Synthesis of biomass derived carbon materials for environmental engineering and energy storage applications

NASA Astrophysics Data System (ADS)

Huggins, Mitchell Tyler

Biomass derived carbon (BC) can serve as an environmentally and cost effective material for both remediation and energy production/storage applications. The use of locally derived biomass, such as unrefined wood waste, provides a renewable feedstock for carbon material production compared to conventional unrenewable resources like coal. Additionally, energy and capital cost can be reduced through the reduction in transport and processing steps and the use of spent material as a soil amendment. However, little work has been done to evaluate and compare biochar to conventional materials such as granular activated carbon or graphite in advanced applications of Environmental Engineering. In this work I evaluated the synthesis and compared the performance of biochar for different applications in wastewater treatment, nutrient recovery, and energy production and storage. This includes the use of biochar as an electrode and filter media in several bioelectrochemical systems (BES) treating synthetic and industrial wastewater. I also compared the treatment efficiency of granular biochar as a packed bed adsorbent for the primary treatment of high strength brewery wastewater. My studies conclude with the cultivation of fungal biomass to serve as a template for biochar synthesis, controlling the chemical and physical features of the feedstock and avoiding some of the limitations of waste derived materials.

Use of municipal solid waste incineration bottom ashes in alkali-activated materials, ceramics and granular applications: A review.

PubMed

Silva, R V; de Brito, J; Lynn, C J; Dhir, R K

2017-10-01

This paper presents a literature review on the incorporation of municipal solid waste incinerated bottom ash as raw material in several markets, other than those where it is conventionally used, such as geotechnical applications and road pavement construction. The main findings of an ample selection of experimental investigations on the use of the bottom ash as precursor of alkali-activated materials, as an adsorbent material for the removal of hazardous elements from wastewater and landfill gases, as soil replacement in agricultural activities, as partial or complete substitute of raw materials for the manufacture of ceramic-based products, as landfill cover and as biogas production enhancer, were gathered, collated and analysed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Performance of the Fluidized Bed Steam Reforming Product Under Hydraulically Unsaturated Conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neeway, James J.; Qafoku, Nikolla; Williams, Benjamin D.

2014-05-01

Currently, several candidates for secondary waste immobilization at the Hanford site in the State of Washington, USA are being considered. To demonstrate the durability of the product in the unsaturated Integrated Disposal Facility (IDF) at the site, a series of tests have been performed one of the candidate materials using the Pressurized Unsaturated Flow (PUF) system. The material that was tested was the Fluidized Bed Steam Reformer (FBSR) granular product and the granular product encapsulated in a geopolymer matrix. The FBSR product is composed primarily of an insoluble sodium aluminosilicate matrix with the dominant phases being feldspathoid minerals mostly nepheline,more » sodalite, and nosean. The PUF test method allows for the accelerated weathering of materials, including radioactive waste forms, under hydraulically unsaturated conditions, thus mimicking the open-flow and transport properties that most likely will be present at the IDF. The experiments show a trend of decreasing tracer release as a function of time for several of the elements released from the material including Na, Si, Al, and Cs. However, some of the elements, notably I and Re, show a steady release throughout the yearlong test. This result suggests that the release of these minerals from the sodalite cage occurs at a different rate compared with the dissolution of the predominant nepheline phase.« less

Radioactive Demonstrations Of Fluidized Bed Steam Reforming (FBSR) With Hanford Low Activity Wastes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jantzen, C. M.; Crawford, C. L.; Burket, P. R.

Several supplemental technologies for treating and immobilizing Hanford low activity waste (LAW) are being evaluated. One immobilization technology being considered is Fluidized Bed Steam Reforming (FBSR) which offers a low temperature (700-750?C) continuous method by which wastes high in organics, nitrates, sulfates/sulfides, or other aqueous components may be processed into a crystalline ceramic (mineral) waste form. The granular waste form produced by co-processing the waste with kaolin clay has been shown to be as durable as LAW glass. The FBSR granular product will be monolithed into a final waste form. The granular component is composed of insoluble sodium aluminosilicate (NAS)more » feldspathoid minerals such as sodalite. Production of the FBSR mineral product has been demonstrated both at the industrial, engineering, pilot, and laboratory scales on simulants. Radioactive testing at SRNL commenced in late 2010 to demonstrate the technology on radioactive LAW streams which is the focus of this study.« less

INTERPRETATION OF SPLP RESULTS FOR ASSESSING RISK TO GROUNDWATER FROM LAND-APPLIED GRANULAR WASTE

EPA Science Inventory

Scientists and engineers often rely on results from the synthetic precipitation leaching procedure (SPLP) to assess the risk of groundwater contamination posed by the land application of granular solid wastes. The concentrations of pollutants in SPLP leachate can be measured and ...

Properties of lightweight cement-based composites containing waste polypropylene

NASA Astrophysics Data System (ADS)

Záleská, Martina; Pavlíková, Milena; Pavlík, Zbyšek

2016-07-01

Improvement of buildings thermal stability represents an increasingly important trend of the construction industry. This work aims to study the possible use of two types of waste polypropylene (PP) for the development of lightweight cement-based composites with enhanced thermal insulation function. Crushed PP waste originating from the PP tubes production is used for the partial replacement of silica sand by 10, 20, 30, 40 and 50 mass%, whereas a reference mixture without plastic waste is studied as well. First, basic physical and thermal properties of granular PP random copolymer (PPR) and glass fiber reinforced PP (PPGF) aggregate are studied. For the developed composite mixtures, basic physical, mechanical, heat transport and storage properties are accessed. The obtained results show that the composites with incorporated PP aggregate exhibit an improved thermal insulation properties and acceptable mechanical resistivity. This new composite materials with enhanced thermal insulation function are found to be promising materials for buildings subsoil or floor structures.

Radiochemical Analyses of the Filter Cake, Granular Activated Carbon, and Treated Ground Water from the DTSC Stringfellow Superfund Site Pretreatment Plant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Esser, B K; McConachie, W; Fischer, R

2005-09-16

The Department of Toxic Substance Control (DTSC) requested that Lawrence Livermore National Laboratory (LLNL) evaluate the treatment process currently employed at the Department's Stringfellow Superfund Site Pretreatment Plant (PTP) site to determine if wastes originating from the site were properly managed with regards to their radioactivity. In order to evaluate the current management strategy, LLNL suggested that DTSC characterize the effluents from the waste treatment system for radionuclide content. A sampling plan was developed; samples were collected and analyzed for radioactive constituents. Following is brief summary of those results and what implications for waste characterization may be made. (1) Themore » sampling and analysis provides strong evidence that the radionuclides present are Naturally Occurring Radioactive Material (NORM). (2) The greatest source of radioactivity in the samples was naturally occurring uranium. The sample results indicate that the uranium concentration in the filter cake is higher than the Granular Activated Carbon (GAC) samples. (11 -14 and 2-6 ppm respectively). (3) No radiologic background for geologic materials has been established for the Stringfellow site, and comprehensive testing of the process stream has not been conducted. Without site-specific testing of geologic materials and waste process streams, it is not possible to conclude if filter cake and spent GAC samples contain radioactivity concentrated above natural background levels, or if radionuclides are being concentrated by the waste treatment process. Recommendation: The regulation of Technologically Enhanced, Naturally Occurring Radioactive Materials (T-NORM) is complex. Since the results of this study do not conclusively demonstrate that natural radioactive materials have not been concentrated by the treatment process it is recommended that the DTSC consult with the Department of Health Services (DHS) Radiological Health Branch to determine if any further action is warranted. If it were deemed desirable to establish a background for the Stringfellow setting LLNL would recommend that additional samples be taken and analyzed by LLNL using the same methods presented in this report.« less

En masse pyrolysis of flexible printed circuit board wastes quantitatively yielding environmental resources.

PubMed

Kim, Jang Won; Lee, Albert S; Yu, Seunggun; Han, Jeong Whan

2018-01-15

This paper reports the recycling of flexible printed circuit board (FPCB) waste through carbonization of polyimide by dual pyrolysis processes. The organic matter was recovered as pyrolyzed oil at low temperatures, while valuable metals and polyimide-derived carbon were effectively recovered through secondary high temperature pyrolysis. The major component of organics extracted from FPCB waste comprised of epoxy resins were identified as pyrolysis oils containing bisphenol-A. The valuable metals (Cu, Ni, Ag, Sn, Au, Pd) in waste FPCB were recovered as granular shape and quantitatively analyzed via ICP-OES. In attempt to produce carbonaceous material with increased degree of graphitization at low heat-treatment conditions, the catalytic effect of transition metals within FPCB waste was investigated for the efficient carbonization of polyimide films. The morphology of the carbon powder was observed by scanning electron microscopy and graphitic carbonization was investigated with X-ray analysis. The protocols outlined in this study may allow for propitious opportunities to salvage both organic and inorganic materials from FPCB waste products for a sustainable future. Copyright © 2017 Elsevier B.V. All rights reserved.

Radioactive Demonstration Of Mineralized Waste Forms Made From Hanford Low Activity Waste (Tank SX-105, Tank AN-103, And AZ-101/102) By Fluidized Bed Steam Reformation (FBSR)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jantzen, C. M.; Crawford, C. L.; Bannochie, C. J.

Fluidized Bed Steam Reforming (FBSR) is a robust technology for the immobilization of a wide variety of radioactive wastes. Applications have been tested at the pilot scale for the high sodium, sulfate, halide, organic and nitrate wastes at the Hanford site, the Idaho National Laboratory (INL), and the Savannah River Site (SRS). Due to the moderate processing temperatures, halides, sulfates, and technetium are retained in mineral phases of the feldspathoid family (nepheline, sodalite, nosean, carnegieite, etc). The feldspathoid minerals bind the contaminants such as Tc-99 in cage (sodalite, nosean) or ring (nepheline) structures to surrounding aluminosilicate tetrahedra in the feldspathoidmore » structures. The granular FBSR mineral waste form that is produced has a comparable durability to LAW glass based on the short term PCT testing in this study, the INL studies, SPFT and PUF testing from previous studies as given in the columns in Table 1-3 that represent the various durability tests. Monolithing of the granular product was shown to be feasible in a separate study. Macro-encapsulating the granular product provides a decrease in leaching compared to the FBSR granular product when the geopolymer is correctly formulated.« less

Aggregate material formulated with MSWI bottom ash and APC fly ash for use as secondary building material.

PubMed

del Valle-Zermeño, R; Formosa, J; Chimenos, J M; Martínez, M; Fernández, A I

2013-03-01

The main goal of this paper is to obtain a granular material formulated with Municipal Solid Waste Incineration (MSWI) bottom ash (BA) and air pollution control (APC) fly ash to be used as secondary building material. Previously, an optimum concrete mixture using both MSWI residues as aggregates was formulated. A compromise between the environmental behavior whilst maximizing the reuse of APC fly ash was considered and assessed. Unconfined compressive strength and abrasion resistance values were measured in order to evaluate the mechanical properties. From these results, the granular mixture was not suited for certain applications owing to the high BA/APC fly ash content and low cement percentages used to reduce the costs of the final product. Nevertheless, the leaching test performed showed that the concentrations of all heavy metals were below the limits established by the current Catalan legislation for their reutilization. Therefore, the material studied might be mainly used in embankments, where high mechanical properties are not needed and environmental safety is assured. Copyright © 2012 Elsevier Ltd. All rights reserved.

Enhancing anaerobic digestion of complex organic waste with carbon-based conductive materials.

PubMed

Dang, Yan; Holmes, Dawn E; Zhao, Zhiqiang; Woodard, Trevor L; Zhang, Yaobin; Sun, Dezhi; Wang, Li-Ying; Nevin, Kelly P; Lovley, Derek R

2016-11-01

The aim of this work was to study the methanogenic metabolism of dog food, a food waste surrogate, in laboratory-scale reactors with different carbon-based conductive materials. Carbon cloth, carbon felt, and granular activated carbon all permitted higher organic loading rates and promoted faster recovery of soured reactors than the control reactors. Microbial community analysis revealed that specific and substantial enrichments of Sporanaerobacter and Methanosarcina were present on the carbon cloth surface. These results, and the known ability of Sporanaerobacter species to transfer electrons to elemental sulfur, suggest that Sporanaerobacter species can participate in direct interspecies electron transfer with Methanosarcina species when carbon cloth is available as an electron transfer mediator. Copyright © 2016 Elsevier Ltd. All rights reserved.

Stimulation of the anaerobic digestion of the dry organic fraction of municipal solid waste (OFMSW) with carbon-based conductive materials.

PubMed

Dang, Yan; Sun, Dezhi; Woodard, Trevor L; Wang, Li-Ying; Nevin, Kelly P; Holmes, Dawn E

2017-08-01

Growth of bacterial and archaeal species capable of interspecies electron exchange was stimulated by addition of conductive materials (carbon cloth or granular activated carbon (GAC)) to anaerobic digesters treating dog food (a substitute for the dry-organic fraction of municipal solid waste (OFMSW)). Methane production (772-1428mmol vs <80mmol), volatile solids removal (78%-81% vs 54%-64%) and COD removal efficiencies (∼80% vs 20%-30%) were all significantly higher in reactors amended with GAC or carbon cloth than controls. OFMSW degradation was also significantly accelerated and VFA concentrations were substantially lower in reactors amended with conductive materials. These results suggest that both conductive materials (carbon cloth and GAC) can promote conversion of OFMSW to methane even in the presence of extremely high VFA concentrations (∼500mM). Copyright © 2017 Elsevier Ltd. All rights reserved.

Engineering water repellency in granular materials for ground applications

NASA Astrophysics Data System (ADS)

Lourenco, Sergio; Saulick, Yunesh; Zheng, Shuang; Kang, Hengyi; Liu, Deyun; Lin, Hongjie

2017-04-01

Synthetic water repellent granular materials are a novel technology for constructing water-tight barriers and fills that is both inexpensive and reliant on an abundant local resource - soils. Our research is verifying its stability, so that perceived risks to practical implementation are identified and alleviated. Current ground stabilization measures are intrusive and use concrete, steel, and glass fibres as reinforcement elements (e.g. soil nails), so more sustainable approaches that require fewer raw materials are strongly recommended. Synthetic water repellent granular materials, with persistent water repellency, have been tested for water harvesting and proposed as landfill and slope covers. By chemically, physically and biologically adjusting the magnitude of water repellency, they offer the unique advantage of controlling water infiltration and allow their deployment as semi-permeable or impermeable materials. Other advantages include (1) volumetric stability, (2) high air permeability and low water permeability, (3) suitability for flexible applications (permanent and temporary usage), (4) improved adhesion aggregate-bitumen in pavements. Application areas include hydraulic barriers (e.g. for engineered slopes and waste containment), pavements and other waterproofing systems. Chemical treatments to achieve water repellency include the use of waxes, oils and silicone polymers which affect the soil particles at sub-millimetric scales. To date, our research has been aimed at demonstrating their use as slope covers and establishing the chemical compounds that develop high and stable water repellency. Future work will determine the durability of the water repellent coatings and the mechanics and modelling of processes in such soils.

Granular flow: Dry and wet

NASA Astrophysics Data System (ADS)

Mitarai, N.; Nakanishi, H.

2012-04-01

Granular material is a collection of macroscopic particles that are visible with naked eyes. The non-equilibrium nature of the granular materials makes their rheology quite different from that of molecular systems. In this minireview, we present the unique features of granular materials focusing on the shear flow of dry granular materials and granule-liquid mixture.

Impact Compaction of a Granular Material

NASA Astrophysics Data System (ADS)

Fenton, Gregg; Asay, Blaine; Todd, Steve; Grady, Dennis

2017-06-01

The dynamic behavior of granular materials has importance to a variety of engineering applications. Although, the mechanical behavior of granular materials have been studied extensively for several decades, the dynamic behavior of these materials remains poorly understood. High-quality experimental data are needed to improve our general understanding of granular material compaction physics. This paper describes how an instrumented plunger impact system can be used to measure the compaction process for granular materials at high and controlled strain rates and subsequently used for computational modelling. The experimental technique relies on a gas-gun driven plunger system to generate a compaction wave through a volume of granular material. This volume of material has been redundantly instrumented along the bed length to track the progression of the compaction wave, and the piston displacement is measured with Photon Doppler Velocimetry (PDV). Using the gathered experimental data along with the initial material tap density, a granular material equation of state can be determined.

Process and equipment development for hot isostatic pressing treatability study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bateman, Ken; Wahlquist, Dennis; Malewitz, Tim

2015-03-01

Battelle Energy Alliance (BEA), LLC, has developed processes and equipment for a pilot-scale hot isostatic pressing (HIP) treatability study to stabilize and volume reduce radioactive calcine stored at Idaho National Laboratory (INL). In 2009, the U. S. Department of Energy signed a Record of Decision with the state of Idaho selecting HIP technology as the method to treat 5,800 yd^3 (4,400 m^3) of granular zirconia and alumina calcine produced between 1953 and 1992 as a waste byproduct of spent nuclear fuel reprocessing. Since the 1990s, a variety of radioactive and hazardous waste forms have been remotely treated using HIP withinmore » INL hot cells. To execute the remote process at INL, waste is loaded into a stainless-steel or aluminum can, which is evacuated, sealed, and placed into a HIP furnace. The HIP simultaneously heats and pressurizes the waste, reducing its volume and increasing its durability. Two 1 gal cans of calcine waste currently stored in a shielded cask were identified as candidate materials for a treatability study involving the HIP process. Equipment and materials for cask-handling and calcine transfer into INL hot cells, as well as remotely operated equipment for waste can opening, particle sizing, material blending, and HIP can loading have been designed and successfully tested. These results demonstrate BEA’s readiness for treatment of INL calcine.« less

Contactor/filter improvements

DOEpatents

Stelman, David

1989-01-01

A contactor/filter arrangement for removing particulate contaminants from a gaseous stream includes a housing having a substantially vertically oriented granular material retention member with upstream and downstream faces, a substantially vertically oriented microporous gas filter element, wherein the retention member and the filter element are spaced apart to provide a zone for the passage of granular material therethrough. The housing further includes a gas inlet means, a gas outlet means, and means for moving a body of granular material through the zone. A gaseous stream containing particulate contaminants passes through the gas inlet means as well as through the upstream face of the granular material retention member, passing through the retention member, the body of granular material, the microporous gas filter element, exiting out of the gas outlet means. Disposed on the upstream face of the filter element is a cover screen which isolates the filter element from contact with the moving granular bed and collects a portion of the particulates so as to form a dust cake having openings small enough to exclude the granular material, yet large enough to receive the dust particles. In one embodiment, the granular material is comprised of prous alumina impregnated with CuO, with the cover screen cleaned by the action of the moving granular material as well as by backflow pressure pulses.

Spatio-structural granularity of biological material entities

PubMed Central

2010-01-01

Background With the continuously increasing demands on knowledge- and data-management that databases have to meet, ontologies and the theories of granularity they use become more and more important. Unfortunately, currently used theories and schemes of granularity unnecessarily limit the performance of ontologies due to two shortcomings: (i) they do not allow the integration of multiple granularity perspectives into one granularity framework; (ii) they are not applicable to cumulative-constitutively organized material entities, which cover most of the biomedical material entities. Results The above mentioned shortcomings are responsible for the major inconsistencies in currently used spatio-structural granularity schemes. By using the Basic Formal Ontology (BFO) as a top-level ontology and Keet's general theory of granularity, a granularity framework is presented that is applicable to cumulative-constitutively organized material entities. It provides a scheme for granulating complex material entities into their constitutive and regional parts by integrating various compositional and spatial granularity perspectives. Within a scale dependent resolution perspective, it even allows distinguishing different types of representations of the same material entity. Within other scale dependent perspectives, which are based on specific types of measurements (e.g. weight, volume, etc.), the possibility of organizing instances of material entities independent of their parthood relations and only according to increasing measures is provided as well. All granularity perspectives are connected to one another through overcrossing granularity levels, together forming an integrated whole that uses the compositional object perspective as an integrating backbone. This granularity framework allows to consistently assign structural granularity values to all different types of material entities. Conclusions The here presented framework provides a spatio-structural granularity framework for all domain reference ontologies that model cumulative-constitutively organized material entities. With its multi-perspectives approach it allows querying an ontology stored in a database at one's own desired different levels of detail: The contents of a database can be organized according to diverse granularity perspectives, which in their turn provide different views on its content (i.e. data, knowledge), each organized into different levels of detail. PMID:20509878

Obtaining of granular fertilizers based on ashes from combustion of waste residues and ground bones using phosphorous solubilization by bacteria Bacillus megaterium.

PubMed

Rolewicz, M; Rusek, P; Borowik, K

2018-06-15

The article presents research results on obtaining phosphorus granulated fertilizers on the basis of microbiologically activated sewage sludge ashes, ground bones and dried blood from meat industry. Granulation tests were carried out using a laboratory pan granulator as well as on an experimental pilot plant. The aim of the studies was to select the proper composition of the mixture of raw materials and binding agents to obtain granulated fertilizers from waste materials such as MSSA and MBM and bacteria lyophilisate. Obtained fertilizer samples were subjected to physical tests (granulation tests etc.) and quality assessment. The tests confirmed that it was possible to produce granulated phosphate fertilizers using the Bacillus megaterium for solubilization of phosphorus in a simple process. Copyright © 2017 Elsevier Ltd. All rights reserved.

Contactor/filter improvements

DOEpatents

Stelman, D.

1988-06-30

A contactor/filter arrangement for removing particulate contaminants from a gaseous stream is described. The filter includes a housing having a substantially vertically oriented granular material retention member with upstream and downstream faces, a substantially vertically oriented microporous gas filter element, wherein the retention member and the filter element are spaced apart to provide a zone for the passage of granular material therethrough. A gaseous stream containing particulate contaminants passes through the gas inlet means as well as through the upstream face of the granular material retention member, passing through the retention member, the body of granular material, the microporous gas filter element, exiting out of the gas outlet means. A cover screen isolates the filter element from contact with the moving granular bed. In one embodiment, the granular material is comprised of porous alumina impregnated with CuO, with the cover screen cleaned by the action of the moving granular material as well as by backflow pressure pulses. 6 figs.

Addition of granular activated carbon and trace elements to favor volatile fatty acid consumption during anaerobic digestion of food waste.

PubMed

Capson-Tojo, Gabriel; Moscoviz, Roman; Ruiz, Diane; Santa-Catalina, Gaëlle; Trably, Eric; Rouez, Maxime; Crest, Marion; Steyer, Jean-Philippe; Bernet, Nicolas; Delgenès, Jean-Philippe; Escudié, Renaud

2018-07-01

The effect of supplementing granular activated carbon and trace elements on the anaerobic digestion performance of consecutive batch reactors treating food waste was investigated. The results from the first batch suggest that addition of activated carbon favored biomass acclimation, improving acetic acid consumption and enhancing methane production. Adding trace elements allowed a faster consumption of propionic acid. A second batch proved that a synergy existed when activated carbon and trace elements were supplemented simultaneously. The degradation kinetics of propionate oxidation were particularly improved, reducing significantly the batch duration and improving the average methane productivities. Addition of activated carbon favored the growth of archaea and syntrophic bacteria, suggesting that interactions between these microorganisms were enhanced. Interestingly, microbial analyses showed that hydrogenotrophic methanogens were predominant. This study shows for the first time that addition of granular activated carbon and trace elements may be a feasible solution to stabilize food waste anaerobic digestion. Copyright © 2018 Elsevier Ltd. All rights reserved.

Rheology of dense suspensions of non colloidal particles

NASA Astrophysics Data System (ADS)

Guazzelli, Élisabeth

2017-06-01

Dense suspensions are materials with broad applications both in industrial processes (e.g. waste disposal, concrete, drilling muds, metalworking chip transport, and food processing) and in natural phenomena (e.g. flows of slurries, debris, and lava). Despite its long research history and its practical relevance, the mechanics of dense suspensions remain poorly understood. The major difficulty is that the grains interact both by hydrodynamic interactions through the liquid and by mechanical contact. These systems thus belong to an intermediate regime between pure suspensions and granular flows. We show that we can unify suspension and granular rheology under a common framework by transferring the frictional approach of dry granular media to wet suspensions of spherical particles. We also discuss non-Newtonian behavior such as normal-stress differences and shear-induced migration. Beyond the classical problem of dense suspension of hard spheres which is far from being completely resolved, there are also entirely novel avenues of study concerning more complex mixtures of particles and fluids such as those involving other types of particles (e.g. fibers) or non-Newtonian fluids that we will also address.

Quality of poultry litter-derived granular activated carbon.

PubMed

Qiu, Guannan; Guo, Mingxin

2010-01-01

Utilization of poultry litter as a source material for generating activated carbon is a value-added and environmentally beneficial approach to recycling organic waste. In this study, the overall quality of poultry litter-derived granular activated carbon was systematically evaluated based on its various physical and chemical properties. Granular activated carbon generated from pelletized poultry litter following a typical steam-activation procedure possessed numerous micropores in the matrix. The product exhibited a mean particle diameter of 2.59 mm, an apparent density of 0.45 g cm(-3), a ball-pan hardness of 91.0, an iodine number of 454 mg g(-1), and a BET surface area of 403 m(2) g(-1). It contained high ash, nitrogen, phosphorus contents and the trace elements Cu, Zn, and As. Most of the nutrients and toxic elements were solidified and solution-unextractable. In general, poultry litter-based activated carbon demonstrated overall quality comparable to that of low-grade commercial activated carbon derived from coconut shell and bituminous coal. It is promising to use poultry litter as a feedstock to manufacture activated carbon for wastewater treatment.

SYSTEMATIC SCANNING ELECTRON MICROSCOPY TECHNIQUE FOR EVALUATING COMBINED BIOLOIGCAL/GRANULAR ACTIVATED CARBON TREATMENT PROCESSES

EPA Science Inventory

A systematic scanning election microscope analytical technique has been developed to examine granular activated carbon used a a medium for biomass attachment in liquid waste treatment. The procedure allows for the objective monitoring, comparing, and trouble shooting of combined ...

Friction on a granular-continuum interface: Effects of granular media

NASA Astrophysics Data System (ADS)

Ecke, Robert; Geller, Drew

We consider the frictional interactions of two soft plates with interposed granular material subject to normal and shear forces. The plates are soft photo-elastic material, have length 50 cm, and are separated by a gap of variable width from 0 to 20 granular particle diameters. The granular materials are two-dimensional rods that are bi-dispersed in size to prevent crystallization. Different rod materials with frictional coefficients between 0 . 04 < μ < 0 . 5 are used to explore the effects of inter-granular friction on the effective friction of a granular medium. The gap is varied to test the dependence of the friction coefficient on the thickness of the granular layer. Because the soft plates absorb most of the displacement associated with the compressional normal force, the granular packing fractions are close to a jamming threshold, probably a shear jamming criterion. The overall shear and normal forces are measured using force sensors and the local strain tensor over a central portion of the gap is obtained using relative displacements of fiducial markers on the soft elastic material. These measurements provide a good characterization of the global and local forces giving rise to an effective friction coefficient. Funded by US DOE LDRD Program.

Summary of Calcine Disposal Development Using Hot Isostatic Pressing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bateman, Ken; Wahlquist, Dennis; Hart, Edward

2015-03-01

Battelle Energy Alliance, LLC, has demonstrated the effectiveness of the hot isostatic press (HIP) process for treatment of hazardous high-level waste known as calcine that is stored at the Idaho Nuclear Technology and Engineering Center (INTEC) at Idaho National Laboratory. HIP trials performed with simulated calcines at Idaho National Laboratory’s Materials and Fuels Complex and an Australian Nuclear Science and Technology Organization facility from 2007 to 2010 produced a dense, monolithic waste form with increased chemical durability and effective (storage) volume reductions of ~10 to ~70% compared to granular calcine forms. In December 2009, the U.S. Department of Energy signedmore » an amended Record of Decision selecting HIP technology as the treatment method for the 4,400 m3 of granular zirconia and alumina calcine stored at INTEC. Testing showed that HIP treatment reduces the risks associated with radioactive and hazardous constituent release, post-production handling, and long-term (repository) storage of calcines and would result in estimated storage cost savings in the billions of dollars. Battelle Energy Alliance has the ability to complete pilot-scale HIP processing of INTEC calcine, which is the next necessary step in implementing HIP processing as a calcine treatment method.« less

A hydrodynamic model for granular material flows including segregation effects

NASA Astrophysics Data System (ADS)

Gilberg, Dominik; Klar, Axel; Steiner, Konrad

2017-06-01

The simulation of granular flows including segregation effects in large industrial processes using particle methods is accurate, but very time-consuming. To overcome the long computation times a macroscopic model is a natural choice. Therefore, we couple a mixture theory based segregation model to a hydrodynamic model of Navier-Stokes-type, describing the flow behavior of the granular material. The granular flow model is a hybrid model derived from kinetic theory and a soil mechanical approach to cover the regime of fast dilute flow, as well as slow dense flow, where the density of the granular material is close to the maximum packing density. Originally, the segregation model has been formulated by Thornton and Gray for idealized avalanches. It is modified and adapted to be in the preferred form for the coupling. In the final coupled model the segregation process depends on the local state of the granular system. On the other hand, the granular system changes as differently mixed regions of the granular material differ i.e. in the packing density. For the modeling process the focus lies on dry granular material flows of two particle types differing only in size but can be easily extended to arbitrary granular mixtures of different particle size and density. To solve the coupled system a finite volume approach is used. To test the model the rotational mixing of small and large particles in a tumbler is simulated.

