Fluidization and transport of vibrated granular matter : a review of landmark and recent contributions

We present a short retrospective review of the existing literature about the dynamics of (dry) granular matter under the effect of vibrations. The main objective is the development of an integrated resource where vital information about past findings and recent discoveries is provided in a single treatment. Special attention is paid to those works where successful synthetic routes to as-yet unknown phenomena were identified. Such landmark results are analyzed, while smoothly blending them with a history of the field and introducing possible categorizations of the prevalent dynamics. Although no classification is perfect, and it is hard to distillate general properties out of specific observations or realizations, two possible ways to interpret the existing results are defined according to the type of forcing or the emerging (ensuing) regime of motion. In particular, first results concerning the case where vibrations and gravity are concurrent (vertical shaking) are examined, then the companion situation with vibrations perpendicular to gravity (horizontal shaking) is described. Universality classes are introduced as follows: 1) Regimes where sand self-organizes leading to highly regular geometrical "pulsating" patterns (thin layer case); 2) Regimes where the material undergoes "fluidization" and develops an internal multicellular convective state (tick layers case); 3) Regimes where the free interface separating the sand from the overlying gas changes inclination or develops a kind a patterned configuration consisting of stable valleys and mountains or travelling waves; 4) Regimes where segregation is produced, i.e. particles of a given size tend to be separated from the other grains. Where possible, an analogy or parallelism is drawn with respect to the companion field of fluid-dynamics for which the assumption of "continuum" can be applied

Convective states and patterning behavior in Lunar Regolith under the effect of vertical vibrations

In the field of space exploration, it is essential to deal with solid “particles” for various applications, for example transporting lunar and Martian soil (typically regolith), for mining, to study geological aspects and establish habitats on the Moon or Mars. However, methods to handle these materials remain untested because they are made of abrasive and reactive components which by their nature make them hard to handle mechanically. In the present project, novel strategies to manipulate such granular systems based on the application of “vibrations” are explored. Special attention is devoted to the unique states which are produced when such materials are subjected to concurrent vibrations and gravity (vertical shaking). By means of a concerted approach based on experimental work in synergy with relevant computational tools for systems where the assumption of continuum is not applicable, we show that circumstances exist where lunar regolith can behave as a kind of “fluid” and produce interesting patterning behaviors. The problem is parametrically investigated by allowing the frequency and spatial amplitude of the imposed vibrations to span relatively wide intervals for different depths of the considered layer of material (simulant). The results are critically discussed and placed in a proper theoretical context through comparisons with earlier experimental findings where the analysis was limited to monodisperse collection of particles (spheres with fixed density and diameter as opposed to the irregular shape and varying size of lunar regolith)

Effect of vertical and horizontal vibrations, vessel size and layer height on the fluidization of lunar regolith

In the coming years with such a major focus being applied to the further exploration and eventual habitation of the Moon and Mars, it has never been more important to further the understanding of how to manipulate the resources abundantly available on these planets. Along these lines, this project aims to develop novel ways of handling the regolith that makes up the lunar soil by use of “vibrations”. The final objective is the definition and validation of a new approach able to overcome well-known drawbacks related to these materials due to their extremely abrasive and reactive nature, which makes their manipulation and transport particularly difficult, especially in the low gravity lunar environment. Through the application of vibrations with various orientations to small samples of lunar regolith simulant, the solid granular material can be forced to display a fluidlike convective behavior, forming structures such as self-sustaining heaps. The effect that varying the height of the bed of lunar regolith simulant has on the mode and rate of convection exhibited by the bed is investigated while the size of the vessel containing the bed is also varied to assess the influence of this additional parameter. Some recent experimental findings are critically discussed in relation to the resulting (enhanced) ability to manipulate and transport lunar regolith

Particle Vibration, an instrument to study particle accumulation structures on board the International Space Station

