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Akihiko Itoh

Bio: Akihiko Itoh is an academic researcher from Oita University. The author has contributed to research in topics: Duct (flow) & Superficial velocity. The author has an hindex of 3, co-authored 4 publications receiving 35 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, a model for the analysis of heat transfer to the unburned paper is employed to predict the flame spread rate in the presence of multiple flames in the air.

23 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the existence of a disturbance wave on a liquid film flowing concurrently with an up-or a down-wards gas flow in a vertical circular pipe and compared it with that in a horizontal duct.
Abstract: The generation of a disturbance wave on a liquid film flowing concurrently with an up-or a down-wards gas flow in a vertical circular pipe is investigated both theoretically and experimentally and compared with that in a horizontal duct. It is made clear that the disturbance wave is generated when the velocity of liquid particles exceeds that of interfacial waves. This is similar to the case of a horizontal duct. The boundary of the existence of the disturbance wave, however, depends strongly on the gravitational force, i.e., the orientation of the pipe line and the direction of the flow in a low gas flow rate region. This is because the gravitational force affects the wave velocity but not the mean liquid flow in a horizontal line, and vice versa in a vertical line ; and also because an annular film cannot be formed in the vertical upward flow if the gas velocity is low, i.e., the interfacial shear force is small.

7 citations

Journal ArticleDOI
TL;DR: In this article, the effect of the aspect ratio of the duct cross-section on a liquid film flowing concurrently with an air stream was investigated using three horizontal ducts, and the results were summarized as follows: the boundary of flow patterns between the pebble wave flow and the disturbance wave flow strongly depends on the duct height.
Abstract: The effect of the aspect ratio of the duct cross-section on a liquid film flowing concurrently with an air stream was investigated using three horizontal ducts. The dimensions of the duct are 10 mm×40 mm (height×width), 40 mm×40 mm and 10 mm×80 mm. The results are summarized as follows: The boundary of flow patterns between the pebble wave flow and the disturbance wave flow strongly depends on the duct height. On the other hand, the boundary between a smooth surface flow and a two-dimensional wave flow as well as the nonwetting regime depends mainly on the duct width. The reason is that the volumetric flux of the liquid flow in the vicinity of the side walls of the duct is considerably larger than that in the central part of the duct width due to the formation of meniscus. Therefore, only the experimental values for the film parameters obtained at the central part of duct width are useful for comparison with the theoretical results obtained by the assumption that the flow is two-dimensional, even if the aspect ratio of duct seems to be sufficiently small.

6 citations

Journal ArticleDOI
TL;DR: In this article, a thin liquid film flowing concurrently with an air stream was investigated with regard to waves generated when superficial velocity of air was less than about 10 m/s and water flow rate was considerably low.
Abstract: A thin liquid film flowing concurrently with an air stream was investigated with regard to waves generated when superficial velocity of air was less than about 10 m/s and water flow rate was considerably low. It was made clear theoretically and verified by an experiment that a special wave, named viscous wave by the authors, is generated on the thin liquid film when film thickness was less than a definite value which depended on liquid properties, i.e., 0.255 mm at 20°C for water. Theory shows that the occurrence of a viscous wave depends more on liquid viscosity than on surface tension, and that the wave velocity is lower than liquid surface velocity. The viscous wave occurs always in the vicinity of the nonwetting region, signifying that the occurrence of it reduces the minimum film thickness, which causes a breakdown of liquid film.

1 citations


Cited by
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Journal ArticleDOI
TL;DR: A review of the essential ingredients needed to make a mathematical model of fire spread through a fuel bed is given in this article, where a unified mathematical treatment is presented, which permits a more objective comparison of the different physical models.

205 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of liquid viscosity on the flow patterns of upward air-liquid two-phase flow in a vertical tube of 19.2 mm in inner diameter and about 5.4 m in length were investigated.

77 citations

Journal ArticleDOI
Tohru Fukano1
TL;DR: In this paper, a constant electric current method (CECM) is proposed for conductance measurement. But the performance of the CECM is limited due to the fact that the output from the sensor electrode is independent of the location of gas phase, and the sensitivity of detecting the change in the hold-up is higher in the case of thinner film thickness.

74 citations

Journal ArticleDOI
TL;DR: In this paper, a microgravity environment was used to create a stationary model aerosol consisting of relatively large (100-300 μm diameter), initially motionless particles, and the development of individual particle flames, motion of individual particles and overall aerosol combustion process could be observed simultaneously.

44 citations

Journal ArticleDOI
TL;DR: In this paper, a geometrical model for fire propagation through arrays of vertically mounted fuel elements is considered, and a critical slope can be found beyond which heat transfer is no longer rate limiting.

31 citations