Experimental Aspects of Shearing Granular Materials

2002 ◽  
Author(s):  
Yulong Ding
Keyword(s):  
Granular Materials ◽  
High Speed ◽  
Model Systems ◽  
Experimental Techniques ◽  
High Speed Photography ◽  
Non Invasive ◽  
Positron Emission ◽  
Shear Cells ◽  
Fluidised Beds ◽  
Rotating Drums

Flow of granular materials has been a subject of numerous investigations in the past few decades. A number of experimental techniques have been used in these studies. Examples include PEPT (Positron Emission Particle Tracking), NMR (Nuclear Magnetic Resonance), HSP (High-Speed Photography), and various tomographic methods. These techniques have been used to study a number of model systems such as rotating drums, chute flows, vibro-beds, hopper flows, fluidised beds, and shear cells, in order to gain an insight into the behaviour of granular flows. In this paper, a brief review of these experimental techniques and model systems will be made first. Attention will then be paid to the work on rotating drums and fluidised beds using the non-invasive PEPT technique. Finally, future directions of the experimental aspects of shearing granular materials will be discussed.

scholarly journals Non-Invasive Detection of Vortex Street Cavitation

2017 ◽  
Vol 21 (2) ◽  
Author(s):  
Francisco  Botero ◽  
Adriana Milena Castro Peralta
Keyword(s):  
High Speed ◽  
Vortex Street ◽  
High Speed Photography ◽  
Laser Vibrometer ◽  
Angle Of Incidence ◽  
Vortex Generation ◽  
Non Invasive ◽  
Statistical Indicator ◽  
Cavitation Tunnel ◽  
Airborne Noise

<p><strong><em>Objective:</em></strong> This paper introduces a methodology for the non-intrusive detection of von Kármán vortex street cavitation. It is based on the cyclostationary analysis of the airborne noise radiated by the collapsing bubbles.</p><p><strong><em>Materials and methods:</em></strong> A hydrodynamic profile is mounted in the test section of a high-speed cavitation tunnel and the phenomenon is reproduced under controlled conditions of flow and pressure. The angle of incidence is kept constant. Flow velocity is varied to regulate the vortex generation frequency and pressure is adjusted to control the cavitation onset. High-speed photography is used to confirm the occurrence of cavitation in the core of the vortices. A laser vibrometer pointing to the upper surface of the profile validates the fluid-structure interaction due to the vortex shedding. A microphone is used to sense the sound produced by the phenomenon and transmitted to the environment.</p><p><strong><em>Results and discussion:</em></strong> The cyclic coherence showed out uncoupled evidence of the periodic detachment of vortices and the presence or absence of cavitation in their cores, reaching values close to 0.7 for specific frequencies.</p><p><strong><em>Conclusion:</em></strong> A non-intrusive monitoring approach along with a statistical indicator were implemented to allow the diagnosis of such phenomena.</p>

Motion of a granular avalanche in a convex and concave curved chute: experiments and theoretical predictions

1993 ◽  
Vol 342 (1666) ◽  
pp. 573-600 ◽  
Keyword(s):  
Granular Materials ◽  
High Speed ◽  
Friction Angle ◽  
High Speed Photography ◽  
Single Pile ◽  
Curvature Effects ◽  
Angle Of Friction ◽  
Internal Angle ◽  
Bed Friction ◽  
Granular Avalanche

This paper deals with the theoretical-numerical and experimental treatment of two dimensional avalanches of cohesionless granular materials moving down a confined curved chute. Depth-averaged field equations of balance of mass and linear momentum as prescribed by Savage & Hutter (1991) are used. They describe the temporal evolution of the depth averaged streamwise velocity and the distribution of the avalanche depth and involve two phenomenological parameters, the internal angle of friction, ϕ,and the bed friction angle, δ, both as constitutive properties of Coulomb-type behaviour. The equations incorporate weak to moderate curvature effects of the bed. Experiments were carried out with different granular materials in a chute with partly convex and partly concave curved geometry. In these experiments the motion of the granular avalanche is followed from the moment of release to its standstill by using high speed photography, whence recording the geometry of the avalanche as a function of position and time. Two different bed linings, drawing paper and no. 120 SIA sandpaper, were used to vary the bed friction angle, δ. Both, the internal angle of friction, ϕ, and the bed friction angle, δ, were measured, and their values used in the theoretical model. Because of the bump and depending upon the granulate-bed combination an initial single pile of granular avalanche could evolve as a single pile throughout its motion and be deposited above or below the bump in the bed; or it could separate in the course of the motion into two piles which are separately deposited above and below the bump. Comparison of the experimental findings with the computational results proved to lead to good to excellent correspondence between experiment and theory. Even the development of the detailed geometry of the granular avalanche is excellently reproduced by the model equations, if δ < ϕ. Occasional deviations may occur; however, they can in all cases be explained by onsetting instabilities of the numerical scheme or by experimental artefacts that only arise when single particles have shapes prone to rolling.

Crack divergence phenomena in tempered glass

2020 ◽  
Vol 13 (3) ◽  
pp. 115-129
Author(s):  
Shin’ichi Aratani
Keyword(s):  
Optimal Design ◽  
High Speed ◽  
Glass Plate ◽  
Acute Angle ◽  
Divergence Angle ◽  
High Speed Photography ◽  
Tempered Glass ◽  
Thick Glass

High speed photography using the Cranz-Schardin camera was performed to study the crack divergence and divergence angle in thermally tempered glass. A tempered 3.5 mm thick glass plate was used as a specimen. It was shown that two types of bifurcation and branching existed as the crack divergence. The divergence angle was smaller than the value calculated from the principle of optimal design and showed an acute angle.

Experimental study of hydrodynamic effects in the inverse water hydrocarbon emulsions flow in microchannels

2016 ◽  
Vol 11 (1) ◽  
pp. 30-37 ◽  
Author(s):  
A.A. Rakhimov ◽  
A.T. Akhmetov
Keyword(s):  
High Speed ◽  
Petroleum Industry ◽  
Chemical Compounds ◽  
High Viscosity ◽  
Blocking Effect ◽  
High Speed Photography ◽  
Simple Chemical ◽  
Reported Study ◽  
Dynamic Blocking ◽  
Hydrodynamic Effects

The paper presents results of hydrodynamic and rheological studies of the inverse water hydrocarbon emulsions. The success of the application of invert emulsions in the petroleum industry due, along with the high viscosity of the emulsion, greatly exceeding the viscosity of the carrier phase, the dynamic blocking effect, which consists in the fact that the rate of flow of emulsions in capillary structures and cracks falls with time to 3-4 orders, despite the permanent pressure drop. The reported study shows an increase in viscosity with increasing concentration or dispersion of emulsion. The increase in dispersion of w/o emulsion leads to an acceleration of the onset of dynamic blocking. The use of microfluidic devices, is made by soft photolithography, along with high-speed photography (10,000 frames/s), allowed us to see in the blocking condition the deformation of the microdroplets of water in inverse emulsion prepared from simple chemical compounds.

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