Bed Composition Research Articles

Largest Lyapunov exponent and Shannon entropy: Two indices to analyze mixing in fluidized beds

The quality of mixing in fluidized beds greatly influences performance in many applications. Assessing quality of mixing involves measuring the mixing rate and evaluating the bed mixedness. Quantifying the bed mixedness is typically done using mixing indices. However, the application of existing mixing indices to fluidized beds can be problematic due to aeration and complications from the particle phase in the Two-Fluid Model (TFM).The objectives of this study are twofold. First, the largest Lyapunov exponent is proposed to quantify mixing in fluidized beds. Its effectiveness is shown on a mono-disperse bed with varying gas velocities. The increase in mixing rate with higher gas velocity is accurately represented by the largest Lyapunov exponent. Second, the Shannon entropy mixing index is adopted to quantify the bed mixedness for TFM results. This index is tested on a bi-disperse bed to predict segregation and evaluate the effect of bed composition and superficial gas velocity on this process. The effect on segregation is reflected in the entropy components: distributional entropy showed minimal variation, whereas conditional entropy was significantly affected. Evaluating bed mixedness at different length scales showed that increasing bin spatial resolution slightly reduced conditional entropy. The results are validated against experimental data.

Modelling the impact of sediment composition on long-term estuarine morphodynamics

Sediment composition, characterized by different contents of cohesive and non-cohesive sediments, is known to play a role on long-term estuarine and deltaic morphodynamics, but the exact impact is poorly understood. We establish a two-dimensional morphodynamic model to investigate the influence of different sediment compositions on the development of a schematic fluvio-deltaic system driven by river and tides. Though excluding the density effects, results suggest that the model captures the development of distributary channels and elongated sand bars with resemblance to that in the Yangtze Estuary. Sensitivity simulations show fundamentally different channel-shoal patterns take shape under different sediment compositions. Ebb dominance and associated seaward sediment flushing lead to faster morphodynamic development and more prograded delta under larger river discharge and sediment supply. We detect a positive correlation between the content of cohesive sediment and the speed of development, particularly cohesive sediment content is <50%. However, when the proportion of mud is larger (i.e., 50–75%), a deceleration of the morphological development occurs after 200 years. A sand-dominated environment exhibits the largest channel numbers and fast channel formation near the mouth within the first 300 morphodynamic years. Spatial distribution of bottom sediments changes with morphology, exhibiting increasing mud deposits near the mouth, whilst the sand remains inside the estuary. This study indicates the importance and need for a more realistic representation of bed compositions in long-term estuarine morphodynamic simulations.

Effects of repeated drawdown flushing on riverbed fine sediment dynamics downstream from a dam

Sediment accumulation in reservoirs is frequently a problem, impelling dam managers to implement strategies such as drawdown flushing to limit siltation. Drawdown and other sediment removal methods may induce riverbed clogging downstream of dams, especially in river sections where water is diverted, thereby reducing transport capacity. In this study, we investigate the effects of drawdown flushing downstream of the Plan d’Arem run-of-the-river dam (Upper Garonne, Spain – France border) using an adaptive inter-site comparison strategy to consider a range of spatial and temporal conditions, which allow us to separate the effects of dam storage and flushing from other potential factors. Drawdown flushing has been undertaken three times during the study period over a short span of time (2 months). We couple bed material sampling, which provides direct information on bed composition, with airborne infrared thermal imaging to better interpret whether fine sediment interstitial storage within the bed is associated with clogging. We also measure bed surface grain size and bed mobility in order to investigate their potential role in controlling fine sediment dynamics. We identify surface grain size and water diversion as the main factors controlling fine sediment spatial distribution, with coarse-grained bed-surfaces and by-passing promoting fine sediment enrichment. As a result, sites located upstream and within the by-passed reached of the Plan d’Arem dam show higher fine sediment interstitial storage than sites downstream from the by-passed reach. Results from thermal imagery demonstrate such interstitial storage does not induce clogging effect. The reaches with the most important sediment storage host a high number of cool-water patches, indicating water exchanges with the hyporheic zone. Post-flushing bed composition indicates systematic export of fine sediments from the bed matrix at all sites after the first operation, afterwards fine levels remain low after the second and the third flushing. The low impact of dam flushing in term of clogging is interpreted by the fact that the interstitial material is very sandy.

