Brazil Nut Effect Research Articles

Contact parameter calibration for flax threshing materials using machine learning and the Brazil nut effect

Contact parameters between agricultural granular mixtures are crucial for the development and simulation optimization of agricultural machinery but are challenging to measure experimentally. This study utilizes the Brazil nut effect (BNE) to use particle volume concentration as a macroscopic response indicator and to calibrate six contact parameters of flax threshing material. By combining optimized Latin hypercube sampling with vibration segregation simulation tests, the study generates input parameters for training the PSO-BP model, which is optimized using an improved Non-dominated Sorting Genetic Algorithm (NSGA-II). The objective is to minimize the volume concentration error of flax seeds, short stems, and capsule shells between simulation and physical tests, resulting in an optimal Pareto set. Validation through static and dynamic repose angle tests shows errors within 5% (static) and 4% (dynamic), respectively, confirming the reliability of the calibration results and the research method.

The intruder motion in a cubic granular container

The Brazil nut effect is a key issue impeding the uniform distribution of particles in a mixed granular system. Extensive research was conducted on this segregation phenomenon in the 1990s and 2000s to identify the mechanisms and influencing factors involved. However, due to limitations in experimental techniques, the scope and effectiveness of research have been restricted. In this study, the Hall-effect magnetic sensing technique was utilized to track the motion of a single magnetic sphere (referred to as the intruder) within a cubic granular bed. This tracking method allowed for the measurement of the intruder's equilibrium positions as well as its trajectories. In a vibration-fluidized cubic granular container, an interesting phenomenon was observed: the intruder displayed a unique periodic helical oscillatory motion near the corner of the cubic container, with the oscillation amplitude gradually attenuating until stabilizing at its equilibrium position. A discrete element method simulation was carried out, revealing that the granular convection flow ascends from the center and descends near the container walls, with a faster flow rate at the four corners. An equation of motion was established accordingly for an intruder in such a convective granular flow, providing a comprehensive explanation for the observed intruder behavior. As a result of this comprehensive approach, we have uncovered the unique phenomenon of different mechanisms collectively driving the periodic spiral oscillation of the intruder before it eventually rested in its equilibrium position, a phenomenon whose mechanism has not previously been investigated in the literature.

Wave‐Driven Vertical Sorting of Density‐Varying Particles

AbstractIt has been recognized that the vertical sorting of polydispersed sand grains via the “Brazil Nut effect” can lead to inverse grading (upward coarsening) in the surface layer of a sand bed. However, the addition of nonnative particles not inherently observed on the beach, characterized by different densities and sizes, may complicate the vertical sorting processes and the fate of the nonnative particles. For example, olivine particles, which may be released on natural sandy beaches to facilitate carbon dioxide capture via weathering from wave action, have a density about 25% larger than the typical native sands. An Eulerian‐Lagrangian model, which couples Computational Fluid Dynamics for the fluid phase and Discrete Element Method for the particle phase was utilized to investigate how the so‐called “Reverse Brazil Nut effect” due to the larger density of nonnative (olivine) particles may be counteracted by the so‐called “Brazil Nut effect” for a range of nonnative particle sizes. Numerical simulations showed that the higher‐density nonnative particles tended to sink into the sand bed consistent with the “Reverse Brazil Nut effect”; however, the vertical sorting structure of native sand, driven by the “Brazil Nut effect,” also was a controlling factor determining the fate of nonnative particles. To maintain the presence of the nonnative (olivine) particles in the active layer of sediment transport, the higher‐density nonnative particle size must be larger than the mean native sand size found at the bottom of the active layer.

An Efficient Numerical Approach to Modeling the Effects of Particle Shape on Rubble-pile Dynamics

We present an approach for the inclusion of nonspherical constituents in high-resolution N-body discrete element method (DEM) simulations. We use aggregates composed of bonded spheres to model nonspherical components. Though the method may be applied more generally, we detail our implementation in the existing N-body code pkdgrav. It has long been acknowledged that nonspherical grains confer additional shear strength and resistance to flow when compared with spheres. As a result, we expect that rubble-pile asteroids will also exhibit these properties and may behave differently than comparable rubble piles composed of idealized spheres. Since spherical particles avoid some significant technical challenges, most DEM gravity codes have used only spherical particles or have been confined to relatively low resolutions. We also discuss the work that has gone into improving performance with nonspherical grains, building on pkdgrav's existing leading-edge computational efficiency among DEM gravity codes. This allows for the addition of nonspherical shapes while maintaining the efficiencies afforded by pkdgrav's tree implementation and parallelization. As a test, we simulated the gravitational collapse of 25,000 nonspherical bodies in parallel. In this case, the efficiency improvements allowed for an increase in speed by nearly a factor of 3 when compared with the naive implementation. Without these enhancements, large runs with nonspherical components would remain prohibitively expensive. Finally, we present the results of several small-scale tests: spin-up due to the YORP effect, tidal encounters, and the Brazil nut effect. In all cases, we find that the inclusion of nonspherical constituents has a measurable impact on simulation outcomes.