The scientific and technological aspects of the PARTICLE VIBRATION Project (also known as T-PAOLA i.e. "Thermovibrationally-driven Particle self-Assembly and Ordering mechanisms in Low grAvity") are described in detail. The project relies on the combined use of the Selectable Optical Diagnostics Instrument (SODI), a Class-2 device developed by ESA for scientific experiments in the field of fluids on board the International Space Station, and the Microgravity Science Glovebox (MSG), a Class-1 general purpose facility under the responsibility of NASA. The related modular architecture has recently been expanded under the umbrella of new scientific research funded by the UK Space Agency to allow for a novel class of experiments dealing with multiphase (solid-liquid) flows. The final aim of this microgravity project is the identification of new dispersed-phase self-organization phenomena driven by the application of vibrations and the ensuing development of new contactless particle manipulations strategies. In the present paper, emphasis is given to the related space hardware and software, the experiment protocol, the ground tests and procedures and all the adaptations that had to be implemented to overcome a number of technological and physical issues, both general and system-specific

Impact of surfactant depletion on foam in porous media

Foam can be applied as an Enhanced Oil Recovery (EOR) process. Foam stability in porous mediadecreases with decreasing surfactant concentration. It is also known that foam collapses belowa “limiting water saturation” in porous media. However, there isn’t a complete theory for the relationship between surfactant concentration and the water saturation below which foam coarsens ina specific porous medium. The aim of this study was to find a relationship between the surfactantconcentration, the foam bubble radius, and the limiting water saturation. This research gathersand analyses experimental data from the literature on foam properties in porous media. The foamswere stabilized with the same anionic surfactant (AOS), at different surfactant concentrations andporous media.The experimental data shows that for a specific porous medium, the limiting water saturation exponentially decreases with increasing surfactant concentration. These results can be explainedby the surfactant depletion from the solution to the gas-water interface. This work shows that thelimiting water saturation approximates the water saturation for which the gas-water interfacial-areais equal to the surface-area that could be covered by the surfactant molecules in the surfactant solution in the given porous medium. A fundamental assumption in this calculation is that gas bubblesin the porous medium correspond to pore size, as is thought to apply to foams at water saturationsabove the limiting water saturation.The general implication of these results is that from two known parameters, the third parameter canbe calculated (the three parameters are surfactant concentration, the average foam bubble sizeand limiting water saturation). A possible implication on the modelling of the foam flood in porousmedia was investigated in this research. The observed relationship was applied to a simulation ofsurfactant-alternating-gas injection in a homogenous reservoir with a uniform residual oil saturation. In this simulation the limiting water saturation was a function of the foam bubble size and thesurfactant concentratio

Impact of surfactant depletion on foam in porous media

Foam can be applied as an Enhanced Oil Recovery (EOR) process. Foam stability in porous mediadecreases with decreasing surfactant concentration. It is also known that foam collapses belowa “limiting water saturation” in porous media. However, there isn’t a complete theory for the relationship between surfactant concentration and the water saturation below which foam coarsens ina specific porous medium. The aim of this study was to find a relationship between the surfactantconcentration, the foam bubble radius, and the limiting water saturation. This research gathersand analyses experimental data from the literature on foam properties in porous media. The foamswere stabilized with the same anionic surfactant (AOS), at different surfactant concentrations andporous media.The experimental data shows that for a specific porous medium, the limiting water saturation exponentially decreases with increasing surfactant concentration. These results can be explainedby the surfactant depletion from the solution to the gas-water interface. This work shows that thelimiting water saturation approximates the water saturation for which the gas-water interfacial-areais equal to the surface-area that could be covered by the surfactant molecules in the surfactant solution in the given porous medium. A fundamental assumption in this calculation is that gas bubblesin the porous medium correspond to pore size, as is thought to apply to foams at water saturationsabove the limiting water saturation.The general implication of these results is that from two known parameters, the third parameter canbe calculated (the three parameters are surfactant concentration, the average foam bubble sizeand limiting water saturation). A possible implication on the modelling of the foam flood in porousmedia was investigated in this research. The observed relationship was applied to a simulation ofsurfactant-alternating-gas injection in a homogenous reservoir with a uniform residual oil saturation. In this simulation the limiting water saturation was a function of the foam bubble size and thesurfactant concentrationApplied Geophysics and PetrophysicsPetroleum Engineerin