Wildfire, extreme precipitation and debris flows, oh my! Channel response to compounding disturbances in a mountain stream in the Upper Colorado Basin, USA

AbstractCompounding changes in climate and human activities stand to increase sediment input to rivers in many landscapes, including via discrete perturbations such as post‐fire debris flows. Because sediment supply is a dominant control on river morphology, understanding mountain river responses to sediment regime perturbations is critical to predicting and addressing downstream effects to infrastructure, water security and aquatic habitat. A growing body of literature explores the causes, likelihood, size and composition of post‐fire debris flows, but the channel response to these disturbances remains poorly studied. This study used repeat field surveys, time‐lapse photographs and pre‐ and post‐disturbance remote sensing datasets to document and analyse space‐ and time‐varying channel response to post‐fire debris flows along a steep mountain stream in the Upper Colorado River Basin, USA. Specifically, we evaluated channel morphology and bed composition changes, correlations between channel changes and valley and channel attributes, and the relative importance of spring snowmelt versus summer monsoon events. Several cross‐sectional channel change types were observed from lidar a month after post‐fire debris‐flow events, including channelized and braided incision into deposits, incision into the pre‐fire channel bed, bank erosion and no change. Channel changes were most correlated with pre‐fire channel width, valley width and unit stream power, and these relationships could be tested in other burned locations to evaluate their transferability. Repeat channel surveys before and after snowmelt indicate rapid recovery and channel narrowing following major sediment disturbances, although sediment deposits remained in the channel margins. Together, these results highlight the importance of field and remote sensing‐based channel surveys to improve understanding of, and potential to predict, mountain channel response to compounding climate disturbances.

Aqueous Photolysis of Water-Soluble Brown Carbon from Simulated Prescribed and Wildfire Biomass Burning.

This work, as part of the Georgia Wildland fire Simulation Experiment (G-WISE) campaign, explores the aqueous photolysis of water-soluble brown carbon (W-BrC) in biomass burning aerosols from the combustion of fuel beds collected from three distinct ecoregions in Georgia: Piedmont, Coastal Plain, and Blue Ridge. Burns were conducted under conditions representative of wildfires, which are common unplanned occurrences in Southeastern forests (low fuel moisture content), and prescribed fires, which are commonly used in forest management (higher fuel moisture content). Upon exposure to radiation from UV lamps equivalent to approximately 5 h in the atmosphere, the absorption spectra of all six samples exhibited up to 40% photobleaching in the UV range (280-400 nm) and as much as 30% photo-enhancement in the visible range (400-500 nm). Together, these two effects reduced the absorption Ångström exponent (AAE), a measure of the wavelength dependence of the spectrum, from 6.0-7.9 before photolysis to 5.0-5.7 after. Electrospray ionization ultrahigh-resolution mass spectrometry analysis shows the potential formation of oligomeric chromophores due to aqueous photolysis. This work provides insight into the impacts that aqueous photolysis has on W-BrC in biomass burning aerosols and its dependence on fuel bed composition and moisture content.

A hot, hydrothermally influenced microbial-tidal flat setting in the Palaeoarchaean Moodies Group, Barberton Greenstone Belt, South Africa

Abstract Sandy, microbial-mat-laminated sediments are common in estuarine and tidal environments of the Palaeoarchean Moodies Group (ca. 3.22 Ga); they are interspersed with numerous expressions of mafic to intermediate (sub-) volcanism, including sills, stockwork dykes, lavas, and air-fall tuffs. We describe abundant fluid-escape structures up to 6 m in height associated with this facies in the Saddleback Syncline of the central Barberton Greenstone Belt. The fluid-escape conduits fed small sand volcanoes during prolonged and/or recurring discharge of gases, liquids, and solids. They are filled by sand, sericitic clay, and fine-grained organic matter of former microbial mats. In comparison to the mean composition of adjacent beds of identical composition, the conduits are enriched in Fe, Cr, Ti, and Mg. This suggests that fluid-escape was not only a consequence of overpressure buildup from decaying microbial mats in the shallow subsurface or of water-level fluctuations but also due to periodic or continuous release of hydrothermal fluids circulating in the thermal aureole above the cooling Lomati River Sill of Moodies age. Such an inference is also supported by textures characteristic of in-place argillaceous and sericitic alteration and by Raman spectroscopy of carbonaceous matter (RSCM) indicating temperatures ca. 50 to 100°C above the regional maximum metamorphic temperature of 320 to 380°C. Pre-compaction carbonate and/or silica cementation also preserved the abundant carbonaceous laminae interpreted as benthic microbial mats. Analogue recent hot spring deposits suggest that surficial hydrothermal activity in the medium-energy siliciclastic tidal zone would have significantly boosted microbial growth.