Failure evolution in granular material retained by rigid wall in active mode

NASA Astrophysics Data System (ADS)

Pietrzak, Magdalena; Leśniewska, Danuta

2012-10-01

This paper presents a detailed study of a selected small scale model test, performed on a sample of surrogate granular material, retained by a rigid wall (typical geotechnical problem of earth thrust on a retaining wall). The experimental data presented in this paper show that the deformation of granular sample behind retaining wall can undergo some cyclic changes. The nature of these cycles is not clear - it is probably related to some micromechanical features of granular materials, which are recently extensively studied in many research centers in the world. Employing very precise DIC (PIV) method can help to relate micro and macro-scale behavior of granular materials.

TRANSFORMATION AND MOBILIZATION OF ARSENIC ADSORBED ON GRANULAR FERRIC HYDROXIDE UNDER BIO-REDUCTIVE CONDITIONS

EPA Science Inventory

Biotic and abiotic reduction of arsenic (V) and iron (III) influences the partioning of arsenic (As) between the solid and aqueous phases in soils, sediments and wastes. In this study, laboratory experiments on arsenic adsorbed on granular ferric hydroxide (GFH) was performed to ...

Gravity and Granular Materials

NASA Technical Reports Server (NTRS)

Behringer, R. P.; Hovell, Daniel; Kondic, Lou; Tennakoon, Sarath; Veje, Christian

1999-01-01

We describe experiments that probe a number of different types of granular flow where either gravity is effectively eliminated or it is modulated in time. These experiments include the shaking of granular materials both vertically and horizontally, and the shearing of a 2D granular material. For the shaken system, we identify interesting dynamical phenomena and relate them to standard simple friction models. An interesting application of this set of experiments is to the mixing of dissimilar materials. For the sheared system we identify a new kind of dynamical phase transition.

Developing a Magnetic Resonance Imaging measurement of the forces within 3D granular materials under external loads

NASA Astrophysics Data System (ADS)

Elrington, Stefan; Bertrand, Thibault; Frey, Merideth; Shattuck, Mark; O'Hern, Corey; Barrett, Sean

2014-03-01

Granular materials are comprised of an ensemble of discrete macroscopic grains that interact with each other via highly dissipative forces. These materials are ubiquitous in our everyday life ranging in scale from the granular media that forms the Earth's crust to that used in agricultural and pharmaceutical industries. Granular materials exhibit complex behaviors that are poorly understood and cannot be easily described by statistical mechanics. Under external loads individual grains are jammed into place by a network of force chains. These networks have been imaged in quasi two-dimensional and on the outer surface of three-dimensional granular materials. Our goal is to use magnetic resonance imaging (MRI) to detect contact forces deep within three-dimensional granular materials, using hydrogen-1 relaxation times as a reporter for changes in local stress and strain. To this end, we use a novel pulse sequence to narrow the line width of hydrogen-1 in rubber. Here we present our progress to date, and prospects for future improvements.

Time-resolved dynamics of granular matter by random laser emission

NASA Astrophysics Data System (ADS)

Folli, Viola; Ghofraniha, Neda; Puglisi, Andrea; Leuzzi, Luca; Conti, Claudio

2013-07-01

Because of the huge commercial importance of granular systems, the second-most used material in industry after water, intersecting the industry in multiple trades, like pharmacy and agriculture, fundamental research on grain-like materials has received an increasing amount of attention in the last decades. In photonics, the applications of granular materials have been only marginally investigated. We report the first phase-diagram of a granular as obtained by laser emission. The dynamics of vertically-oscillated granular in a liquid solution in a three-dimensional container is investigated by employing its random laser emission. The granular motion is function of the frequency and amplitude of the mechanical solicitation, we show how the laser emission allows to distinguish two phases in the granular and analyze its spectral distribution. This constitutes a fundamental step in the field of granulars and gives a clear evidence of the possible control on light-matter interaction achievable in grain-like system.

Optimization of metals and plastics recovery from electric cable wastes using a plate-type electrostatic separator.

PubMed

Richard, Gontran; Touhami, Seddik; Zeghloul, Thami; Dascalescu, Lucien

2017-02-01

Plate-type electrostatic separators are commonly employed for the selective sorting of conductive and non-conductive granular materials. The aim of this work is to identify the optimal operating conditions of such equipment, when employed for separating copper and plastics from either flexible or rigid electric wire wastes. The experiments are performed according to the response surface methodology, on samples composed of either "calibrated" particles, obtained by manually cutting of electric wires at a predefined length (4mm), or actual machine-grinded scraps, characterized by a relatively-wide size distribution (1-4mm). The results point out the effect of particle size and shape on the effectiveness of the electrostatic separation. Different optimal operating conditions are found for flexible and rigid wires. A separate processing of the two classes of wire wastes is recommended. Copyright © 2016 Elsevier Ltd. All rights reserved.

Numerical investigations on flow dynamics of prismatic granular materials using the discrete element method

NASA Astrophysics Data System (ADS)

Hancock, W.; Weatherley, D.; Wruck, B.; Chitombo, G. P.

2012-04-01

The flow dynamics of granular materials is of broad interest in both the geosciences (e.g. landslides, fault zone evolution, and brecchia pipe formation) and many engineering disciplines (e.g chemical engineering, food sciences, pharmaceuticals and materials science). At the interface between natural and human-induced granular media flow, current underground mass-mining methods are trending towards the induced failure and subsequent gravitational flow of large volumes of broken rock, a method known as cave mining. Cave mining relies upon the undercutting of a large ore body, inducement of fragmentation of the rock and subsequent extraction of ore from below, via hopper-like outlets. Design of such mines currently relies upon a simplified kinematic theory of granular flow in hoppers, known as the ellipsoid theory of mass movement. This theory assumes that the zone of moving material grows as an ellipsoid above the outlet of the silo. The boundary of the movement zone is a shear band and internal to the movement zone, the granular material is assumed to have a uniformly high bulk porosity compared with surrounding stagnant regions. There is however, increasing anecdotal evidence and field measurements suggesting this theory fails to capture the full complexity of granular material flow within cave mines. Given the practical challenges obstructing direct measurement of movement both in laboratory experiments and in-situ, the Discrete Element Method (DEM [1]) is a popular alternative to investigate granular media flow. Small-scale DEM studies (c.f. [3] and references therein) have confirmed that movement within DEM silo flow models matches that predicted by ellipsoid theory, at least for mono-disperse granular material freely outflowing at a constant rate. A major draw-back of these small-scale DEM studies is that the initial bulk porosity of the simulated granular material is significantly higher than that of broken, prismatic rock. In this investigation, more realistic granular material geometries are simulated using the ESyS-Particle [2] DEM simulation software on cluster supercomputers. Individual grains of the granular material are represented as convex polyhedra. Initially the polyhedra are packed in a low bulk porosity configuration prior to commencing silo flow simulations. The resultant flow dynamics are markedly different to that predicted by ellipsoid theory. Initially shearing occurs around the silo outlet however rapidly shear localization in a particular direction dominates other directions, causing preferential movement in that direction. Within the shear band itself, the granular material becomes hgihly dilated however elsewhere the bulk porosity remains low. The low porosity within these regions promotes entrainment whereby large volumes of granular material interlock and begin to rotate and translate as a single rigid body. In some cases, entrainment may result in complete overturning of a large volume of material. The consequences of preferential shear localization and in particular, entrainment, for granular media flow in cave mines and natural settings (such as brecchia pipes) is a topic of ongoing research to be presented at the meeting.

Introduction

NASA Astrophysics Data System (ADS)

Starosvetsky, Yuli; Jayaprakash, K. R.; Hasan, Md. Arif; Vakakis, Alexander F.

The study of mechanics of granular media dates back to the era of Coulomb. He was the first to postulate the yield condition for homogeneous solids and also conditions for failure in granular media [1-4]. In fact the ideal Coulomb material is the simplest granular material model wherein the shear stress along a plane is linearly proportional to the normal stress on that plane. This can be considered analogous to the Coulomb friction model in cohesion-free interfaces between solids. Initial research in this domain focused mainly on the statics of granular materials from a soil mechanics perspective. However, as the applications of granular materials broadened, the objectives of different research communities contradicted. For example, in geophysics or soil mechanics the objective is to regard granular media with properties of a solid in order to take considerable loads without yielding; on the other hand, in food grain or pharmaceutical industries the granular media is considered as fluids and their rheological properties are of interest. In fact granular media can exhibit both of these behaviors (and also the properties of a gas), and such unique features pave the way for their broad range applications...

Impact compaction of a granular material

DOE PAGES

Fenton, Gregg; Asay, Blaine; Dalton, Devon

2015-05-19

The dynamic behavior of granular materials has importance to a variety of engineering applications. Structural seismic coupling, planetary science, and earth penetration mechanics, are just a few of the application areas. Although the mechanical behavior of granular materials of various types have been studied extensively for several decades, the dynamic behavior of such materials remains poorly understood. High-quality experimental data are needed to improve our general understanding of granular material compaction physics. This study will describe how an instrumented plunger impact system can be used to measure pressure-density relationships for model materials at high and controlled strain rates and subsequentlymore » used for computational modeling.« less

MGM - MS Reilly holds a container used in the MGM experiment

NASA Image and Video Library

1998-03-04

S89-E-5328 (27 Jan 1998) --- This Electronic Still Camera (ESC) image shows astronaut James F. Reilly, mission specialist, holding the Mechanics of Granular Materials (MGM) experiment. The MGM experiment is aimed at understanding the behavior of granular materials, such as sand or salt, under very low confining pressure. This pressure is the force that keeps a granular material ?sticking together?. The experiment has applications in a wide range of fields, including earthquake engineering; coastal and off-shore engineering; mining; transportation of granular materials; soil erosion; the handling of granular materials such as grains and powders; off-road vehicles; geology of the Earth; and planetary geology and exploration. Findings from the experiment may lead to improved selection and preparation of building sites, better management of undeveloped land, and improved handling of materials in chemical, agricultural and other industries.

Production of granular activated carbon from food-processing wastes (walnut shells and jujube seeds) and its adsorptive properties.

PubMed

Bae, Wookeun; Kim, Jongho; Chung, Jinwook

2014-08-01

Commercial activated carbon is a highly effective absorbent that can be used to remove micropollutants from water. As a result, the demand for activated carbon is increasing. In this study, we investigated the optimum manufacturing conditions for producing activated carbon from ligneous wastes generated from food processing. Jujube seeds and walnut shells were selected as raw materials. Carbonization and steam activation were performed in a fixed-bed laboratory electric furnace. To obtain the highest iodine number, the optimum conditions for producing activated carbon from jujube seeds and walnut shells were 2 hr and 1.5 hr (carbonization at 700 degrees C) followed by 1 hr and 0.5 hr (activation at 1000 degrees C), respectively. The surface area and iodine number of activated carbon made from jujube seeds and walnut shells were 1,477 and 1,184 m2/g and 1,450 and 1,200 mg/g, respectively. A pore-distribution analysis revealed that most pores had a pore diameter within or around 30-40 angstroms, and adsorption capacity for surfactants was about 2 times larger than the commercial activated carbon, indicating that waste-based activated carbon can be used as alternative. Implications: Wastes discharged from agricultural and food industries results in a serious environmental problem. A method is proposed to convert food-processing wastes such as jujube seeds and walnut shells into high-grade granular activated carbon. Especially, the performance of jujube seeds as activated carbon is worthy of close attention. There is little research about the application ofjujube seeds. Also, when compared to two commercial carbons (Samchully and Calgon samples), the results show that it is possible to produce high-quality carbon, particularly from jujube seed, using a one-stage, 1,000 degrees C, steam pyrolysis. The preparation of activated carbon from food-processing wastes could increase economic return and reduce pollution.

Micro-scale investigation on the quasi-static behavior of granular material

NASA Astrophysics Data System (ADS)

Li, Xia

Granular material exhibits complex responses when subjected to various external loading. Fundamental mechanisms have not been well established so far, including that about the critical state, one of the most important concepts in the modern soil mechanics. With the recognition that granular material is discrete in nature, the basic understanding can only be obtained from the particle scale. The complexity in granular material behavior lies in the fact that the macroscopic behavior of granular material is determined by not only the interactions operating at contacts, but also how the particles become arranged in space to form an internal structure. This research is aimed to microscopically investigate the influence of the internal structure and the fundamental mechanism about the critical state. In view of the extensive laboratory test data already available in the literature, a numerical simulation method, DEM, is employed as the tool to conduct particle-scale investigations. The contact model for two in-contact circular disks is derived theoretically from the elasticity theory, and the result is a linear contact model with constant stiffness and lateral sliding. Based on the contact model, a systematic series of numerical tests has been implemented, and the results can successfully reproduce the main characteristics in the behavior of natural granular material, under various loading conditions. The macro-micro relationship is the link between the investigations at the two worlds. The key point is to describe the internal structure with the two dual cell systems, a particle cell system and a void cell system. Based on these two systems, the stress and strain in a uniform field are equivalently expressed in terms of the contact forces/relative displacements, and the micro-geometrical variables. With the microstructural definition of the stress tensor, the stress state of granular material is studied microscopically. The stress-fabric-force relation is derived, based on the variables describing the statistics of the contact forces and the contact vectors. By studying the evolution of the micro-quantities during shearing, how the internal structure affects the macro stress state under different loading condition is revealed. With the assumption that the influence of the local variance in stress is ignorable, the response of granular material can be investigated based on the void cell system. Starting from the behavior of a single void cell, the evolutions of the internal structure and its influence on the response of granular material are explained. The stress ratio and the dilatancy behavior of granular material are investigated. The influences of the void ratio, the mean normal stress and the drainage condition are discussed. The fundamental mechanism of the critical state is studied in the framework of thermodynamics with properly considering the influence of the internal structure. The normalized stress ratio tensor at critical state is associated with the critical void cell anisotropy, corresponding to the maximal energy dissipation. The (e, p) relationship at critical state is associated with the critical combination of the void cell size and the contact interactions, corresponding to the minimal free energy. The investigation on the influence of the internal structure anisotropy on the granular material behavior and the critical state is carried out. The results show that at small strain levels, the behavior of granular material is mainly affected by the initial fabric. As shearing continuous, the internal structure of granular material is gradually changed. The granular material approaches the critical state, which is irrespective with the initial internal structure. The critical state of granular material is not unique. With different loading modes, the critical state of granular material, including both the critical stress ratio and the critical (e, p) relations, are found to be different. A fabric tensor is defined based on the characteristics of the void cells. The laboratory method to quantify the fabric anisotropy is proposed by deviatoric shearing. 3D numerical simulations have been carried out to investigate the influence of the loading mode, which is found to be an important factor in the large strain behavior of granular material. With the obtained microscopic understanding, the influence of contact model on granular material behavior is investigated. A method to quantify the fabric anisotropy is proposed. And a simple discussion on the state variable used in the elasto-plastic constitutive model is given.

Multiscale Phenomena in the Solid-Liquid Transition State of a Granular Material: Analysis and Modelling of Dense Granular Materials

DTIC Science & Technology

2011-09-26

most challenging to characterize and model of the gamut of granular behaviour encountered in practice. In particular, it exhibits self-organized...is intrinsically multiscale and is arguably one of, if not, the most challenging to characterize and model of the gamut of granular behaviour...the most challenging to characterize and model of the gamut of granular behaviour encountered in practice. In particular, it exhibits self-organized

Using Space for a Better Foundation on Earth: Mechanics of Granular Materials. Educational Brief. Grades 5-8.

ERIC Educational Resources Information Center

Alshibli, Khalid

This publication presents a science activity and instructional information on mechanics of granular materials, interparticle friction and geometric interlocking between particles which is a fundamental concept in many fields like earthquakes. The activity described in this document focuses on the principal strength of granular materials,…

Development and Demonstration of Material Properties Database and Software for the Simulation of Flow Properties in Cementitious Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, F.; Flach, G.

This report describes work performed by the Savannah River National Laboratory (SRNL) in fiscal year 2014 to develop a new Cementitious Barriers Project (CBP) software module designated as FLOExcel. FLOExcel incorporates a uniform database to capture material characterization data and a GoldSim model to define flow properties for both intact and fractured cementitious materials and estimate Darcy velocity based on specified hydraulic head gradient and matric tension. The software module includes hydraulic parameters for intact cementitious and granular materials in the database and a standalone GoldSim framework to manipulate the data. The database will be updated with new data asmore » it comes available. The software module will later be integrated into the next release of the CBP Toolbox, Version 3.0. This report documents the development efforts for this software module. The FY14 activities described in this report focused on the following two items that form the FLOExcel package; 1) Development of a uniform database to capture CBP data for cementitious materials. In particular, the inclusion and use of hydraulic properties of the materials are emphasized; and 2) Development of algorithms and a GoldSim User Interface to calculate hydraulic flow properties of degraded and fractured cementitious materials. Hydraulic properties are required in a simulation of flow through cementitious materials such as Saltstone, waste tank fill grout, and concrete barriers. At SRNL these simulations have been performed using the PORFLOW code as part of Performance Assessments for salt waste disposal and waste tank closure.« less

Development of a New Analog Test System Capable of Modeling Tectonic Deformation Incorporating the Effects of Pore Fluid Pressure

NASA Astrophysics Data System (ADS)

Zhang, M.; Nakajima, H.; Takeda, M.; Aung, T. T.

2005-12-01

Understanding and predicting the tectonic deformation within geologic strata has been a very important research subject in many fields such as structural geology and petroleum geology. In recent years, such research has also become a fundamental necessity for the assessment of active fault migration, site selection for geological disposal of radioactive nuclear waste and exploration for methane hydrate. Although analog modeling techniques have played an important role in the elucidation of the tectonic deformation mechanisms, traditional approaches have typically used dry materials and ignored the effects of pore fluid pressure. In order for analog models to properly depict the tectonic deformation of the targeted, large-prototype system within a small laboratory-scale configuration, physical properties of the models, including geometry, force, and time, must be correctly scaled. Model materials representing brittle rock behavior require an internal friction identical to the prototype rock and virtually zero cohesion. Granular materials such as sand, glass beads, or steel beads of dry condition have been preferably used for this reason in addition to their availability and ease of handling. Modeling protocols for dry granular materials have been well established but such model tests cannot account for the pore fluid effects. Although the concept of effective stress has long been recognized and the role of pore-fluid pressure in tectonic deformation processes is evident, there have been few analog model studies that consider the effects of pore fluid movement. Some new applications require a thorough understanding of the coupled deformation and fluid flow processes within the strata. Taking the field of waste management as an example, deep geological disposal of radioactive waste has been thought to be an appropriate methodology for the safe isolation of the wastes from the human environment until the toxicity of the wastes decays to non-hazardous levels. For the deep geological disposal concept, besides containing the wastes with engineering methods such as the glassification of the radioactive wastes, the geological formation itself is expected to serve as a natural barrier that retards migration of radionuclides. To evaluate the long-term safety of deep geological disposal, a better understanding of the fate and transport of radionuclides in a geologically heterogeneous environment is necessary. To meet such requirements, a new analog test sandbox model system was developed. This model system allows the pore fluid flows to be controlled during the model tests and permits the study of flow and transport phenomena in the deformed heterogeneous model. One- or two-dimensional fluid flow is controlled using a side-wall piston. Deformation processes can be observed through a transparent front panel, and pore fluid movement can be also visualized using a color tracer. In this study, the scaling requirements for analog modeling, including pore water pressure, are discussed based on the theory of dimensional analysis, supplemented by data from a series of laboratory shear tests, and a detailed description of the model system. Preliminary experimental results are presented.

Using Space for a Better Foundation on Earth: Mechanics of Granular Materials. Educational Brief. Grades 9-12.

ERIC Educational Resources Information Center

Alshibli, Khalid

This publication presents a science activity and instructional information on the mechanics of granular materials, interparticle friction and geometric interlocking between particles which is a fundamental concept in many fields like in the study of earthquakes. This document describes the Mechanics of Granular Materials (MGM) experiments which…

Dynamics of Granular Materials

NASA Technical Reports Server (NTRS)

Behringer, Robert P.

1996-01-01

Granular materials exhibit a rich variety of dynamical behavior, much of which is poorly understood. Fractal-like stress chains, convection, a variety of wave dynamics, including waves which resemble capillary waves, l/f noise, and fractional Brownian motion provide examples. Work beginning at Duke will focus on gravity driven convection, mixing and gravitational collapse. Although granular materials consist of collections of interacting particles, there are important differences between the dynamics of a collections of grains and the dynamics of a collections of molecules. In particular, the ergodic hypothesis is generally invalid for granular materials, so that ordinary statistical physics does not apply. In the absence of a steady energy input, granular materials undergo a rapid collapse which is strongly influenced by the presence of gravity. Fluctuations on laboratory scales in such quantities as the stress can be very large-as much as an order of magnitude greater than the mean.

Treatment of semivolatile compounds in high strength wastes using an anaerobic expanded-bed GAC reactor

EPA Science Inventory

The potential of the anaerobic, expanded bed granular activated carbon (GAC) reactor in treating a high strength waste containing RCRA semivolatile organic compounds (VOCs) was studied. Six semivolatiles, orthochlorophenol, nitrobenzene, naphthalene, para-nitrophenol, lindane, a...

Flowability of granular materials with industrial applications - An experimental approach

NASA Astrophysics Data System (ADS)

Torres-Serra, Joel; Romero, Enrique; Rodríguez-Ferran, Antonio; Caba, Joan; Arderiu, Xavier; Padullés, Josep-Manel; González, Juanjo

2017-06-01

Designing bulk material handling equipment requires a thorough understanding of the mechanical behaviour of powders and grains. Experimental characterization of granular materials is introduced focusing on flowability. A new prototype is presented which performs granular column collapse tests. The device consists of a channel whose design accounts for test inspection using visualization techniques and load measurements. A reservoir is attached where packing state of the granular material can be adjusted before run-off to simulate actual handling conditions by fluidisation and deaeration of the pile. Bulk materials on the market, with a wide range of particle sizes, can be tested with the prototype and the results used for classification in terms of flowability to improve industrial equipment selection processes.

Pressure regulator

DOEpatents

Ebeling, Jr., Robert W.; Weaver, Robert B.

1979-01-01

The pressure within a pressurized flow reactor operated under harsh environmental conditions is controlled by establishing and maintaining a fluidized bed of uniformly sized granular material of selected density by passing the gas from the reactor upwardly therethrough at a rate sufficient to fluidize the bed and varying the height of the bed by adding granular material thereto or removing granular material therefrom to adjust the backpressure on the flow reactor.

Resilient Modulus Characterization of Alaskan Granular Base Materials

DOT National Transportation Integrated Search

2010-08-01

Resilient modulus (MR) of base course material is an important material input for : pavement design. In Alaska, due to distinctiveness of local climate, material source, : fines content and groundwater level, resilient properties of D-1 granular base...

TESTING AND ANALYSES OF CHAT AND ASPHALT-CONTAINING CHAT

EPA Science Inventory

Granular mine waste are generated from the extraction and beneficiation of lead/zinc minerals. The fine gravel waste, commonly known as chat, in the Tristate Mining District contains elevated levels of lead, zinc and cadmium which can result in potentially serious human health a...

TREATMENT OF VOCS IN HIGH STRENGTH WASTES USING AN ANAEROBIC EXPANDED-BED GAS REACTOR

EPA Science Inventory

The potential of the expanded-bed granular activated carbon (GAC) anaerobic reactor in treating a high strength waste containing RCRA volatile organic compounds (VOCs) was studied. A total of six VOCs, methylene chloride, chlorobenzene, carbon tetrachloride, chloroform, toluene ...

Calcined Waste Storage at the Idaho Nuclear Technology and Engineering Center

DOE Office of Scientific and Technical Information (OSTI.GOV)

M. D. Staiger

2007-06-01

This report provides a quantitative inventory and composition (chemical and radioactivity) of calcined waste stored at the Idaho Nuclear Technology and Engineering Center. From December 1963 through May 2000, liquid radioactive wastes generated by spent nuclear fuel reprocessing were converted into a solid, granular form called calcine. This report also contains a description of the calcine storage bins.

On Critical States, Rupture States and Interlocking Strength of Granular Materials.

PubMed

Szalwinski, Chris M

2017-07-27

The Mohr-Coulomb theory of strength identifies cohesion and internal friction as the two principal contributions to the shear strength of a granular material. The contribution of cohesion in over-compacted granular materials has been challenged and replacing cohesion with interlocking has been proposed. A theory of rupture strength that includes interlocking is derived herein. The physics-chemistry concept of critical state is elaborated to accommodate granular materials, based on empirical definitions established in the fields of soil mechanics and bulk solids' flow. A surface in state space, called the critical compaction surface, separates over-compacted states from lightly compacted states. The intersection of this surface with the Mohr-Coulomb envelope forms the critical state surface for a granular material. The rupture strength of an over-compacted granular material is expressed as the sum of cohesion, internal friction and interlocking strength. Interlocking strength is the shear strength contribution due to over-compaction and vanishes at critical state. The theory allows migrations from one critical state to another. Changes in specific volume during such migrations are related to changes in mean-normal effective stress and uncoupled from changes in shearing strain. The theory is reviewed with respect to two established research programs and underlying assumptions are identified.

A thermomechanical constitutive model for cemented granular materials with quantifiable internal variables. Part II - Validation and localization analysis

NASA Astrophysics Data System (ADS)

Das, Arghya; Tengattini, Alessandro; Nguyen, Giang D.; Viggiani, Gioacchino; Hall, Stephen A.; Einav, Itai

2014-10-01

We study the mechanical failure of cemented granular materials (e.g., sandstones) using a constitutive model based on breakage mechanics for grain crushing and damage mechanics for cement fracture. The theoretical aspects of this model are presented in Part I: Tengattini et al. (2014), A thermomechanical constitutive model for cemented granular materials with quantifiable internal variables, Part I - Theory (Journal of the Mechanics and Physics of Solids, 10.1016/j.jmps.2014.05.021). In this Part II we investigate the constitutive and structural responses of cemented granular materials through analyses of Boundary Value Problems (BVPs). The multiple failure mechanisms captured by the proposed model enable the behavior of cemented granular rocks to be well reproduced for a wide range of confining pressures. Furthermore, through comparison of the model predictions and experimental data, the micromechanical basis of the model provides improved understanding of failure mechanisms of cemented granular materials. In particular, we show that grain crushing is the predominant inelastic deformation mechanism under high pressures while cement failure is the relevant mechanism at low pressures. Over an intermediate pressure regime a mixed mode of failure mechanisms is observed. Furthermore, the micromechanical roots of the model allow the effects on localized deformation modes of various initial microstructures to be studied. The results obtained from both the constitutive responses and BVP solutions indicate that the proposed approach and model provide a promising basis for future theoretical studies on cemented granular materials.

TESTING AND ANALYSES OF CHAT AND ASPHALT-CONTAINING CHAT (PRESENTATION)

EPA Science Inventory

Granular mine waste are generated from the extraction and beneficiation of lead/zinc minerals. The fine gravel waste, commonly known as chat, in the Tristate Mining District contains elevated levels of lead, zinc and cadmium which can result in potentially serious human health a...

A road pavement full-scale test track containing stabilized bottom ashes.

PubMed

Toraldo, E; Saponaro, S

2015-01-01

This paper reports the results of a road pavement full-scale test track built by using stabilized bottom ash (SBA) from an Italian municipal solid waste incinerator as the aggregate in granular foundation, cement-bound mixes and asphalt concretes. The investigation focused on both the performance and the environmental compatibility of such mixes, especially with regard to the effects of mixing, laying and compaction. From the road construction point of view, the performance related to the effects of mixing, laying and compaction on constructability was assessed, as well as the volumetric and the mechanical properties. Environmental aspects were investigated by leaching tests. The results suggested that SBA meets the environmental Italian law for the reuse of non-hazardous waste and could be used as road material with the procedures, plants and equipment currently used for road construction.

Comparison of Novel Carboneous Structures to Treat Nitroaromatic Impacted Water

DTIC Science & Technology

2015-12-01

MS-15-D-047 Abstract Carboneous materials such as carbon nanotube (CNT), granular activated carbon (GAC), and biochar are promising materials...TECHNOLOGIES ...................................................49 A.3 GRANULAR ACTIVATED CARBON (GAC) ............................................50 A.4...GENERAL ISSUE In this study, we compared the adsorptive capacity of bituminous-coal based granular activated carbon (GAC) versus pristine novel

Experimental study on the signs of particulate structures formation in annular geometry of rapid granular shear flows

NASA Astrophysics Data System (ADS)

Ritvanen, J.; Jalali, P.

2009-06-01

Rapid granular shear flow is a classical example in granular materials which exhibits both fluid-like and solid-like behaviors. Another interesting feature of rapid granular shear flows is the formation of ordered structures upon shearing. Certain amount of granular material, with uniform size distribution, is required to be loaded in the container in order to shear it under stable conditions. This work concerns the experimental study of rapid granular shear flows in annular Couette geometry. The flow is induced by continuous rotation of the plate over the top of the granular bed in an annulus. The compressive pressure, driving torque, instantaneous bed height from three symmetric locations and rotational speed of the shearing plate are measured. The annulus has a capacity of up to 15 kg of spherical steel balls of 3 mm in diameter. Rapid shear flow experiments are performed in one compressive force and rotation rate. The sensitivity of fluctuations is then investigated by different means through monodisperse packing. In this work, we present the results of the experiments showing how the flow properties depend on the amount of loaded granular material which is varied by small amounts between different experiments. The flow can exist in stable (fixed behavior) and unstable (time-dependent behavior) regimes as a function of the loaded material. We present the characteristics of flow to detect the formation of any additional structured layer in the annulus. As a result, an evolution graph for the bed height has been obtained as material is gradually added. This graph shows how the bed height grows when material increases. Using these results, the structure inside the medium can be estimated at extreme stable and unstable conditions.