Intruder trajectory tracking in a three-dimensional vibration-driven granular system: Unveiling the mechanism of the Brazil nut effect

We employ a Hall-effect magnetic sensor array to accurately track the trajectory of a single magnetic sphere, referred to as the “intruder,” within a three-dimensional vibro-fluidized granular bed to unravel the underlying physical mechanism governing the motion of the intruder. Within the acceleration range of 3.5 g ≥ Γ ≥ 1.5 g, we find that, regardless of the intruder’s initial position, it consistently reaches the same equilibrium depth when the vibration acceleration (Γ) and frequency (ω) are fixed. For Γ ≤ 2.5 g, the equilibrium position lies on the surface of the granular bed, while for Γ > 2.5 g, it shifts below the surface. Additionally, intruders with different densities exhibit varying equilibrium depths, with higher density resulting in a deeper equilibrium position. To understand the mechanism behind the intruder’s upward or downward motion, we measure its rising or sinking velocities under different vibration parameters. Our findings demonstrate that the rising velocity of the intruder, under varying vibration accelerations (Γ) and frequencies (ω), can be collapsed using the ratio Γ/ω, while the sinking velocity remains unaffected by the vibration strength. This confirms that the upward motion of the larger sphere, associated with the Brazil nut effect, primarily arises from the void-filling mechanism of the bed particles. Furthermore, our experiments reveal that the presence of convection within the bed particles has minimal impact on the motion of the intruder.

A calibration method for contact parameters of agricultural particle mixtures inspired by the Brazil nut effect (BNE): The case of tiger nut tuber-stem-soil mixture

The lack of calibration methods for the contact parameters of agricultural particle mixtures limits the numerical simulation optimization of agricultural equipment. In this study, a novel method for calibrating contact parameters in agricultural particle mixtures inspired by the Brazil nut effect was proposed. The effectiveness of the proposed method was evaluated using a case study of a tiger nut tuber-stem-soil mixture. The intrinsic and contact parameters of monomaterials were first determined by conventional tests to provide data for vibration simulation tests. Vibration segregation tests were then performed on binary mixtures. The determination coefficient R2 between the physical and simulation data of the target particle volume concentration in the mixture was used as a response indicator. The second-order response surface regression model between the contact parameters and R2 was fitted by response surface methodology (RSM). The significance of the effect of the contact parameters on the indicator was quantified, and the optimal values of each parameter were determined. Finally, the applicability and accuracy of the calibrated parameters were verified using the self-flow sieving test. The results showed that the distribution of the mixture on the sieving surface and in the receiving box obtained from the calibrated test best matched the physical test results; at this time, the maximum relative errors of the physical and simulated values of the mass percentages of the tuber, stem and soil in the bin were 8.2%, 7.6%, and 6.5%, respectively, indicating that the calibrated parameters have good applicability and accuracy. The calibration test method can guide the calibration of contact parameters for other agricultural particle mixtures.

Culinary fluid mechanics and other currents in food science

This review describes recent scientific advances in the context of the culinary arts. It is written as a menu, starting with the physics of drinks, followed by the main course, and ending with complex desserts. Recent discoveries are reviewed, particularly in fluid mechanics and soft matter physics, and their relevance to food science is highlighted. Many phenomena like the Cheerios effect, coffee-ring effect, Brazil nut effect, Leidenfrost effect, and Marangoni effect are described and illustrated by epicurean examples.

Resonance‐induced acceleration of theRBNE‐BNEsegregation inversion

AbstractThe experimental and simulation results indicate that the reverse Brazil nut effect (RBNE)‐Brazil nut effect (BNE) segregation inversion happens faster in the circular‐bottom container than that in the flat‐bottom container. The starting location of the sinkage of heavier grains at the top layer is triggered with certain randomness in the latter, whereas it first occurs at either of the lateral edges of the bottom in the former. The occurrence of standing‐wave resonant spots of higher and lower granular temperature accelerates the RBNE‐BNE transition. From the elastic collision model of single grain, the bottom with a larger angle leads to more energy transfer from the vertical direction. The simulation results of a monodisperse granular bed confirm that the circular‐bottom container possesses a higher granular temperature and a lower packing density at the lateral edges of the circular bottom, whereas the flat‐bottom container has a uniform distribution with a standing‐wave period.