Effects of bed pumice content on lahar erosion: An example from Changbaishan volcano, China

Understanding the erosion of sediments by lahars contributes to future modeling and hazard assessment. However, studying the erosion mechanism of lahars in the field is challenging due to their suddenness and danger. We conducted a series of experiments to investigate the erosion associated with five different bed sediments (with a volume percentage of pumice ranging from 3%–32%), four channel slopes and released flows with four different discharges. The experiments showed that a pumice content of 32% in the erodible bed induces significant changes in the flow dynamics, erosion patterns, and erosion intensity of lahars. The maximum flow depth and mean velocity of lahars are positively related to the channel slope and discharge and inversely related to the pumice content. The initial peak erosion depth appears at the front of the erodible bed or slightly downstream, with additional erosion peaks occurring in the middle and lower reaches of the bed. The maximum erosion depth shifts from downstream to upstream as the pumice content increases. The erosion intensity of lahars exhibits a positive correlation with the bed pumice content, channel slope, discharge, and shear stress. Increasing the pumice content reduces the bed resistance and enhances the collisional stress and erosion wave effect of lahars, thus intensifying erosion. The pumice upwelling and erosion wave effect result in an irregular profile in the erodible bed. A new entrainment formula for erodible bed containing pumice was developed based on flume tests and theoretical analysis. This study helps to understand the effects of bed composition on lahar erosion and provides new insights into lahar erosion mechanism.

Deciphering Controls of Pore‐Pressure Evolution on Sediment Bed Erosion by Debris Flows

AbstractPore‐fluid pressure (PP) plays an important role in bed erosion, but the mechanisms that control PP evolution and the resulting feedbacks on flow dynamics are unclear. Here, we develop a general formulation, allowing quantification of the propensity for PP evolution of saturated and unsaturated bed sediments. We conduct erosion experiments by systematically varying grain composition and water content of beds, for investigating effects of PP evolution on flow erosion. With increasing water content, PP shows a slight rise in deforming beds with drained behavior but significant larger rise in undrained beds. Regardless of bed composition, the erosion rate of beds presents a synchronous change tendency with PP evolution due to the loss in basal friction. PP instigates positive feedback that induces a remarkable gain of flow velocity and momentum on wet beds with undrained behavior. Our results help explain observations of volume growth and long run out of debris flows.

Measurements of morphodynamics of a sheltered beach along the Dutch Wadden Sea

Abstract. A field campaign was carried out at a sheltered sandy beach with the aim of gaining new insights into the driving processes behind sheltered beach morphodynamics. Detailed measurements of the local hydrodynamics, bed-level changes and sediment composition were collected at a man-made beach on the leeside of the barrier island Texel, bordering the Marsdiep basin that is part of the Dutch Wadden Sea. The dataset consists of (1) current, wave and turbidity measurements from a dense cross-shore array and a 3 km alongshore array; (2) sediment composition data from beach surface samples; (3) high-temporal-resolution RTK-GNSS beach profile measurements; (4) a pre-campaign spatially covering topobathy map; and (5) meteorological data. This paper outlines how these measurements were set up and how the data have been processed, stored and can be accessed. The novelty of this dataset lies in the detailed approach to resolve forcing conditions on a sheltered beach, where morphological evolution is governed by a subtle interplay between tidal and wind-driven currents, waves and bed composition, primarily due to the low-energy (near-threshold) forcing. The data are publicly available at 4TU Centre for Research Data at: https://doi.org/10.4121/19c5676c-9cea-49d0-b7a3-7c627e436541 (Van der Lugt et al., 2023).