Granular materials interacting with thin flexible rods

NASA Astrophysics Data System (ADS)

Neto, Alfredo Gay; Campello, Eduardo M. B.

2017-04-01

In this work, we develop a computational model for the simulation of problems wherein granular materials interact with thin flexible rods. We treat granular materials as a collection of spherical particles following a discrete element method (DEM) approach, while flexible rods are described by a large deformation finite element (FEM) rod formulation. Grain-to-grain, grain-to-rod, and rod-to-rod contacts are fully permitted and resolved. A simple and efficient strategy is proposed for coupling the motion of the two types (discrete and continuum) of materials within an iterative time-stepping solution scheme. Implementation details are shown and discussed. Validity and applicability of the model are assessed by means of a few numerical examples. We believe that robust, efficiently coupled DEM-FEM schemes can be a useful tool to the simulation of problems wherein granular materials interact with thin flexible rods, such as (but not limited to) bombardment of grains on beam structures, flow of granular materials over surfaces covered by threads of hair in many biological processes, flow of grains through filters and strainers in various industrial segregation processes, and many others.

Partial filling of a honeycomb structure by granular materials for vibration and noise reduction

NASA Astrophysics Data System (ADS)

Koch, Sebastian; Duvigneau, Fabian; Orszulik, Ryan; Gabbert, Ulrich; Woschke, Elmar

2017-04-01

In this paper, the damping effect of granular materials is explored to reduce the vibration and noise of mechanical structures. To this end, a honeycomb structure with high stiffness is used to contain a granular filling which presents the possiblity for the distribution of the granular material to be designed. As a particular application example, the oil pan bottom of a combustion engine is used to investigate the influence on the vibration behavior and the sound emission. The effect of the honeycomb structure along with the granular mass, distribution, and type on the vibration behaviour of the structure is investigated via laser scanning vibrometry. From this, an optimized filling is determined and then its noise suppression level validated on an engine test bench through measurements with an acoustic array.

Radioactive Demonstration Of Mineralized Waste Forms Made From Hanford Low Activity Waste (Tank Farm Blend) By Fluidized Bed Steam Reformation (FBSR)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jantzen, C. M.; Crawford, C. L.; Bannochie, C. J.

The U.S. Department of Energy’s Office of River Protection (ORP) is responsible for the retrieval, treatment, immobilization, and disposal of Hanford’s tank waste. A key aspect of the River Protection Project (RPP) cleanup mission is to construct and operate the Hanford Tank Waste Treatment and Immobilization Plant (WTP). The WTP will separate the tank waste into high-level and low-activity waste (LAW) fractions, both of which will subsequently be vitrified. The projected throughput capacity of the WTP LAW Vitrification Facility is insufficient to complete the RPP mission in the time frame required by the Hanford Federal Facility Agreement and Consent Order,more » also known as the Tri-Party Agreement (TPA), i.e. December 31, 2047. Supplemental Treatment is likely to be required both to meet the TPA treatment requirements as well as to more cost effectively complete the tank waste treatment mission. The Supplemental Treatment chosen will immobilize that portion of the retrieved LAW that is not sent to the WTP’s LAW Vitrification facility into a solidified waste form. The solidified waste will then be disposed on the Hanford site in the Integrated Disposal Facility (IDF). Fluidized Bed Steam Reforming (FBSR) offers a moderate temperature (700-750°C) continuous method by which LAW can be processed irrespective of whether the waste contain organics, nitrates, sulfates/sulfides, chlorides, fluorides, volatile radionuclides or other aqueous components. The FBSR technology can process these wastes into a crystalline ceramic (mineral) waste form. The mineral waste form that is produced by co-processing waste with kaolin clay in an FBSR process has been shown to be comparable to LAW glass, i.e. leaches Tc-99, Re and Na at <2g/m 2 during ASTM C1285 (Product Consistency) durability testing. Monolithing of the granular FBSR product was investigated to prevent dispersion during transport or burial/storage. Monolithing in an inorganic geopolymer binder, which is amorphous, macro-encapsulates the granules, and the monoliths pass ANSI/ANS 16.1 and ASTM C1308 durability testing with Re achieving a Leach Index (LI) of 9 (the Hanford Integrated Disposal Facility, IDF, criteria for Tc-99) after a few days and Na achieving an LI of >6 (the Hanford IDF criteria for Na) in the first few hours. The granular and monolithic waste forms also pass the EPA Toxicity Characteristic Leaching Procedure (TCLP) for all Resource Conservation and Recovery Act (RCRA) components at the Universal Treatment Standards (UTS). Two identical Benchscale Steam Reformers (BSR) were designed and constructed at SRNL, one to treat non-radioactive simulants and the other to treat actual radioactive wastes. The results from the non-radioactive BSR were used to determine the parameters needed to operate the radioactive BSR in order to confirm the findings of non-radioactive FBSR pilot scale and engineering scale tests and to qualify an FBSR LAW waste form for applications at Hanford. Radioactive testing commenced using SRS LAW from Tank 50 chemically trimmed to look like Hanford’s blended LAW known as the Rassat simulant as this simulant composition had been tested in the non-radioactive BSR, the non-radioactive pilot scale FBSR at the Science Applications International Corporation-Science and Technology Applications Research (SAIC-STAR) facility in Idaho Falls, ID and in the TTT Engineering Scale Technology Demonstration (ESTD) at Hazen Research Inc. (HRI) in Denver, CO. This provided a “tie back” between radioactive BSR testing and non-radioactive BSR, pilot scale, and engineering scale testing. Approximately six hundred grams of non-radioactive and radioactive BSR product were made for extensive testing and comparison to the non-radioactive pilot scale tests performed in 2004 at SAIC-STAR and the engineering scale test performed in 2008 at HRI with the Rassat simulant. The same mineral phases and off-gas species were found in the radioactive and non-radioactive testing. The granular ESTD and BSR products (radioactive and non-radioactive) were analyzed for total constituents and durability tested as a granular waste form. A subset of the granular material was stabilized in a clay based geopolymer matrix at 42% and 65% FBSR loadings and durability tested as a monolith waste form. The 65 wt% FBSR loaded monolith made with clay (radioactive) was more durable than the 67-68 wt% FBSR loaded monoliths made from fly ash (non-radioactive) based on short term PCT testing. Long term, 90 to 107 day, ASTM C1308 testing (similar to ANSI/ANS 16.1 testing) was only performed on two fly ash geopolymer monoliths at 67-68 wt% FBSR loading and three clay geopolymer monoliths at 42 wt% FBSR loading. More clay geopolymers need to be made and tested at longer times at higher FBSR loadings for comparison to the fly ash monoliths. Monoliths made with metakaolin (heat treated) clay are of a more constant composition and are very reactive as the heat treated clay is amorphous and alkali activated. The monoliths made with fly ash are subject to the inherent compositional variation found in fly ash as it is a waste product from burning coal and it contains unreactive components such as mullite. However, both the fly ash and the clay based monoliths perform well in long term ASTM C1308 testing.« less

Advances in design and modeling of porous materials

NASA Astrophysics Data System (ADS)

Ayral, André; Calas-Etienne, Sylvie; Coasne, Benoit; Deratani, André; Evstratov, Alexis; Galarneau, Anne; Grande, Daniel; Hureau, Matthieu; Jobic, Hervé; Morlay, Catherine; Parmentier, Julien; Prelot, Bénédicte; Rossignol, Sylvie; Simon-Masseron, Angélique; Thibault-Starzyk, Frédéric

2015-07-01

This special issue of the European Physical Journal Special Topics is dedicated to selected papers from the symposium "High surface area porous and granular materials" organized in the frame of the conference "Matériaux 2014", held on November 24-28, 2014 in Montpellier, France. Porous materials and granular materials gather a wide variety of heterogeneous, isotropic or anisotropic media made of inorganic, organic or hybrid solid skeletons, with open or closed porosity, and pore sizes ranging from the centimeter scale to the sub-nanometer scale. Their technological and industrial applications cover numerous areas from building and civil engineering to microelectronics, including also metallurgy, chemistry, health, waste water and gas effluent treatment. Many emerging processes related to environmental protection and sustainable development also rely on this class of materials. Their functional properties are related to specific transfer mechanisms (matter, heat, radiation, electrical charge), to pore surface chemistry (exchange, adsorption, heterogeneous catalysis) and to retention inside confined volumes (storage, separation, exchange, controlled release). The development of innovative synthesis, shaping, characterization and modeling approaches enables the design of advanced materials with enhanced functional performance. The papers collected in this special issue offer a good overview of the state-of-the-art and science of these complex media. We would like to thank all the speakers and participants for their contribution to the success of the symposium. We also express our gratitude to the organization committee of "Matériaux 2014". We finally thank the reviewers and the staff of the European Physical Journal Special Topics who made the publication of this special issue possible.

Discrete element modeling of free-standing wire-reinforced jammed granular columns

NASA Astrophysics Data System (ADS)

Iliev, Pavel S.; Wittel, Falk K.; Herrmann, Hans J.

2018-02-01

The use of fiber reinforcement in granular media is known to increase the cohesion and therefore the strength of the material. However, a new approach, based on layer-wise deployment of predetermined patterns of the fiber reinforcement has led self-confining and free-standing jammed structures to become viable. We have developed a novel model to simulate fiber-reinforced granular materials, which takes into account irregular particles and wire elasticity and apply it to study the stability of unconfined jammed granular columns.

The recycling of comminuted glass-fiber-reinforced resin from electronic waste.

PubMed

Duan, Huabo; Jia, Weifeng; Li, Jinhui

2010-05-01

The reuse of comminuted glass-fiber-reinforced resin with various granularities gathered from printed circuit manufacturing residues was investigated. As fillers, these residues were converted into polymeric composite board by an extrusion and injection process using polypropylene as a bonding agent. The mechanical properties of the reproduced composite board were examined by considering the effects of mass fraction and glass-fiber distribution. Interfacial-layer micrograph analysis of the composite material fracture surface was used to study the fiber reinforcement mechanism. Results showed that using comminuted glass-fiber-reinforced resin as a filler material greatly enhanced the performance properties of the composite board. Although the length and diameter of filler varied, these variations had no appreciable effect on the mechanical properties of the processed board. Maximum values of 48.30 MPa for flexural strength, 31.34 MPa for tensile strength, and 31.34 J/m for impact strength were achieved from a composite board containing mass fractions of 30, 10, and 20% glass-fiber-reinforced resin waste, respectively. It was found that the maximum amount of recyclate that could be added to a composite board was 30% of weight. Beyond these percentages, the materials blend became unmanageable and the mixture less amenable to impregnation with fiber. Presented studies indicated that comminuted glass-fiber-reinforced resin waste-filled polypropylene composites are promising candidates for structural applications where high stiffness and fracture resistance are required.

Jetting and flooding of granular backfill materials : [summary].

DOT National Transportation Integrated Search

2015-03-01

Granular backfill materials on highway projects are often compacted by mechanical methods. : This requires the contractor to place backfill material into loose lifts of varying thickness : and use compaction equipment to reduce air voids and increase...

Heavy Metals in Water Percolating Through Soil Fertilized with Biodegradable Waste Materials.

PubMed

Wierzbowska, Jadwiga; Sienkiewicz, Stanisław; Krzebietke, Sławomir; Bowszys, Teresa

The influence of manure and composts on the leaching of heavy metals from soil was evaluated in a model lysimeter experiment under controlled conditions. Soil samples were collected from experimental fields, from 0- to 90-cm layers retaining the layout of the soil profile layers, after the second crop rotation cycle with the following plant species: potatoes, spring barley, winter rapeseed, and winter wheat. During the field experiment, 20 t DM/ha of manure, municipal sewage sludge composted with straw (SSCS), composted sewage sludge (SSC), dried granular sewage sludge (DGSS), "Dano" compost made from non-segregated municipal waste (CMMW), and compost made from municipal green waste (CUGW) was applied, i.e., 10 t DM/ha per crop rotation cycle. The concentrations (μg/dm 3 ) of heavy metals in the leachate were as follows: Cd (3.6-11.5) < Mn (4.8-15.4) < Cu (13.4-35.5) < Zn (27.5-48.0) < Cr (36.7-96.5) < Ni (24.4-165.8) < Pb (113.8-187.7). Soil fertilization with organic waste materials did not contaminate the percolating water with manganese or zinc, whereas the concentrations of the other metals increased to the levels characteristic of unsatisfactory water quality and poor water quality classes. The copper and nickel content of percolating water depended on the concentration of those metals introduced into the soil with organic waste materials. The concentrations of Cd in the leachate increased, whereas the concentrations of Cu and Ni decreased with increasing organic C content of organic fertilizers. The widening of the C/N ratio contributed to Mn leaching. The concentrations of Pb, Cr, and Mn in the percolating water were positively correlated with the organic C content of soil.

Effects of Noise and Vibration on the Solid to Liquid Fluidization Transition in Small Dense Granular Systems Under Shear

NASA Astrophysics Data System (ADS)

Melhus, Martin Frederic

2011-07-01

Granular materials exhibit bulk properties that are distinct from conventional solids, liq- uids, and gases, due to the dissipative nature of the inter-granular forces. Understanding the fundamentals of granular materials draws upon and gives insight into many fields at the current frontiers of physics, such as plasticity of solids, fracture and friction, com- plex systems such as colloids, foams and suspensions, and a variety of biological systems. Particulate flows are widespread in geophysics, and are also essential to many industries. Despite the importance of these phenomena, we lack a theoretical model that explains most behaviors of granular materials. Since granular assemblies are highly dissipative, they are often far from mechanical equilibrium, making most classical analyses inappli- cable. A theory for dilute granular systems exists, but for dense granular systems (by far the majority of granular systems in the real world) no comparable theory is accepted. We approach this problem by examining the fluidization, or transition from solid to liquid, in dense granular systems. In this study, the separate effects of random noise and vibration on the static to flowing transition of a dense granular assembly under planar shear is studied numerically using soft contact particle dynamics simulations in two dimensions. We focus on small systems in a thin planar Couette cell, examining the bistable region while increasing shear, with varying amounts of random noise or vibration, and determine the statistics of the shear required for the onset of flow. We find that the applied power is the key parameter in determining the magnitude of the effects of the noise or vibration, with vibration frequency also having an influence. Similarities and differences between noise and vibration are determined, and the results compare favorably with a two phase model for dense granular flow.

Granular flows in constrained geometries

NASA Astrophysics Data System (ADS)

Murthy, Tejas; Viswanathan, Koushik

Confined geometries are widespread in granular processing applications. The deformation and flow fields in such a geometry, with non-trivial boundary conditions, determine the resultant mechanical properties of the material (local porosity, density, residual stresses etc.). We present experimental studies of deformation and plastic flow of a prototypical granular medium in different nontrivial geometries- flat-punch compression, Couette-shear flow and a rigid body sliding past a granular half-space. These geometries represent simplified scaled-down versions of common industrial configurations such as compaction and dredging. The corresponding granular flows show a rich variety of flow features, representing the entire gamut of material types, from elastic solids (beam buckling) to fluids (vortex-formation, boundary layers) and even plastically deforming metals (dead material zone, pile-up). The effect of changing particle-level properties (e.g., shape, size, density) on the observed flows is also explicitly demonstrated. Non-smooth contact dynamics particle simulations are shown to reproduce some of the observed flow features quantitatively. These results showcase some central challenges facing continuum-scale constitutive theories for dynamic granular flows.

Physics of Granular Materials: Investigations in Support of Astrobiology

NASA Technical Reports Server (NTRS)

Marshall, John R.

2002-01-01

This publication list is submitted as a summary of the work conducted under Cooperative Agreement 1120. The goal of the 1120 research was to study granular materials within a planetary, astrophysical, and astrobiological context. This involved research on the physical, mechanical and electrostatic properties of granular systems, as well as the examination of these materials with atomic force microscopy and x-ray analysis. Instruments for analyzing said materials in planetary environments were developed, including the MECA (Mars Environment Compatibility Assessment) experiment for the MSP '01 lander, the ECHOS/MATADOR experiment for the MSP '03 lander, an ISRU experiment for the '03 lander, and MiniLEAP technology. Flight experiments for microgravity (Space Station and Shuttle) have also been developed for the study of granular materials. As expressed in the publications, work on 1120 encompassed laboratory research, theoretical modeling, field experiments, and flight experiments: a series of successful new models were developed for understanding the behavior of triboelectrostatically charged granular masses, and 4 separate instruments were selected for space flight. No inventions or patents were generated by the research under this Agreement.

The behavior of a macroscopic granular material in vortex flow

NASA Astrophysics Data System (ADS)

Nishikawa, Asami

A granular material is defined as a collection of discrete particles such as powder and grain. Granular materials display a large number of complex behaviors. In this project, the behavior of macroscopic granular materials under tornado-like vortex airflow, with varying airflow velocity, was observed and studied. The experimental system was composed of a 9.20-cm inner diameter acrylic pipe with a metal mesh bottom holding the particles, a PVC duct, and an airflow source controlled by a variable auto-transformer, and a power-meter. A fixed fan blade was attached to the duct's inner wall to create a tornado-like vortex airflow from straight flow. As the airflow velocity was increased gradually, the behavior of a set of same-diameter granular materials was observed. The observed behaviors were classified into six phases based on the macroscopic mechanical dynamics. Through this project, we gained insights on the significant parameters for a computer simulation of a similar system by Heath Rice [5]. Comparing computationally and experimentally observed phase diagrams, we can see similar structure. The experimental observations showed the effect of initial arrangement of particles on the phase transitions.

Invited Article: Refractive index matched scanning of dense granular materials

NASA Astrophysics Data System (ADS)

Dijksman, Joshua A.; Rietz, Frank; Lőrincz, Kinga A.; van Hecke, Martin; Losert, Wolfgang

2012-01-01

We review an experimental method that allows to probe the time-dependent structure of fully three-dimensional densely packed granular materials and suspensions by means of particle recognition. The method relies on submersing a granular medium in a refractive index matched fluid. This makes the resulting suspension transparent. The granular medium is then visualized by exciting, layer by layer, the fluorescent dye in the fluid phase. We collect references and unreported experimental know-how to provide a solid background for future development of the technique, both for new and experienced users.

Using Advanced Computing in Applied Dynamics: From the Dynamics of Granular Material to the Motion of the Mars Rover

DTIC Science & Technology

2013-08-26

USING ADVANCED COMPUTING IN APPLIED DYNAMICS : FROM THE DYNAMICS OF GRANULAR MATERIAL TO THE MOTION OF THE MARS ROVER Dan Negrut NVIDIA CUDA...USING ADVANCED COMPUTING IN APPLIED DYNAMICS : FROM THE DYNAMICS OF GRANULAR MATERIAL TO THE MOTION OF THE MARS ROVER 5a. CONTRACT NUMBER W911NF-11-F...University of Parma, Italy • Drs. Paramsothy Jayakumar & David Lamb, US Army TARDEC • Mihai Anitescu, University of Chicago & Argonne National Lab

Transesterification of sago starch and waste palm cooking oil in densified CO2

NASA Astrophysics Data System (ADS)

Muljana, H.; Sugih, A. K.; Christina, N.; Fangdinata, K.; Renaldo, J.; Rudy; Heeres, H. J.; Picchioni, F.

2017-07-01

In this work, the synthesis of biodegradable and yet renewable thermoplastics materials through a transesterification reaction of sago starch and waste palm cooking oil (WPO) in densified CO2 as the solvent is reported. The aim of this research is to investigate the potential used of sago starch and WPO as raw materials in the thermoplastics starch synthesis. The starch esters was successfully synthesized using sago starch and WPO as reagent in densified CO2 as shown from the presence of carbonyl group (C=O, 1743 cm-1) in the FT-IR spectra coupled with the presence of the proton (1H-NMR) of the fatty acid in the starch backbone (0.8 - 2 ppm). The product crystallinity decreases as shown in XRD results and resulting with a change in the thermal properties (melting and crystalline temperature) of the products. In addition, the products show a different granular morphology and a higher hydrophobicity compared with native sago starch. This research shows the potential used of sago starch and WPO in the thermoplastics starch synthesis and opens a new perspective on the product application.

Slide Conveying of Granular Materials-Thinking Out of the Glovebox

NASA Technical Reports Server (NTRS)

Goddard, J. D.; Didwania, A. K.; Nott, P. R.

2000-01-01

The vibratory conveyor, routinely employed for normal-gravity transport of granular materials, usually consists of a continuous open trough vibrated sinusoidally to induce axial movement of a granular material. Motivated in part by a hypothetical application in zero gravity, we propose a novel modification of the vibratory conveyor based on a closed 2d trough operating in a "slide-conveying" mode, with the granular mass remaining permanently in contact with the trough walls. We present a detailed analysis of the mechanics of transport, based on a rigid-slab model for the granular mass with frictional (Coulomb) slip at the upper and lower walls. The form of the vibration cycle plays a crucial role, and the optimal conveying cycle is not the commonly assumed rectilinear sinusoidal motion. The conveying efficiency for the novel slide conveyor will be presented for several simple vibration cycles, including one believed to represent the theoretical optimum.

Design of the Long-term Waste Management Facility for Historic LLRW Port Hope Project - 13322

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, Don; Barton, David; Case, Glenn

2013-07-01

The Municipality of Port Hope is located on the northern shores of Lake Ontario approximately 100 km east of Toronto, Ontario, Canada. Starting in the 1930's, radium and later uranium processing by Eldorado Gold Mines Limited (subsequently Eldorado Nuclear Limited) (Eldorado) at their refinery in Port Hope resulted in the generation of process residues and wastes that were disposed of indiscriminately throughout the Municipality until about the mid-1950's. These process residues contained radium (Ra- 226), uranium, arsenic and other contaminants. Between 1944 and 1988, Eldorado was a Federal Crown Corporation, and as such, the Canadian Federal Government has assumed responsibilitymore » for the clean-up and long-term management of the historic waste produced by Eldorado during this period. The Port Hope Project involves the construction and development of a new long-term waste management facility (LTWMF), and the remediation and transfer of the historic wastes located within the Municipality of Port Hope to the new LTWMF. The new LTWMF will consist of an engineered above-ground containment mound designed to contain and isolate the wastes from the surrounding environment for the next several hundred years. The design of the engineered containment mound consists of a primary and secondary composite base liner system and composite final cover system, made up of both natural materials (e.g., compacted clay, granular materials) and synthetic materials (e.g., geo-synthetic clay liner, geo-membrane, geo-textiles). The engineered containment mound will cover an area of approximately 13 hectares and will contain the estimated 1.2 million cubic metres of waste that will be generated from the remedial activities within Port Hope. The LTWMF will also include infrastructure and support facilities such as access roads, administrative offices, laboratory, equipment and personnel decontamination facilities, waste water treatment plant and other ancillary facilities. Preliminary construction activities for the Port Hope LTWMF commenced in 2012 and are scheduled to continue over the next few years. The first cell of the engineered containment mound is scheduled to be constructed in 2015 with waste placement into the Port Hope LTWMF anticipated over the following seven year period. (authors)« less

Ion exchange of several radionuclides on the hydrous crystalline silicotitanate, UOP IONSIV IE-911

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huckman, M.E.; Latheef, I.M.; Anthony, R.G.

1999-04-01

The crystalline silicotitanate, UOP IONSIV IE-911, is a proven material for removing radionuclides from a wide variety of waste streams. It is superior for removing several radionuclides from the highly alkaline solutions typical of DOE wastes. This laboratory previously developed an equilibrium model applicable to complex solutions for IE-910 (the power form of the granular IE-911), and more recently, the authors have developed several single component ion-exchange kinetic models for predicting column breakthrough curves and batch reactor concentration histories. In this paper, the authors model ion-exchange column performance using effective diffusivities determined from batch kinetic experiments. This technique is preferablemore » because the batch experiments are easier, faster, and cheaper to perform than column experiments. They also extend these ideas to multicomponent systems. Finally, they evaluate the ability of the equilibrium model to predict data for IE-911.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsumura, Yukihiko; Nuessle, F.W.; Antal, M.J. Jr.

Recently, carbonaceous materials were proved to be effective catalysts for hazardous waste decomposition in supercritical water. Gasification of the carbonaceous catalyst itself is also expected, however, under supercritical conditions. Thus, it is essential to determine the gasification rate of the carbonaceous materials during this process to determine the active lifetime of the catalysts. For this purpose, the gasification characteristics of granular coconut shell activated carbon in supercritical water alone (600-650{degrees}C, 25.5-34.5 MPa) were investigated. The gasification rate at subatmospheric pressure agreed well with the gasification rate at supercritical conditions, indicating the same reaction mechanism. Methane generation under these conditions ismore » via pyrolysis, and thus is not affected by the water pressure. An iodine number increase of 25% was observed as a result of the supercritical water gasification.« less

Effects of granular charge on flow and mixing

NASA Astrophysics Data System (ADS)

Shinbrot, T.; Herrmann, H. J.

2008-12-01

Sandstorms in the desert have long been reported to produce sparks and other electrical disturbances - indeed as long ago as 1850, Faraday commented on the peculiarities of granular charging during desert sandstorms. Similarly, lightning strikes within volcanic dust plumes have been repeatedly reported for over half a century, but remain unexplained. The problem of granular charging has applied, as well as natural, implications, for charged particle clouds frequently generate spectacularly devastating dust explosions in granular processing plants, and sand becomes strongly electrified by helicopters traveling in desert environments. The issue even has implications for missions to the Moon and to Mars, where charged dust degrades solar cells viability and clings to spacesuits, limiting the lifetime of their joints. Despite the wide-ranging importance of granular charging, even the simplest aspects of its causes remain elusive. To take one example, sand grains in the desert manage to charge one another despite having only similar materials to rub against over expanses of many miles - thus existing theories of charging due to material differences fail entirely to account for the observed charging of desert sands. In this talk, we describe recent progress made in identifying underlying causes of granular charging, both in desert-like environments and in industrial applications, and we examine effects of granular charging on flow, mixing and separation of common granular materials. We find that charging of identical grains can occur under simple laboratory conditions, and we make new predictions for the effects of this charging on granular behaviours.

Evaluation of geofabric in undercut on MSE wall stability : executive summary report.

DOT National Transportation Integrated Search

2011-05-01

Compaction of granular base materials at sites with fine grained native soils often causes unwanted material loss due to penetration. In 2007, ODOT began placing geofabrics in the undercut of MSE walls at the soil/ granular material interface to faci...

DEM modeling of flexible structures against granular material avalanches

NASA Astrophysics Data System (ADS)

Lambert, Stéphane; Albaba, Adel; Nicot, François; Chareyre, Bruno

2016-04-01

This article presents the numerical modeling of flexible structures intended to contain avalanches of granular and coarse material (e.g. rock slide, a debris slide). The numerical model is based on a discrete element method (YADE-Dem). The DEM modeling of both the flowing granular material and the flexible structure are detailed before presenting some results. The flowing material consists of a dry polydisperse granular material accounting for the non-sphericity of real materials. The flexible structure consists in a metallic net hanged on main cables, connected to the ground via anchors, on both sides of the channel, including dissipators. All these components were modeled as flexible beams or wires, with mechanical parameters defined from literature data. The simulation results are presented with the aim of investigating the variability of the structure response depending on different parameters related to the structure (inclination of the fence, with/without brakes, mesh size opening), but also to the channel (inclination). Results are then compared with existing recommendations in similar fields.

Measurements of the frame acoustic properties of porous and granular materials

NASA Astrophysics Data System (ADS)

Park, Junhong

2005-12-01

For porous and granular materials, the dynamic characteristics of the solid component (frame) are important design factors that significantly affect the material's acoustic properties. The primary goal of this study was to present an experimental method for measuring the vibration characteristics of this frame. The experimental setup was designed to induce controlled vibration of the solid component while minimizing the influence from coupling between vibrations of the fluid and the solid component. The Biot theory was used to verify this assumption, taking the two dilatational wave propagations and interactions into account. The experimental method was applied to measure the dynamic properties of glass spheres, lightweight microspheres, acoustic foams, and fiberglass. A continuous variation of the frame vibration characteristics with frequency similar to that of typical viscoelastic materials was measured. The vibration amplitude had minimal effects on the dynamic characteristics of the porous material compared to those of the granular material. For the granular material, materials comprised of larger particles and those under larger vibration amplitudes exhibited lower frame wave speeds and larger decay rates.

Granular avalanches on the Moon: Mass-wasting conditions, processes, and features

NASA Astrophysics Data System (ADS)

Kokelaar, B. P.; Bahia, R. S.; Joy, K. H.; Viroulet, S.; Gray, J. M. N. T.

2017-09-01

Seven lunar crater sites of granular avalanches are studied utilizing high-resolution images (0.42-1.3 m/pixel) from the Lunar Reconnaissance Orbiter Camera; one, in Kepler crater, is examined in detail. All the sites are slopes of debris extensively aggraded by frictional freezing at their dynamic angle of repose, four in craters formed in basaltic mare and three in the anorthositic highlands. Diverse styles of mass wasting occur, and three types of dry-debris flow deposit are recognized: (1) multiple channel-and-lobe type, with coarse-grained levees and lobate terminations that impound finer debris, (2) single-surge polylobate type, with subparallel arrays of lobes and fingers with segregated coarse-grained margins, and (3) multiple-ribbon type, with tracks reflecting reworked substrate, minor levees, and no coarse terminations. The latter type results from propagation of granular erosion-deposition waves down slopes dominantly of fine regolith, and it is the first recognized natural example. Dimensions, architectures, and granular segregation styles of the two coarse-grained deposit types are like those formed in natural and experimental avalanches on Earth, although the timescale of motion differs due to the reduced gravity. Influences of reduced gravity and fine-grained regolith on dynamics of granular flow and deposition appear slight, but we distinguish, for the first time, extensive remobilization of coarse talus by inundation with finer debris. The (few) sites show no clear difference attributable to the contrasting mare basalt and highland megaregolith host rocks and their fragmentation. This lunar study offers a benchmarking of deposit types that can be attributed to formation without influence of liquid or gas.

