Ultra High-speed Video Camera Research Articles

Observation of Microexplosions in Spray Flames of Light Oil-Water Emulsions (2nd Report, Influence of Temporal and Spatial Resolution in High Speed Videography)

Microexplosions of light oil-water emulsified fuel droplets were successfully documented using a high speed video camera with laser illumination. The temperature profile and the local frequency of explosion occurrence were estimated in open spray flames of water-in-oil type emulsion formed using an air-assist atomizer with a set of ring pilot burners. The estimates of the local frequency of the explosion occurrence were made in the upstream region of spray flames, since their temperature profiles indicated that the heat release was accelerated in the upstream region from the nozzle tip up to the height of 80 mm. Microexplosions were frequently observed in the upstream region where no microexplosion phenomenon was observed in the former study. In addition, all of those had very small spatial and temporal scales. It is probable that the principal factor having effects on the heat release of emulsion spray flame is not the microexplosions of larger droplets, as former theories predicted, but those of smaller ones. We, furthermore, observed the microexplosions of smaller droplets using an ultra high speed video camera, the frame rate of which was 106 frames/s. It was observed that the smaller droplets, whose diameter were less than 50 μm, exploded in the spray flame and their temporal and spatial scales were around 10 μs and 300 μm, respectively.

538 トンボの飛行力学に基づくミニロボットの開発

This report describes the development of mini-sized robot based on the flight mechanics of dragonfly. At first, the motion analyses of flapping and feathering motion of dragonfly's wing are carried out from the image data recorded by the ultra-high speed video camera under the free flight conditions. Applying the results obtained to the dynamic analysis of wing motion based on the flight mechanics, the thrust and lift forces of fore and hind wings are estimated. The predicted results by this theoretical model are reasonable and it may be applicable to artificial-wing design.

異波長重畳レーザにおけるレーザ誘起プラズマとキーホールおよび反射光挙動

This paper deals with the behavior of a keyhole and a laser-induced plasma observed during laser welding of several metals with a single YAG laser or superimposed two beams through the ultra high-speed video camera, with the objective of understanding enhanced beam absorption due to two different wavelength laser beams. Moreover, reflected YAG laser beams were measured by photodiodes, and the relationship between the keyhole behavior and the reflected-laser photodiode signal was investigated to clarify rapid welding phenomena. It was observed that the behavior of a keyhole and a laser-induced plasma during laser welding was considerably different between a single beam and combined two different beams. And the reflected light intensity during welding with the superimposed two different laser beams lowered in the earlier stage than that with a single pulsed YAG laser beam.

Ultrahigh-speed video camera with an in-situ storage image sensor

Ultrahigh-speed video camera with an in-situ storage image sensor

F-0930 昆虫の羽ばたき機構 : 第2報,胸部外骨格の構造特性と翅の振動特性(G02-3 運動・生長)(G02 バイオエンジニアリング部門一般講演)

The aim of this second paper is to elucidate the relation between morphology of flight muscles and function of wings. The paper describes two experiments: measuring the structural characteristics of thoracic exoskeleton in the indirect-flight-muscle type of insects and the vibration characteristics of wing in the direct-flight-muscle type of insects. In the indirect-flight-muscle type of insects, the deflections of thoracic exoskeleton are measured under the static load. As results, the obtained load-deflection diagrams show linear relation between them. In the direct-flight-muscle type of insects, the ultra high speed video camera is used to record the wing motion under the free flight conditions by making use of their nature of high sensitivity to light. The frequencies of wing vibration are determined from the analyses of recorded data on videotapes. It is found that the vibration frequencies depend on the wing mass in the case of losing weight and independent on it in the case of gaining weight.

Velocity measurement of compressible air flows utilizing a high-speed video camera

PIV-measurements of the flow above a pitching airfoil were conducted in a transonic wind tunnel. An ultra high-speed video camera was used for separate recording of two exposures. The data was analysed using the cross-correlation method. The results show the applicability of the technique in high speed flows.

Visualization of Fluid Motion at Permeable Structure by Ultra High-Speed Video Camera

A fluid motion at permeable layer constructed model of precast concrete armor unit was visualized in ossillatory flow. Many turbulence measurements have been ever done by point measurement techniques such as LDA. In this study, a method of measurement has been conducted by a particle tracking velocimetry for 2-D space. It has been composed of Kalman's filtering theory, the Chai-Square-test and initial evaluation of velocities of particles which newly appear in the flame. Images of 30μm diameter particles were taken using a ultra high-speed video camera and Argon-ion laser slit illumination.