the experimental observations and CFD calculations; the predicted relationship between the flame height and the burning rate agreed with experimental data.

76 citations