Adhesion Testing Device for 3D Printed Objects on Diverse Printing Bed Materials: Design and Evaluation

The persistent challenge of adhesion in Fused Filament Fabrication (FFF) technology is deeply rooted in the mechanical and chemical properties of utilized materials, necessitating the exploration of potential resolutions. This involves adjustments targeting the interplay of printing parameters, the mechanical fortification of print beds, and the integration of more adhesive materials, resonating across user levels, from enthusiasts to complex industrial configurations. An in-depth investigation is outlined in this paper, detailing the plan for a systematically designed device. Engineered for FFF device installation, the device facilitates the detachment of printed models, while precisely recording the detachment process, capturing the maximum force, and its progression over time. The primary objective is fabricating a comprehensive measurement apparatus, created for adhesion assessment. The device is adaptable across diverse FFF machines and print bed typologies, conforming to pre-defined conditions, with key features including compactness, facile manipulability, and capacity for recurrent measurements. This pursuit involves evaluating adhesion levels in prints made from diverse materials on varying print bed compositions, aiming to establish a comprehensive database. This repository facilitates judicious material and bed type selection, emphasizing maximal compatibility. Emphasis is placed on operating within a thermally stable context, a pivotal prerequisite for consistent and reproducible results.

Production of light olefins from methanol using catalytic fixed bed reactor with different catalytic bed composition

Methanol to olefin conversion has captured the attention of the industry as olefins are feed material to many polymer industries. In this work methanol conversion to olefins was investigated over beds of (i) physical mixture of metal oxides with ZSM-5 (PMB) and (ii) metal impregnated over ZSM-5 (MLB). ZSM-5 used in the current study was pre modified by boric acid treatment for modifying catalytic active site composition. Two different metals from alkaline series: calcium and magnesium & from transition metal series: iron and copper were selected. PMB studies were performed on 1:1 (by weight) metal oxides and BZSM-5 whereas for MLB studies, 10 % metal was loaded. Performance studies of the two different bed composition were performed at 500°C, 100 ml/min N2 flow with 1 g catalyst in a fixed bed reactor. 100 % conversion was obtained on MLB studies in presence of Cu, Mg and Fe whereas in PMB studies, 100 % conversion could be obtained over FeO+BZSM-5 bed. The order of olefins yield obtained was in the following order: BZSM-5 > Mg/BZSM-5 > Cu/BZSM-5 > CuO+BZSM-5 > CaO+BZSM-5 > Fe/BZSM-5 > FeO+BZSM-5 > CaO+BZSM-5 > MgO+BZSM-5. It was observed that maximum methane yield was obtained in presence of physical mixture. Gaseous products other than olefins with high composition of C1–C4 hydrocarbons were formed in presence of Mg and Ca whereas the metal impregnated modified-ZSM-5 produced higher content of olefins with Cu loaded catalysts in both bed composition. Metal impregnated catalysts as well as physical mixtures were characterized by BET, FTIR and XRD, FESEM for surface area, topology, crystallinity etc. Spent catalysts were characterized for coke deposition using TGA.

Composition, distribution and biometric aspects of sea grasses beds along the Sudanese red sea coast

Composition, distribution and biometric aspects of sea grasses beds along the Sudanese red sea coast

Artificial intelligence prediction and thermodynamic analysis on particle agglomeration/defluidization during waste incineration: Effect of sand bed composition and agglomeration indices

In the incineration process, agglomeration is caused by the combustion of wastes containing adhesion materials such as alkalis and earth alkalis. Alkali oxides not only have a low melting point but also can react with Si to form low-melting-point eutectics. Most of the researches focused on the inlet materials, however, the properties of sand bed materials are also playing an important role on defluidization process. A comprehensive analysis of sand compositions on the prediction of defluidization tendency is carried out. Variation of sand properties before and after fluidized bed operation is estimated by XRF characterization, and the effect of particle size distribution is also in consideration. Experimental results indicated that defluidization time decreases with the increasing particle size of all sand sources. Higher temperature promotes agglomeration/defluidization. According to the agglomeration indices calculation, indicator Al + Ca + Mg/(Na + K + Fe) can be used to estimate the defluidization tendency before fluidized bed operation for particle sizes below 770 μm. In contrast, for a particle size of 920 μm, Al + Ca + Mg + Fe /(Na + K) can be utilized to qualitatively characterize the defluidization time. On the other hand, the Support Vector Regression (SVR) model was the best model for predicting the defluidization time (R2 of 93.40% and MSE of 3470). Causal analysis shows particle size, K2O, and Na2O were the top three most important factors that affect the particle agglomeration. The results are helpful to the evaluation of the agglomeration tendency of sand bed materials before using fluidized bed waste incineration agglomeration in terms of qualitative analysis and quantitative analysis.

