Dry Glass Beads Research Articles

Gravity fingering control on evaporation and deep drainage in a 3D porous medium

Water infiltration in soils is a fundamental hydrologic process that determines the water availability for plant roots and the rate of recharge to deep groundwater bodies. When both the initial water saturation of the soil and the water infiltration rate is low, the infiltration front becomes unstable, resulting in gravity fingers that act as preferential flow channels. Preferential flow may allow for the rapid bypass of water through the evaporation zone, thereby promoting deep drainage of water into the subsoil even in arid and semi-arid regions, where the potential evapotranspiration (PET) is high and the mean annual precipitation (MAP) is low. Here, we investigate experimentally the impact of gravity fingering on deep drainage coupled with surface evaporation in a 3D porous medium. We use a cylindrical vessel packed with dry glass beads, and reproduce seasonal climatic patterns consisting of relatively short rainfall events alternating with periods of intense evaporation. We vary the volume of rainfall events and the interval between rainfall events to replicate climate conditions. We record the mass of water in the system throughout the experiment, and determine the partition between evaporation and deep drainage before and after the onset of fingering. We find that in semi-arid conditions, the fraction of water that bypasses the evaporation zone increases fourfold after gravity fingering starts. This finding has potentially important implications for understanding infiltration dynamics in arid environments and ecosystems’ response in regions susceptible to desertification.

Experimental study on bulk modulus and dissipation of dry and wet granular samples under vertical vibration

Dry granular materials are composed of a dense random packing of macroscopic grains. As a small amount of liquid is added to granular samples, the liquid bridge forces, i.e. the forces between liquid and the grains, have an influence on the mechanical properties of wet granular material, and some of these properties are quite different from those of dry granular materials. In this work, by measuring the acceleration of the sample chamber and the force exerted on it by the shaker, the variations of bulk modulus and energy dissipation of both dry and wet glass bead samples with pressure and viscosity under vertical vibration are studied. The results are shown below. 1) Under low saturation, the bulk modulus of dry and wet glass bead sample are both described by a power law scaling law with pressure, which is close to the power law relationship predicted by the efficient medium theory on the basis of Hertz contact potential. A small amount of liquid can increase the bulk modulus of glass bead sample. At the same pressure and liquid content, the bulk modulus of wet glass bead sample increases with liquid viscosity increasing. Based on Hertzian contact mechanics, an efficient elastic network model is proposed to illustrate the mechanism of increasing bulk modulus of wet glass bead samples. 2) The energy dissipation of dry and wet glass bead sample decrease following the power law of pressure, and the energy dissipation of wet glass bead samples is proportional to the kinematic viscosity of liquid. 3) With the increase of strain amplitude, the softening behavior of the wet glass bead sample is similar to that of the dry glass bead sample, when the strain amplitude is higher than the strain threshold value. The kinematic viscosity of liquid inhibits the softening behavior of glass bead sample.

Influence of grain size on dynamic characterizations of laser-driven grain ejection

When intense laser pulse irradiates a target surface, the energetic processes of generation and expansion of laser-induced plasma will affect a localized pressure impulse around the irradiation zone. As a result, pulsed laser ablating granular target can drive a physical phenomenon of grain ejection. In this work, taking dry glass beads with different grain sizes as an example of granular targets and using high-speed video camera, we experimentally investigate the grain-size dependent dynamics of grain ejection driven by nanosecond laser pulses. The measured video sequences clearly exhibit that the laser-driven grain ejection process can be separated into two regimes: early-stage fast ejecting process and later-stage slow ejecting process. We find that there exists an obvious grain size effect on the kinetic energy of grains in the early-stage ejecting process. In addition, the temporal evolution of transient ejection of a curtain diameter <inline-formula><tex-math id="M6">\begin{document}$ D\left(t\right) $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20220243_M6.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20220243_M6.png"/></alternatives></inline-formula> corresponding to the later-stage ejecting process obeys the well-known “point source” law, <inline-formula><tex-math id="M7">\begin{document}$ {D\left(t\right)=\alpha t}^{\beta } $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20220243_M7.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20220243_M7.png"/></alternatives></inline-formula>, where both parameters <inline-formula><tex-math id="M8">\begin{document}$ \alpha $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20220243_M8.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20220243_M8.png"/></alternatives></inline-formula> and <inline-formula><tex-math id="M9">\begin{document}$ \beta $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20220243_M9.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20220243_M9.png"/></alternatives></inline-formula> depend on grain size. The observations mentioned above can be reasonably explained by considering the grain size dependent efficiency of impulse coupling between grain and plasma flow and plasma features generated by interaction of laser pulse with granular targets. These experimental results improve the understanding of the mechanism of laser-driven grain ejection.