Advances in the simulation and automated measurement of well-sorted granular material: 2. Direct measures of particle properties

USGS Publications Warehouse

Buscombe, Daniel D.; Rubin, David M.

2012-01-01

1. In this, the second of a pair of papers on the structure of well-sorted natural granular material (sediment), new methods are described for automated measurements from images of sediment, of: 1) particle-size standard deviation (arithmetic sorting) with and without apparent void fraction; and 2) mean particle size in material with void fraction. A variety of simulations of granular material are used for testing purposes, in addition to images of natural sediment. Simulations are also used to establish that the effects on automated particle sizing of grains visible through the interstices of the grains at the very surface of a granular material continue to a depth of approximately 4 grain diameters and that this is independent of mean particle size. Ensemble root-mean squared error between observed and estimated arithmetic sorting coefficients for 262 images of natural silts, sands and gravels (drawn from 8 populations) is 31%, which reduces to 27% if adjusted for bias (slope correction between observed and estimated values). These methods allow non-intrusive and fully automated measurements of surfaces of unconsolidated granular material. With no tunable parameters or empirically derived coefficients, they should be broadly universal in appropriate applications. However, empirical corrections may need to be applied for the most accurate results. Finally, analytical formulas are derived for the one-step pore-particle transition probability matrix, estimated from the image's autocorrelogram, from which void fraction of a section of granular material can be estimated directly. This model gives excellent predictions of bulk void fraction yet imperfect predictions of pore-particle transitions.

Advances in the simulation and automated measurement of well-sorted granular material: 2. Direct measures of particle properties

NASA Astrophysics Data System (ADS)

Buscombe, D.; Rubin, D. M.

2012-06-01

In this, the second of a pair of papers on the structure of well-sorted natural granular material (sediment), new methods are described for automated measurements from images of sediment, of: 1) particle-size standard deviation (arithmetic sorting) with and without apparent void fraction; and 2) mean particle size in material with void fraction. A variety of simulations of granular material are used for testing purposes, in addition to images of natural sediment. Simulations are also used to establish that the effects on automated particle sizing of grains visible through the interstices of the grains at the very surface of a granular material continue to a depth of approximately 4 grain diameters and that this is independent of mean particle size. Ensemble root-mean squared error between observed and estimated arithmetic sorting coefficients for 262 images of natural silts, sands and gravels (drawn from 8 populations) is 31%, which reduces to 27% if adjusted for bias (slope correction between observed and estimated values). These methods allow non-intrusive and fully automated measurements of surfaces of unconsolidated granular material. With no tunable parameters or empirically derived coefficients, they should be broadly universal in appropriate applications. However, empirical corrections may need to be applied for the most accurate results. Finally, analytical formulas are derived for the one-step pore-particle transition probability matrix, estimated from the image's autocorrelogram, from which void fraction of a section of granular material can be estimated directly. This model gives excellent predictions of bulk void fraction yet imperfect predictions of pore-particle transitions.

Alternative granular media for the metal casting industry. Final report, September 30, 1994

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guichelaar, P.J.; Ramrattan, S.N.; Tieder, R.E.

1995-09-01

Silica sand for foundry use is inexpensive to purchase, readily transported and widely available. As a result, it is universally used. However, three factors are becoming increasingly significant as more environmental regulations are promulgated. First, the disposal of waste foundry sand has become an excessively burdensome cost. Second, the phase changes which occur in the silica structure on heating and cooling cause thermal breakdown of the sand into smaller unusable fractions. Third, silica is a relatively weak mineral. Alternatives to silica sand which can withstand the rigors of repetitive reuse must be seriously evaluated as a way to control productionmore » costs of the domestic metal casting industry. Chromite sands, olivine sands and carbon sands have each been successfully used to solve operating problems and thus have developed their specific niches in the foundry materials inventory. However, there are several other materials that are candidates for replacing silica sand, such as fused alumina, sintered bauxite and sintered oil well proppants. These media, and others that are generically similar, are manufactured for specific purposes. Compositions and shapes could be readily tailored for used in a metal casting environment of total recycling and materials conservation. This study examines materials that are readily available as alternatives to silica sand from a functionality perspective and a cost perspective. Some of the alternative materials are natural and others are synthetic and thus referring to them as ``sands`` has the potential to cause confusion; the generic term ``granular medium`` is used in this study to mean any material that could functionally substitute for silica sand in the foundry process.« less

Rational Selection of Tailored Amendment Mixtures and Composites for In Situ Remediation of Contaminated Sediments

DTIC Science & Technology

2008-12-01

Certification Program GAC granular activated carbon HGR sulfur impregnated activated carbon MCA Menzie Cura and Associates MRM Minimum Required...determination of iodine number was followed. The materials tested were granular activated carbon (GAC), alumina powder, ATS, apatite, bentonite, barite...materials tested were granular activated carbon (GAC), alumina powder, ATS, apatite, bentonite, barite, ConSep 20 and 42%, and ATC. The Iodine Number

Mechanics of Granular Materials (MGM)

NASA Technical Reports Server (NTRS)

Alshibli, Khalid A.; Costes, Nicholas C.; Porter, Ronald F.

1996-01-01

The constitutive behavior of uncemented granular materials such as strength, stiffness, and localization of deformations are to a large extend derived from interparticle friction transmitted between solid particles and particle groups. Interparticle forces are highly dependent on gravitational body forces. At very low effective confining pressures, the true nature of the Mohr envelope, which defines the Mohr-Coulomb failure criterion for soils, as well as the relative contribution of each of non-frictional components to soil's shear strength cannot be evaluated in terrestrial laboratories. Because of the impossibility of eliminating gravitational body forces on earth, the weight of soil grains develops interparticle compressive stresses which mask true soil constitutive behavior even in the smallest samples of models. Therefore the microgravity environment induced by near-earth orbits of spacecraft provides unique experimental opportunities for testing theories related to the mechanical behavior of terrestrial granular materials. Such materials may include cohesionless soils, industrial powders, crushed coal, etc. This paper will describe the microgravity experiment, 'Mechanics of Granular Materials (MGM)', scheduled to be flown on Space Shuttle-MIR missions. The paper will describe the experiment's hardware, instrumentation, specimen preparation procedures, testing procedures in flight, as well as a brief summary of the post-mission analysis. It is expected that the experimental results will significantly improve the understanding of the behavior of granular materials under very low effective stress levels.

Eco-friendly porous concrete using bottom ash aggregate for marine ranch application.

PubMed

Lee, Byung Jae; Prabhu, G Ganesh; Lee, Bong Chun; Kim, Yun Yong

2016-03-01

This article presents the test results of an investigation carried out on the reuse of coal bottom ash aggregate as a substitute material for coarse aggregate in porous concrete production for marine ranch applications. The experimental parameters were the rate of bottom ash aggregate substitution (30%, 50% and 100%) and the target void ratio (15%, 20% and 25%). The cement-coated granular fertiliser was substituted into a bottom ash aggregate concrete mixture to improve marine ranch applications. The results of leaching tests revealed that the bottom ash aggregate has only a negligible amount of the ten deleterious substances specified in the Ministry of Environment - Enforcement Regulation of the Waste Management Act of Republic Korea. The large amount of bubbles/air gaps in the bottom ash aggregate increased the voids of the concrete mixtures in all target void ratios, and decreased the compressive strength of the porous concrete mixture; however, the mixture substituted with 30% and 10% of bottom ash aggregate and granular fertiliser, respectively, showed an equal strength to the control mixture. The sea water resistibility of the bottom ash aggregate substituted mixture was relatively equal to that of the control mixture, and also showed a great deal of improvement in the degree of marine organism adhesion compared with the control mixture. No fatality of fish was observed in the fish toxicity test, which suggested that bottom ash aggregate was a harmless material and that the combination of bottom ash aggregate and granular fertiliser with substitution rates of 30% and 10%, respectively, can be effectively used in porous concrete production for marine ranch application. © The Author(s) 2015.

Granular Material Scoop and Near-Vertical Lifting Feeder/Conveyor

NASA Technical Reports Server (NTRS)

Walton, Otis (Inventor); Vollmer, Hubert J. (Inventor)

2017-01-01

An integrated granular-material scoop and near-vertical lifting feeder/conveyor includes special connections and skirts between a bullnose rotating scoop and an open-helical screw that provides the rotations and material lift and evacuation. A conical working-face of the bullnose rotating scoop has symmetrically distributed graters and vents to break loose and force-in granular material from natural deposits and cargo holds. The bullnose rotating scoop and the open-helical screw its attached to move the material into a continuous layer on the inside surface of an outer stationary sheathing. A motor drive attached to the open-helical screw above at the delivery end provides the lifting force necessary.

Granular crystals: Nonlinear dynamics meets materials engineering

DOE PAGES

Porter, Mason A.; Kevrekidis, Panayotis G.; Daraio, Chiara

2015-11-01

In this article, the freedom to choose the size, stiffness, and spatial distribution of macroscopic particles in a lattice makes granular crystals easily tailored building blocks for shock-absorbing materials, sound-focusing devices, acoustic switches, and other exotica.

Arsenic partitioning among particle-size fractions of mine wastes and stream sediments from cinnabar mining districts.

PubMed

Silva, Veronica; Loredo, Jorge; Fernández-Martínez, Rodolfo; Larios, Raquel; Ordóñez, Almudena; Gómez, Belén; Rucandio, Isabel

2014-10-01

Tailings from abandoned mercury mines represent an important pollution source by metals and metalloids. Mercury mining in Asturias (north-western Spain) has been carried out since Roman times until the 1970s. Specific and non-specific arsenic minerals are present in the paragenesis of the Hg ore deposit. As a result of intensive mining operations, waste materials contain high concentrations of As, which can be geochemically dispersed throughout surrounding areas. Arsenic accumulation, mobility and availability in soils and sediments are strongly affected by the association of As with solid phases and granular size composition. The objective of this study was to examine phase associations of As in the fine grain size subsamples of mine wastes (La Soterraña mine site) and stream sediments heavily affected by acid mine drainage (Los Rueldos mine site). An arsenic-selective sequential procedure, which categorizes As content into seven phase associations, was applied. In spite of a higher As accumulation in the finest particle-size subsamples, As fractionation did not seem to depend on grain size since similar distribution profiles were obtained for the studied granulometric fractions. The presence of As was relatively low in the most mobile forms in both sites. As was predominantly linked to short-range ordered Fe oxyhydroxides, coprecipitated with Fe and partially with Al oxyhydroxides and associated with structural material in mine waste samples. As incorporated into short-range ordered Fe oxyhydroxides was the predominant fraction at sediment samples, representing more than 80% of total As.

Implicit continuum mechanics approach to heat conduction in granular materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Massoudi, M.; Mehrabadi, M.

In this paper, we derive a properly frame-invariant implicit constitutive relationship for the heat flux vector for a granular medium (or a density-gradient-type fluid). The heat flux vector is commonly modeled by Fourier’s law of heat conduction, and for complex materials such as nonlinear fluids, porous media, or granular materials, the coefficient of thermal conductivity is generalized by assuming that it would depend on a host of material and kinematic parameters such as temperature, shear rate, porosity, concentration, etc. In this paper, we extend the approach of Massoudi [Massoudi, M. Math. Methods Appl. Sci. 2006, 29, 1585; Massoudi, M. Math.more » Methods Appl. Sci. 2006, 29, 1599], who provided explicit constitutive relations for the heat flux vector for flowing granular materials; in order to do so, we use the implicit scheme suggested by Fox [Fox, N. Int. J. Eng. Sci. 1969, 7, 437], who obtained implicit relations in thermoelasticity.« less

Laboratory Investigation on the Effects of Natural Fine Aggregates and Recycled Waste Tire Rubber in Pervious Concrete to Develop More Sustainable Pavement Materials

NASA Astrophysics Data System (ADS)

Bonicelli, Alessandra; Fuentes, Luis G.; Khalil Dawd Bermejo, Ibrahim

2017-10-01

Pervious concrete pavement is a recognized sustainable solution for urban roads. To enhance mechanical properties of pervious concrete material, in order to allow wider use of this technology, a lot of studies are going on all over the world. The use of a little percentage of fine aggregates is proven to increase the material resistance without an excessive reduction of permeability. This study aimed to evaluate the effect of replacing the fine virgin aggregates with r cycled tire rubber. 14 different mixes were analysed in terms of indirect tensile strength resistance, void content and density. Two different dimensions of crumb rubber were studied, as well as two different dosages, which were applied to different no-fine control mixes. All results were compared with the same control mixes containing natural fine aggregate. The mixes had a fixed granulometric curve but varied in water/cement ratio; this in order to evaluate the effect of recycled rubber depending to w/c ratio of the mix. An image analysis was also conducted to verify the rubber distribution in the mixture and the cracking surfaces. The experimental analysis showed that a correct proportioning of fine sand significantly increased the strength of the material. Moreover, the use of recycled waste tire rubber, gave interesting improvements respect to the no-fine control mixes, even though the developed resistance was lower respect to mixes containing mineral sand. This result was expected because of the cementing property of mineral sand. Although, the important result was that it was possible to use waste tire rubber in pervious concrete, with an appropriate dosage and granular dimension, for increasing the performance of traditional mix design, in order to achieve pavement materials more and more sustainable.

Consideration of reinforcement mechanism in the short fiber mixing granular materials by granular element simulations

NASA Astrophysics Data System (ADS)

Mori, Kentaro; Kaneko, Kenji; Hashizume, Yutaka

2017-06-01

The short fiber mixing method is well known as one of the method to improve the strength of gran- ular soils in geotechnical engineering. Mechanical properties of the short fiber mixing granular materials are influenced by many factors, such as the mixture ratio of the short fiber, the material of short fiber, the length, and the orientation. In particular, the mixture ratio of the short fibers is very important in mixture design. In the past study, we understood that the strength is reduced by too much short fiber mixing by a series of tri-axial compression experiments. Namely, there is "optimum mixture ratio" in the short fiber mixing granular soils. In this study, to consider the mechanism of occurrence of the optimum mixture ratio, we carried out the numerical experiments by granular element method. As the results, we can understand that the strength decrease when too much grain-fiber contact points exist, because a friction coefficient is smaller than the grain-grain contact points.

Granular Materials and Risks in ISRU

NASA Technical Reports Server (NTRS)

Behringer, Robert P.; Wilki8nson, R. Allen

2004-01-01

Working with soil, sand, powders, ores, cement and sintered bricks, excavating, grading construction sites, driving off-road, transporting granules in chutes and pipes, sifting gravel, separating solids from gases, and using hoppers are so routine that it seems straightforward to execute these operations on the Moon and Mars as we do on Earth. We discuss how little these processes are understood and point out the nature of trial-and-error practices that are used in today s massive over-design. Nevertheless, such designs have a high failure rate. Implementation and extensive incremental scaling up of industrial processes are routine because of the inadequate predictive tools for design. We present a number of pragmatic scenarios where granular materials play a role, the risks involved, what some of the basic issues are, and what understanding is needed to greatly reduce the risks. This talk will focus on a particular class of granular flow issues, those that pertain to dense materials, their physics, and the failure problems associated with them. In particular, key issues where basic predictability is lacking include stability of soils for the support of vehicles and facilities, ability to control the flow of dense materials (jamming and flooding/unjamming at the wrong time), the ability to predict stress profiles (hence create reliable designs) for containers such as bunkers or silos. In particular, stress fluctuations, which are not accounted for in standard granular design models, can be very large as granular materials flows, and one result is frequent catastrophic failure of granular devices.

Granular Materials and Risks In ISRU

NASA Technical Reports Server (NTRS)

Behringer, Robert P.; Wilkinson, R. Allen

2004-01-01

Working with soil, sand, powders, ores, cement and sintered bricks, excavating, grading construction sites, driving off-road, transporting granules in chutes and pipes, sifting gravel, separating solids from gases, and using hoppers are so routine that it seems straightforward to execute these operations on the Moon and Mars as we do on Earth. We discuss how little these processes are understood and point out the nature of trial-and-error practices that are used in today's massive over-design. Nevertheless, such designs have a high failure rate. Implementation and extensive incremental scaling up of industrial processes are routine because of the inadequate predictive tools for design. We present a number of pragmatic scenarios where granular materials play a role, the risks involved, what some of the basic issues are, and what understanding is needed to greatly reduce the risks. This talk will focus on a particular class of granular flow issues, those that pertain to dense materials, their physics, and the failure problems associated with them. In particular, key issues where basic predictability is lacking include stability of soils for the support of vehicles and facilities, ability to control the flow of dense materials (jamming and flooding/unjamming at the wrong time), the ability to predict stress profiles (hence create reliable designs) for containers such as bunkers or silos. In particular, stress fluctuations, which are not accounted for in standard granular design models, can be very large as granular materials flows, and one result is frequent catastrophic failure of granular devices.

Force Transmission Modes of Non-Cohesive and Cohesive Materials at the Critical State.

PubMed

Wang, Ji-Peng

2017-08-31

This paper investigates the force transmission modes, mainly described by probability density distributions, in non-cohesive dry and cohesive wet granular materials by discrete element modeling. The critical state force transmission patterns are focused on with the contact model effect being analyzed. By shearing relatively dense and loose dry specimens to the critical state in the conventional triaxial loading path, it is observed that there is a unique critical state force transmission mode. There is a universe critical state force distribution pattern for both the normal contact forces and tangential contact forces. Furthermore, it is found that using either the linear Hooke or the non-linear Hertz model does not affect the universe force transmission mode, and it is only related to the grain size distribution. Wet granular materials are also simulated by incorporating a water bridge model. Dense and loose wet granular materials are tested, and the critical state behavior for the wet material is also observed. The critical state strength and void ratio of wet granular materials are higher than those of a non-cohesive material. The critical state inter-particle distribution is altered from that of a non-cohesive material with higher probability in relatively weak forces. Grains in non-cohesive materials are under compressive stresses, and their principal directions are mainly in the axial loading direction. However, for cohesive wet granular materials, some particles are in tension, and the tensile stresses are in the horizontal direction on which the confinement is applied. The additional confinement by the tensile stress explains the macro strength and dilatancy increase in wet samples.

Force Transmission Modes of Non-Cohesive and Cohesive Materials at the Critical State

PubMed Central

2017-01-01

This paper investigates the force transmission modes, mainly described by probability density distributions, in non-cohesive dry and cohesive wet granular materials by discrete element modeling. The critical state force transmission patterns are focused on with the contact model effect being analyzed. By shearing relatively dense and loose dry specimens to the critical state in the conventional triaxial loading path, it is observed that there is a unique critical state force transmission mode. There is a universe critical state force distribution pattern for both the normal contact forces and tangential contact forces. Furthermore, it is found that using either the linear Hooke or the non-linear Hertz model does not affect the universe force transmission mode, and it is only related to the grain size distribution. Wet granular materials are also simulated by incorporating a water bridge model. Dense and loose wet granular materials are tested, and the critical state behavior for the wet material is also observed. The critical state strength and void ratio of wet granular materials are higher than those of a non-cohesive material. The critical state inter-particle distribution is altered from that of a non-cohesive material with higher probability in relatively weak forces. Grains in non-cohesive materials are under compressive stresses, and their principal directions are mainly in the axial loading direction. However, for cohesive wet granular materials, some particles are in tension, and the tensile stresses are in the horizontal direction on which the confinement is applied. The additional confinement by the tensile stress explains the macro strength and dilatancy increase in wet samples. PMID:28858238

Terminal velocity of liquids and granular materials dispersed by a high explosive

NASA Astrophysics Data System (ADS)

Loiseau, J.; Pontalier, Q.; Milne, A. M.; Goroshin, S.; Frost, D. L.

2018-05-01

The explosive dispersal of a layer of solid particles or a layer of liquid surrounding a spherical high-explosive charge generates a turbulent, multiphase flow. Shock compression of the material layer during the initial acceleration may partially consolidate the material, leading to the formation of jet-like structures when the layer fragments and sheds particles upon release. Similarly, release of a shock-compressed liquid shell causes the nucleation of cavitation sites, leading to the radial breakup of the shell and the formation of jets upon expansion. In the current study, a wide variety of granular materials and liquids were explosively dispersed. The maximum terminal jet tip or shell velocity was measured using high-speed videography. Charges were constructed using thin-walled glass bulbs of various diameters and contained a central C-4 charge surrounded by the material to be dispersed. This permitted variation of the ratio of material mass to charge mass ( M/ C) from 4 to 300. Results indicated that material velocity broadly correlates with predictions of the Gurney model. For liquids, the terminal velocity was accurately predicted by the Gurney model. For granular materials, Gurney over-predicted the terminal velocity by 25-60%, depending on the M/ C ratio, with larger M/ C values exhibiting larger deficits. These deficits are explained by energy dissipation during the collapse of voids in the granular material bed. Velocity deficits were insensitive to the degree of jetting and granular material properties. Empirical corrections to the Gurney model are presented with improved agreement with the dry powder experimental velocities.

Terminal velocity of liquids and granular materials dispersed by a high explosive

NASA Astrophysics Data System (ADS)

Loiseau, J.; Pontalier, Q.; Milne, A. M.; Goroshin, S.; Frost, D. L.

2018-04-01

The explosive dispersal of a layer of solid particles or a layer of liquid surrounding a spherical high-explosive charge generates a turbulent, multiphase flow. Shock compression of the material layer during the initial acceleration may partially consolidate the material, leading to the formation of jet-like structures when the layer fragments and sheds particles upon release. Similarly, release of a shock-compressed liquid shell causes the nucleation of cavitation sites, leading to the radial breakup of the shell and the formation of jets upon expansion. In the current study, a wide variety of granular materials and liquids were explosively dispersed. The maximum terminal jet tip or shell velocity was measured using high-speed videography. Charges were constructed using thin-walled glass bulbs of various diameters and contained a central C-4 charge surrounded by the material to be dispersed. This permitted variation of the ratio of material mass to charge mass (M/C) from 4 to 300. Results indicated that material velocity broadly correlates with predictions of the Gurney model. For liquids, the terminal velocity was accurately predicted by the Gurney model. For granular materials, Gurney over-predicted the terminal velocity by 25-60%, depending on the M/C ratio, with larger M/C values exhibiting larger deficits. These deficits are explained by energy dissipation during the collapse of voids in the granular material bed. Velocity deficits were insensitive to the degree of jetting and granular material properties. Empirical corrections to the Gurney model are presented with improved agreement with the dry powder experimental velocities.

Granular materials flow like complex fluids

NASA Astrophysics Data System (ADS)

Kou, Binquan; Cao, Yixin; Li, Jindong; Xia, Chengjie; Li, Zhifeng; Dong, Haipeng; Zhang, Ang; Zhang, Jie; Kob, Walter; Wang, Yujie

2017-11-01

Granular materials such as sand, powders and foams are ubiquitous in daily life and in industrial and geotechnical applications. These disordered systems form stable structures when unperturbed, but in the presence of external influences such as tapping or shear they `relax', becoming fluid in nature. It is often assumed that the relaxation dynamics of granular systems is similar to that of thermal glass-forming systems. However, so far it has not been possible to determine experimentally the dynamic properties of three-dimensional granular systems at the particle level. This lack of experimental data, combined with the fact that the motion of granular particles involves friction (whereas the motion of particles in thermal glass-forming systems does not), means that an accurate description of the relaxation dynamics of granular materials is lacking. Here we use X-ray tomography to determine the microscale relaxation dynamics of hard granular ellipsoids subject to an oscillatory shear. We find that the distribution of the displacements of the ellipsoids is well described by a Gumbel law (which is similar to a Gaussian distribution for small displacements but has a heavier tail for larger displacements), with a shape parameter that is independent of the amplitude of the shear strain and of the time. Despite this universality, the mean squared displacement of an individual ellipsoid follows a power law as a function of time, with an exponent that does depend on the strain amplitude and time. We argue that these results are related to microscale relaxation mechanisms that involve friction and memory effects (whereby the motion of an ellipsoid at a given point in time depends on its previous motion). Our observations demonstrate that, at the particle level, the dynamic behaviour of granular systems is qualitatively different from that of thermal glass-forming systems, and is instead more similar to that of complex fluids. We conclude that granular materials can relax even when the driving strain is weak.

Simulation of cemented granular materials. I. Macroscopic stress-strain response and strain localization.

PubMed

Estrada, Nicolas; Lizcano, Arcesio; Taboada, Alfredo

2010-07-01

This is the first of two papers investigating the mechanical response of cemented granular materials by means of contact dynamics simulations. In this paper, a two-dimensional polydisperse sample with high-void ratio is constructed and then sheared in a simple shear numerical device at different confinement levels. We study the macroscopic response of the material in terms of mean and deviatoric stresses and strains. We show that the introduction of a local force scale, i.e., the tensile strength of the cemented bonds, causes the material to behave in a rigid-plastic fashion, so that a yield surface can be easily determined. This yield surface has a concave-down shape in the mean:deviatoric stress plane and it approaches a straight line, i.e., a Coulomb strength envelope, in the limit of a very dense granular material. Beyond yielding, the cemented structure gradually degrades until the material eventually behaves as a cohesionless granular material. Strain localization is also investigated, showing that the strains concentrate in a shear band whose thickness increases with the confining stress. The void ratio inside the shear band at the steady state is shown to be a material property that depends only on contact parameters.

Simulating Regoliths in a Microgravity Environment

NASA Astrophysics Data System (ADS)

Murdoch, N.; Rozitis, B.; Green, S. F.; Michel, P.; Losert, W.; de Lophem, T. L.

2011-10-01

The dynamics of granular materials are involved in the evolution of solid planets and small bodies in our Solar System, whose surfaces are generally covered with regolith. An understanding of granular dynamics appears also to be critical for the design and/or operations of landers, sampling devices and rovers to be included in space missions. The AstEx experiment uses a microgravity modified Taylor-Couette shear cell to investigate granular motion caused by shear and shear reversal forces under the microgravity conditions of parabolic flight. The results will lead to a greater understanding of the mechanical response of granular materials subject to external forces in varying gravitational environments.

40 CFR 278.4 - Certification and recordkeeping requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... WASTES (CONTINUED) CRITERIA FOR THE MANAGEMENT OF GRANULAR MINE TAILINGS (CHAT) IN ASPHALT CONCRETE AND PORTLAND CEMENT CONCRETE IN TRANSPORTATION CONSTRUCTION PROJECTS FUNDED IN WHOLE OR IN PART BY FEDERAL...

Beyond the material grave: Life Cycle Impact Assessment of leaching from secondary materials in road and earth constructions.

PubMed

Schwab, Oliver; Bayer, Peter; Juraske, Ronnie; Verones, Francesca; Hellweg, Stefanie

2014-10-01

In industrialized countries, large amounts of mineral wastes are produced. They are re-used in various ways, particularly in road and earth constructions, substituting primary resources such as gravel. However, they may also contain pollutants, such as heavy metals, which may be leached to the groundwater. The toxic impacts of these emissions are so far often neglected within Life Cycle Assessments (LCA) of products or waste treatment services and thus, potentially large environmental impacts are currently missed. This study aims at closing this gap by assessing the ecotoxic impacts of heavy metal leaching from industrial mineral wastes in road and earth constructions. The flows of metals such as Sb, As, Pb, Cd, Cr, Cu, Mo, Ni, V and Zn originating from three typical constructions to the environment are quantified, their fate in the environment is assessed and potential ecotoxic effects evaluated. For our reference country, Germany, the industrial wastes that are applied as Granular Secondary Construction Material (GSCM) carry more than 45,000 t of diverse heavy metals per year. Depending on the material quality and construction type applied, up to 150 t of heavy metals may leach to the environment within the first 100 years after construction. Heavy metal retardation in subsoil can potentially reduce the fate to groundwater by up to 100%. One major challenge of integrating leaching from constructions into macro-scale LCA frameworks is the high variability in micro-scale technical and geographical factors, such as material qualities, construction types and soil types. In our work, we consider a broad range of parameter values in the modeling of leaching and fate. This allows distinguishing between the impacts of various road constructions, as well as sites with different soil properties. The findings of this study promote the quantitative consideration of environmental impacts of long-term leaching in Life Cycle Assessment, complementing site-specific risk assessment, for the design of waste management strategies, particularly in the construction sector. Copyright © 2014 Elsevier Ltd. All rights reserved.

Resilient moduli of typical Missouri soils and unbound granular base materials.

DOT National Transportation Integrated Search

2009-01-01

The objective of this project was to determine the resilient moduli for common Missouri subgrade soils and typical unbound granular base materials in accordance with the AASHTO T 307 test method. The results allow Missouri Department of Transportatio...

Noise Propagation and Uncertainty Quantification in Hybrid Multiphysics Models: Initiation and Reaction Propagation in Energetic Materials

DTIC Science & Technology

2016-05-23

general model for heterogeneous granular media under compaction and (ii) the lack of a reliable multiscale discrete -to-continuum framework for...dynamics. These include a continuum- discrete model of heat dissipation/diffusion and a continuum- discrete model of compaction of a granular material with...the lack of a general model for het- erogeneous granular media under compac- tion and (ii) the lack of a reliable multi- scale discrete -to-continuum

USE OF GRANULAR GRAPHITE FOR ELECTROLYTIC DECHLORINATION OF TRICHLOROETHYLENE

EPA Science Inventory

Granular graphite is a potential electrode material for the electrochemical remediation of refractory chlorinated organic compounds such as trichloroethylene (TCE). However, the use of granular graphite can complicate the experimental results. On one hand, up to 99% of TCE was re...

