Investigations of fundamental properties of underwater shock waves by high-speed photography

1995 ◽  
Author(s):  
Shigeru Itoh ◽  
O. Suzuki ◽  
Shirou Nagano ◽  
Masahiro Fujita
Keyword(s):  
Shock Waves ◽  
High Speed ◽  
High Speed Photography ◽  
Fundamental Properties ◽  
Underwater Shock

Investigation of a converging underwater shock wave using high-speed photography

1995 ◽  
Author(s):  
Shigeru Itoh ◽  
S. Kubota ◽  
Shirou Nagano ◽  
I. Morita ◽  
A. Chiba ◽  
...  
Keyword(s):  
Shock Wave ◽  
High Speed ◽  
High Speed Photography ◽  
Underwater Shock Wave ◽  
Underwater Shock

scholarly journals Bubbles with shock waves and ultrasound: a review

2015 ◽  
Vol 5 (5) ◽  
pp. 20150019 ◽  
Author(s):  
Siew-Wan Ohl ◽  
Evert Klaseboer ◽  
Boo Cheong Khoo
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Biomedical Applications ◽  
High Speed ◽  
Experimental Studies ◽  
High Intensity Focused Ultrasound ◽  
High Speed Photography ◽  
Sound Waves ◽  
Bubble Cloud ◽  
Bubble Interaction

The study of the interaction of bubbles with shock waves and ultrasound is sometimes termed ‘acoustic cavitation'. It is of importance in many biomedical applications where sound waves are applied. The use of shock waves and ultrasound in medical treatments is appealing because of their non-invasiveness. In this review, we present a variety of acoustics–bubble interactions, with a focus on shock wave–bubble interaction and bubble cloud phenomena. The dynamics of a single spherically oscillating bubble is rather well understood. However, when there is a nearby surface, the bubble often collapses non-spherically with a high-speed jet. The direction of the jet depends on the ‘resistance' of the boundary: the bubble jets towards a rigid boundary, splits up near an elastic boundary, and jets away from a free surface. The presence of a shock wave complicates the bubble dynamics further. We shall discuss both experimental studies using high-speed photography and numerical simulations involving shock wave–bubble interaction. In biomedical applications, instead of a single bubble, often clouds of bubbles appear (consisting of many individual bubbles). The dynamics of such a bubble cloud is even more complex. We shall show some of the phenomena observed in a high-intensity focused ultrasound (HIFU) field. The nonlinear nature of the sound field and the complex inter-bubble interaction in a cloud present challenges to a comprehensive understanding of the physics of the bubble cloud in HIFU. We conclude the article with some comments on the challenges ahead.

scholarly journals High-speed photography of shock waves with an adaptive illumination

2020 ◽  
Vol 45 (6) ◽  
pp. 1547 ◽  
Author(s):  
Vid Agrež ◽  
Tomaž Požar ◽  
Rok Petkovšek
Keyword(s):  
Shock Waves ◽  
High Speed ◽  
High Speed Photography

Detonation Behaviors of Nitromethane with Various Initiating Shock Pressure

2007 ◽  
Vol 566 ◽  
pp. 41-46 ◽  
Author(s):  
Hideki Hamashima ◽  
Akinori Osada ◽  
Shigeru Itoh ◽  
Yukio Kato
Keyword(s):  
Shock Waves ◽  
High Speed ◽  
Shock Pressure ◽  
High Speed Photography ◽  
Detailed Structure ◽  
Complicated Structure ◽  
Low Velocity ◽  
Cavitation Field ◽  
Liquid Explosives ◽  
Multiple Shock

Some liquid explosives have two different detonation behaviors: high velocity detonation (HVD) or low velocity detonation (LVD). The detonation behavior depends on the level of the initiating shock pressure. The detailed structure of LVD in liquid explosives has not yet been clarified. A physical model was proposed that LVD is not a self-reactive detonation, but rather a supported-reactive detonation from the cavitation field generated by precursor shock waves. In this study, high-speed photography was used to investigate the detonation behavior of nitromethane (NM) with the various initiating shock pressures. Stable LVD was not observed, only transient LVD was observed. A very complicated structure of LVD was observed: the interaction of multiple precursor shock waves, multiple oblique shock waves, and a cavitation field. Multiple shock waves propagating in non-detonating NM were observed for shock pressures below the range required for LVD, while above the LVD range HVD was observed.