Interpretation of bender element test results using sliding Fourier transform method

Identification of the arrival point of the shear wave in bender element tests is a task that can have ambiguous results. The contamination of the received shear wave signal with a weak P-wave component, which can emerge either directly from the transmitter or reflect from the side boundary, makes the judgement involved in this task dubious. The different available procedures to mark the arrival times of the shear wave are often prone to errors. A method is proposed to identify the time of the arrival of the shear wave. The predominant frequency of the received signal is first evaluated and then, with the help of the sliding Fourier transform approach, the arrival of the shear wave is identified. The method does not require any manual intervention. The proposed approach is applied to bender element tests performed on dry and saturated sand and glass beads by varying (i) input frequency of the signal, (ii) confining pressure, and (iii) void ratio. Results for different cases, including those obtained by using resonant column tests, are found to be very promising.

Surface flow profiles for dry and wet granular materials by Particle Tracking Velocimetry; the effect of wall roughness

.Two-dimensional Particle Tracking Velocimetry (PTV) is a promising technique to study the behaviour of granular flows. The aim is to experimentally determine the free surface width and position of the shear band from the velocity profile to validate simulations in a split-bottom shear cell geometry. The position and velocities of scattered tracer particles are tracked as they move with the bulk flow by analyzing images. We then use a new technique to extract the continuum velocity field, applying coarse-graining with the postprocessing toolbox MercuryCG on the discrete experimental PTV data. For intermediate filling heights, the dependence of the shear (or angular) velocity on the radial coordinate at the free surface is well fitted by an error function. From the error function, we get the width and the centre position of the shear band. We investigate the dependence of these shear band properties on filling height and rotation frequencies of the shear cell for dry glass beads for rough and smooth wall surfaces. For rough surfaces, the data agrees with the existing experimental results and theoretical scaling predictions. For smooth surfaces, particle-wall slippage is significant and the data deviates from the predictions. We further study the effect of cohesion on the shear band properties by using small amount of silicon oil and glycerol as interstitial liquids with the glass beads. While silicon oil does not lead to big changes, glycerol changes the shear band properties considerably. The shear band gets wider and is situated further inward with increasing liquid saturation, due to the correspondingly increasing trend of particles to stick together.Graphical abstract

Stick-slip behaviours of dry glass beads in triaxial compression

Consolidated undrained triaxial compression tests are conducted on standard cylindrical samples of nearly monodisperse glass beads, initially assembled in a dense state by a funnel pouring technique. Deviator stress, volumetric strain and induced pore air pressure are measured as functions of vertical strain under different confining stress and vertical strain rates. We find that in stick phase the glass beads accumulate energy and regain strength, which can lead to slow sliding in volumetric strain curve without stress drop in deviatoric stress curve for confining stress of 1000 kPa. Particularly after the previous slip event, as the deviatoric stress increases, the volume of sample repetitively compacts and then dilates before reaching the next slip events under high confining stress, which never happens at the lower. In slip phase, a stress drop coincides with a jump of volumetric strain and vertical strain, which make the pore air pressure grow sharply. The effects of confining stress and vertical strain rate on stick-slip instabilities are discussed in dry dense glass beads samples.

Experimental and numerical study of cylindrical triaxial test on mono-sized glass beads under quasi-static loading condition

This paper aims at studying the shear behavior of homogeneous granular materials by conventional triaxial test. The work is performed both in laboratory tests and by discrete element method simulations. Conventional triaxial tests are performed on glass beads packing, while a cylindrical rigid wall boundary condition based on lame formula and a series of procedures are proposed to simulate the conventional triaxial test. The experimental results on dry and saturated glass beads samples have been studied to find out the effect of saturation condition on the shear behavior. The comparisons between experimental and numerical results show that the numerical model can reproduce deviatoric curves satisfactorily in experimental conditions as long as experimental sample remains cylindrical. It correctly describes the volumetric strains of a numerical sample up to the peak value. Additionally, a parametric study on the influence of main micromechanical parameters has been carried out, which has been compared to experimental tests with glass beads of different textures. The comparison highlights the significant effect of friction coefficients and rolling resistance coefficients on global behavior of granular materials.