Particle size effect on strength, failure, and shock behavior in polytetrafluoroethylene-Al-W granular composite materials

NASA Astrophysics Data System (ADS)

Herbold, E. B.; Nesterenko, V. F.; Benson, D. J.; Cai, J.; Vecchio, K. S.; Jiang, F.; Addiss, J. W.; Walley, S. M.; Proud, W. G.

2008-11-01

The variation of metallic particle size and sample porosity significantly alters the dynamic mechanical properties of high density granular composite materials processed using a cold isostatically pressed mixture of polytetrafluoroethylene (PTFE), aluminum (Al), and tungsten (W) powders. Quasistatic and dynamic experiments are performed with identical constituent mass fractions with variations in the size of the W particles and pressing conditions. The relatively weak polymer matrix allows the strength and fracture modes of this material to be governed by the granular type behavior of agglomerated metal particles. A higher ultimate compressive strength was observed in relatively high porosity samples with small W particles compared to those with coarse W particles in all experiments. Mesoscale granular force chains of the metallic particles explain this unusual phenomenon as observed in hydrocode simulations of a drop-weight test. Macrocracks forming below the critical failure strain for the matrix and unusual behavior due to a competition between densification and fracture in dynamic tests of porous samples were also observed. Numerical modeling of shock loading of this granular composite material demonstrated that the internal energy, specifically thermal energy, of the soft PTFE matrix can be tailored by the W particle size distribution.

ICPP tank farm closure study. Volume 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spaulding, B.C.; Gavalya, R.A.; Dahlmeir, M.M.

1998-02-01

The disposition of INEEL radioactive wastes is now under a Settlement Agreement between the DOE and the State of Idaho. The Settlement Agreement requires that existing liquid sodium bearing waste (SBW), and other liquid waste inventories be treated by December 31, 2012. This agreement also requires that all HLW, including calcined waste, be disposed or made road ready to ship from the INEEL by 2035. Sodium bearing waste (SBW) is produced from decontamination operations and HLW from reprocessing of SNF. SBW and HLW are radioactive and hazardous mixed waste; the radioactive constituents are regulated by DOE and the hazardous constituentsmore » are regulated by the Resource Conservation and Recovery Act (RCRA). Calcined waste, a dry granular material, is produced in the New Waste Calcining Facility (NWCF). Two primary waste tank storage locations exist at the ICPP: Tank Farm Facility (TFF) and the Calcined Solids Storage Facility (CSSF). The TFF has the following underground storage tanks: four 18,400-gallon tanks (WM 100-102, WL 101); four 30,000-gallon tanks (WM 103-106); and eleven 300,000+ gallon tanks. This includes nine 300,000-gallon tanks (WM 182-190) and two 318,000 gallon tanks (WM 180-181). This study analyzes the closure and subsequent use of the eleven 300,000+ gallon tanks. The 18,400 and 30,000-gallon tanks were not included in the work scope and will be closed as a separate activity. This study was conducted to support the HLW Environmental Impact Statement (EIS) waste separations options and addresses closure of the 300,000-gallon liquid waste storage tanks and subsequent tank void uses. A figure provides a diagram estimating how the TFF could be used as part of the separations options. Other possible TFF uses are also discussed in this study.« less

Resilient moduli of typical Missouri soils and unbound granular base materials

DOT National Transportation Integrated Search

2008-03-01

The objective of this project is to accurately determine the resilient moduli for common Missouri subgrade soils and unbound granular base materials in accordance with the AASHTO T 307 test method. The test results included moduli data from 27 common...

Origin of Granular Capillarity Revealed by Particle-Based Simulations

NASA Astrophysics Data System (ADS)

Fan, Fengxian; Parteli, Eric J. R.; Pöschel, Thorsten

2017-05-01

When a thin tube is dipped into water, the water will ascend to a certain height, against the action of gravity. While this effect, termed capillarity, is well known, recent experiments have shown that agitated granular matter reveals a similar behavior. Namely, when a vertical tube is inserted into a container filled with granular material and is then set into vertical vibration, the particles rise up along the tube. In the present Letter, we investigate the effect of granular capillarity by means of numerical simulations and show that the effect is caused by convection of the granular material in the container. Moreover, we identify two regimes of behavior for the capillary height Hc∞ depending on the tube-to-particle-diameter ratio, D /d . For large D /d , a scaling of Hc∞ with the inverse of the tube diameter, which is reminiscent of liquids, is observed. However, when D /d decreases down to values smaller than a few particle sizes, a uniquely granular behavior is observed where Hc∞ increases linearly with the tube diameter.

Modeling of Abrasion and Crushing of Unbound Granular Materials During Compaction

NASA Astrophysics Data System (ADS)

Ocampo, Manuel S.; Caicedo, Bernardo

2009-06-01

Unbound compacted granular materials are commonly used in engineering structures as layers in road pavements, railroad beds, highway embankments, and foundations. These structures are generally subjected to dynamic loading by construction operations, traffic and wheel loads. These repeated or cyclic loads cause abrasion and crushing of the granular materials. Abrasion changes a particle's shape, and crushing divides the particle into a mixture of many small particles of varying sizes. Particle breakage is important because the mechanical and hydraulic properties of these materials depend upon their grain size distribution. Therefore, it is important to evaluate the evolution of the grain size distribution of these materials. In this paper an analytical model for unbound granular materials is proposed in order to evaluate particle crushing of gravels and soils subjected to cyclic loads. The model is based on a Markov chain which describes the development of grading changes in the material as a function of stress levels. In the model proposed, each particle size is a state in the system, and the evolution of the material is the movement of particles from one state to another in n steps. Each step is a load cycle, and movement between states is possible with a transition probability. The crushing of particles depends on the mechanical properties of each grain and the packing density of the granular material. The transition probability was calculated using both the survival probability defined by Weibull and the compressible packing model developed by De Larrard. Material mechanical properties are considered using the Weibull probability theory. The size and shape of the grains, as well as the method of processing the packing density are considered using De Larrard's model. Results of the proposed analytical model show a good agreement with the experimental tests carried out using the gyratory compaction test.

Chaos emerging in soil failure patterns observed during tillage: Normalized deterministic nonlinear prediction (NDNP) and its application.

PubMed

Sakai, Kenshi; Upadhyaya, Shrinivasa K; Andrade-Sanchez, Pedro; Sviridova, Nina V

2017-03-01

Real-world processes are often combinations of deterministic and stochastic processes. Soil failure observed during farm tillage is one example of this phenomenon. In this paper, we investigated the nonlinear features of soil failure patterns in a farm tillage process. We demonstrate emerging determinism in soil failure patterns from stochastic processes under specific soil conditions. We normalized the deterministic nonlinear prediction considering autocorrelation and propose it as a robust way of extracting a nonlinear dynamical system from noise contaminated motion. Soil is a typical granular material. The results obtained here are expected to be applicable to granular materials in general. From a global scale to nano scale, the granular material is featured in seismology, geotechnology, soil mechanics, and particle technology. The results and discussions presented here are applicable in these wide research areas. The proposed method and our findings are useful with respect to the application of nonlinear dynamics to investigate complex motions generated from granular materials.

A new perspective of particle adsorption: Dispersed oil and granular materials interactions in simulated coastal environment.

PubMed

Meng, Long; Bao, Mutai; Sun, Peiyan

2017-09-15

This study, adsorption behaviors of dispersed oil in seawaters by granular materials were explored in simulation environment. We quantitatively demonstrated the dispersed oil adsorbed by granular materials were both dissolved petroleum hydrocarbons (DPHs) and oil droplets. Furthermore, DPHs were accounted for 42.5%, 63.4%, and 85.2% (35.5% was emulsion adsorption) in the adsorption of dispersed oil by coastal rocks, sediments, and bacterial strain particles respectively. Effects of controlling parameters, such as temperature, particle size and concentration on adsorption of petroleum hydrocarbons were described in detail. Most strikingly, adsorption concentration was followed a decreasing order of bacterial strain (0.5-2μm)>sediments (0.005-0.625mm)>coastal rocks (0.2-1cm). With particle concentration or temperature increased, adsorption concentration increased for coastal rocks particle but decreased for sediments particle. Besides, particle adsorption rate of petroleum hydrocarbons (n-alkanes and PAHs) was different among granular materials during 60 days. Copyright © 2017 Elsevier Ltd. All rights reserved.

Installing Mechanics of Granular Materials (MGM) Experiment Test Cell

NASA Technical Reports Server (NTRS)

1996-01-01

Astronaut Carl Walz installs Mechanics of Granular Materials (MGM) test cell on STS-79. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: NASA/John Space Center

Mechanical analysis and force chain determination in granular materials using digital image correlation.

PubMed

Chen, Fanxiu; Zhuang, Qi; Zhang, Huixin

2016-06-20

The mechanical behaviors of granular materials are governed by the grain properties and microstructure of the materials. We conducted experiments to study the force transmission in granular materials using plane strain tests. The large amount of nearly continuous displacement data provided by the advanced noncontact experimental technique of digital image correlation (DIC) has provided a means to quantify local displacements and strains at the particle level. The average strain of each particle could be calculated based on the DIC method, and the average stress could be obtained using Hooke's law. The relationship between the stress and particle force could be obtained based on basic Newtonian mechanics and the balance of linear momentum at the particle level. This methodology is introduced and validated. In the testing procedure, the system is tested in real 2D particle cases, and the contact forces and force chain are obtained and analyzed. The system has great potential for analyzing a real granular system and measuring the contact forces and force chain.

Dynamic compaction of granular materials

PubMed Central

Favrie, N.; Gavrilyuk, S.

2013-01-01

An Eulerian hyperbolic multiphase flow model for dynamic and irreversible compaction of granular materials is constructed. The reversible model is first constructed on the basis of the classical Hertz theory. The irreversible model is then derived in accordance with the following two basic principles. First, the entropy inequality is satisfied by the model. Second, the corresponding ‘intergranular stress’ coming from elastic energy owing to contact between grains decreases in time (the granular media behave as Maxwell-type materials). The irreversible model admits an equilibrium state corresponding to von Mises-type yield limit. The yield limit depends on the volume fraction of the solid. The sound velocity at the yield surface is smaller than that in the reversible model. The last one is smaller than the sound velocity in the irreversible model. Such an embedded model structure assures a thermodynamically correct formulation of the model of granular materials. The model is validated on quasi-static experiments on loading–unloading cycles. The experimentally observed hysteresis phenomena were numerically confirmed with a good accuracy by the proposed model. PMID:24353466

Dynamic Effective Mass of Granular Media

NASA Astrophysics Data System (ADS)

Hsu, Chaur-Jian; Johnson, David L.; Ingale, Rohit A.; Valenza, John J.; Gland, Nicolas; Makse, Hernán A.

2009-02-01

We develop the concept of frequency dependent effective mass, Mtilde (ω), of jammed granular materials which occupy a rigid cavity to a filling fraction of 48%, the remaining volume being air of normal room condition or controlled humidity. The dominant features of Mtilde (ω) provide signatures of the dissipation of acoustic modes, elasticity, and aging effects in the granular medium. We perform humidity controlled experiments and interpret the data in terms of a continuum model and a “trap” model of thermally activated capillary bridges at the contact points. The results suggest that attenuation of acoustic waves in granular materials can be influenced significantly by the kinetics of capillary condensation between the asperities at the contacts.

Sounds of Failure: Passive Acoustic Measurements of Excited Vibrational Modes

NASA Astrophysics Data System (ADS)

Brzinski, Theodore A.; Daniels, Karen E.

2018-05-01

Granular materials can fail through spontaneous events like earthquakes or brittle fracture. However, measurements and analytic models which forecast failure in this class of materials, while of both fundamental and practical interest, remain elusive. Materials including numerical packings of spheres, colloidal glasses, and granular materials have been known to develop an excess of low-frequency vibrational modes as the confining pressure is reduced. Here, we report experiments on sheared granular materials in which we monitor the evolving density of excited modes via passive monitoring of acoustic emissions. We observe a broadening of the distribution of excited modes coincident with both bulk and local plasticity, and evolution in the shape of the distribution before and after bulk failure. These results provide a new interpretation of the changing state of the material on its approach to stick-slip failure.

Sounds of Failure: Passive Acoustic Measurements of Excited Vibrational Modes.

PubMed

Brzinski, Theodore A; Daniels, Karen E

2018-05-25

Granular materials can fail through spontaneous events like earthquakes or brittle fracture. However, measurements and analytic models which forecast failure in this class of materials, while of both fundamental and practical interest, remain elusive. Materials including numerical packings of spheres, colloidal glasses, and granular materials have been known to develop an excess of low-frequency vibrational modes as the confining pressure is reduced. Here, we report experiments on sheared granular materials in which we monitor the evolving density of excited modes via passive monitoring of acoustic emissions. We observe a broadening of the distribution of excited modes coincident with both bulk and local plasticity, and evolution in the shape of the distribution before and after bulk failure. These results provide a new interpretation of the changing state of the material on its approach to stick-slip failure.

Reduction of intergranular exchange coupling and grain size for high Ku CoPt-based granular media: Metal-oxide buffer layer and multiple oxide boundary materials

NASA Astrophysics Data System (ADS)

Tham, Kim Kong; Kushibiki, Ryosuke; Kamada, Tomonari; Hinata, Shintaro; Saito, Shin

2018-05-01

Investigation of magnetic properties and microstructure of granular media with various multiple oxides as the grain boundary material is reported. Saturation magnetization (Ms), uniaxial magnetocrystalline anisotropy (Ku), and magnetic grain diameter (GD) of the granular media show linear correlation with volume weighted average for melting point (Tm) of each oxides (Tmave). Ku of magnetic grains (Kugrain) shows a trade-off relation with GD that it is a big challenge to satisfy both high Kugrain and small GD by only controlling Tmave. To obtain a granular medium with appropriate Kugrain, GD, and low degree of intergranular exchange coupling, the combination of Tmave control of grain boundary material by mixing oxides and employment of a buffer layer are required. Here the degree of intergranular exchange coupling is estimated from the slope of M-H loop at around coercivity (α). By applying this technique, a typical granular medium with Kugrain of 1.0×107 erg/cm3, GD of 5.1 nm, and α of 1.2 is realized.

A two-phase flow model for submarine granular flows: With an application to collapse of deeply-submerged granular columns

NASA Astrophysics Data System (ADS)

Lee, Cheng-Hsien; Huang, Zhenhua

2018-05-01

The collapse process of a submerged granular column is strongly affected by its initial packing. Previous models for particle response time, which is used to quantify the drag force between the solid and liquid phases in rheology-based two-phase flow models, have difficulty in simulating the collapse process of granular columns with different initial concentrations (initial packing conditions). This study introduces a new model for particle response time, which enables us to satisfactorily model the drag force between the two phases for a wide range of volume concentration. The present model can give satisfactory results for both loose and dense packing conditions. The numerical results have shown that (i) the initial packing affects the occurrence of contractancy/diltancy behavior during the collapse process, (ii) the general buoyancy and drag force are strongly affected by the initial packing through contractancy and diltancy, and (iii) the general buoyancy and drag force can destabilize the granular material in loose packing condition but stabilize the granular material in dense packing condition. The results have shown that the collapse process of a densely-packed granular column is more sensitive to particle response time than that of a loosely-packed granular column.

Beyond the material grave: Life Cycle Impact Assessment of leaching from secondary materials in road and earth constructions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwab, Oliver; Karlsruhe Institute of Technology, Institute for Geography and Geoecology, Adenauerring 20, 76131 Karlsruhe; Bayer, Peter, E-mail: bayer@erdw.ethz.ch

Highlights: • We model environmental impacts of leaching from secondary construction material. • Industrial wastes in construction contain up to 45,000 t heavy metals per year (D). • In a scenario, 150 t are leached to the environment within 100 years after construction. • All heavy metals but As, Sb and Mo are adsorbed by 20 cm subsoil in this scenario. • Environmental impacts depend on material, pollutant, construction type, and geography. - Abstract: In industrialized countries, large amounts of mineral wastes are produced. They are re-used in various ways, particularly in road and earth constructions, substituting primary resources suchmore » as gravel. However, they may also contain pollutants, such as heavy metals, which may be leached to the groundwater. The toxic impacts of these emissions are so far often neglected within Life Cycle Assessments (LCA) of products or waste treatment services and thus, potentially large environmental impacts are currently missed. This study aims at closing this gap by assessing the ecotoxic impacts of heavy metal leaching from industrial mineral wastes in road and earth constructions. The flows of metals such as Sb, As, Pb, Cd, Cr, Cu, Mo, Ni, V and Zn originating from three typical constructions to the environment are quantified, their fate in the environment is assessed and potential ecotoxic effects evaluated. For our reference country, Germany, the industrial wastes that are applied as Granular Secondary Construction Material (GSCM) carry more than 45,000 t of diverse heavy metals per year. Depending on the material quality and construction type applied, up to 150 t of heavy metals may leach to the environment within the first 100 years after construction. Heavy metal retardation in subsoil can potentially reduce the fate to groundwater by up to 100%. One major challenge of integrating leaching from constructions into macro-scale LCA frameworks is the high variability in micro-scale technical and geographical factors, such as material qualities, construction types and soil types. In our work, we consider a broad range of parameter values in the modeling of leaching and fate. This allows distinguishing between the impacts of various road constructions, as well as sites with different soil properties. The findings of this study promote the quantitative consideration of environmental impacts of long-term leaching in Life Cycle Assessment, complementing site-specific risk assessment, for the design of waste management strategies, particularly in the construction sector.« less

Some exact velocity profiles for granular flow in converging hoppers

NASA Astrophysics Data System (ADS)

Cox, Grant M.; Hill, James M.

2005-01-01

Gravity flow of granular materials through hoppers occurs in many industrial processes. For an ideal cohesionless granular material, which satisfies the Coulomb-Mohr yield condition, the number of known analytical solutions is limited. However, for the special case of the angle of internal friction δ equal to ninety degrees, there exist exact parametric solutions for the governing coupled ordinary differential equations for both two-dimensional wedges and three-dimensional cones, both of which involve two arbitrary constants of integration. These solutions are the only known analytical solutions of this generality. Here, we utilize the double-shearing theory of granular materials to determine the velocity field corresponding to these exact parametric solutions for the two problems of gravity flow through converging wedge and conical hoppers. An independent numerical solution for other angles of internal friction is shown to coincide with the analytical solution.

Effect of Anisotropy on the Resilient Behaviour of a Granular Material in Low Traffic Pavement

PubMed Central

Jing, Peng; Nowamooz, Hossein; Chazallon, Cyrille

2017-01-01

Granular materials are often used in pavement structures. The influence of anisotropy on the mechanical behaviour of granular materials is very important. The coupled effects of water content and fine content usually lead to more complex anisotropic behaviour. With a repeated load triaxial test (RLTT), it is possible to measure the anisotropic deformation behaviour of granular materials. This article initially presents an experimental study of the resilient repeated load response of a compacted clayey natural sand with three fine contents and different water contents. Based on anisotropic behaviour, the non-linear resilient model (Boyce model) is improved by the radial anisotropy coefficient γ3 instead of the axial anisotropy coefficient γ1. The results from both approaches (γ1 and γ3) are compared with the measured volumetric and deviatoric responses. These results confirm the capacity of the improved model to capture the general trend of the experiments. Finally, finite element calculations are performed with CAST3M in order to validate the improvement of the modified Boyce model (from γ1 to γ3). The modelling results indicate that the modified Boyce model with γ3 is more widely available in different water contents and different fine contents for this granular material. Besides, based on the results, the coupled effects of water content and fine content on the deflection of the structures can also be observed. PMID:29207504

Effect of Anisotropy on the Resilient Behaviour of a Granular Material in Low Traffic Pavement.

PubMed

Jing, Peng; Nowamooz, Hossein; Chazallon, Cyrille

2017-12-03

Granular materials are often used in pavement structures. The influence of anisotropy on the mechanical behaviour of granular materials is very important. The coupled effects of water content and fine content usually lead to more complex anisotropic behaviour. With a repeated load triaxial test (RLTT), it is possible to measure the anisotropic deformation behaviour of granular materials. This article initially presents an experimental study of the resilient repeated load response of a compacted clayey natural sand with three fine contents and different water contents. Based on anisotropic behaviour, the non-linear resilient model (Boyce model) is improved by the radial anisotropy coefficient γ ₃ instead of the axial anisotropy coefficient γ ₁. The results from both approaches ( γ ₁ and γ ₃) are compared with the measured volumetric and deviatoric responses. These results confirm the capacity of the improved model to capture the general trend of the experiments. Finally, finite element calculations are performed with CAST3M in order to validate the improvement of the modified Boyce model (from γ ₁ to γ ₃). The modelling results indicate that the modified Boyce model with γ ₃ is more widely available in different water contents and different fine contents for this granular material. Besides, based on the results, the coupled effects of water content and fine content on the deflection of the structures can also be observed.

77 FR 59979 - Pure Magnesium (Granular) From China

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-01

... (Granular) From China Determination On the basis of the record \\1\\ developed in the subject five-year review... magnesium (granular) from China would be likely to lead to continuation or recurrence of material injury to... China: Investigation No.731-TA- 895 (Second Review). Issued: September 25, 2012. By order of the...

Relationship between electrical conductivity anisotropy and fabric anisotropy in granular materials during drained triaxial compressive tests: a numerical approach

NASA Astrophysics Data System (ADS)

Niu, Qifei; Revil, André; Li, Zhaofeng; Wang, Yu-Hsing

2017-07-01

The anisotropy of granular media and its evolution during shearing are important aspects required in developing physics-based constitutive models in Earth sciences. The development of relationships between geoelectrical properties and the deformation of porous media has applications to the monitoring of faulting and landslides. However, such relationships are still poorly understood. In this study, we first investigate the definition of the electrical conductivity anisotropy tensor of granular materials in presence of surface conductivity of the grains. Fabric anisotropy is related to the components of the fabric tensor. We define an electrical anisotropy factor based on the Archie's exponent second-order symmetric tensor m of granular materials. We use numerical simulations to confirm a relationship between the evolution of electrical and fabric anisotropy factors during shearing. To realize the simulations, we build a virtual laboratory in which we can easily perform synthetic experiments. We first simulate drained compressive triaxial tests of loose and dense granular materials (porosity 0.45 and 0.38, respectively) using the discrete element method. Then, the electrical conductivity tensor of a set of deformed synthetic samples is computed using the finite-difference method. The numerical results show that shear strains are responsible for a measurable anisotropy in the bulk conductivity of granular media. The observed electrical anisotropy response, during shearing, is distinct for dense and loose synthetic samples. Electrical and fabric anisotropy factors exhibit however a unique linear correlation, regardless of the shear strain and the initial state (porosity) of the synthetic samples. The practical implication of this finding confirms the usefulness of the electrical conductivity method in studying the fabric tensor of granular media. This result opens the door in using time-lapse electrical resistivity to study non-intrusively the evolution of anisotropy of soils and granular rocks during deformation, for instance during landslides, and to use the evolution of the conductivity tensor to monitor mechanical properties.

On the finite length-scale of compressible shock-waves formed in free-surface flows of dry granular materials down a slope

NASA Astrophysics Data System (ADS)

Faug, Thierry

2017-04-01

The Rankine-Hugoniot jump conditions traditionally describe the theoretical relationship between the equilibrium state on both sides of a shock-wave. They are based on the crucial assumption that the length-scale needed to adjust the equilibrium state upstream of the shock to downstream of it is too small to be of significance to the problem. They are often used with success to describe the shock-waves in a number of applications found in both fluid and solid mechanics. However, the relations based on jump conditions at singular surfaces may fail to capture some features of the shock-waves formed in complex materials, such as granular matter. This study addresses the particular problem of compressible shock-waves formed in flows of dry granular materials down a slope. This problem is for instance relevant to full-scale geophysical granular flows in interaction with natural obstacles or man-made structures, such as topographical obstacles or mitigation dams respectively. Steady-state jumps formed in granular flows and travelling shock-waves produced at the impact of a granular avalanche-flow with a rigid wall are considered. For both situations, new analytical relations which do not consider that the granular shock-wave shrinks into a singular surface are derived, by using balance equations in their depth-averaged forms for mass and momentum. However, these relations need additional inputs that are closure relations for the size and the shape of the shock-wave, and a relevant constitutive friction law. Small-scale laboratory tests and numerical simulations based on the discrete element method are shortly presented and used to infer crucial information needed for the closure relations. This allows testing some predictive aspects of the simple analytical approach proposed for both steady-state and travelling shock-waves formed in free-surface flows of dry granular materials down a slope.

Characterising fabric, force distributions and porosity evolution in sheared granular media

NASA Astrophysics Data System (ADS)

Mair, Karen; Abe, Steffen; Jettestuen, Espen

2014-05-01

Active faults, landslides, subglacial tills and poorly or unconsolidated sands essentially contain accumulations of granular debris that evolve under load. Both the macroscopic motions and the bulk fluid flow characteristics that result are determined by the particular grain scale processes operating in this deformed or transformed granular material. A relevant question is how the local behavior at the individual granular contacts actually sums up, and in particular how the load bearing skeleton (an important expression of connected load) and spatial distribution of pore space (and hence fluid pathways) are linked. Here we investigate the spatial distribution of porosity with granular rearrangements (specifically contact force network characteristics) produced in 3D discrete element models of granular layers under shear. We use percolation measures to identify, characterize, compare and track the evolution of strongly connected contact force networks. We show that specific topological measures used in describing the networks, such as number of contacts and coordination number, are sensitive to grain size distribution of the material as well as loading conditions. In addition we probe the 3D spatial distribution of porosity as a function of increasing strain. Two cases will be considered. The first, a non-fracture regime where configurational changes occur during shear but grain size distribution remains constant. This would be expected for a soil or granular material under relatively low normal loading. Secondly we consider a fragmentation regime where the grain size distributions of the granular material evolve with accumulated strain. This mirrors the scenario for faults or basal shear zones of slides under higher normal stress where comminution is typically a mark of increasing maturity and plays a major role in the poro-perm evolution of the system. We will present the correlated and anti-correlated features appearing in our simulations as well as discussing the triggers and relative persistence of fluid pathway creation versus destruction mechanisms. We will also demonstrate how the individual grain interactions are manifested in the macroscopic sliding behavior we observe.

Characterization and Leaching Tests of the Fluidized Bed Steam Reforming (FBSR) Waste Form for LAW Immobilization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neeway, James J.; Qafoku, Nikolla; Brown, Christopher F.

2013-10-01

Several supplemental technologies for treating and immobilizing Hanford low activity waste (LAW) have been evaluated. One such immobilization technology is the Fluidized Bed Steam Reforming (FBSR) granular product. The FBSR granular product is composed of insoluble sodium aluminosilicate (NAS) feldspathoid minerals. Production of the FBSR mineral product has been demonstrated both at the industrial and laboratory scale. Pacific Northwest National Laboratory (PNNL) was involved in an extensive characterization campaign. This goal of this campaign was study the durability of the FBSR mineral product and the mineral product encapsulated in a monolith to meet compressive strength requirements. This paper gives anmore » overview of results obtained using the ASTM C 1285 Product Consistency Test (PCT), the EPA Test Method 1311 Toxicity Characteristic Leaching Procedure (TCLP), and the ASTMC 1662 Single-Pass Flow-Through (SPFT) test. Along with these durability tests an overview of the characteristics of the waste form has been collected using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), microwave digestions for chemical composition, and surface area from Brunauer, Emmett, and Teller (BET) theory.« less

Characterization and Leaching Tests of the Fluidized Bed Steam Reforming (FBSR) Waste Form for LAW Immobilization - 13400

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neeway, James J.; Qafoku, Nikolla P.; Peterson, Reid A.

2013-07-01

Several supplemental technologies for treating and immobilizing Hanford low activity waste (LAW) have been evaluated. One such immobilization technology is the Fluidized Bed Steam Reforming (FBSR) granular product. The FBSR granular product is composed of insoluble sodium aluminosilicate (NAS) feldspathoid minerals. Production of the FBSR mineral product has been demonstrated both at the industrial and laboratory scale. Pacific Northwest National Laboratory (PNNL) was involved in an extensive characterization campaign. The goal of this campaign was to study the durability of the FBSR mineral product and the encapsulated FBSR product in a geo-polymer monolith. This paper gives an overview of resultsmore » obtained using the ASTM C 1285 Product Consistency Test (PCT), the EPA Test Method 1311 Toxicity Characteristic Leaching Procedure (TCLP), and the ASTMC 1662 Single-Pass Flow-Through (SPFT) test. Along with these durability tests an overview of the characteristics of the waste form has been collected using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), microwave digestions for chemical composition, and surface area from Brunauer, Emmett, and Teller (BET) theory. (authors)« less

Self-Structuring of Granular material under Capillary Bulldozing

NASA Astrophysics Data System (ADS)

Dumazer, Guillaume; Sandnes, Bjørnar; Ayaz, Monem; Måløy, Knut Jørgen; Flekkøy, Eirik

2017-06-01

An experimental observation of the structuring of a granular suspension under the progress of a gas/liquid meniscus in a narrow tube is reported here. The granular material is moved and compactifies as a growing accumulation front. The frictional interaction with the confining walls increases until the pore capillary entry pressure is reached. The gas then penetrates the clogged granular packing and a further accumulation front is formed at the far side of the plug. This cyclic process continues until the gas/liquid interface reaches the tube's outlet, leaving a trail of plugs in the tube. Such 1D pattern formation belongs to a larger family of patterning dynamics observed in 2D Hele-Shaw geometry. The cylindrical geometry considered here provides an ideal case for a theoretical modelling for forced granular matter oscillating between a long frictional phase and a sudden viscous fluidization.

