scholarly journals Shear flow characteristics of densely packed granular material subjected to slow deformations

2013 ◽  
Vol 46 ◽  
Author(s):  
Subodh Dhakal
Keyword(s):  
Shear Flow ◽  
High Speed ◽  
Rotational Velocity ◽  
Flow Characteristics ◽  
Video Camera ◽  
Rotation Group ◽  
Particle Rotation ◽  
Moving Wall ◽  
High Speed Video Camera ◽  
Jammed State

The densely packed assembly of granular materials subjected to slow deformations is studied experimentally in the 2D shear flow apparatus. High speed video camera and subsequent image processing techniques help to document the positions of the particles in the flow. Effective algorithms are formulated to determine the particle rotation, group size and local particle concentrations. Experimental results depict that the consecutive cycles of solid like (jammed) and fluid like (un-jammed) states characterize the flow. The jammed state is represented by negligible mobilization of particles, whereas the un-jammed state is represented by considerable mobilization of particles. The rotational and translational kinetic energy shares their dominancy in the jammed and un-jammed states respectively. Nevertheless, rotational counterpart also increases quite high in un-jammed state. There exists clearly a gradient of translational and rotational velocity across the shear cell especially in the un-jammed state indicating the phenomenon of strain localization. The un-jammed state originates because of the breaking and buckling of few columns near to the inner moving wall as noticed by previous researchers, and the jammed state regenerates once the broken and buckled columns regrouped into new columns. The dilatation phenomenon is found to be associated with the un-jamming states indicated by the drop in the local particle concentrations.

scholarly journals New method of contact detection in experimental granular shear flow

2010 ◽  
Vol 40 ◽  
pp. 77-84
Author(s):  
Subodh Dhakal
Keyword(s):  
Shear Flow ◽  
High Speed ◽  
Video Camera ◽  
Detection Algorithm ◽  
Contact Detection ◽  
Physical Experiments ◽  
High Speed Video Camera ◽  
Flow Apparatus ◽  
Percent Accuracy ◽  
Processing Techniques

Different assemblies of granular materials are generated with varying solid fractions and are sheared in the 2D experimental shear flow apparatus with the objective of developing efficient contact detection methodology. The flow is recorded by high speed video camera, and the spatial positions of particle centers are obtained through image processing techniques. The experimental setup was managed to inspect the collision, collision time and collision partners while the experiment is on. Important observations of pre- and post- collision phenomena were made in order to find the precise criteria for distinguishing contacts. Based on these observations together with simple rules of physics, new contact detection algorithm is proposed. The results obtained from proposed method are compared with the visual observations in the digital video of the physical experiment with the help of motion analytical and particle tracking PTV software. It is revealed that the proposed method could detect the contacts with more than 90 percent accuracy in an average and is considerably accurate than the existing methods of contact detection in the physical experiments.

Effects of Combustor Aerodynamics on the Ignition of Solid Fuel

1994 ◽  
Author(s):  
Jing-Tang Yang ◽  
Cliff Yuh-Yih Wu ◽  
Hung-Tsann Yang
Keyword(s):  
Turbulence Intensity ◽  
Solid Fuel ◽  
High Speed ◽  
Recirculation Zone ◽  
Reverse Flow ◽  
Flow Characteristics ◽  
Video Camera ◽  
Sudden Expansion ◽  
Ignition Process ◽  
High Speed Video Camera

A traditional and a modified backward-facing steps were designed to investigate the effects of flow characteristics on the ignition of the solid fuel slab in a sudden expansion combustor. Experiments were conducted separately in the cold flow for the turbulent flow field and in a hot oxidizing flow stream for the ignition tests. The velocity flowfield was measured by a laser-Doppler anemometer (LDA) and the ignition process was observed by a high-speed video camera. The inlet flow velocity for the cold flowfield measurements was kept at 15 m/s, but was varied for the ignition tests, whereas the step height of the backstep was 29 mm. The results show that the higher turbulence intensity in the boundary layer near the separated point did not always cause a higher turbulence intensity in the recirculation zone. However, the combustor with a modified backstep generated greater reverse flow rate, turbulence intensity and Reynolds stress in the recirculation zone. As a result, the ignition delay of solid fuel in the modified combustor was significantly reduced as compared with the traditional combustor.