Development of a novel methodology to determine mill power draw

This paper presents an approach that has been developed to calculate the power draw of each size within a distribution of charge in a tumbling mill. Positron Emission Particle Tracking (PEPT) and the Discrete Element Method (DEM) are used to test the methodology. Experiments are conducted using dry spherical glass bead charge in a laboratory scale tumbling mill, which is mounted with a torque transducer and tachometer to provide measurements of mill power. Particle tracking information from PEPT is used to reconstruct the motion of glass beads and infer the overall charge behaviour, while DEM is employed to simulate particle motion and interaction, with collision mechanics calculated using the Hertz–Mindlin contact model. For both sets of data, the product of torque and average angular velocities in discrete cells are accumulated to obtain mill power. This method is found to be within statistical agreement with measured power for all cases investigated.

Dry ice blasting as a substitution for the conventional electroplating pre-treatments

For high quality electroplated products, surfaces must be thoroughly pre-treated. For this purpose electroplating currently needs a variety of chemical baths. The used chemicals are injurious to health and harmful to the environment. In addition, the conventional pre-treatment has a long process time which results in high costs. Dry ice blasting alone or in combination with other processes has the potential to completely substitute these conventional pre-treatment processes. Three process sequences as pre-treatment methods prior to electroplating were investigated on the aluminium alloys AlSi12 and AlMg3. The used processes are dry ice blasting, tempering during dry ice blasting and glass bead blasting followed by dry ice blasting. The influence of the parameters on the surface roughness, surface topography and surface tension of the workpieces was examined. A model to describe the correlation between the dry ice blasting parameters and surface parameters was developed. Finally, an adhesion test of electroplated specimen was conducted in order to determine the suitability of these alternative pre-treatment processes.

Observed Effects of Interparticle Friction and Particle Size on Shear Behavior of Granular Materials

AbstractThis paper presents an experimental study on the shear behavior of granular materials, focusing on the effects of interparticle friction and particle size, which are of fundamental importance but are not yet well understood. The experimental program consisted of a large number of direct shear tests on glass beads of varying sizes and interparticle friction conditions, performed under a range of packing densities and normal stress levels. Test data were interpreted in terms of the stress–dilatancy relationship and shear strength parameters. The study indicates that under otherwise similar testing conditions, oil-lubricated glass beads tend to have substantially lower shear strength as compared with water-lubricated, water-flooded, and dry glass beads. It has also been found that at similar particle size uniformity, increasing mean particle size (d50) leads to more dilatant shear response and higher shear strength. A generalized stress–dilatancy relation is proposed, which introduces a variable dila...

Colloid mobilization and transport during capillary fringe fluctuations.

Capillary fringe fluctuations due to changing water tables lead to displacement of air-water interfaces in soils and sediments. These moving air-water interfaces can mobilize colloids. We visualized colloids interacting with moving air-water interfaces during capillary fringe fluctuations by confocal microscopy. We simulated capillary fringe fluctuations in a glass-bead-filled column. We studied four specific conditions: (1) colloids suspended in the aqueous phase, (2) colloids attached to the glass beads in an initially wet porous medium, (3) colloids attached to the glass beads in an initially dry porous medium, and (4) colloids suspended in the aqueous phase with the presence of a static air bubble. Confocal images confirmed that the capillary fringe fluctuations affect colloid transport behavior. Hydrophilic negatively charged colloids initially suspended in the aqueous phase were deposited at the solid-water interface after a drainage passage, but then were removed by subsequent capillary fringe fluctuations. The colloids that were initially attached to the wet or dry glass bead surface were detached by moving air-water interfaces in the capillary fringe. Hydrophilic negatively charged colloids did not attach to static air-bubbles, but hydrophobic negatively charged and hydrophilic positively charged colloids did. Our results demonstrate that capillary fringe fluctuations are an effective means for colloid mobilization.