Realization of the Brazil-nut effect in charged colloids without external driving

Sedimentation is a ubiquitous phenomenon across many fields of science, such as geology, astrophysics, and soft matter. Sometimes, sedimentation leads to unusual phenomena, such as the Brazil-nut effect, where heavier (granular) particles reside on top of lighter particles after shaking. We show experimentally that a Brazil-nut effect can be realized in a binary colloidal system of long-range repulsive charged particles driven purely by Brownian motion and electrostatics without the need for activity. Using theory, we argue that not only the mass-per-charge for the heavier particles needs to be smaller than the mass-per-charge for the lighter particles but also that at high overall density, the system can be trapped in a long-lived metastable state, which prevents the occurrence of the equilibrium Brazil-nut effect. Therefore, we envision that our work provides valuable insights into the physics of strongly interacting systems, such as partially glassy and crystalline structures. Finally, our theory, which quantitatively agrees with the experimental data, predicts that the shapes of sedimentation density profiles of multicomponent charged colloids are greatly altered when the particles are charge-regulating with more than one ion species involved. Hence, we hypothesize that sedimentation experiments can aid in revealing the type of ion adsorption processes that determine the particle charge and possibly the value of the corresponding equilibrium constants.

Simulating impact-induced shaking as a triggering mechanism for mass movements on Bennu

Observations of near-Earth asteroid Bennu have revealed a dynamic surface composed of unconsolidated material. The OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) mission found numerous locations exhibiting evidence of mass movements of surface material. Mass movements can be a major factor in the surface evolution of a small near-Earth asteroid, and the Small Carry-on Impactor (SCI) experiment on asteroid Ryugu has shown that seismic shaking can trigger it. We selected one mass movement site on Bennu to conduct a detailed survey of the surface boulder arrangement and geomorphology. Using these data, we created dynamical simulations of mass movement events at this site initiated by seismic shaking, and we found a mass flux comparable to estimates from the site survey. The frequency ranges of the shakings are similar to what would be produced by a 0.5-m-diameter impactor, for which the expected crater size is of a scale widely seen on Bennu (32 m). In addition, the simulation exhibited the Brazil nut effect, where finer particles percolate towards greater depth, in this case up to 1.5 m. Our results demonstrate that impact-induced seismic shaking is a viable mechanism for the initiation of mass movements, and a plausible explanation for the scarcity of fine regolith, on Bennu's surface.

Investigation of mixing homogeneity of binary particle systems in high-shear wet granulator by DEM

To provide a theoretical foundation and a good understanding for the real manufacturing granulation process, this paper investigates the effect of particle properties on the mixing process in the high-shear wet granulator, a common equipment in one of the key technologies in the growth of the pharmaceutical industry that has rarely been used to examine particle mixing-related problems in previous numerical simulations. The discrete element method (DEM) and the relative standard deviation (RSD) to explore binary particle systems with a range of sizes, densities, and volume fractions, and measure the mixing homogeneity of the particles. Results show that, for binary particle systems, particle size, density, and volume fraction all significantly affect mixing homogeneity, with good mixing occurring for a single size and a 1:1 volume fraction for the same density. Similar Brazil nut effect and Reverse-Brazil nut effect occurrences were discovered for many particle systems at various stages. There is a size threshold for a given binary particle system. Then, in a binary system, particles of a single size and density had nearly similar vertical driving forces, and these forces may vary by up to 10 times with changes in size or density. In the end, granular temperature rises with radial position and reaches its highest point at the pelletizer’s wall and the top of the impeller. Density has less of an impact on granule velocity fluctuation than size.

Chutes Too Narrow: The Brazil Nut Effect and the Blessings of the Fall

Chutes Too Narrow: The Brazil Nut Effect and the Blessings of the Fall

Numerical Comparison of Contact Force Models in the Discrete Element Method

The discrete element method (DEM) is usually applied in analyzing the scientifical origin/evolution of the asteroids and the landing/sampling of the regolith. In order to manage the contact between the non-spherical granules, the Polygonal Contact Model (PCM) has been introduced into the DEM method. This paper applies four different contact force models in the newly-proposed DEM algorithm to analyze their difference and implication. The four contact force models include one linear model and three nonlinear models derived from the complete Mindlin–Deresiewicz equations. By considering the macroscopical results and calculation efficiency, the single-collision and multiple-collision cases are analyzed by comparing the four contact models. Specifically, the restitution coefficient, the angular velocity, the rebound angle, and the kinetic energy are applied as indicators for the single collision. The multiple-collision case is studied under the Brazil nut effect with ellipsoidal granules. Additionally, the softening feasibility is also discussed by decreasing the Young’s modulus of the material, mainly analyzing the outgoing results and the calculation efficiency.

