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.

Motion of a granular avalanche in an exponentially curved chute: experiments and theoretical predictions

1991 ◽  
Vol 334 (1633) ◽  
pp. 93-138 ◽  
Keyword(s):  
Granular Materials ◽  
Friction Angle ◽  
Similarity Solutions ◽  
Initial Condition ◽  
Curvature Effects ◽  
Angle Of Friction ◽  
Theoretical Predictions ◽  
Internal Angle ◽  
Bed Friction ◽  
Granular Avalanche

This paper describes a model to predict the flow of an initially stationary mass of cohesionless granular material down a rough curved bed, and checks it against laboratory experiments that were conducted with several cohesionless granular materials that are released from rest and travel in an exponentially curved chute. We use the depth-averaged field equations of balance of mass and linear momentum as presented by Savage & Hutter (1990). These equations are evolution equations for the transversely averaged stream wise velocity and the distribution of avalanche depths and involve two phenomenological parameters, the internal angle of friction, ϕ, and a bed friction angle, δ, both as constitutive properties of Coulomb-type behaviour. We present the model but do not derive its equations, which are presented in two variants that incorporate weak and strong curvature effects. For granular avalanches which start as parabolic piles, the governing equations (incorporating weak curvature effects) permit similarity solutions. These solutions preserve the parabolic shape and have simple velocity distributions. We present the equations again without detailed explanations. Experiments were performed with seven different granular materials (two classes of glass beads, Vestolen plastic particles, two samples of quartz granules and two types of crunched marmor particles). Piles of finite masses of such granular materials with various initial geometries were released from rest in a 100 mm wide chute having an exponentially curved bed that was lined with Makrolon (a plexiglass), drawing-paper and sandpaper. The granular masses under motion were photographed and video filmed and thus the geometry of the avalanche was recorded as a function of position and time. With all materials and for all the bed linings, the angle of repose and the bed friction angle were determined. The former was identified with the static internal angle of friction. Using a second measuring technique, the effects of the chute walls on the bed friction angle was experimentally determined and incorporated in an effective bed friction angle which thus showed a linear dependence on the pile depth. Coefficients of restitution were also estimated for the particles on the different bed linings. The numerical integration scheme for the general model that was proposed earlier by Savage & Hutter (1989) is a lagrangian finite difference scheme which incorporates numerical diffusion. We present this scheme and analyse its reliability when the numerical diffusion is varied. We also discuss the integration procedure for the similarity solutions. Comparison of the theoretical results with experiments pertain to the similarity model (SM) and the general equation model (GM). Crucial in such comparisons is the identification of initial condition which is not unique from the observational data. For SM it is shown that no initial condition can be found, in general, that would yield computational predictions of the evolution of the position of the leading and trailing edges of the granular avalanche in sufficient agreement with observations. When depth-to-length ratios of the initial pile geometry and the curvature of the bed are sufficiently small, however, then the SM solutions may be used for diagnostic purposes. We finally compare experimental results with computational findings of the GM equations for many combinations of masses of the granular materials and bed linings. It is found that experimental results and theoretical predictions agree satisfactorily if the internal angle of friction, ϕ, exceeds the total bed friction angle, δ, or is not close to it. Limited variations of the bed friction angle along the bed do not seem to have a sizeable effect on the computational results, but it is important that dynamic values rather than static values for ϕ and δ are used in the computations. When δ is very close to ϕ and δ < ϕ , the computational travel time of the granular avalanche exceeds the travel time of experiments considerably. Furthermore, when avalanche masses are reasonably small and coefficients of restitution of the granules on the bed relatively high, again the predictions of the theory overestimate travel times and underestimate avalanche lengths. Thus the theory does seem to be reasonable when the bed friction angle is definitely smaller than the internal angle of friction.

scholarly journals SIMULASI PERGERAKAN RUNTUHAN LONGSOR MENGGUNAKAN MODEL SAVAGE-HUTTER DENGAN FINITE VOLUME METHOD

2018 ◽  
Vol 7 (2) ◽  
pp. 88
Author(s):  
ALIFANDA PINKAN LUDICA ◽  
P. H. GUNAWAN ◽  
ANIQ A. ROHMAWATI
Keyword(s):  
Finite Volume Method ◽  
Finite Volume ◽  
Friction Angle ◽  
One Dimension ◽  
Angle Of Friction ◽  
Sediment Types ◽  
Collocated Grid ◽  
Internal Angle ◽  
Volume Method ◽  
Bed Friction

The avalanche is simulated using the Savage-Hutter model with Finite Volume Method (FVM) as a numerical solution in one dimension. The scheme used in FVM is collocated-grid. The aim of this research is to observe the avalanche based on different sediment types on the incline bed with the same initial sediment height. These simulations produce the value of velocity and height avalanche. For each type of sediment has a difference in velocity and height of avalanche affected by the internal angle of friction and the bed friction angle. Sediments with the highest bed friction angle have highest speed. The average velocity of each sediment are Quartz with u = 10.627, Yellow Sand with u = 7.437, and Rice with u = 2.1178 at time t = 1.

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.

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.

scholarly journals Prey Capturing Dynamics and Nanomechanically Graded Cutting Apparatus of Dragonfly Nymph

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 559
Author(s):  
Lakshminath Kundanati ◽  
Prashant Das ◽  
Nicola M. Pugno
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
High Speed ◽  
Prey Capture ◽  
High Speed Photography ◽  
Sensory Organs ◽  
Dragonfly Nymph ◽  
Drag Forces ◽  
Predatory Insects ◽  
Dragonfly Nymphs

Aquatic predatory insects, like the nymphs of a dragonfly, use rapid movements to catch their prey and it presents challenges in terms of movements due to drag forces. Dragonfly nymphs are known to be voracious predators with structures and movements that are yet to be fully understood. Thus, we examine two main mouthparts of the dragonfly nymph (Libellulidae: Insecta: Odonata) that are used in prey capturing and cutting the prey. To observe and analyze the preying mechanism under water, we used high-speed photography and, electron microscopy. The morphological details suggest that the prey-capturing labium is a complex grasping mechanism with additional sensory organs that serve some functionality. The time taken for the protraction and retraction of labium during prey capture was estimated to be 187 ± 54 ms, suggesting that these nymphs have a rapid prey mechanism. The Young’s modulus and hardness of the mandibles were estimated to be 9.1 ± 1.9 GPa and 0.85 ± 0.13 GPa, respectively. Such mechanical properties of the mandibles make them hard tools that can cut into the exoskeleton of the prey and also resistant to wear. Thus, studying such mechanisms with their sensory capabilities provides a unique opportunity to design and develop bioinspired underwater deployable mechanisms.

Droplet transfer behavior of narrow gap laser wire filling welding

2019 ◽  
Vol 33 (01n03) ◽  
pp. 1940045 ◽  
Author(s):  
Z. Zhang ◽  
R. Wang ◽  
G. Gou ◽  
H. Chen ◽  
W. Gao
Keyword(s):  
Welding Speed ◽  
High Speed ◽  
Transition Period ◽  
High Speed Photography ◽  
Narrow Gap ◽  
Droplet Transfer ◽  
Transfer Behavior ◽  
Feeding Speed ◽  
Wire Feeding ◽  
Droplet Transition

In this paper, we study the droplet transition behavior of narrow gap laser wire filling welding under the condition of changing welding speed and wire feeding speed, and it was observed by high-speed photography. It was found that with the increase of welding speed, the frequency of droplet transfer was reduced and the transition period was prolonged. With the increase of wire feeding speed, the wire was not fully melted and finally inserted into the molten pool.

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