Three‐Dimensional Multiphase Segmentation of X‐Ray CT Data of Porous Materials Using a Bayesian Markov Random Field Framework

Advancements in noninvasive imaging methods such as X‐ray computed tomography (CT) have led to a recent surge of applications in porous media research with objectives ranging from theoretical aspects of pore‐scale fluid and interfacial dynamics to practical applications such as enhanced oil recovery and advanced contaminant remediation. While substantial efforts and resources have been devoted to advance CT technology, microscale analysis, and fluid dynamics simulations, the development of efficient and stable three‐dimensional multiphase image segmentation methods applicable to large data sets is lacking. To eliminate the need for wet–dry or dual‐energy scans, image alignment, and subtraction analysis, commonly applied in X‐ray micro‐CT, a segmentation method based on a Bayesian Markov random field (MRF) framework amenable to true three‐dimensional multiphase processing was developed and evaluated. Furthermore, several heuristic and deterministic combinatorial optimization schemes required to solve the labeling problem of the MRF image model were implemented and tested for computational efficiency and their impact on segmentation results. Test results for three grayscale data sets consisting of dry glass beads, partially saturated glass beads, and partially saturated crushed tuff obtained with synchrotron X‐ray micro‐CT demonstrate great potential of the MRF image model for three‐dimensional multiphase segmentation. While our results are promising and the developed algorithm is stable and computationally more efficient than other commonly applied porous media segmentation models, further potential improvements exist for fully automated operation.

Mechanisms for Acoustic Absorption in Dry and Weakly Wet Granular Media

The dissipation of an elastic wave in dry and wet glass bead packings is measured using multiple sound scattering. The interplay of a linear viscoelastic loss and a nonlinear frictional one is observed in dry media. The Mindlin model provides a qualitative description of the experiment, but fails to quantitatively account for the data due to grain roughness. In weakly wet media, we find that the dissipation is dominated by a linear viscous loss due to the liquid films trapped at the grain surface asperities. Adding more liquid enables us to form the capillary menisci but does not increase the energy loss.

Pressure Head Profile within Growing Fingers in Initially Dry Glass Beads

Wetting front instability is one of the mechanisms producing preferential flow in soils. In this study, we measured the pressure head within growing fingers in three-dimensional soil columns and examined the applicability of the prefingered flow theory and the similarity solution. The pressure head within a growing finger was measured during infiltration into a porous medium consisting of fine over coarse layered glass beads in a transparent, acrylic column. To ensure the measurement of pressure heads within growing fingers whose pathways cannot be known a priori, we made 10 insertion ports for every measurement position in the column. The fingertip velocity was essentially constant with time, while the infiltration rate increased. Fingers merged as they grew, which complicated the finger flow physics in three dimensions. The profiles of the pressure head were nearly linear during early finger growth. As the finger lengthened, the pressure head at all measured points decreased to an almost constant value. The prefingered flow model showed good applicability not only to induction zone formation, but also to the early finger growth when it remained saturated. Conversely, the similarity solution was not as applicable to growing fingers that were not in a steady state.

Avalanching flow of cohesive powders

The flow dynamics of cohesive powders is investigated in rotating cylinders with an L : R ratio of 3 : 1 using experiments and DEM simulations. Flow onset and steady-state behavior are compared for free-flowing (cohesionless) dry glass beads, wet glass beads, and “dry” cohesive powders (lactose, microcrystalline cellulose). The avalanching dynamics of powders is substantially different from those observed for free-flowing or wet-cohesive glass beads. Dry cohesive powders exhibit history-dependent flow dynamics, significant dilation, aperiodic avalanche frequencies, and variable avalanche size. These behaviors also provide a route for effective characterization of cohesive forces under dilated conditions characteristic of unconfined flows.