Surface instabilities in shock loaded granular media

NASA Astrophysics Data System (ADS)

Kandan, K.; Khaderi, S. N.; Wadley, H. N. G.; Deshpande, V. S.

2017-12-01

The initiation and growth of instabilities in granular materials loaded by air shock waves are investigated via shock-tube experiments and numerical calculations. Three types of granular media, dry sand, water-saturated sand and a granular solid comprising PTFE spheres were experimentally investigated by air shock loading slugs of these materials in a transparent shock tube. Under all shock pressures considered here, the free-standing dry sand slugs remained stable while the shock loaded surface of the water-saturated sand slug became unstable resulting in mixing of the shocked air and the granular material. By contrast, the PTFE slugs were stable at low pressures but displayed instabilities similar to the water-saturated sand slugs at higher shock pressures. The distal surfaces of the slugs remained stable under all conditions considered here. Eulerian fluid/solid interaction calculations, with the granular material modelled as a Drucker-Prager solid, reproduced the onset of the instabilities as seen in the experiments to a high level of accuracy. These calculations showed that the shock pressures to initiate instabilities increased with increasing material friction and decreasing yield strain. Moreover, the high Atwood number for this problem implied that fluid/solid interaction effects were small, and the initiation of the instability is adequately captured by directly applying a pressure on the slug surface. Lagrangian calculations with the directly applied pressures demonstrated that the instability was caused by spatial pressure gradients created by initial surface perturbations. Surface instabilities are also shown to exist in shock loaded rear-supported granular slugs: these experiments and calculations are used to infer the velocity that free-standing slugs need to acquire to initiate instabilities on their front surfaces. The results presented here, while in an idealised one-dimensional setting, provide physical understanding of the conditions required to initiate instabilities in a range of situations involving the explosive dispersion of particles.

Granular giant magnetoresistive materials and their ferromagnetic resonances

NASA Astrophysics Data System (ADS)

Rubinstein, M.; Das, B. N.; Koon, N. C.; Chrisey, D. B.; Horwitz, J.

1994-11-01

Ferromagnetic resonance (FMR) can reveal important information on the size and shape of the ferromagnetic particles which are dispersed in granular giant magnetoresistive (GMR) materials. We have investigated the FMR spectra of three different types of granular GMR material, each with different properties: (1) melt-spun ribbons of Fe5Co15Cu80 and Co20Cu80, (2) thin films of Co20Cu80 produced by pulsed laser deposition, and (3) a granular multilayer film of (Cu(50 A)/Fe(10 A)) x 50. We interpret the linewidth of these materials in as simple a manner as possible, as a 'powder pattern' of noninteracting ferromagnetic particles. The linewidth of the melt-spun ribbons is caused by a completely random distribution of crystalline anisotropy axes. The linewidth of these samples is strongly dependent upon the annealing temperature: the linewidth of the as-spun sample is 2.5 kOe (appropriate for single-domain particles) while the linewidth of a melt-spun sample annealed at 900 C for 15 min is 3.8 kOe (appropriate for larger, multidomain particles). The linewidth of the granular multilayer is attributed to a restricted distribution of shape anisotropies, as expected from a discontinuous multilayer, and is only 0.98 kOe with the magnetic field in the plane of the film.

Ferromagnetic-resonance studies of granular giant-magnetoresistive materials

NASA Astrophysics Data System (ADS)

Rubinstein, M.; Das, B. N.; Koon, N. C.; Chrisey, D. B.; Horwitz, J.

1994-07-01

Ferromagnetic resonance (FMR) can reveal important information on the size and shape of the ferromagnetic particles which are dispersed in granular giant magnetoresistive (GMR) materials. We have investigated the FMR spectra of three different types of granular GMR material, each with different properties: (1) melt-spun ribbons of Fe5Co15Cu80 and Co20Cu80, (2) thin films of Co20Cu80 produced by pulsed laser deposition, and (3) a granular multilayer film of [Cu(50 Å)/Fe(10 Å)]×50. We interpret the linewidth of these materials in as simple a manner as possible, as a ``powder pattern'' of noninteracting ferromagnetic particles. The linewidth of the melt-spun ribbons is caused by a completely random distribution of crystalline anisotropy axes. The linewidth of these samples is strongly dependent upon the annealing temperature: the linewidth of the as-spun sample is 2.5 kOe (appropriate for single-domain particles) while the linewidth of a melt-spun sample annealed at 900 °C for 15 min is 4.5 kOe (appropriate for larger, multidomain particles). The linewidth of the granular multilayer is attributed to a restricted distribution of shape anisotropies, as expected from a discontinuous multilayer, and is only 0.98 kOe when the applied magnetic field is in the plane of the film.

Measurements of Acoustic Properties of Porous and Granular Materials and Application to Vibration Control

NASA Technical Reports Server (NTRS)

Park, Junhong; Palumbo, Daniel L.

2004-01-01

For application of porous and granular materials to vibro-acoustic controls, a finite dynamic strength of the solid component (frame) is an important design factor. The primary goal of this study was to investigate structural vibration damping through this frame wave propagation for various poroelastic materials. A measurement method to investigate the vibration characteristics of the frame was proposed. The measured properties were found to follow closely the characteristics of the viscoelastic materials - the dynamic modulus increased with frequency and the degree of the frequency dependence was determined by its loss factor. The dynamic stiffness of hollow cylindrical beams containing porous and granular materials as damping treatment was measured also. The data were used to extract the damping materials characteristics using the Rayleigh-Ritz method. The results suggested that the acoustic structure interaction between the frame and the structure enhances the dissipation of the vibration energy significantly.

Open problems in active chaotic flows: Competition between chaos and order in granular materials.

PubMed

Ottino, J. M.; Khakhar, D. V.

2002-06-01

There are many systems where interaction among the elementary building blocks-no matter how well understood-does not even give a glimpse of the behavior of the global system itself. Characteristic for these systems is the ability to display structure without any external organizing principle being applied. They self-organize as a consequence of synthesis and collective phenomena and the behavior cannot be understood in terms of the systems' constitutive elements alone. A simple example is flowing granular materials, i.e., systems composed of particles or grains. How the grains interact with each other is reasonably well understood; as to how particles move, the governing law is Newton's second law. There are no surprises at this level. However, when the particles are many and the material is vibrated or tumbled, surprising behavior emerges. Systems self-organize in complex patterns that cannot be deduced from the behavior of the particles alone. Self-organization is often the result of competing effects; flowing granular matter displays both mixing and segregation. Small differences in either size or density lead to flow-induced segregation and order; similar to fluids, noncohesive granular materials can display chaotic mixing and disorder. Competition gives rise to a wealth of experimental outcomes. Equilibrium structures, obtained experimentally in quasi-two-dimensional systems, display organization in the presence of disorder, and are captured by a continuum flow model incorporating collisional diffusion and density-driven segregation. Several open issues remain to be addressed. These include analysis of segregating chaotic systems from a dynamical systems viewpoint, and understanding three-dimensional systems and wet granular systems (slurries). General aspects of the competition between chaos-enhanced mixing and properties-induced de-mixing go beyond granular materials and may offer a paradigm for other kinds of physical systems. (c) 2002 American Institute of Physics.

RADIOACTIVE DEMONSTRATION OF FINAL MINERALIZED WASTE FORMS FOR HANFORD WASTE TREATMENT PLANT SECONDARY WASTE BY FLUIDIZED BED STEAM REFORMING USING THE BENCH SCALE REFORMER PLATFORM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crawford, C.; Burket, P.; Cozzi, A.

2012-02-02

The U.S. Department of Energy's Office of River Protection (ORP) is responsible for the retrieval, treatment, immobilization, and disposal of Hanford's tank waste. Currently there are approximately 56 million gallons of highly radioactive mixed wastes awaiting treatment. A key aspect of the River Protection Project (RPP) cleanup mission is to construct and operate the Waste Treatment and Immobilization Plant (WTP). The WTP will separate the tank waste into high-level and low-activity waste (LAW) fractions, both of which will subsequently be vitrified. The projected throughput capacity of the WTP LAW Vitrification Facility is insufficient to complete the RPP mission in themore » time frame required by the Hanford Federal Facility Agreement and Consent Order, also known as the Tri-Party Agreement (TPA), i.e. December 31, 2047. Therefore, Supplemental Treatment is required both to meet the TPA treatment requirements as well as to more cost effectively complete the tank waste treatment mission. In addition, the WTP LAW vitrification facility off-gas condensate known as WTP Secondary Waste (WTP-SW) will be generated and enriched in volatile components such as {sup 137}Cs, {sup 129}I, {sup 99}Tc, Cl, F, and SO{sub 4} that volatilize at the vitrification temperature of 1150 C in the absence of a continuous cold cap (that could minimize volatilization). The current waste disposal path for the WTP-SW is to process it through the Effluent Treatment Facility (ETF). Fluidized Bed Steam Reforming (FBSR) is being considered for immobilization of the ETF concentrate that would be generated by processing the WTP-SW. The focus of this current report is the WTP-SW. FBSR offers a moderate temperature (700-750 C) continuous method by which WTP-SW wastes can be processed irrespective of whether they contain organics, nitrates, sulfates/sulfides, chlorides, fluorides, volatile radionuclides or other aqueous components. The FBSR technology can process these wastes into a crystalline ceramic (mineral) waste form. The mineral waste form that is produced by co-processing waste with kaolin clay in an FBSR process has been shown to be as durable as LAW glass. Monolithing of the granular FBSR product is being investigated to prevent dispersion during transport or burial/storage, but is not necessary for performance. A Benchscale Steam Reformer (BSR) was designed and constructed at the SRNL to treat actual radioactive wastes to confirm the findings of the non-radioactive FBSR pilot scale tests and to qualify the waste form for applications at Hanford. BSR testing with WTP SW waste surrogates and associated analytical analyses and tests of granular products (GP) and monoliths began in the Fall of 2009, and then was continued from the Fall of 2010 through the Spring of 2011. Radioactive testing commenced in 2010 with a demonstration of Hanford's WTP-SW where Savannah River Site (SRS) High Level Waste (HLW) secondary waste from the Defense Waste Processing Facility (DWPF) was shimmed with a mixture of {sup 125/129}I and {sup 99}Tc to chemically resemble WTP-SW. Prior to these radioactive feed tests, non-radioactive simulants were also processed. Ninety six grams of radioactive granular product were made for testing and comparison to the non-radioactive pilot scale tests. The same mineral phases were found in the radioactive and non-radioactive testing.« less

Conversion of agricultural residues into activated carbons for water purification: Application to arsenate removal.

PubMed

Torres-Perez, Jonatan; Gerente, Claire; Andres, Yves

2012-01-01

The conversion of two agricultural wastes, sugar beet pulp and peanut hulls, into sustainable activated carbons is presented and their potential application for the treatment of arsenate solution is investigated. A direct and physical activation is selected as well as a simple chemical treatment of the adsorbents. The material properties, such as BET surface areas, porous volumes, elemental analysis, ash contents and pH(PZC), of these alternative carbonaceous porous materials are determined and compared with a commercial granular activated carbon. An adsorption study based on experimental kinetic and equilibrium data is conducted in a batch reactor and completed by the use of different models (intraparticle diffusion, pseudo-second-order, Langmuir and Freundlich) and by isotherms carried out in natural waters. It is thus demonstrated that sugar beet pulp and peanut hulls are good precursors to obtain activated carbons for arsenate removal.

The Use of Empirical Methods for Testing Granular Materials in Analogue Modelling

PubMed Central

Montanari, Domenico; Agostini, Andrea; Bonini, Marco; Corti, Giacomo; Del Ventisette, Chiara

2017-01-01

The behaviour of a granular material is mainly dependent on its frictional properties, angle of internal friction, and cohesion, which, together with material density, are the key factors to be considered during the scaling procedure of analogue models. The frictional properties of a granular material are usually investigated by means of technical instruments such as a Hubbert-type apparatus and ring shear testers, which allow for investigating the response of the tested material to a wide range of applied stresses. Here we explore the possibility to determine material properties by means of different empirical methods applied to mixtures of quartz and K-feldspar sand. Empirical methods exhibit the great advantage of measuring the properties of a certain analogue material under the experimental conditions, which are strongly sensitive to the handling techniques. Finally, the results obtained from the empirical methods have been compared with ring shear tests carried out on the same materials, which show a satisfactory agreement with those determined empirically. PMID:28772993

Compaction Behavior of Granular Materials

NASA Astrophysics Data System (ADS)

Endicott, Mark R.; Kenkre, V. M.; Glass, S. Jill; Hurd, Alan J.

1996-03-01

We report the results of our recent study of compaction of granular materials. A theoretical model is developed for the description of the compaction of granular materials exemplified by granulated ceramic powders. Its predictions are compared to observations of uniaxial compaction tests of ceramic granules of PMN-PT, spray dried alumina and rutile. The theoretical model employs a volume-based statistical mechanics treatment and an activation analogy. Results of a computer simulation of random packing of discs in two dimensions are also reported. The effect of type of particle size distribution and other parameters of that distribution on the calculated quantities are discussed. We examine the implications of the results of the simulation for the theoretical model.

Healing in Unconsolidated Granular Earth Materials: a Mechanistic Theory

NASA Astrophysics Data System (ADS)

Lieou, C.; Daub, E. G.; Ecke, R. E.; Johnson, P. A.

2017-12-01

Abstract: Rock materials often display long-time relaxation, commonly termed aging or ``slow dynamics'', after the cessation of acoustic perturbations. In this presentation, we focus on unconsolidated rock materials and propose to explain such nonlinear relaxation through the Shear-Transformation-Zone (STZ) theory of granular media, adapted for small stresses and strains. The theory attributes the observed relaxation to the slow change of positions of constituent grains, and posits that the aging process can be described in three stages: fast recovery before some characteristic time associated with the fast nonlinear plasticity carriers, log-linear recovery of the elastic modulus at intermediate times, and gradual turnover to equilibrium steady-state behavior at long times. We demonstrate good agreement with experiments on aging in granular materials such as simulated fault gouge after an external disturbance.

An Experimental Investigation on the Generation of a Stable Arch in Granular Materials Using a Developed Trapdoor Apparatus

NASA Astrophysics Data System (ADS)

Ahmadi, Ali; Seyedi Hosseininia, Ehsan

2017-06-01

This paper discusses the formation of stable arches in granular materials by using a series of laboratory tests. To this aim, a developed trapdoor apparatus is designed to find dimensions of arches formed over the door in cohesionless aggregates. This setup has two new important applications. In order to investigate the maximum width of the opening generated exactly on the verge of failure, the door can be open to an arbitrary size. In addition, the box containing granular materials (or base angle) is able to be set on optional angles from zero to 90 degrees with respect to the horizontal. Therefore, it is possible to understand the effect of different levels of gravity accelerations on the formed arches. It is observed that for all tested granular materials, increasing the door size and decreasing the base angle, both cause to increase the width and height of the arch. Moreover, the shape of all arches is governed by a parabola. Furthermore, the maximum door width is approximately five to 8.6 times the particle size, depending on the internal friction angle of materials and the base angle.

Mechanics of Granular Materials-3 (MGM-3)

NASA Technical Reports Server (NTRS)

Sture, Stein; Alshibi, Khalid; Guynes, Buddy (Technical Monitor)

2002-01-01

Scientists are going to space to understand how earthquakes and other forces disturb grains of soil and sand. They will examine how the particle arrangement and structure of soils, grains and powders are changed by external forces and gain knowledge about the strength, stiffness and volume changes properties of granular materials at low pressures. The Mechanics of Granular Materials (MGM) experiment uses the microgravity of orbit to test sand columns under conditions that cannot be obtained in experiments on Earth. Research can only go so far on Earth because gravity-induced stresses complicate the analysis and change loads too quickly for detailed analysis. This new knowledge will be applied to improving foundations for buildings, managing undeveloped land, and handling powdered and granular materials in chemical, agricultural, and other industries. NASA wants to understand the way soil behaves under different gravity levels so that crews can safely build habitats on Mars and the Moon. Future MGM experiments will benefit from extended tests aboard the International Space Station, including experiments under simulated lunar and Martian gravity in the science centrifuge.

Visualizing Perturbation Decay in Shocked Granular Materials

NASA Astrophysics Data System (ADS)

Cooper, Marcia; Vogler, Tracy

2017-06-01

A new experiment continuously visualizing shock wave perturbation decay through an increasing thickness of granular material has been tested with a gas gun. The experiment confines powders of either tungsten carbide or cerium oxide into a wedge geometry formed by tilting the downstream observation window, plated with a reflective aluminum film, at a shallow angle from the driver plate. The driver is machined with a sinusoidal wavy pattern for incident shock wave perturbation. After projectile impact, the perturbed shock wave passes through the granular material, first emerging at the wedge toe. Image sequences collected at 5 MHz of reflectivity loss at the plated window-granular material interface capture the spatial variation in wave propagation with increasing sample thickness. Extracting the evolving wavy pattern from the images determines the temporal perturbation amplitude. The data are compared to continuum and mesoscale simulations in normalized terms of perturbation amplitude and wavelength. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Mechanics of Granular Materials (MGM) Test Cell

NASA Technical Reports Server (NTRS)

1998-01-01

A test cell for Mechanics of Granular Materials (MGM) experiment is shown approximately 20 and 60 minutes after the start of an experiment on STS-89. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: NASA/Marshall Space Flight Center (MSFC)

Mechanics of Granular Materials Test Cell

NASA Technical Reports Server (NTRS)

1998-01-01

A test cell for Mechanics of Granular Materials (MGM) experiment is shown from all three sides by its video camera during STS-89. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: NASA/Marshall Space Flight Center (MSFC)

Computational Modeling of Sinkage of Objects into Porous Bed under Cyclic Loading

NASA Astrophysics Data System (ADS)

Sheikh, B.; Qiu, T.; Liu, X.

2017-12-01

This work is a companion of another abstract submitted to this session on the computational modeling for the prediction of underwater munitions. In the other abstract, the focus is the hydrodynamics and sediment transport. In this work, the focus is on the geotechnical aspect and granular material behavior when the munitions interact with the porous bed. The final goal of the project is to create and utilize a comprehensive modeling framework, which integrates the flow and granular material models, to simulate and investigate the motion of the munitions. In this work, we present the computational modeling of one important process: the sinkage of rigid-body objects into porous bed under cyclic loading. To model the large deformation of granular bed materials around sinking objects under cyclic loading, a rate-independent elasto-plastic constitutive model is implemented into a Smoothed Particle Hydrodynamics (SPH) model. The effect of loading conditions (e.g., amplitude and frequency of shaking), object properties (e.g., geometry and density), and granular bed material properties (e.g., density) on object singkage is discussed.

Vesta and low gravity impact mixing

NASA Astrophysics Data System (ADS)

Hoffmann, Martin; Nathues, Andreas; Vincent, Jean-Baptiste; Sierks, Holger

2013-04-01

Re-impacting material in the velocity range of a few meters per second to a couple of hundred meters per second encounters the surface of Vesta. Studying Vesta's ejecta blankets, this specific constraint has to be taken into account. As on other planetary bodies, young craters are characterized by ray patterns. Combining this information with the evidence of Vesta's unique compaction patterns, the kinematics of the deposition process and its consequences for the spectral properties can be studied. We attempt to tackle the following questions: From which depth of a primary crater and to which extent does ejected material contribute to the mixing of surface material? What are the consequences for the local morphology and a global layer of regolith? Experiments of slow impacts into granular material resulted in the following significant effects: 1) Different depth to diameter ratios, and different profiles of the impact crater have been found, indicating transition from three dimensional interaction to surface effects. 2) The inner surfaces as well as their ejecta blanket showed quite different mixtures of material from different depths of the target area. These are interpreted as the result of pattern formation, slope and boundary effects. 3) At sufficiently low velocity and suitable projectile density the transition from inelastic to elastic interaction has been observed. 4) Between the elastic response of very slow impacts and a violent irregular agitation of the material by faster impacts, a regime of de-voiding and hence of compaction has been observed. 5) The action of force chains (Daniels et al. 2004, Rivas et al. 2011) became apparent inside the granular material, which efficiently trap energy (Daraio et al. 2006) and lead to the ray system. These results confirm and expand previous experimental, simulated and theoretically investigated evidence on the behavior of mobilized granular material. As already demonstrated by Cook and Mortensen (1967), low velocity impacts into granular material lead to anything but a simple crater morphology. Unusual scaling laws (Uehara et al. 2003) and much more diverse phase patterns than in ordinary solid media have to be taken into account, if a consistent interpretation of the formation of a crater in very deep regolith is attempted (e.g. Opsomer et al. 2011). Additional effects are due to the low gravity environment on a small planetary body like Vesta (Tancredi et al. 2012). On Vesta many apparent counterparts to the results of the experiments can be found, as demonstrated by some examples. On a global scale, the multitude of small, unresolved primary and secondary impacts into the granular regolith contributes to the observed maturity on Vesta even after short time scales. References Cook, M. A., Mortensen, K. S. 1967. Impact cratering in granular materials. J. Appl. Phys. 38, 5125-5128. Daniels, K. E., Coppock, J. E., Behringer, R. P. 2004. Dynamics of meteor impacts. Chaos 14, 84. Daraio, C., Nesterenko, V. F., Herbold, E. B., Jin S. 2006. Energy trapping and shock desintegration in a composite granular medium. Phys. Rev. Lett. 96, 058002, 1-4. Opsomer, E., Ludewig, F., Vandewalle, N. 2011. Phase transitions in vibrated granular systems in microgravity. Phys. Rev. E84, 051306, 1-5. Rivas, N., Ponce, S., Gellet, B., Risso, D., Soto, R., Cordero, P. 2011. Sudden chain energy transfer events in vibrated granular media. Phys. Rev. Lett. 106, 088001, 1-4. Tancredi, G., Maciel, A., Heredia, L., Richeri, P., Nesmachnow, S. 2012. Granular physics in low-gravity environments using discrete element method. Monthly Not. Royal Astron. Soc. 420, 3368-3380. Uehara, J. S., Ambroso, M. A., Ojha, R. J., Durian, D. J. 2003. Low-speed impact craters in loose granular media. Phys. Rev. Lett. 90, 194301, 1-4.

Granular dynamics under shear with deformable boundaries

NASA Astrophysics Data System (ADS)

Geller, Drew; Backhaus, Scott; Ecke, Robert

2015-03-01

Granular materials under shear develop complex patterns of stress as the result of granular positional rearrangements under an applied load. We consider the simple planar shear of a quasi two-dimensional granular material consisting of bi-dispersed nylon cylinders confined between deformable boundaries. The aspect ratio of the gap width to total system length is 50, and the ratio of particle diameter to gap width is about 10. This system, designed to model a long earthquake fault with long range elastic coupling through the plates, is an interesting model system for understanding effective granular friction because it essentially self tunes to the jamming condition owing to the hardness of the grains relative to that of the boundary material, a ratio of more than 1000 in elastic moduli. We measure the differential strain displacements of the plates, the inhomogeneous stress distribution in the plates, the positions and angular orientations of the individual grains, and the shear force, all as functions of the applied normal stress. There is significant stick-slip motion in this system that we quantify through our quantitative measurements of both the boundary and the grain motion, resulting in a good characterization of this sheared 2D hard sphere system.

Granular-front formation in free-surface flow of concentrated suspensions

NASA Astrophysics Data System (ADS)

Leonardi, Alessandro; Cabrera, Miguel; Wittel, Falk K.; Kaitna, Roland; Mendoza, Miller; Wu, Wei; Herrmann, Hans J.

2015-11-01

A granular front emerges whenever the free-surface flow of a concentrated suspension spontaneously alters its internal structure, exhibiting a higher concentration of particles close to its front. This is a common and yet unexplained phenomenon, which is usually believed to be the result of fluid convection in combination with particle size segregation. However, suspensions composed of uniformly sized particles also develop a granular front. Within a large rotating drum, a stationary recirculating avalanche is generated. The flowing material is a mixture of a viscoplastic fluid obtained from a kaolin-water dispersion with spherical ceramic particles denser than the fluid. The goal is to mimic the composition of many common granular-fluid materials, such as fresh concrete or debris flow. In these materials, granular and fluid phases have the natural tendency to separate due to particle settling. However, through the shearing caused by the rotation of the drum, a reorganization of the phases is induced, leading to the formation of a granular front. By tuning the particle concentration and the drum velocity, it is possible to control this phenomenon. The setting is reproduced in a numerical environment, where the fluid is solved by a lattice-Boltzmann method, and the particles are explicitly represented using the discrete element method. The simulations confirm the findings of the experiments, and provide insight into the internal mechanisms. Comparing the time scale of particle settling with the one of particle recirculation, a nondimensional number is defined, and is found to be effective in predicting the formation of a granular front.

Granular-front formation in free-surface flow of concentrated suspensions.

PubMed

Leonardi, Alessandro; Cabrera, Miguel; Wittel, Falk K; Kaitna, Roland; Mendoza, Miller; Wu, Wei; Herrmann, Hans J

2015-11-01

A granular front emerges whenever the free-surface flow of a concentrated suspension spontaneously alters its internal structure, exhibiting a higher concentration of particles close to its front. This is a common and yet unexplained phenomenon, which is usually believed to be the result of fluid convection in combination with particle size segregation. However, suspensions composed of uniformly sized particles also develop a granular front. Within a large rotating drum, a stationary recirculating avalanche is generated. The flowing material is a mixture of a viscoplastic fluid obtained from a kaolin-water dispersion with spherical ceramic particles denser than the fluid. The goal is to mimic the composition of many common granular-fluid materials, such as fresh concrete or debris flow. In these materials, granular and fluid phases have the natural tendency to separate due to particle settling. However, through the shearing caused by the rotation of the drum, a reorganization of the phases is induced, leading to the formation of a granular front. By tuning the particle concentration and the drum velocity, it is possible to control this phenomenon. The setting is reproduced in a numerical environment, where the fluid is solved by a lattice-Boltzmann method, and the particles are explicitly represented using the discrete element method. The simulations confirm the findings of the experiments, and provide insight into the internal mechanisms. Comparing the time scale of particle settling with the one of particle recirculation, a nondimensional number is defined, and is found to be effective in predicting the formation of a granular front.

Universal scaling of permeability through the granular-to-continuum transition

NASA Astrophysics Data System (ADS)

Wadsworth, F. B.; Scheu, B.; Heap, M. J.; Kendrick, J. E.; Vasseur, J.; Lavallée, Y.; Dingwell, D. B.

2015-12-01

Magmas fragment forming a transiently granular material, which can weld back to a fluid-continuum. This process results in dramatic changes in the gas-volume fraction of the material, which impacts the gas permeability. We collate published data for the gas-volume fraction and permeability of volcanic and synthetic materials which have undergone this process to different amounts and note that in all cases there exists a discontinuity in the relationship between these two properties. By discriminating data for which good microstructural information are provided, we use simple scaling arguments to collapse the data in both the still-granular, high gas-volume fraction regime and the fluid-continuum low gas-volume fraction regime such that a universal description can be achieved. We use this to argue for the microstructural meaning of the well-described discontinuity between gas-permeability and gas-volume fraction and to infer the controls on the position of this transition between dominantly granular and dominantly fluid-continuum material descriptions. As a specific application, we consider the transiently granular magma transported through and deposited in fractures in more-coherent magmas, thought to be a primary degassing pathway in high viscosity systems. We propose that our scaling coupled with constitutive laws for densification can provide insights into the longevity of such degassing channels, informing sub-surface pressure modelling at such volcanoes.

The Quantified Characterization Method of the Micro-Macro Contacts of Three-Dimensional Granular Materials on the Basis of Graph Theory.

PubMed

Guan, Yanpeng; Wang, Enzhi; Liu, Xiaoli; Wang, Sijing; Luan, Hebing

2017-08-03

We have attempted a multiscale and quantified characterization method of the contact in three-dimensional granular material made of spherical particles, particularly in cemented granular material. Particle contact is defined as a type of surface contact with voids in its surroundings, rather than a point contact. Macro contact is a particle contact set satisfying the restrictive condition of a two-dimensional manifold with a boundary. On the basis of graph theory, two dual geometrical systems are abstracted from the granular pack. The face and the face set, which satisfies the two-dimensional manifold with a boundary in the solid cell system, are extracted to characterize the particle contact and the macro contact, respectively. This characterization method is utilized to improve the post-processing in DEM (Discrete Element Method) from a micro perspective to describe the macro effect of the cemented granular material made of spherical particles. Since the crack has the same shape as its corresponding contact, this method is adopted to characterize the crack and realize its visualization. The integral failure route of the sample can be determined by a graph theory algorithm. The contact force is assigned to the weight value of the face characterizing the particle contact. Since the force vectors can be added, the macro contact force can be solved by adding the weight of its corresponding faces.

Dilatant shear bands in solidifying metals.