scholarly journals Experimental Study of Kerosene Ignition and Flame Stabilization in a Supersonic Combustor

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Yu Meng ◽  
Hongbin Gu ◽  
Xinyu Zhang
Keyword(s):  
Shock Waves ◽  
Combustion Chamber ◽  
High Speed ◽  
Flame Stabilization ◽  
Supersonic Combustion ◽  
Chamber Pressure ◽  
High Speed Photography ◽  
Flame Stability ◽  
Whole Process ◽  
Stable Flame

Abstract A supersonic kerosene ignition and flame stabilization experiments were conducted on a directly connected supersonic combustion test bench. The kerosene fuel was jetted by wall jet at Ma 2.5 airflow. High-speed photography was used to record the CH* emission during ignition, extinguishing and evolution of the flame. Experiments of different equivalence ratios were performed. The processes of ignition, flame holding, and extinguishing were observed as well. The experiment showed the characteristics of ignition core initiation and extension. The time of ignition increased with the increase of equivalence ratios. Flame stability during the process of Ma 2.5 at the entrance of the combustion chamber was also studied. An equilibrium flame pattern of shock wave and flame was discovered in the experiment. In the stable flame state, shock waves near the kerosene jet orifice promote atomization and blending, and the combustion chamber pressure with stable flame makes the shock waves stable near the kerosene jet orifice, thus forming the flame stability model. The whole process and characteristics of kerosene ignition, flame holding and extinguishing are revealed in the experiment.

Production of Rice Powder Milling Flour Device and Characterization by Numerical Simulation

2016 ◽  
Author(s):  
Osamu Higa ◽  
Ken Shimojima ◽  
Yoshikazu Higa ◽  
Ayumi Takemoto ◽  
Shigeru Itoh ◽  
...  
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Pressure Vessel ◽  
High Speed ◽  
Internal Diameter ◽  
Manufacturing Cost ◽  
Cylindrical Pressure Vessel ◽  
Underwater Shock ◽  
Institute Of Technology ◽  
Rice Powder

Rice powder is of interest in Japan, because it can be processed into various foods. However, conventional methods of manufacturing rice-powder generate heat when crushing the rice. National Institute of Technology, Okinawa College (ONCT) has been developing a pressure vessel for producing rice powder using underwater shock waves. The merits of this process are the dry condition and the lack of heating, and a decrease in the manufacturing cost can be expected, using this method. A power supply for generating the shock waves, a pressure vessel for crushing and, a device for the transportation of the rice were developed. The amount of flour that could be milled by the first prototype device was approximately 450g per hour. Then, the pressure vessel was improved to increase the rate of milling. Toward achieving this target, the characteristics of rice processing using shock waves were evaluated. First, a shock wave crushed the rice, which was trapped in transparent acrylic blocks. At the same time, the transmitted shock wave was observed using a high speed camera. From the result of the observation, the speeds of the wave passing through the acrylic blocks and rice was calculated. A linear relationship between the shock wave velocity (Us) and particle velocity (Up) in a material has been empirically found. The propagation of a shock wave in the pressure vessel was calculated by computer simulation. Moreover, a cylindrical pressure vessel with an internal diameter of 150mm was developed. Silicone hoses are installed in the pressure vessel, and the rice passes through in the hoses. The shock wave is generated by the electrical collapse induced by supplying a high voltage to the gap between electrodes in the center of the vessel. The rice is milled into flour by these phenomena, and rice is continuously supplied to the pressure vessel by a classification device and the transport device. The amount of flour milled per hour was verified experimentally.

Sign in / Sign up

Export Citation Format

Share Document