Publications (5)8.12 Total impact
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Article: Influence of liquid layers on energy absorption during particle impact
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ABSTRACT: Particuology j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / p a r t i c a b s t r a c t The influence of the thickness of a covering liquid layer and its viscosity as well as the impact velocity on energy loss during the normal impact on a flat steel wall of spherical granules with a liquid layer was studied. Free-fall experiments were performed to obtain the restitution coefficient of elastic–plastic -Al 2 O 3 granules by impact on the liquid layer, using aqueous solutions of hydroxypropyl methylcellulose with different concentrations for variation of viscosity (1–300 mPa s). In the presence of a liquid layer, increase of liquid viscosity decreases the restitution coefficient and the minimum thickness of the liquid layer at which the granule sticks to the wall. The measured restitution coefficients were compared with experiments performed without liquid layer. In contrast to the dry restitution coefficient, due to viscous losses at lower impact velocity, higher energy dissipation was obtained. A rational explanation for the effects obtained was given by results of numerically solved force and energy balances for a granule impact on a liquid layer on the wall. The model takes into account forces acting on the granule including viscous, surface tension, capillary, contact, drag, buoyancy and gravitational forces. Good agreement between simulations and experiments has been achieved.Particuology. 01/2009; 7:245-259. -
Article: Impact on soft sand: void collapse and jet formation.
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ABSTRACT: Very fine sand is prepared in a well-defined and fully decompactified state by letting gas bubble through it. After turning off the gas stream, a steel ball is dropped on the sand. On impact of the ball, sand is blown away in all directions ("splash") and an impact crater forms. When this cavity collapses, a granular jet emerges and is driven straight into the air. A second jet goes downwards into the air bubble entrained during the process, thus pushing surface material deep into the ground. The air bubble rises slowly towards the surface, causing a granular eruption. In addition to the experiments and the discrete particle simulations we present a simple continuum theory to account for the void collapse leading to the formation of the upward and downward jets.Physical Review Letters 12/2004; 93(19):198003. · 7.37 Impact Factor -
Article: Impact
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ABSTRACT: According to Shoemaker, the "impact of solid bodies is the most fundamental process that has taken place on the terrestrial planets", as they shape the surfaces of all solar system bodies. A lot of information on this process has been extracted from remote observations of impact craters on planetary surfaces. However, the nature of the geophysical impact events is that they are non-reproducible. Moreover, their scale is enormous and direct observations are not possible. Therefore, we choose an alternate and of course downscaled experimental approach in order to guarantee reproducible results: We prepare very fine sand in a well defined and fully decompactified state by letting gas bubble through it. After turning off the gas stream, we let a steel ball fall on the sand. The series of events in the experiments and corresponding discrete particle simulations is as follows: On impact of the ball, sand is blown away in all directions ("splash") and an impact crater forms. When this cavity collapses, a granular jet emerges and is driven straight into the air. A second jet goes downwards into the air bubble entrained during the process, thus pushing surface material deep into the ground. The air bubble rises slowly towards the surface, causing a granular eruption. In addition to the experiments and the discrete particle simulations we present a simple continuum theory to account for the void collapse leading to the formation of the upward and downward jets. We show that the phenomenon is robust and even works for oblique impacts: the upward jet is then shooting backwards, in the direction where the projectile came from.07/2004; -
Article: Validation of a Discrete Particle Model in a 2D Spout‐Fluid Bed Using Non‐Intrusive Optical Measuring Techniques
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ABSTRACT: To gain insight into the hydrodynamics of spout-fluid beds, an experimental and numerical study was carried out. Particle image velocimetry was successfully developed and applied to determine particle velocity profiles, whereas voidage profiles were determined by digital image analysis. A 3D hard-sphere discrete particle model was used to simulate the flow in a spout-fluid bed. The simulations and experiments showed a similar influence of the background fluidization velocity on the spout behaviour.On a mené une étude expérimentale et numérique afin de mieux comprendre l'hydrodynamique des lits fluidisés jaillissants. On a développé et appliqué avec succès une méthode de vélocimétrie à imagerie de particules pour déterminer les profils de vitesse des particules, tandis que les profils de vide étaient déterminés par l'analyse d'image. L'écoulement dans un lit fluidisé jaillissant a été simulé à l'aide d'un modèle de particules discret de sphères dures tridimensionnel. Les simulations et expériences montrent une influence comparable de la vitesse de fluidisation propre sur le comportement du bec.The Canadian Journal of Chemical Engineering 01/2004; 82(1):30 - 36. · 0.75 Impact Factor -
Article: Discrete Particle Model for simulating liquid-solid fluidization
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ABSTRACT: We have used the discrete particle model combined with computational fluid dynamics for the continuous phase (DPM) to simulate the fluidization of 0.165 mm glass particles in water, and compare with the experiments of Zivkovic et al. (2009). The added mass and lubrication forces are included in the model, whereas they are generally neglected in the simulation of gas-solid and also most of the liquid-solid systems. The statistical quantities related to the discrete phase were calculated using the space and / or time averages (pressure drop, bed height, stress developed in the system …). The expansion curve of the fluidized bed, obtained using the DPM, has a similar trend as the experimental one. This expansion curve depends on the choice of the drag force which is the key element in the two-way coupling between the solid and liquid phases. The granular temperature of the solid phase is calculated from the fluctuating velocities of the particles. As in the experiments, the granular temperature is nearly equal to the square root of the superficial liquid velocity, and reaches a ceiling at high velocities when an equilibrium between the kinetic and collisional momentum transfer is reached. The particle velocity fluctuations are anisotropic. Small and large scale fluctuations are observed and their influence on the local granular temperature is shown explicitly. In contrast to the gas-solid fluidization, the choice of the restitution coefficient has a minor influence on the statistical behavior of the liquid fluidized bed. The inclusion in the model of the added mass force and viscous lubrication forces between colliding particles does not have a significant impact on the macroscopic bed properties.
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Institutions
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2004–2009
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Universiteit Twente
- • Faculty of Science and Technology (TNW)
- • Group of Physics of Fluids (POF)
Enschede, Provincie Overijssel, Netherlands
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