PubMed

Gourlay, C M; Dahle, A K

2007-01-04

Compacted granular materials expand in response to shear, and can exhibit different behaviour from that of the solids, liquids and gases of which they are composed. Application of the physics of granular materials has increased the understanding of avalanches, geological faults, flow in hoppers and silos, and soil mechanics. During the equiaxed solidification of metallic alloys, there exists a range of solid fractions where the microstructure consists of a geometrically crowded disordered assembly of crystals saturated with liquid. It is therefore natural to ask if such a microstructure deforms as a granular material and what relevance this might have to solidification processing. Here we show that partially solidified alloys can exhibit the characteristics of a cohesionless granular material, including Reynolds' dilatancy and strain localization in dilatant shear bands 7-18 mean crystals wide. We show that this behaviour is important in defect formation during high pressure die casting of Al and Mg alloys, a global industry that contributes over $7.3 billion to the USA's economy alone and is used in the manufacture of products that include mobile-phone covers and steering wheels. More broadly, these findings highlight the potential to apply the principles and modelling approaches developed in granular mechanics to the field of solidification processing, and also indicate the possible benefits that might be gained from exploring and exploiting further synergies between these fields.

Ultrafine-grained mineralogy and matrix chemistry of olivine-rich chondritic interplanetary dust particles

NASA Technical Reports Server (NTRS)

Rietmeijer, F. J. M.

1989-01-01

Olivine-rich chondritic interplanetary dust particles (IDPs) are an important subset of fluffy chondritic IDPs collected in the earth's stratosphere. Particles in this subset are characterized by a matrix of nonporous, ultrafine-grained granular units. Euhedral single crystals, crystals fragments, and platey single crystals occur dispersed in the matrix. Analytical electron microscopy of granular units reveals predominant magnesium-rich olivines and FeNi-sulfides embedded in amorphous carbonaceous matrix material. The variable ratio of ultrafine-grained minerals vs. carbonaceous matrix material in granular units support variable C/Si ratios, and some fraction of sulfur is associated with carbonaceous matrix material. The high Mg/(Mg+Fe) ratios in granular units is similar to this distribution in P/Comet Halley dust. The chondritic composition of fine-grained, polycrystalline IDPs gradually breaks down into nonchondritic, and ultimately, single mineral compositions as a function of decreased particle mass. The relationship between particle mass and composition in the matrix of olivine-rich chondritic IDPs is comparable with the relationship inferred for P/Comet Halley dust.

Effective friction of granular flows made of non-spherical particles

NASA Astrophysics Data System (ADS)

Somfai, Ellák; Nagy, Dániel B.; Claudin, Philippe; Favier, Adeline; Kálmán, Dávid; Börzsönyi, Tamás

2017-06-01

Understanding the rheology of dense granular matter is a long standing problem and is important both from the fundamental and the applied point of view. As the basic building blocks of granular materials are macroscopic particles, the nature of both the response to deformations and the dissipation is very different from that of molecular materials. In the absence of large gradients, the best approach formulates the constitutive equation as an effective friction: for sheared granular matter the ratio of the off-diagonal and the diagonal elements of the stress tensor depends only on dynamical parameters, in particular the inertial number. In this work we employ numerical simulations to extend this formalism to granular packings made of frictionless elongated particles. We measured how the shape of the particles affects the effective friction, volume fraction and first normal stress difference, and compared it to the spherical particle case. We had to introduce polydispersity in particle size in order to keep the systems of the more elongated particles disordered.

A trans-phase granular continuum relation and its use in simulation

NASA Astrophysics Data System (ADS)

Kamrin, Ken; Dunatunga, Sachith; Askari, Hesam

The ability to model a large granular system as a continuum would offer tremendous benefits in computation time compared to discrete particle methods. However, two infamous problems arise in the pursuit of this vision: (i) the constitutive relation for granular materials is still unclear and hotly debated, and (ii) a model and corresponding numerical method must wear ``many hats'' as, in general circumstances, it must be able to capture and accurately represent the material as it crosses through its collisional, dense-flowing, and solid-like states. Here we present a minimal trans-phase model, merging an elastic response beneath a fictional yield criterion, a mu(I) rheology for liquid-like flow above the static yield criterion, and a disconnection rule to model separation of the grains into a low-temperature gas. We simulate our model with a meshless method (in high strain/mixing cases) and the finite-element method. It is able to match experimental data in many geometries, including collapsing columns, impact on granular beds, draining silos, and granular drag problems.

Negative permittivity and permeability spectra of Cu/yttrium iron garnet hybrid granular composite materials in the microwave frequency range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsutaoka, Takanori, E-mail: tsutaok@hiroshima-u.ac.jp; Fukuyama, Koki; Kinoshita, Hideaki

2013-12-23

The relative complex permittivity and permeability spectra of the coagulated copper and yttrium iron garnet (Cu/YIG) hybrid granular composite materials have been studied in the microwave range. The insulator to metal transition was observed at the percolation threshold of Cu particle content (φ{sub Cu} = 16.0 vol. %) in the electrical conductivity. In the percolation threshold, the low frequency plasmonic state caused by the metallic Cu particle networks was observed. The percolated Cu/YIG granular composites show simultaneous negative permittivity and permeability spectra under external magnetic fields.

Sound-absorbing slabs and structures based on granular materials (bound and unbound). [energy absorbing efficiency of porous material

NASA Technical Reports Server (NTRS)

Petre-Lazar, S.; Popeea, G.

1974-01-01

Sound absorbing slabs and structures made up of bound or unbound granular materials are considered and how to manufacture these elements at the building site. The raw material is a single grain powder (sand, expanded blast furnace slag, etc.) that imparts to the end products an apparent porosity of 25-45% and an energy dissipation within the structure leading to absorption coefficients that can be compared with those of mineral wool and urethane.

Fine granular of shredded waste tyre for road kerb application as improvised road furniture

NASA Astrophysics Data System (ADS)

Munikanan, Vikneswaran; Yahya, Muhamad Azani; Yusof, Mohammed Alias; Radzi, Muhammad Haris Fauzan

2018-02-01

Solid waste management in Malaysia was still in a backward stage. Population growth, urbanization and rapid industrialization led to an increase in the solid waste generated by society. Solid waste management is one of the main problems faced by the community, especially in the city. Solid waste management costs of the collection, collecting, transporting waste to the landfill, is very high. The quantity of solid waste should be reduced in order to reduce government spending. Moreover, improper solid waste management caused a negative impact on people and the environment. Method of recycling is one of the best alternatives to reduce the number of solid waste. Therefore, this study was to identify methods of recycling used tires to be used in civil engineering. This study was conducted to determine the effectiveness and properties of rubber from used tires to be add in the road kerb design.

Advanced Magnetic Materials Methods and Numerical Models for Fluidization in Microgravity and Hypogravity

NASA Technical Reports Server (NTRS)

Atwater, James; Wheeler, Richard, Jr.; Akse, James; Jovanovic, Goran; Reed, Brian

2013-01-01

To support long-duration manned missions in space such as a permanent lunar base, Mars transit, or Mars Surface Mission, improved methods for the treatment of solid wastes, particularly methods that recover valuable resources, are needed. The ability to operate under microgravity and hypogravity conditions is essential to meet this objective. The utilization of magnetic forces to manipulate granular magnetic media has provided the means to treat solid wastes under variable gravity conditions by filtration using a consolidated magnetic media bed followed by thermal processing of the solid wastes in a fluidized bed reactor. Non-uniform magnetic fields will produce a magnetic field gradient in a bed of magnetically susceptible media toward the distributor plate of a fluidized bed reactor. A correctly oriented magnetic field gradient will generate a downward direct force on magnetic media that can substitute for gravitational force in microgravity, or which may augment low levels of gravity, such as on the Moon or Mars. This approach is termed Gradient Magnetically Assisted Fluidization (G-MAFB), in which the magnitude of the force on the fluidized media depends upon the intensity of the magnetic field (H), the intensity of the field gradient (dH/dz), and the magnetic susceptibility of the media. Fluidized beds based on the G-MAFB process can operate in any gravitational environment by tuning the magnetic field appropriately. Magnetic materials and methods have been developed that enable G-MAFB operation under variable gravity conditions.

A Simple Method for Determination of the Density of Granular Materials

ERIC Educational Resources Information Center

Tsutsumanova, G. G.; Kirilov, K. M.; Russev, S. C.

2012-01-01

A simple experiment using low cost equipment for the determination of the density of granular materials, without immersing them in a liquid, is presented. It is based only on the ideal gas state equation, so it is a good experimental task for undergraduate and high school students. (Contains 2 tables and 5 figures.)

DEM study on the interaction between wet cohesive granular materials and tools

NASA Astrophysics Data System (ADS)

Tsuji, Takuya; Matsui, Yu; Nakagawa, Yuta; Kadono, Yuuichi; Tanaka, Toshitsugu

2013-06-01

A model based on discrete element method has been developed for the interaction between wet cohesive granular materials and mechanical tools with complex geometry. To obtain realistic results, the motion of 52.5 million particles has been simulated and the formation of multiple shear bands during an excavation process by a bulldozer blade was observed.

Submicron and Nanoparticulate Matter Removal by HEPA-Rated Media Filters and Packed Beds of Granular Materials

NASA Technical Reports Server (NTRS)

Perry, J. L.; Agui, J. H.; Vijayakimar, R

2016-01-01

Contaminants generated aboard crewed spacecraft by diverse sources consist of both gaseous chemical contaminants and particulate matter. Both HEPA media filters and packed beds of granular material, such as activated carbon, which are both commonly employed for cabin atmosphere purification purposes have efficacy for removing nanoparticulate contaminants from the cabin atmosphere. The phenomena associated with particulate matter removal by HEPA media filters and packed beds of granular material are reviewed relative to their efficacy for removing fine (less than 2.5 micrometers) and ultrafine (less than 0.01 micrometers) sized particulate matter. Considerations are discussed for using these methods in an appropriate configuration to provide the most effective performance for a broad range of particle sizes including nanoparticulates.

A constitutive law for dense granular flows.

PubMed

Jop, Pierre; Forterre, Yoël; Pouliquen, Olivier

2006-06-08

A continuum description of granular flows would be of considerable help in predicting natural geophysical hazards or in designing industrial processes. However, the constitutive equations for dry granular flows, which govern how the material moves under shear, are still a matter of debate. One difficulty is that grains can behave like a solid (in a sand pile), a liquid (when poured from a silo) or a gas (when strongly agitated). For the two extreme regimes, constitutive equations have been proposed based on kinetic theory for collisional rapid flows, and soil mechanics for slow plastic flows. However, the intermediate dense regime, where the granular material flows like a liquid, still lacks a unified view and has motivated many studies over the past decade. The main characteristics of granular liquids are: a yield criterion (a critical shear stress below which flow is not possible) and a complex dependence on shear rate when flowing. In this sense, granular matter shares similarities with classical visco-plastic fluids such as Bingham fluids. Here we propose a new constitutive relation for dense granular flows, inspired by this analogy and recent numerical and experimental work. We then test our three-dimensional (3D) model through experiments on granular flows on a pile between rough sidewalls, in which a complex 3D flow pattern develops. We show that, without any fitting parameter, the model gives quantitative predictions for the flow shape and velocity profiles. Our results support the idea that a simple visco-plastic approach can quantitatively capture granular flow properties, and could serve as a basic tool for modelling more complex flows in geophysical or industrial applications.

IN-PLACE REGENERATION OF SVE LOADED GAC USING FENTON'S REAGENTS

EPA Science Inventory

Ten out of the 25 most frequently detected groundwater contaminants at hazardous waste sites are chlorinated volatile organic compounds (VOCs) 1 . Trichloroethylene (TCE) and tetrachloroethylene (PCE) are among the top three 1 . Granular activated carbon (GAC) adsorption is w...

IN-PLACE REGENERATION OF SVE LOADED GAC USING FENTON'S REAGENTS

EPA Science Inventory

Ten out of the 25 most frequently detected groundwater contaminants at hazardous waste sites are chlorinated volatile organic compounds (VOCs) 1. Trichloroethylene (TCE) and tetrachloroethylene (PCE) are among the top three 1. Granular activated carbon (GAC) adsorption is widel...

Microbial dynamics in anaerobic digestion reactors for treating organic urban residues during the start-up process.

PubMed

Alcántara-Hernández, R J; Taş, N; Carlos-Pinedo, S; Durán-Moreno, A; Falcón, L I

2017-06-01

Anaerobic digestion of organic residues offers economic benefits via biogas production, still methane (CH 4 ) yield relies on the development of a robust microbial consortia for adequate substrate degradation, among other factors. In this study, we monitor biogas production and changes in the microbial community composition in two semi-continuous stirred tank reactors during the setting process under mesophilic conditions (35°C) using a 16S rDNA high-throughput sequencing method. Reactors were initially inoculated with anaerobic granular sludge from a brewery wastewater treatment plant, and gradually fed organic urban residues (4·0 kg VS m -3  day -1 ) . The inocula and biomass samples showed changes related to adaptations of the community to urban organic wastes including a higher relative proportion of Clostridiales, with Ruminococcus spp. and Syntrophomonas spp. as recurrent species. Candidatus Cloacamonas spp. (Spirochaetes) also increased from ~2·2% in the inoculum to >10% in the reactor biomass. The new community consolidated the cellulose degradation and the propionate and amino acids fermentation processes. Acetoclastic methanogens were more abundant in the reactor, where Methanosaeta spp. was found as a key player. This study demonstrates a successful use of brewery treatment plant granular sludge to obtain a robust consortium for methane production from urban organic solid waste in Mexico. This study describes the selection of relevant bacteria and archaea in anaerobic digesters inoculated with anaerobic granular sludge from a brewery wastewater treatment plant. Generally, these sludge granules are used to inoculate reactors digesting organic urban wastes. Though, it is still not clearly understood how micro-organisms respond to substrate variations during the reactor start-up process. After feeding two reactors with organic urban residues, it was found that a broader potential for cellulose degradation was developed including Bacteroidetes, Firmicutes and Spirochaetes. These results clarify the bacterial processes behind new reactors establishment for treating organic wastes in urban areas. © 2017 The Society for Applied Microbiology.

Wet granular materials

NASA Astrophysics Data System (ADS)

Mitarai, Namiko; Nori, Franco

2006-04-01

Most studies on granular physics have focused on dry granular media, with no liquids between the grains. However, in geology and many real world applications (e.g. food processing, pharmaceuticals, ceramics, civil engineering, construction, and many industrial applications), liquid is present between the grains. This produces inter-grain cohesion and drastically modifies the mechanical properties of the granular media (e.g. the surface angle can be larger than 90 degrees). Here we present a review of the mechanical properties of wet granular media, with particular emphasis on the effect of cohesion. We also list several open problems that might motivate future studies in this exciting but mostly unexplored field.

Compaction of granular materials composed of deformable particles

NASA Astrophysics Data System (ADS)

Nguyen, Thanh Hai; Nezamabadi, Saeid; Delenne, Jean-Yves; Radjai, Farhang

2017-06-01

In soft particle materials such as metallic powders the particles can undergo large deformations without rupture. The large elastic or plastic deformations of the particles are expected to strongly affect the mechanical properties of these materials compared to hard particle materials more often considered in research on granular materials. Herein, two numerical approaches are proposed for the simulation of soft granular systems: (i) an implicit formulation of the Material Point Method (MPM) combined with the Contact Dynamics (CD) method to deal with contact interactions, and (i) Bonded Particle Model (BPM), in which each deformable particle is modeled as an aggregate of rigid primary particles using the CD method. These two approaches allow us to simulate the compaction of an assembly of elastic or plastic particles. By analyzing the uniaxial compaction of 2D soft particle packings, we investigate the effects of particle shape change on the stress-strain relationship and volume change behavior as well as the evolution of the microstructure.

Parallel Program Systems for the Analysis of Wave Processes in Elastic-Plastic, Granular, Porous and Multi-Blocky Media

NASA Astrophysics Data System (ADS)

Sadovskaya, Oxana; Sadovskii, Vladimir

2017-04-01

Under modeling the wave propagation processes in geomaterials (granular and porous media, soils and rocks) it is necessary to take into account the structural inhomogeneity of these materials. Parallel program systems for numerical solution of 2D and 3D problems of the dynamics of deformable media with constitutive relationships of rather general form on the basis of universal mathematical model describing small strains of elastic, elastic-plastic, granular and porous materials are worked out. In the case of an elastic material, the model is reduced to the system of equations, hyperbolic by Friedrichs, written in terms of velocities and stresses in a symmetric form. In the case of an elastic-plastic material, the model is a special formulation of the Prandtl-Reuss theory in the form of variational inequality with one-sided constraints on the stress tensor. Generalization of the model to describe granularity and the collapse of pores is obtained by means of the rheological approach, taking into account different resistance of materials to tension and compression. Rotational motion of particles in the material microstructure is considered within the framework of a mathematical model of the Cosserat continuum. Computational domain may have a blocky structure, composed of an arbitrary number of layers, strips in a layer and blocks in a strip from different materials with self-consistent curvilinear interfaces. At the external boundaries of computational domain the main types of dissipative boundary conditions in terms of velocities, stresses or mixed boundary conditions can be given. Shock-capturing algorithm is proposed for implementation of the model on supercomputers with cluster architecture. It is based on the two-cyclic splitting method with respect to spatial variables and the special procedures of the stresses correction to take into account plasticity, granularity or porosity of a material. An explicit monotone ENO-scheme is applied for solving one-dimensional systems of equations at the stages of splitting method. The parallelizing of computations is carried out using the MPI library and the SPMD technology. The data exchange between processors occurs at step "predictor" of the finite-difference scheme. Program systems allow simulate the propagation of waves produced by external mechanical effects in a medium, aggregated of arbitrary number of heterogeneous blocks. Some computations of dynamic problems with and without taking into account the moment properties of a material were performed on clusters of ICM SB RAS (Krasnoyarsk) and JSCC RAS (Moscow). Parallel program systems 2Dyn_Granular, 3Dyn_Granular, 2Dyn_Cosserat, 3Dyn_Cosserat and 2Dyn_Blocks_MPI for numerical solution of 2D and 3D elastic-plastic problems of the dynamics of granular media and problems of the Cosserat elasticity theory, as well as for modeling of the dynamic processes in multi-blocky media with pliant viscoelastic, porous and fluid-saturated interlayers on cluster systems were registered by Rospatent.

Influence of temperature on the electrical conductivity of leachate from municipal solid waste.

PubMed

Grellier, Solenne; Robain, Henri; Bellier, Gérard; Skhiri, Nathalie

2006-09-01

A bioreactor landfill is designed to manage municipal solid waste, through accelerated waste biodegradation, and stabilisation of the process by means of the controlled addition of liquid, i.e. leachate recirculation. The measurement of electrical resistivity by Electrical Resistivity Tomography (ERT) allows to monitor water content present in the bioreactors. Variations in electrical resistivity are linked to variations in moisture content and temperature. In order to overcome this ambiguity, two laboratory experiments were carried out to establish a relationship between temperature and electrical conductivity: the first set of measurements was made for leachate alone, whereas the second set was made with two different granular media saturated with leachate. Both experiments confirm a well known increase in conductivity of about 2% degrees C(-1). However, higher suspended matter concentrations lead to a lower dependence of electrical conductivity on temperature. Furthermore, for various porous media saturated with an identical leachate, the higher the specific surface of the granular matrix, the lower the effective bulk electrical conductivity. These observations show that a correct understanding of the electrical properties of liquids requires the nature and (in particular) the size of the electrical charge carriers to be taken into account.

Planning for the Collection and Analysis of Samples of Martian Granular Materials Potentially to be Returned by Mars Sample Return

NASA Astrophysics Data System (ADS)

Carrier, B. L.; Beaty, D. W.

2017-12-01

NASA's Mars 2020 rover is scheduled to land on Mars in 2021 and will be equipped with a sampling system capable of collecting rock cores, as well as a specialized drill bit for collecting unconsolidated granular material. A key mission objective is to collect a set of samples that have enough scientific merit to justify returning to Earth. In the case of granular materials, we would like to catalyze community discussion on what we would do with these samples if they arrived in our laboratories, as input to decision-making related to sampling the regolith. Numerous scientific objectives have been identified which could be achieved or significantly advanced via the analysis of martian rocks, "regolith," and gas samples. The term "regolith" has more than one definition, including one that is general and one that is much more specific. For the purpose of this analysis we use the term "granular materials" to encompass the most general meaning and restrict "regolith" to a subset of that. Our working taxonomy includes the following: 1) globally sourced airfall dust (dust); 2) saltation-sized particles (sand); 3) locally sourced decomposed rock (regolith); 4) crater ejecta (ejecta); and, 5) other. Analysis of martian granular materials could serve to advance our understanding areas including habitability and astrobiology, surface-atmosphere interactions, chemistry, mineralogy, geology and environmental processes. Results of these analyses would also provide input into planning for future human exploration of Mars, elucidating possible health and mechanical hazards caused by the martian surface material, as well as providing valuable information regarding available resources for ISRU and civil engineering purposes. Results would also be relevant to matters of planetary protection and ground-truthing orbital observations. We will present a preliminary analysis of the following, in order to generate community discussion and feedback on all issues relating to: What are the specific reasons (and their priorities) for collecting samples of granular materials? How do those reasons translate to sampling priorities? In what condition would these samples be expected to be received? What is our best projection of the approach by which these samples would be divided, prepared, and analyzed to achieve our objectives?

Investigation of sub-slab pressure field extension in specified granular fill materials incorporating a sump-based soil depressurisation system for radon mitigation.

PubMed

Hung, Le Chi; Goggins, Jamie; Fuente, Marta; Foley, Mark

2018-05-14

Design of bearing layers (granular fill material layers) is important for a house with a soil depressurisation (SD) system for indoor radon mitigation. These layers should not only satisfy the bearing capacity and serviceability criteria but should also provide a sufficient degree of the air permeability for the system. Previous studies have shown that a critical parameter for a SD system is the sub-slab pressure field extension in the bearing layers, but this issue has not been systematically investigated. A series of two-dimensional computational fluid dynamic simulations that investigate the behaviour of the sub-slab pressure field extension developed in a SD system is presented in this paper. The SD system considered in this paper consists of a granular fill material layer and a radon sump. The granular fill materials are 'T1 Struc' and 'T2 Perm', which are standard materials for building in the Republic of Ireland. Different conditions, which might be encountered in a practical situation, were examined. The results show that the air permeability and thickness of the granular fill materials are the two key factors which affect the sub slab pressure field extension (SPFE) significantly. Furthermore, the air permeability of native soil is found to be a fundamental factor for the SPFE so that it should be well understood when designing a SD system. Therefore, these factors should be considered sufficiently in each practical situation. Finally, a significant improvement of the pressure field extension can be achieved by ensuring air tightness of the SD system. Copyright © 2018 Elsevier B.V. All rights reserved.

APC fly ashes stabilized with Portland cement for further development of road sub-base aggregates

NASA Astrophysics Data System (ADS)

Formosa, J.; Giro-Paloma, J.; Maldonado-Alameda, A.; Huete-Hernández, S.; Chimenos, J. M.

2017-10-01

Although waste-to-energy plants allow reducing the mass and volume of municipal solid waste (MSW) incinerated, an average around 30 % of the total content remains as bottom ash (BA) and air pollution control (APC) ashes at the end of combustion process. While weathered bottom ash (WBA) is considered a non-hazardous residue that can be revalorized as a secondary aggregate, APC fly ashes generated during the flue gas treatment are classified as hazardous waste and are handled in landfill disposal after stabilization, usually with Portland cement (OPC). However, taking into account the amount of APC residues produced and the disposing cost in landfill, their revalorization is an important issue that could be effectively addressed. As MSW can be incinerated producing bottom ashes (BA) or air pollutant control (APC) residues, the development of a mortar formulated with APC fly ash as secondary building material is a significant risk to the environment for their content of heavy metals. In this way, Design of Experiment (DoE) was used for the improvement of granular material (GM) formulation composed by APC and OPC for further uses as road sub-base aggregate. DoE analysis was successful in the modelling and optimization the formulation as function of the mechanical properties and APC amount. Consequently, an optimal mortar formulation (OMF) of around 50 wt.% APC and 50 wt.% OPC was considered. The OMF leachates and abrasion resistance have been analyzed. These results have demonstrated the viability of OMF as non-hazardous material feasible to be used as secondary aggregate. Moreover, it would be possible to consider the environmental assessment of a GM composed by ≈20 wt.% of OMF and ≈80 wt.% of WBA in order to improve mechanical properties and heavy metals stabilization.

Mixture design and treatment methods for recycling contaminated sediment.

PubMed

Wang, Lei; Kwok, June S H; Tsang, Daniel C W; Poon, Chi-Sun

2015-01-01

Conventional marine disposal of contaminated sediment presents significant financial and environmental burden. This study aimed to recycle the contaminated sediment by assessing the roles and integration of binder formulation, sediment pretreatment, curing method, and waste inclusion in stabilization/solidification. The results demonstrated that the 28-d compressive strength of sediment blocks produced with coal fly ash and lime partially replacing cement at a binder-to-sediment ratio of 3:7 could be used as fill materials for construction. The X-ray diffraction analysis revealed that hydration products (calcium hydroxide) were difficult to form at high sediment content. Thermal pretreatment of sediment removed 90% of indigenous organic matter, significantly increased the compressive strength, and enabled reuse as non-load-bearing masonry units. Besides, 2-h CO2 curing accelerated early-stage carbonation inside the porous structure, sequestered 5.6% of CO2 (by weight) in the sediment blocks, and acquired strength comparable to 7-d curing. Thermogravimetric analysis indicated substantial weight loss corresponding to decomposition of poorly and well crystalline calcium carbonate. Moreover, partial replacement of contaminated sediment by various granular waste materials notably augmented the strength of sediment blocks. The metal leachability of sediment blocks was minimal and acceptable for reuse. These results suggest that contaminated sediment should be viewed as useful resources. Copyright © 2014 Elsevier B.V. All rights reserved.

40 CFR 278.2 - Applicability.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 28 2013-07-01 2013-07-01 false Applicability. 278.2 Section 278.2 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) CRITERIA FOR THE MANAGEMENT OF GRANULAR MINE TAILINGS (CHAT) IN ASPHALT CONCRETE AND PORTLAND CEMENT CONCRETE IN...

40 CFR 278.2 - Applicability.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 28 2012-07-01 2012-07-01 false Applicability. 278.2 Section 278.2 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) CRITERIA FOR THE MANAGEMENT OF GRANULAR MINE TAILINGS (CHAT) IN ASPHALT CONCRETE AND PORTLAND CEMENT CONCRETE IN...

40 CFR 278.2 - Applicability.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 27 2014-07-01 2014-07-01 false Applicability. 278.2 Section 278.2 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) CRITERIA FOR THE MANAGEMENT OF GRANULAR MINE TAILINGS (CHAT) IN ASPHALT CONCRETE AND PORTLAND CEMENT CONCRETE IN...

40 CFR 278.2 - Applicability.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 27 2011-07-01 2011-07-01 false Applicability. 278.2 Section 278.2 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) CRITERIA FOR THE MANAGEMENT OF GRANULAR MINE TAILINGS (CHAT) IN ASPHALT CONCRETE AND PORTLAND CEMENT CONCRETE IN...

40 CFR 278.2 - Applicability.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 26 2010-07-01 2010-07-01 false Applicability. 278.2 Section 278.2 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) CRITERIA FOR THE MANAGEMENT OF GRANULAR MINE TAILINGS (CHAT) IN ASPHALT CONCRETE AND PORTLAND CEMENT CONCRETE IN...

Mechanics of Granular Materials (MGM) Test Cell

NASA Technical Reports Server (NTRS)

2000-01-01

A test cell for Mechanics of Granular Materials (MGM) experiment is tested for long-term storage with water in the system as plarned for STS-107. This view shows the compressed sand column with the protective water jacket removed. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that cannot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: University of Colorado at Boulder

Mechanics of Granular Materials (MGM) Cell

NASA Technical Reports Server (NTRS)

1996-01-01

One of three Mechanics of Granular Materials (MGM) test cells after flight on STS-79 and before impregnation with resin. Note that the sand column has bulged in the middle, and that the top of the column is several inches lower than the top of the plastic enclosure. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: University of Colorado at Boulder

Mechanics of Granular Materials (MGM) Test Cell

NASA Technical Reports Server (NTRS)

2000-01-01

A test cell for Mechanics of Granular Materials (MGM) experiment is tested for long-term storage with water in the system as plarned for STS-107. This view shows the top of the sand column with the metal platten removed. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that cannot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: University of Colorado at Boulder

Simulation of cemented granular materials. II. Micromechanical description and strength mobilization at the onset of macroscopic yielding.

PubMed

Estrada, Nicolas; Lizcano, Arcesio; Taboada, Alfredo

2010-07-01

This is the second of two papers investigating the mechanical response of cemented granular materials by means of contact dynamics simulations. In this paper, a two-dimensional polydisperse sample with high void ratio is sheared in a load-controlled simple shear numerical device until the stress state of the sample reaches the yield stress. We first study the stress transmission properties of the granular material in terms of the fabric of different subsets of contacts characterized by the magnitude of their normal forces. This analysis highlights the existence of a peculiar force carrying structure in the cemented material, which is reminiscent of the bimodal stress transmission reported for cohesionless granular media. Then, the evolution of contact forces and torques is investigated trying to identify the micromechanical conditions that trigger macroscopic yielding. It is shown that global failure can be associated to the apparition of a group of particles whose contacts fulfill at least one of the local rupture conditions. In particular, these particles form a large region that percolates through the sample at the moment of failure, evidencing the relationship between macroscopic yielding and the emergence of large-scale correlations in the system.