Scientific perspectives on lunar exploration in Europe

Abstract The Moon is a geological history book, preserving information about the history of the Solar System, including the formation and early evolution of the terrestrial planets and their bombardment histories, as well as providing insight into other fundamental Solar System processes. These topics form the basis for science “of the Moon”, but the lunar surface is also a platform for science “on the Moon” and “from the Moon”—including astronomical observations, fundamental physics, and life science investigations. Recently, the Moon has become a destination for technology research and development—in particular for developing in situ resources, human exploration, and habitation, and for its potential use as a waypoint for the human exploration of Mars. This paper, based on recommendations originally proposed in a White Paper for ESA’s SciSpacE strategy, outlines key lunar science questions that may be addressed by future space exploration missions and makes recommendations for the next decades

Impact of Solubilized and Dispersed Crude Oil on Foam in a Porous Medium

Dispersed and solubilized oil can impact bulk foam stability differently. Though aromatic components are more soluble in water than straight-chain aliphatic components, solubilized aromatics do not necessarily impact bulk foam stability, whereas straight-chain aliphatic components can have a detrimental impact (Lee et al., “Stability of Aqueous Foams in the Presence of Oil: On the Importance of Dispersed vs Solubilized Oil”, Ind. Eng. Chem. Res., 52,pp. 66−72, 2013). However, to our knowledge there is no research on the impact of solubilized oil on foam in porous media.The impact of the crude oil, as a separate oleic phase, was studied by co-injection of crude oil, surfactant solution and gas in coreflood, on steady-state mobility, captured by the pressure drop across the core. To investigate if the behaviour of steady-state foam with dispersed crude oil can be explained by the solubilized oil components, we perform foam-flooding experiments with surfactant solution previously equilibrated with crude oil. Furthermore, we conduct foam-flooding experiments with solubilized hexane in surfactant solution, to determine if the straight-chain aliphatic components can explain the behaviour of the solubilized crude oil on steady-state foam mobility as it impacts bulk foam in the literature.The crude oil , as a separate oleic phase, reduces the pressure gradient across the core by a factor of twenty compared to the case without oil. Nonetheless, this pressure gradient was about a factor three higher than we observed by co-injecting crude oil, water without surfactant, and gas, which indicates that some weak foam and emulsion was generated by co-injecting surfactant, crude oil, and gas. In contrast, with solubilized crude oil and with solubilized hexane, the pressure gradient is in the same order of magnitude for co-injection gas and surfactant with and without solubilized oil. These results indicate that solubilized crude oil cannot explain the impact of the crude oil as a separate oleic phase on foam mobility in our case. Furthermore, the impact of solubilized crude oil on steady-state foam mobility cannot be explained as the effect of a solubilized straight-chain aliphatic component such as hexane.The major result of our work is that the impact of solubilized crude oil on foam does not explain the detrimental impact of crude oil in a separate oleic phase on foam in a porous media. Another result is that though co-injected water, gas and crude oil might not generate strong foam, it can result in somewhat higher pressure gradients with surfactant in the aqueous phase than without surfactant. This is possibly caused by smaller oil droplets in presence of surfactant and a weak foam.Applied Geophysics and PetrophysicsPetroleum Engineerin

Role of Gas Type on Foam Transport in Porous Media

We present the results of an experimental investigation of the effect of gas type and composition on foam transport in porous media. Steady-state foam strengths with respect to three cases of distinct gases and two cases containing binary mixtures of these gases were compared. The effects of gas solubility, the stability of lamellae, and the gas diffusion rate across the lamellae were examined. Our experimental results showed that steady-state foam strength is inversely correlated with gas permeability across a liquid lamella, a parameter that characterizes the rate of mass transport. These results are in good agreement with existing observations that the foam strength for a mixture of gases is correlated with the less soluble component. Three hypotheses with different predictions of the underlying mechanism that explain the role of gas type and composition on foam strength are discussed in detail