New practical discrete non-spherical N-body method: Validation with the Brazil nut effect

This paper presents an implementation of the contact dynamics method for discrete non-spherical particles. The algorithm can handle particles with a wide range of geometries as long as they are described in triangular surface meshes. The contact detection between particles is organized into two phases: coarse-grained and fine-grained contact detection. Specifically, different hierarchies of grids are utilized to perform fast contact detection: (a) A spatial sorting method is utilized for coarse-grained contact detection, where each non-spherical particle is represented with a corresponding bounding-sphere (b) The Polygonal Contact Method is introduced into the fine-grained contact detection phase to accurately determine the active contact areas between the interacting particles. These techniques solve the difficulties of determining the action point(s) of contact force and torque between non-spherical particles. The smooth (force-based) method is employed to calculate the contact force and torque, which is generally regarded as conforming to the actual physical process. Particularly, the non-linear Hertz and Mindlin-Deresiewicz theories are adopted to calculate the normal and tangential forces. The non-spherical Brazil nut effect under the shear vibration mode is simulated as validation by comparing with the existing experimental results. The simulation results confirmed that the convection and percolation mechanism mutually affect the nut heap's behavior and finally drive the rise of the Brazil nut from the bottom to the top layer.

Research on size segregation dynamics and processes of a binary mixture dense granular flow

This study employed an experimental approach to investigate the effects of various filling degrees of the granular bed and the rotation speed on size-induced particle segregation behavior in an almost fully filled double-walled rotating drum. The distributions of the concentrations of bicolor particles in the system were obtained via image processing to determine the segregation state. The dynamics of the mixture flow including the statistical distribution, the azimuthal angle and radial direction granular temperature profiles were measured and calculated via particle-tracking velocimetry (PTV). The results were similar for the Brazil-nut effect and its reverse in the radial direction at high or low rotation speeds. When the rotation speed or filling degree was changed, the effect on two different particle sizes in the binary mixture system was inconsistent, and different flow mechanisms led to different segregation patterns. Two phase diagrams with the rotation speed and filling degree and the magnitude and position of the maximum granular temperature as the space enabled the prediction of segregation states.

Multiscale Brazil nut effects in bioturbated sediment

Size segregation in granular materials is a universal phenomenon popularly known as the Brazil nut effect (BNE), from the tendency of larger nuts to end on the top of a shaken container. In nature, fast granular flows bear many similarities with well-studied mixing processes. Instead, much slower phenomena, such as the accumulation of ferromanganese nodules (FN) on the seafloor, have been attributed to the BNE but remain essentially unexplained. Here we document, for the first time, the BNE on sub-millimetre particles in pelagic sediment and propose a size segregation model for the surface mixed layer of bioturbated sediments. Our model explains the size distribution of FN seeds, pointing to a uniform segregation mechanism over sizes ranging from < 1 mm to > 1 cm, which does not depend on selective ingestion by feeding organisms. In addition to explaining FN nucleation, our model has important implications for microfossil dating and the mechanism underlying sedimentary records of the Earth’s magnetic field.

Successful Consolidation of Inoculant Alloy by Controlling Brazil Nut Effect and Capillary Force

Successful Consolidation of Inoculant Alloy by Controlling Brazil Nut Effect and Capillary Force

Large-deviation quantification of boundary conditions on the Brazil nut effect

We present a discrete element method study of the uprising of an intruder immersed in a granular media under vibration, also known as the Brazil Nut Effect. Besides confirming granular ratcheting and convection as leading mechanisms to this odd behavior, we evince the role of the resonance on the rising of the intruder by using periodic boundary conditions (pbc) in the horizontal direction to avoid wall-induced convection. As a result, we obtain a resonance-qualitylike curve of the intruder ascent rate as a function of the external frequency, which is verified for different values of the inverse normalized gravity Γ, as well as the system size. In addition, we introduce a large deviation function analysis which displays a remarkable difference for systems with walls or pbc.

Particle size segregation in two-dimensional circular granular aggregates.

Although many previous studies have focused on the Brazil nut effect, segregation in a self-gravitating circular aggregate remains relatively unexplored. In this paper, size segregation in a two-dimensional assembly of grains in a circular geometry is studied through discrete element method (DEM) numerical simulations. We show that radial segregation within an asteroid submitted to periodic perturbations is not limited to the surface but also occurs in its core. The characteristic time and the overall efficiency of the segregation mechanism are studied as the intensity of the perturbation, the frictional properties, and rotational freedom of individual grains are varied.

Vibration induced segregation of single large particles

The vibration-induced segregation (e.g., rising of one large intruder - so called Brazil Nut Effect (BNE)) is studied by discrete element method. Vibration frequency and amplitude are two dominating factors in the occurrence of BNE and a phase diagram is constructed. For fixed vibration amplitude, segregation only occurs when vibration frequency is within a certain range. Larger vibration amplitude can expand the range of vibration frequency for BNE. Size ratio and the intruder shape are studied under certain vibration conditions. Larger size ratio can enlarge the segregation intensity. The shape of the intruder influences the segregation process by the intruder′s orientation. Standing-like initial orientation can increase the time required for the intruder to reach the top while lying-like initial orientation cannot significantly affect the vertical segregation.