Photo Contest
2014 Photo Contest -Beautiful Flames- The HIGHEST AWARD
Flame cake of the first birthday
Sunghwan YOON, Taejoon NOH, Osamu FUJITA
Division of Mechanical and Space Engineering, Graduate School of Engineering,
Hokkaido University
Explanation
This flame was formed from interaction between acoustic vibration and downward propagating flame in combustion tube of 5 cm diameter and 51cm long. A desired curvature is initially given to the propagating flame by CO2 laser absorption. The combustion tube is half-open at the top end, ignition side. C2H4/O2/CO2 mixture of Le = 1.05 and φ = 0.9 is used as the tested gas. When curved flame is exposed to the acoustic vibration field in the combustion tube, coherent corrugated structure is formed and then it turns to complicated turbulent motion. The picture is one moment of corrugated structure before transition to turbulent motion. This picture seems birthday cake. The lower flame in the picture looks like a cake and the separated flame above the main flame, which is caused by auto ignition, seems a candle flame. Therefore, we name the flame as “Flame cake of the first birthday”.
Camera & Lens: FASTCAM Mini UX100 & NOKTON 25mm F0.95
F-number: F0.95, Frame Rate: 2000 fps at 768×512 pixel resolution, ISO: 5000
2014 Photo Contest -Beautiful Flames- The MERIT AWARD
Fortune telling by “fingering”
Yosuke Uchida1, Kazunori Kuwana1, Genichiro Kushida2
1 Yamagata University
2 Aichi Institute of Technology
Explanation
When a thin paper is burned in a narrow gap of the width about 10 mm, natural convection is suppressed, leading to smoldering combustion without flame. An interesting feature of smoldering combustion is the formation of fingering pattern; a similar instability mechanism to diffusive-thermal instability results in the pattern formation. Complicated patterns including tip branching and local extinction can be observed under certain conditions. We did fortune telling using fingering pattern and got the best luck, which eventually leads to this award!