How Bed Composition Affects Erosion by Debris Flows—An Experimental Assessment

AbstractA solid physical understanding of debris‐flow erosion is needed for both hazard prediction and understanding landscape evolution. However, the processes and forces involved in erosion by debris flows and especially how the erodible surface itself influences erosion are poorly understood. Here, we experimentally investigate the effects of bed composition on debris‐flow erosion, by systematically varying the composition of an erodible bed in a small‐scale debris‐flow flume. The experiments show that water and clay content of an unconsolidated bed significantly control erosion magnitude by affecting the transfer of pore pressure, loading conditions, and contraction‐dilation behavior of the bed. As the water content increases and the bed comes close to saturation, erosion increases rapidly, whereas for clay content an optimum for erosion exists around a clay content of 3%–4%. Our results show that small variations in bed composition can have large effects on debris‐flow erosion, and thus volume growth and hazard potential.

Influence of the Adsorption Bed Composition on the Low-Pressure Fluidization

The paper presents an innovative concept of the fluidization of an adsorption bed carried out under low-pressure conditions. Additionally, different bed mixes were used to test the effects of the bed composition on fluidization. Fluidization was caused by the pressure difference and the velocity of the flowing water vapor. These features make the research presented in this article significantly different from other studies known in the literature and constitute the main novelty of the paper. Silica gel with a particle diameter of 200–250 µm (Geldart group B) with aluminum and carbon nanotube additives was fluidized under reduced pressure (10–25 mbar). The pressure difference results in the flow of water vapor and, consequently, induces fluidization. The pressure in the evaporator was approx. 10 mbar, while in the reaction chamber it was approx. 25 mbar. The pressure difference of about 10–15 mbar allows for a flow of water vapor between the evaporator and the reaction chamber. During the tests, the pressures, temperatures and mass were measured. The pressure drop in the bed was closely related to the mass change in the fluidized bed.

Chopped straw and coffee husks affect bedding chemical composition and the performance and foot pad condition of broiler chickens

Bedding material is a crucial environmental factor for chickens. Coffee husks are waste from the industry that could be reused. The study aimed to analyze the chemical composition of various bedding types and assess their impact on the performance characteristics of broiler chickens and the incidence of footpad dermatitis (FPD). Ross 308 broilers were used in the study. Birds were divided into 3 groups (216 chickens, 72 per group). Group 1 was kept on chopped straw (S). Group 2 was kept on coffee husks (CHs), and the 3rd group (PB) was kept on pellet bedding made from S and CHs in a 1:1 ratio. The dry matter (DM), crude fiber (CF), nitrogen (N), phosphorus (P), potassium (K) content, and the pH of the bedding were analyzed. Production results were examined during 42 days of rearing. FPD was assessed on a point scale. The tissue composition of the carcasses and qualitative physicochemical characteristics of the meat (pH, color, water holding capacity, drip loss) and bone-breaking strength were analyzed. Straw had a higher CF content. In total, the highest N content in CHs was noticed. P content was lower in the S, and K was the highest in the CHs group, followed by S and PB. The pH of the bedding was lower in the CHs group, higher in PB, and highest in S bedding. The DM was decreasing within the days of rearing. A significant interaction was demonstrated between the type of bedding and rearing days on the bedding (manure) composition. On days 1–14, FCR deteriorated in the PB group compared to the S group. The presence of FPD was significantly lower in the PB group than in the others. In the PB group, chickens had a higher slaughter yield than in the S group and a lower weight and liver share than in the CHs group. The weight and proportion of abdominal fat were higher in the group kept on S than on CHs. It can be concluded that coffee husks as a component of pellets had a beneficial effect on reducing FPD in chickens and their slaughter yield and enriched bedding with nutrients, which with poultry manure, could be a good fertilizer for agricultural soils after rearing. It could be recommended to use pelleted bedding.