scholarly journals Detonation effects of shallow buried explosive in sandy soil on target plate acceleration in a small-scale blast test

2018 ◽  
Vol 192 ◽  
pp. 02028
Author(s):  
Hassan Zulkifli Abu ◽  
Ibrahim Aniza ◽  
Mohamad Nor Norazman
Keyword(s):  
Sandy Soil ◽  
High Speed ◽  
Early Stage ◽  
Time History ◽  
Video Camera ◽  
Small Scale ◽  
Target Plate ◽  
Air Blast ◽  
High Speed Video Camera ◽  
The Impact

Small-scale blast tests were carried out to observe and measure the influence of sandy soil towards explosive blast intensity. The tests were to simulate blast impact imparted by anti-vehicular landmine to a lightweight armoured vehicle (LAV). Time of occurrence of the three phases of detonation phase in soil with respect to upward translation time of the test apparatus were recorded using high-speed video camera. At the same time the target plate acceleration was measured using shock accelerometer. It was observed that target plate deformation took place at early stage of the detonation phase before the apparatus moved vertically upwards. Previous data of acceleration-time history and velocity-time history from air blast detonation were compared. It was observed that effects of soil funnelling on blast wave together with the impact from soil ejecta may have contributed to higher blast intensity that characterized detonation in soil, where detonation in soil demonstrated higher plate velocity compared to what occurred in air blast detonation.

In Situ Observation Method for Quantitative Evaluation of Solidification Phenomena and Solidification Cracks during Welding

2014 ◽  
Vol 782 ◽  
pp. 3-7
Author(s):  
Kenji Shinozaki ◽  
Motomichi Yamamoto ◽  
Kohta Kadoi ◽  
Peng Wen
Keyword(s):  
High Speed ◽  
Video Camera ◽  
Solidification Cracking ◽  
In Situ Observation ◽  
High Speed Video Camera ◽  
Varestraint Test ◽  
Solidification Cracks ◽  
Observation Method ◽  
Solidification Crack

Solidification cracking during welding is very serious problem for practical use. Therefore, there are so many reports concerning solidification cracking. Normally, solidification cracking susceptibility of material is quantitatively evaluated using Trans-Varestraint test. On the other hand, local solidification cracking strain was tried to measure precisely using in-situ observation method, called MISO method about 30 years ago. Recently, digital high-speed video camera develops very fast and its image quality is very high. Therefore, we have started to observe solidification crack using in site observation method. In this paper, the local critical strain of a solidification crack was measured and the high temperature ductility curves of weld metals having different dilution ratios and different grain sizes to evaluate quantitatively the effects of dilution ratio and grain size on solidification cracking susceptibility by using an improved in situ observation method.

Study on Magnetic Barrel Machine Equipped with Three-Dimensional Arrangement of Magnets

2007 ◽  
Vol 329 ◽  
pp. 761-766 ◽  
Author(s):  
Y. Zhang ◽  
Masato Yoshioka ◽  
Shin-Ichiro Hira
Keyword(s):  
High Speed ◽  
Permanent Magnets ◽  
Three Dimensional ◽  
Video Camera ◽  
High Speed Video ◽  
High Speed Video Camera ◽  
The Media ◽  
Set Up

At present, a commercially available magnetic barrel machine equipped with permanent magnets has some faults arising from constructional reason. That is, grinding or finishing ability is different from place to place in the machining region, resulting in the limitation on the region we can use in the container of workpieces. Therefore, in this research, authors made the new magnetic barrel machine equipped with three dimensional (3D) magnet arrangement to overcome these faults. The grinding ability of the new 3D magnetic barrel machine converted was experimentally examined, and compared with that of the traditional magnetic barrel machine. As a result, it was shown that we can use much broader region in the new 3D machine. It was also shown that the grinding ability became higher. The distribution of barrel media in action was recorded by means of a high speed video camera. It was clarified that the media rose up higher and were distributed more uniformly in the container by the effect of the magnet block newly set up. It was supposed that this must be the reason for the above-mentioned improvement of grinding ability.