Dynamic Water-Entry Pressure for Initially Dry Glass Beads and Sea Sand

Dynamic water-entry pressure has been considered an important factor in the mechanism of fingered flow formation. We measured and compared dynamic water-entry pressures of air-dried glass beads of 0.4-mm mean particle size and for 0.30- to 0.60-mm (30–50 mesh) sea sand. Two measurements were conducted. First, breakthrough pressures were measured by increasing the supply water pressure incrementally from a low water pressure at which water could not enter the porous medium. Second, the relationship between the supply water pressure and the initial infiltration rate was measured by keeping the supply water pressure constant at several values. Measured values for the 0.4-mm glass beads and the 30- to 50-mesh sea sand showed some differences. While the breakthrough pressure was similar to the advancing capillary pressure for both materials, only the 30- to 50-mesh sea sand showed almost the same value as the water pressure at the inflection point on the initial wetting curve. For the 0.4-mm glass beads, the breakthrough pressure was higher (less negative) than that of the inflection point. Furthermore, the 0.4-mm glass beads showed a sharp jump in the initial infiltration rate when the supply water pressure exceeded the breakthrough pressure, whereas the 30- to 50-mesh sea sand showed an almost linear increase in the initial infiltration rate. These differences are discussed in terms of oscillatory nature of the water-entry pressure. An expression for the dynamic water-entry pressure was fitted to the measured data. The expression was used for estimating the width of fingers formed in the materials during infiltration into layered conditions and was found to be useful for studying fingered flow formation, at least for the glass beads.

Dynamic Water‐Entry Pressure for Initially Dry Glass Beads and Sea Sand

Dynamic Water‐Entry Pressure for Initially Dry Glass Beads and Sea Sand

Codalike Multiple Scattering of Elastic Waves in Dense Granular Media

We study the multiple scattering of short-wavelength ultrasound through the force networks in dry and wet glass bead packings under stress. Over long distance scales, the diffusion approximation is shown to describe adequately the transport of elastic waves dominated by shear waves. The recovered transport mean path reveals a short-range correlation of the force chains. Also we observe the drastic effect of wetting liquids on the energy dissipation in the granular medium. The relevance of these experimental findings for the seismological applications is discussed.

On the Construction and Calibration of Dual‐Probe Heat Capacity Sensors

Dual‐probe heat‐capacity (DPHC) sensors can be used to measure soil heat capacity (C), water content, and temperature. Research was conducted to test design factors that affect sensor calibration, including: (i) calibration media, (ii) diameter and length of the needle probes, (iii) sensor body material, and (vi) duration and total power of the applied heat pulse. All sensors were calibrated in media with known C, including: agar (water), water‐saturated glass beads, and dry glass beads. Calibration consisted of collecting heat pulse data in a given media and then calculating the apparent probe spacing (rapp, distance between heater and detector needles) that yielded correct value of C An ideal sensor would have the same rapp regardless of media type. The rapp for all sensor designs increased as C decreased, on average changing by 6.7% between agar and dry beads. This undesirable result was consistent with previous studies that showed DPHC sensors calibrated in agar overestimated C in drier soils. Needle diameter (1.27 vs. 1.65 mm), sensor body material (urethane vs. high‐conductivity epoxy), and shortening of the detector probe had a small effect on rapp Sensors made with urethane bodies, 1.27‐mm diam. needle probes, and shortened temperature probes showed less sensitivity to calibration media and are therefore recommended. The rapp for this design only increased by 2.6% between dry and water‐saturated wet beads. Apparent probe spacing was not affected by changes in total applied power (400–1600 J m−1) or heat pulse duration (2–16 s) when the correct analytical model was used to compute C

A distinct class of avalanche scars on Mars

We report observations of a set of surface features on Mars that form a distinct class of avalanche scars. These features have a horizontal scale of hundreds of meters, but a depth scale of meters distinguishes them from the shallower features known as slope streaks. The meters-thick avalanche scars have escaped previous attention because of weak contrast between the interiors of the scarred regions and their surroundings. Often the most visible feature is a shadow cast by the trough wall, a band 1–3 pixels wide in Mars Orbiter Camera narrow angle images, indicating maximum depths of 4–10 m. We investigate the morphology of more than 500 such features. Slopes upon which the avalanches occur average about 27°. Impact craters are seen at the heads of some avalanche scars; this subset exhibits statistically wider opening angles. The scars span an estimated several Ma in age. Those found so far occurred mainly in the Olympus Mons lower aureole. We compare shapes of slope streaks to shapes of meters-thick avalanches, and the results support the notion that the two classes are distinct. The newly-discovered avalanches resemble some terrestrial flows of loose, dry material such as dry snow and glass beads. On the basis of these analogs, we suggest a physical model.