Uncertainties in Models Predicting Critical Bed Shear Stress of Cohesionless Particles

Our data show large scatter in the critical Shields stress values for initial sediment motion. The main sources of dispersion are related to the methodological procedures defining the inception of movement (i.e., visual observations or extrapolation of sediment transport rate) and to the estimation of the bed shear stress. The threshold for sediment motion varies with many factors related not only to grain size but also to bed composition (e.g., presence of fine sediments in a coarse matrix), arrangement (e.g., bed roughness, grain orientation, and characteristic lengths of bed structures) and slope. New models to estimate the critical Shields number are proposed using grain size or bed slope or a combination of both. Model parameters and uncertainty are estimated through Bayesian inference using prior knowledge of these parameters and measured data. Apart from the uncertainty in observations, two types of uncertainty can be evaluated: one related to the parameter estimation (i.e., parametric) and one related to the choice of the model (i.e., structural). Finally, a four-parameter model based on the grain size and bed slope yields the best results and demonstrates potential interaction between these two parameters. Model uncertainty, however, remains large, which indicates that other input parameters may be needed to improve the proposed model.

Analytical Model for Graded Sediment Transport in Velocity‐ and Acceleration‐Skewed Oscillatory Sheet Flow

AbstractAn analytical model is proposed for graded sediment transport in velocity‐ and acceleration‐skewed oscillatory sheet flow. The model consists of periodic velocity and sediment concentration formulae over a mobile sediment bed. An active layer is set below the mobile sediment bed level to handle erosion differences among size fractions. The model accounts for velocity phase lead, sediment phase lag, velocity and acceleration asymmetries, and gradation effects. The model is validated using datasets of velocity, concentration, sediment flux, and transport rate. Better performance is obtained by the model when compared to previous formulae. Discussion is conducted for net boundary layer flow, total, and fractional sediment fluxes under both velocity‐ and acceleration‐skewed oscillatory flows, and the result shows the existence of inhibited or promoted transport for different size fractions. The model is applied to describe the sediment size grading curve at different levels. The composition of transported sediment is different from the initial bed composition. The fining of sediment above the initial bed and the coarse below the initial bed are reproduced by the model, which reveals the vertical sorting processes at different locations. Meanwhile, interactions between fractions are substantial in the sheet flow layer but are insignificant in the suspension layer. The model is suitable for non‐cohesive sediment mixtures consisting of fine, medium, and coarse proportions and has implications for predicting nearshore‐graded sediment transport and sorting processes.

Caulerpa cylindracea Spread on Deep Rhodolith Beds Can Be Influenced by the Morphostructural Composition of the Bed

The green alga Caulerpa cylindracea Sonder (Chlorophyta; Bryopsidales) is one of the most invasive alien macroalgae in the Mediterranean Sea, where it is also spreading on rhodolith beds, an important biogenic assemblage typical of deep substrates. Despite the importance of rhodoliths, data on the competitive interactions with C. cylindracea are still scarce. To deepen the knowledge on the topic, C. cylindracea occurrence on the rhodolith bed of Capo Carbonara Marine Protected Area (Italy) was explored. Quantitative analyses of videoframes obtained from Remote Operated Vehicle records in three different MPA sites, Is Piscadeddus, Santa Caterina, and Serpentara, allow for estimates of both the cover of rhodoliths (considering the main morphotypes) and of C. cylindracea, as well as their competition. All sites showed a well-developed rhodolith bed, although some differences were highlighted in their composition in terms of morphotype, shape, and dimension of rhodoliths, as well as in the C. cylindracea cover. In particular, Santa Caterina appeared to be the site with the highest mean total cover of rhodoliths (68%), and of C. cylindracea (25%). The obtained results suggest that different competitive interactions occur between C. cylindracea and rhodolith beds, in relation to the morphostructural composition of the latter and in response to environmental conditions that affect rhodolith bed composition.

Effect of system composition on mixing in binary fluidised beds

The influence of bed composition – that is, the relative proportions of different components – on the mixing of fluidised beds containing mixtures of Geldart group B and D particles is of considerable importance to a variety of contemporary industrial processes, such as plastic recycling and biomass gasification. In this study, we use Positron Emission Particle Tracking (PEPT) to analyse the detailed, three-dimensional flow dynamics of such a system and, from these measurements, determine the rate of mixing as a function of bed composition. Our results show that for comparatively small fractions (ϕD≲30%) of Group D particles, the system’s mixing dynamics are only weakly affected by variations in ϕD. For higher concentrations, however, the mixing effectiveness of the system is observed to decrease sharply, and marked changes in the system’s flow patterns are observed, with a previously undocumented meta-stable state recorded for the highest concentrations of group D particles.