Grease soap particles passing through an elastohydrodynamic contact under side slip conditions

2000 ◽  
Vol 214 (4) ◽  
pp. 317-325 ◽  
Author(s):  
P Eriksson ◽  
V Wikström ◽  
R Larsson
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Previous Investigation ◽  
Video Camera ◽  
Slip Conditions ◽  
High Speed Video ◽  
Elastohydrodynamic Contact ◽  
High Speed Video Camera ◽  
Pure Rolling ◽  
Minimum Film Thickness

In a previous investigation, grease thickener fibres were tracked as they passed through an elastohydrodynamic (EHD) contact in pure rolling using interferometry in a standard ball-and-disc apparatus. In order to capture single thickener fibres, a high-speed video camera was used. Here, the experiments have been repeated introducing different amounts of side slip for different rolling speeds and a faster video camera capable of capturing 4500 frames/s. The contact was lubricated with a continuous supply of grease. Two greases, based on the same synthetic poly(α-olefin) but thickened with Li-12-OH and lithium complex soap respectively, were studied. It was observed that the thickener fibres were stretched both before entering the contact and as they passed through it. Fibres seem to avoid the minimum film thickness regions and, if they enter, the film is restored immediately after passage.

Biomechanical Analysis of a World Record Javelin Throw: A Case Study

1985 ◽  
Vol 1 (1) ◽  
pp. 73-77 ◽  
Author(s):  
Robert J. Gregor ◽  
Marilyn Pink
Keyword(s):  
High Speed ◽  
Video Camera ◽  
The United States ◽  
Track And Field ◽  
Biomechanical Analysis ◽  
World Record ◽  
High Speed Video ◽  
High Speed Video Camera ◽  
Ongoing Project

As part of an ongoing project to evaluate elite track and field throwers in the United States, the javelin competition was filmed during the 1983 Pepsi Invitational Track Meet. A high-speed video camera (Spin Physics SP2000) was positioned orthogonal to the javelin runway to record the release of all throws. During this competition, Tom Petranoff’s world record (99.72 m) was filmed at 200 fields per second. Subsequent frame-by-frame digitization yielded results consistent with reports in the literature. Release velocity was 32.3 m/s and represents one of the highest values ever reported. Angle of release was .57r, javelin attitude at release was .64r» and angle of attack was .07r. While optimum values for these release parameters, in light of published results, remain open to discussion, the results presented here represent unique information on a world record performance and can serve as a basis of comparison for future performances.

Liquid Sheet Disintegration and Atomization Process on a Simplified Airblast Atomizer

1993 ◽  
Vol 115 (3) ◽  
pp. 461-466 ◽  
Author(s):  
G. Lavergne ◽  
P. Trichet ◽  
P. Hebrard ◽  
Y. Biscos
Keyword(s):  
High Speed ◽  
Swirling Flow ◽  
Video Camera ◽  
Frequency Instability ◽  
Liquid Sheet ◽  
Processing Unit ◽  
Spray Formation ◽  
High Speed Video Camera ◽  
The Mean ◽  
Component Phase

Liquid sheet break-up in coflowing shear flow is the mean by which liquids are atomized in practical injectors for gas turbine combustors. The present study explores experimentally the mechanisms of liquid sheet instabilities and spray formation. Experiments are conducted on four airblast geometries. A high-speed video camera associated with an image processing unit was used to study the liquid sheet instabilities. A microphone and a frequency analyzer were used to track the disintegration frequency. Instability amplitude and disintegration length of the liquid sheet were measured. A two-component Phase Doppler Particle Analyzer was used to characterize the resultant spray. The spatial distribution of the particle size is influenced by the swirling flow field. These experimental results will be used to assess models of fuel sheet instabilities and disintegration.

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