Effects of fabric anisotropy on elastic shear modulus of granular soils

NASA Astrophysics Data System (ADS)

Li, Bo; Zeng, Xiangwu

2014-06-01

The fabric anisotropy of a granular soil deposit can strongly influence its engineering properties and behavior. This paper presents the results of a novel experimental study designed to examine the effects of fabric anisotropy on smallstrain stiffness and its evolution with loading on the elastic shear modulus of granular materials under a K 0 condition. Two primary categories of fabric anisotropy, i.e., deposition-induced and particle shape-induced, are investigated. Toyoura sand deposits with relative densities of 40% and 80% were prepared using deposition angles oriented at 0° and 90°. Piezoelectric transducers were used to obtain the elastic shear modulus in the vertical and horizontal directions ( G vh and G hh). The measurements indicate distinct differences in the values of G with respect to the different deposition angles. Particle shapeinduced fabric anisotropy was examined using four selected sands. It was concluded that sphericity is a controlling factor dominating the small-strain stiffness of granular materials. The degree of fabric anisotropy proves to be a good indicatorin the characterization of stress-induced fabric evolution during loading and unloading stress cycles. The experimental data were used to calibrate an existing micromechanical model, which was able to represent the behavior of the granular material and the degree of fabric anisotropy reasonably well.

Apparatus and methods for filtering granular solid material

NASA Technical Reports Server (NTRS)

Backes, Douglas J. (Inventor); Poulter, Clay B. (Inventor); Godfrey, Max R. (Inventor); Tolman, Dennis K. (Inventor); Dutton, Melinda S. (Inventor)

2011-01-01

Apparatuses for screening granular solid particulate material include a generally planar first screen and a second screen. A plurality of apertures extends through the first screen. At least a portion of the second screen is oriented at an angle to the first screen, and apertures extend through a perforated region of the second screen. The second screen includes at least one region configured to prevent at least some particles of solid material from passing through the second screen.

Noise and diffusion of a vibrated self-propelled granular particle

NASA Astrophysics Data System (ADS)

Walsh, Lee; Wagner, Caleb G.; Schlossberg, Sarah; Olson, Christopher; Baskaran, Aparna; Menon, Narayanan

Granular materials are an important physical realization of active matter. In vibration-fluidized granular matter, both diffusion and self-propulsion derive from the same collisional forcing, unlike many other active systems where there is a clean separation between the origin of single-particle mobility and the coupling to noise. Here we present experimental studies of single-particle motion in a vibrated granular monolayer, along with theoretical analysis that compares grain motion at short and long time scales to the assumptions and predictions, respectively, of the active Brownian particle (ABP) model. The results demonstrate that despite the unique relation between noise and propulsion, granular media do show the generic features predicted by the ABP model and indicate that this is a valid framework to predict collective phenomena. Additionally, our scheme of analysis for validating the inputs and outputs of the model can be applied to other granular and non-granular systems.

A Study of SDT in an Ammonium Nitrate (NH4 NO3) Based Granular Explosive

NASA Astrophysics Data System (ADS)

Burns, Malcolm; Taylor, Peter

2007-06-01

In order to study the SDT process in a granular non ideal explosive (NIE) an experimental technique has been developed that allows the granular explosive to be shock initiated at a well controlled ``tap density''. The granular NIE was contained in a PMMA cone and a planar shock was delivered to the explosive through buffer plates of varying material. A combination of piezoelectric probes, ionization pins, PVDF stress gauges and a high speed framing camera were used to measure the input shock pressure and shock and detonation wave positions in the explosive. Four trials were performed to characterize the run to detonation distance versus pressure relationship (Pop plot) of the granular NH4 NO3 explosive. Input pressures ranged from close to the 4GPa predicted CJ pressure of the granular explosive down to 1.4 GPa, giving run distances up to 14mm for the lowest pressure. The data indicates a steady acceleration of the input shock to the detonation velocity, implying significant reaction growth at the shock front. This is in contrast to the behaviour of most high density pressed PBXs which show little growth in shock front velocity before transit to detonation. The experimentally observed initiation behaviour is compared to that predicted by a simple JWL++ reactive burn model for the granular NH4 NO3 explosive which has been fitted to other detonics experiments on this material.

ELECTROCHEMICAL DEGRADATION OF POLYCHLOROBIPHENYLS

EPA Science Inventory

Granular graphite is an ideal conductive material for electrochemical reduction technology applications in the field. Granular graphite was used to enhance the transfer of chlorinated aliphatic compounds in saturated, low permeability soils by electroosmosis. It was also used to ...

The automated design of materials far from equilibrium

NASA Astrophysics Data System (ADS)

Miskin, Marc Z.

Automated design is emerging as a powerful concept in materials science. By combining computer algorithms, simulations, and experimental data, new techniques are being developed that start with high level functional requirements and identify the ideal materials that achieve them. This represents a radically different picture of how materials become functional in which technological demand drives material discovery, rather than the other way around. At the frontiers of this field, materials systems previously considered too complicated can start to be controlled and understood. Particularly promising are materials far from equilibrium. Material robustness, high strength, self-healing and memory are properties displayed by several materials systems that are intrinsically out of equilibrium. These and other properties could be revolutionary, provided they can first be controlled. This thesis conceptualizes and implements a framework for designing materials that are far from equilibrium. We show how, even in the absence of a complete physical theory, design from the top down is possible and lends itself to producing physical insight. As a prototype system, we work with granular materials: collections of athermal, macroscopic identical objects, since these materials function both as an essential component of industrial processes as well as a model system for many non-equilibrium states of matter. We show that by placing granular materials in the context of design, benefits emerge simultaneously for fundamental and applied interests. As first steps, we use our framework to design granular aggregates with extreme properties like high stiffness, and softness. We demonstrate control over nonlinear effects by producing exotic aggregates that stiffen under compression. Expanding on our framework, we conceptualize new ways of thinking about material design when automatic discovery is possible. We show how to build rules that link particle shapes to arbitrary granular packing density. We examine how the results of a design process are contingent upon operating conditions by studying which shapes dissipate energy fastest in a granular gas. We even move to create optimization algorithms for the expressed purpose of material design, by integrating them with statistical mechanics. In all of these cases, we show that turning to machines puts a fresh perspective on materials far from equilibrium. By matching forms to functions, complexities become possibilities, motifs emerge that describe new physics, and the door opens to rational design.

Spatiotemporally Resolved Acoustics in a Photoelastic Granular Material

NASA Astrophysics Data System (ADS)

Owens, Eli; Daniels, Karen

2010-03-01

In granular materials, stress transmission is manifested as force chains that propagate through the material in a branching structure. We send acoustic pulses into a two dimensional photoelastic granular material in which force chains are visible and investigate how the force chains influence the amplitude, speed, and dispersion of the sound waves. We observe particle scale dynamics using two methods, movies which provide spatiotemporally resolved measurements and accelerometers within individual grains. The movies allow us to visualize the sound's path through the material, revealing that the sound travels primarily along the force chains. Using the brightness of the photoelastic particles as a measure of the force chain strength, we observe that the sound travels both faster and at higher amplitude along the strong force chains. An exception to this trend is seen in transient force chains that only exist while the sound is closing particle contacts. We also measure the frequency dependence of the amplitude, speed, and dispersion of the sound wave.

40 CFR 278.4 - Certification and recordkeeping requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 28 2013-07-01 2013-07-01 false Certification and recordkeeping requirements. 278.4 Section 278.4 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) CRITERIA FOR THE MANAGEMENT OF GRANULAR MINE TAILINGS (CHAT) IN ASPHALT CONCRETE AND...

40 CFR 278.4 - Certification and recordkeeping requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 27 2011-07-01 2011-07-01 false Certification and recordkeeping requirements. 278.4 Section 278.4 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) CRITERIA FOR THE MANAGEMENT OF GRANULAR MINE TAILINGS (CHAT) IN ASPHALT CONCRETE AND...

40 CFR 278.4 - Certification and recordkeeping requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 28 2012-07-01 2012-07-01 false Certification and recordkeeping requirements. 278.4 Section 278.4 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) CRITERIA FOR THE MANAGEMENT OF GRANULAR MINE TAILINGS (CHAT) IN ASPHALT CONCRETE AND...

40 CFR 278.4 - Certification and recordkeeping requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 27 2014-07-01 2014-07-01 false Certification and recordkeeping requirements. 278.4 Section 278.4 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) CRITERIA FOR THE MANAGEMENT OF GRANULAR MINE TAILINGS (CHAT) IN ASPHALT CONCRETE AND...

ANAEROBIC/AEROBIC BIODEGRADATION OF PENTACHLOROPHENOL USING GAC FLUIDIXED BED REACTORS: OPTIMIZATION OF THE EMPTY BED CONTACT TIME

EPA Science Inventory

An integrated reactor system has been developed to remediate pentachlorophenol (PCP) containing wastes using sequential anaerobic and aerobic biodegradation. Anaerobically, PCP was degraded to approximately equimolar concentrations (>99%) of chlorophenol (CP) in a granular activa...

Fixed-bed adsorption of reactive azo dye onto granular activated carbon prepared from waste.

PubMed

Ahmad, A A; Hameed, B H

2010-03-15

In this work, the adsorption potential of bamboo waste based granular activated carbon (BGAC) to remove C.I. Reactive Black (RB5) from aqueous solution was investigated using fixed-bed adsorption column. The effects of inlet RB5 concentration (50-200mg/L), feed flow rate (10-30 mL/min) and activated carbon bed height (40-80 mm) on the breakthrough characteristics of the adsorption system were determined. The highest bed capacity of 39.02 mg/g was obtained using 100mg/L inlet dye concentration, 80 mm bed height and 10 mL/min flow rate. The adsorption data were fitted to three well-established fixed-bed adsorption models namely, Adam's-Bohart, Thomas and Yoon-Nelson models. The results fitted well to the Thomas and Yoon-Nelson models with coefficients of correlation R(2)>or=0.93 at different conditions. The BGAC was shown to be suitable adsorbent for adsorption of RB5 using fixed-bed adsorption column. (c) 2009 Elsevier B.V. All rights reserved.

Accretion Dynamics on Wet Granular Materials

NASA Astrophysics Data System (ADS)

Saingier, Guillaume; Sauret, Alban; Jop, Pierre

2017-05-01

Wet granular aggregates are common precursors of construction materials, food, and health care products. The physical mechanisms involved in the mixing of dry grains with a wet substrate are not well understood and difficult to control. Here, we study experimentally the accretion of dry grains on a wet granular substrate by measuring the growth dynamics of the wet aggregate. We show that this aggregate is fully saturated and its cohesion is ensured by the capillary depression at the air-liquid interface. The growth dynamics is controlled by the liquid fraction at the surface of the aggregate and exhibits two regimes. In the viscous regime, the growth dynamics is limited by the capillary-driven flow of liquid through the granular packing to the surface of the aggregate. In the capture regime, the capture probability depends on the availability of the liquid at the saturated interface, which is controlled by the hydrostatic depression in the material. We propose a model that rationalizes our observations and captures both dynamics based on the evolution of the capture probability with the hydrostatic depression.

General scaling relations for locomotion in granular media

NASA Astrophysics Data System (ADS)

Slonaker, James; Motley, D. Carrington; Zhang, Qiong; Townsend, Stephen; Senatore, Carmine; Iagnemma, Karl; Kamrin, Ken

2017-05-01

Inspired by dynamic similarity in fluid systems, we have derived a general dimensionless form for locomotion in granular materials, which is validated in experiments and discrete element method (DEM) simulations. The form instructs how to scale size, mass, and driving parameters in order to relate dynamic behaviors of different locomotors in the same granular media. The scaling can be derived by assuming intrusion forces arise from resistive force theory or equivalently by assuming the granular material behaves as a continuum obeying a frictional yield criterion. The scalings are experimentally confirmed using pairs of wheels of various shapes and sizes under many driving conditions in a common sand bed. We discuss why the two models provide such a robust set of scaling laws even though they neglect a number of the complexities of granular rheology. Motivated by potential extraplanetary applications, the dimensionless form also implies a way to predict wheel performance in one ambient gravity based on tests in a different ambient gravity. We confirm this using DEM simulations, which show that scaling relations are satisfied over an array of driving modes even when gravity differs between scaled tests.

Nonlinear coherent structures in granular crystals

NASA Astrophysics Data System (ADS)

Chong, C.; Porter, Mason A.; Kevrekidis, P. G.; Daraio, C.

2017-10-01

The study of granular crystals, which are nonlinear metamaterials that consist of closely packed arrays of particles that interact elastically, is a vibrant area of research that combines ideas from disciplines such as materials science, nonlinear dynamics, and condensed-matter physics. Granular crystals exploit geometrical nonlinearities in their constitutive microstructure to produce properties (such as tunability and energy localization) that are not conventional to engineering materials and linear devices. In this topical review, we focus on recent experimental, computational, and theoretical results on nonlinear coherent structures in granular crystals. Such structures—which include traveling solitary waves, dispersive shock waves, and discrete breathers—have fascinating dynamics, including a diversity of both transient features and robust, long-lived patterns that emerge from broad classes of initial data. In our review, we primarily discuss phenomena in one-dimensional crystals, as most research to date has focused on such scenarios, but we also present some extensions to two-dimensional settings. Throughout the review, we highlight open problems and discuss a variety of potential engineering applications that arise from the rich dynamic response of granular crystals.

PRODUCTION OF SHEET FROM PARTICULATE MATERIAL

DOEpatents

Blainey, A.

1959-05-12

A process is presented for forming coherent sheet material from particulate material such as granular or powdered metal, granular or powdered oxide, slurries, pastes, and plastic mixes which cohere under pressure. The primary object is to avoid the use of expensive and/ or short lived pressing tools, that is, dies and specially profiled rolls, and so to reduce the cost of the product and to prcvide in a simple manner for the making of the product in a variety of shapes or sizes. The sheet material is formed when the particulate material is laterally confined in a boundary material deformable in all lateral directions under axial pressure and then axially compressing the layer of particulate material together with the boundary material.

A dilation-driven vortex flow in sheared granular materials explains a rheometric anomaly.

PubMed

Krishnaraj, K P; Nott, Prabhu R

2016-02-11

Granular flows occur widely in nature and industry, yet a continuum description that captures their important features is yet not at hand. Recent experiments on granular materials sheared in a cylindrical Couette device revealed a puzzling anomaly, wherein all components of the stress rise nearly exponentially with depth. Here we show, using particle dynamics simulations and imaging experiments, that the stress anomaly arises from a remarkable vortex flow. For the entire range of fill heights explored, we observe a single toroidal vortex that spans the entire Couette cell and whose sense is opposite to the uppermost Taylor vortex in a fluid. We show that the vortex is driven by a combination of shear-induced dilation, a phenomenon that has no analogue in fluids, and gravity flow. Dilatancy is an important feature of granular mechanics, but not adequately incorporated in existing models.

Analog and numerical experiments investigating force chain influences on bed conditions in granular flows

NASA Astrophysics Data System (ADS)

Estep, J.; Dufek, J.

2013-12-01

Granular flows are fundamental processes in several terrestrial and planetary natural events; including surficial flows on volcanic edifices, debris flows, landslides, dune formation, rock falls, sector collapses, and avalanches. Often granular flows can be two-phase, whereby interstitial fluids occupy void space within the particulates. The mobility of granular flows has received significant attention, however the physics that govern their internal behavior remain poorly understood. Here we extend upon previous research showing that force chains can transmit extreme localized forces to the substrates of free surface granular flows, and we combine experimental and computational approaches to further investigate the forces at the bed of simplified granular flows. Analog experiments resolve discrete bed forces via a photoelastic technique, while numerical experiments validate laboratory tests using discrete element model (DEM) simulations. The current work investigates (1) the role of distributed grain sizes on force transmission via force chains, and (2) how the inclusion of interstitial fluids effects force chain development. We also include 3D numerical simulations to apply observed 2D characteristics into real world perspective, and ascertain if the added dimension alters force chain behavior. Previous research showed that bed forces generated by force chain structures can transiently greatly exceed (by several 100%) the bed forces predicted from continuum approaches, and that natural materials are more prone to excessive bed forces than photoelastic materials due to their larger contact stiffnesses. This work suggests that force chain activity may play an important role in the bed physics of dense granular flows by influencing substrate entrainment. Photoelastic experiment image showing force chains in gravity driven granular flow.

Multiscale Phenomena in the Solid-Liquid Transition State of a Granular Material: Analysis, Modeling and Experimentation

DTIC Science & Technology

2010-11-21

The number of undergraduates funded by your agreement who graduated during this period and will receive scholarships or fellowships for further... geology and engineering – to understand and predict the multiscale behaviour of granular materials. Several pioneering achievements have led to...breakage. Purpose of the Research We have recently established, in close collaboration with experimentalists (from geology , physics

Waste Handling and Emplacement Options for Disposal of Radioactive Waste in Deep Boreholes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cochran, John R.; Hardin, Ernest

2015-11-01

Traditional methods cannot be used to handle and emplace radioactive wastes in boreholes up to 16,400 feet (5 km) deep for disposal. This paper describes three systems that can be used for handling and emplacing waste packages in deep borehole: (1) a 2011 reference design that is based on a previous study by Woodward–Clyde in 1983 in which waste packages are assembled into “strings” and lowered using drill pipe; (2) an updated version of the 2011 reference design; and (3) a new concept in which individual waste packages would be lowered to depth using a wireline. Emplacement on coiled tubingmore » was also considered, but not developed in detail. The systems described here are currently designed for U.S. Department of Energy-owned high-level waste (HLW) including the Cesium- 137/Strontium-90 capsules from the Hanford Facility and bulk granular HLW from fuel processing in Idaho.« less

Shear dispersion in dense granular flows

DOE PAGES

Christov, Ivan C.; Stone, Howard A.

2014-04-18

We formulate and solve a model problem of dispersion of dense granular materials in rapid shear flow down an incline. The effective dispersivity of the depth-averaged concentration of the dispersing powder is shown to vary as the Péclet number squared, as in classical Taylor–Aris dispersion of molecular solutes. An extension to generic shear profiles is presented, and possible applications to industrial and geological granular flows are noted.

Note: "Lock-in accelerometry" to follow sink dynamics in shaken granular matter.

PubMed

Sánchez-Colina, G; Alonso-Llanes, L; Martínez, E; Batista-Leyva, A J; Clement, C; Fliedner, C; Toussaint, R; Altshuler, E

2014-12-01

Understanding the penetration dynamics of intruders in granular beds is relevant not only for fundamental physics, but also for geophysical processes and construction on sediments or granular soils in areas potentially affected by earthquakes. While the penetration of intruders in two dimensional (2D) laboratory granular beds can be followed using video recording, this is useless in three dimensional (3D) beds of non-transparent materials such as common sand. Here, we propose a method to quantify the sink dynamics of an intruder into laterally shaken granular beds based on the temporal correlations between the signals from a reference accelerometer fixed to the shaken granular bed, and a probe accelerometer deployed inside the intruder. Due to its analogy with the working principle of a lock-in amplifier, we call this technique lock-in accelerometry.

Challenges in Predicting Planetary Granular Mechanics

NASA Technical Reports Server (NTRS)

Metzger, Philip T.

2005-01-01

Through the course of human history, our needs in agriculture, habitat construction, and resource extraction have driven us to gain more experience working with the granular materials of planet Earth than with any other type of substance in nature, with the possible exception being water. Furthermore, throughout the past two centuries we have seen a dramatic and ever growing interest among scientists and engineers to understand and predict both its static and rheological properties. Ironically, however, despite this wealth of experience we still do not have a fundamental understanding of the complex physical phenomena that emerge even as just ordinary sand is shaken, squeezed or poured. As humanity is now reaching outward through the solar system, not only robotic ally but also with our immediate human presence, the need to understand and predict granular mechanics has taken on a new dimension. We must learn to farm, build and mine the regoliths of other planets where the environmental conditions are different than on Earth, and we are rapidly discovering that the effects of these environmental conditions are not trivial. Some of the relevant environmental features include the regolith formation processes throughout a planet's geologic and hydrologic history, the unknown mixtures of volatiles residing within the soil, the relative strength of gravitation, d the atm9spheric pressure and its seasonal variations. The need to work with soils outside our terrestrial experience base provides us with both a challenge and an opportunity. The challenge is to learn how to extrapolate our experience into these new planetary conditions, enabling the engineering decisions that are needed right now as we take the next few steps in solar system exploration. The opportunity is to use these new planetary environments as laboratories that will help us to see granular mechanics in new ways, to challenge our assumptions, and to help us finally unravel the elusive physics that lie behind complex granular phenomena. Toward these goals, a workshop was held recently at NASA's John F. Kennedy Space Center, attracting over a hundred scientists and engineers from around the world and from a broad crosssection of scientific and engineering disciplines. This talk will provide an out-briefing from that workshop, communicating some of its early findings in regard to lunar and Martian exploration: (1) the requirements for working with granular materials, (2) the challenges that granular materials will pose, (3) the environmental conditions that affect granular mechanics, (4) instruments and measurements that are needed on the Moon and Mars to support granular material research, and (5) some of the possible research avenues that should be pursued.

Production of granular activated carbon from waste walnut shell and its adsorption characteristics for Cu(2+) ion.

PubMed

Kim, J W; Sohn, M H; Kim, D S; Sohn, S M; Kwon, Y S

2001-08-17

Production of granular activated carbon by chemical activation has been attempted employing walnut shells as the raw material. The thermal characteristics of walnut shell were investigated by TG/DTA and the adsorption capacity of the produced activated carbon was evaluated using the titration method. As the activation temperature increased, the iodine value increased. However, a temperature higher than 400 degrees C resulted in a thermal degradation, which was substantiated by scanning electron microscopy (SEM) analysis, and the adsorption capacity decreased. Activation longer than 1h at 375 degrees C resulted in the destruction of the microporous structure of activated carbon. The iodine value increased with the increase in the concentration of ZnCl2 solution. However, excessive ZnCl2 in the solution decreased the iodine value. The extent of activation by ZnCl2 was compared with that by CaCl2 activation. Enhanced activation was achieved when walnut shell was activated by ZnCl2. Applicability of the activated carbon as adsorbent was examined for synthetic copper wastewater. Adsorption of copper ion followed the Freundlich model. Thermodynamic aspects of adsorption have been discussed based on experimental results. The adsorption capacity of the produced activated carbon met the conditions for commercialization and was found to be superior to that made from coconut shell.

Effect of mechanical cleaning with granular material on the permeability of submerged membranes in the MBR process.

PubMed

Siembida, B; Cornel, P; Krause, S; Zimmermann, B

2010-07-01

The research on fouling reduction and permeability loss in membrane bioreactors (MBRs) was carried out at two MBR pilot plants with synthetic and real wastewater. On the one hand, the effect of mechanical cleaning with an abrasive granular material on the performance of a submerged MBR process was tested. Additionally, scanning electron microscopy (SEM) measurements and integrity tests were conducted to check whether the membrane material was damaged by the granulate.The results indicate that the fouling layer formation was significantly reduced by abrasion using the granular material. This technique allowed a long-term operation of more than 600 days at a flux up to 40 L/(m2 h) without chemical cleaning of the membranes. Moreover, it was demonstrated that the membrane bioreactor (MBR) with granulate could be operated with more than 20% higher flux compared to a conventional MBR operation. SEM images and integrity tests showed that in consequence of abrasive cleaning, the granular material left brush marks on the membrane surface, however, the membrane function was not affected.In a parallel experimental set up, the impact of the operationally defined "truly soluble fraction" <0.04 microm from wastewater and activated sludge on the ultrafiltration membrane fouling characteristics was investigated. It was shown that the permeability loss was caused predominantly by the colloidal fraction >0.04 microm rather than by the dissolved fraction of wastewater and activated sludge.

Fabric and connectivity as field descriptors for deformations in granular media

NASA Astrophysics Data System (ADS)

Wan, Richard; Pouragha, Mehdi

2015-01-01

Granular materials involve microphysics across the various scales giving rise to distinct behaviours of geomaterials, such as steady states, plastic limit states, non-associativity of plastic and yield flow, as well as instability of homogeneous deformations through strain localization. Incorporating such micro-scale characteristics is one of the biggest challenges in the constitutive modelling of granular materials, especially when micro-variables may be interdependent. With this motivation, we use two micro-variables such as coordination number and fabric anisotropy computed from tessellation of the granular material to describe its state at the macroscopic level. In order to capture functional dependencies between micro-variables, the correlation between coordination number and fabric anisotropy limits is herein formulated at the particle level rather than on an average sense. This is the essence of the proposed work which investigates the evolutions of coordination number distribution (connectivity) and anisotropy (contact normal) distribution curves with deformation history and their inter-dependencies through discrete element modelling in two dimensions. These results enter as probability distribution functions into homogenization expressions during upscaling to a continuum constitutive model using tessellation as an abstract representation of the granular system. The end product is a micro-mechanically inspired continuum model with both coordination number and fabric anisotropy as underlying micro-variables incorporated into a plasticity flow rule. The derived plastic potential bears striking resemblance to cam-clay or stress-dilatancy-type yield surfaces used in soil mechanics.

Preliminary Results of a Microgravity Investigation to Measure Net Charge on Granular Materials

NASA Technical Reports Server (NTRS)

Green, Robert D.; Myers, Jerry G.; Hansen, Bonnie L.

2003-01-01

Accurate characterization of the electrostatic charge on granular materials has typically been limited to materials with diameters on the order of 10 microns and below due to high settling velocities of larger particles. High settling velocities limit both the time and the acceptable uncertainty with which a measurement can be made. A prototype device has been developed at NASA Glenn Research Center (GRC) to measure coulombic charge on individual particles of granular materials that are 50 to 500 microns in diameter. This device, a novel extension of Millikan's classic oil drop experiment, utilizes the NASA GRC 2.2 second drop tower to extend the range of electrostatic charge measurements to accommodate moderate size granular materials. A dielectric material with a nominal grain diameter between 1.06 and 250 microns was tribocharged using a dry gas jet, suspended in a 5x10x10 cm enclosure during a 2.2 second period of microgravity and exposed to a known electric field. The response was recorded on video and post processed to allow tracking of individual particles. By determining the particle trajectory and velocity, estimates of the coulombic charge were made. Over 30 drops were performed using this technique and the analysis showed that first order approximations of coulombic charge could successfully be obtained, with the mean charge of 3.4E-14 coulombs measured for F-75 Ottawa quartz sand. Additionally, the measured charge showed a near-Gaussian distribution, with a standard deviation of 2.14E -14 coulombs.

Computer-aided analysis for the Mechanics of Granular Materials (MGM) experiment

NASA Technical Reports Server (NTRS)

Parker, Joey K.

1986-01-01

The Mechanics of Granular Materials (MGM) program is planned to provide experimental determinations of the mechanics of granular materials under very low gravity conditions. The initial experiments will use small glass beads as the granular material, and a precise tracking of individual beads during the test is desired. Real-time video images of the experimental specimen were taken with a television camera, and subsequently digitized by a frame grabber installed in a microcomputer. Easily identified red tracer beads were randomly scattered throughout the test specimen. A set of Pascal programs was written for processing and analyzing the digitized images. Filtering the image with Laplacian, dilation, and blurring filters when using a threshold function produced a binary (black on white) image which clearly identified the red beads. The centroids and areas for each bead were then determined. Analyzing a series of the images determined individual red bead displacements throughout the experiment. The system can provide displacement accuracies on the order of 0.5 to 1 pixel is the image is taken directly from the video camera. Digitizing an image from a video cassette recorder introduces an additional repeatability error of 0.5 to 1 pixel. Other programs were written to provide hardcopy prints of the digitized images on a dot-matrix printer.

Dye and its removal from aqueous solution by adsorption: a review.

PubMed

Yagub, Mustafa T; Sen, Tushar Kanti; Afroze, Sharmeen; Ang, H M

2014-07-01

In this review article the authors presented up to-date development on the application of adsorption in the removal of dyes from aqueous solution. This review article provides extensive literature information about dyes, its classification and toxicity, various treatment methods, and dye adsorption characteristics by various adsorbents. One of the objectives of this review article is to organise the scattered available information on various aspects on a wide range of potentially effective adsorbents in the removal of dyes. Therefore, an extensive list of various adsorbents such as natural materials, waste materials from industry, agricultural by-products, and biomass based activated carbon in the removal of various dyes has been compiled here. Dye bearing waste treatment by adsorption using low cost alternative adsorbent is a demanding area as it has double benefits i.e. water treatment and waste management. Further, activated carbon from biomass has the advantage of offering an effected low cost replacement for non-renewable coal based granular activated carbon provided that they have similar or better adsorption on efficiency. The effectiveness of various adsorbents under different physico-chemical process parameters and their comparative adsorption capacity towards dye adsorption has also been presented. This review paper also includes the affective adsorption factors of dye such as solution pH, initial dye concentration, adsorbent dosage, and temperature. The applicability of various adsorption kinetic models and isotherm models for dye removal by wide range of adsorbents is also reported here. Conclusions have been drawn from the literature reviewed and few suggestions for future research are proposed. Copyright © 2014 Elsevier B.V. All rights reserved.

Granular impact cratering by liquid drops: Understanding raindrop imprints through an analogy to asteroid strikes

PubMed Central

Zhao, Runchen; Zhang, Qianyun; Tjugito, Hendro; Cheng, Xiang

2015-01-01

When a granular material is impacted by a sphere, its surface deforms like a liquid yet it preserves a circular crater like a solid. Although the mechanism of granular impact cratering by solid spheres is well explored, our knowledge on granular impact cratering by liquid drops is still very limited. Here, by combining high-speed photography with high-precision laser profilometry, we investigate liquid-drop impact dynamics on granular surface and monitor the morphology of resulting impact craters. Surprisingly, we find that despite the enormous energy and length difference, granular impact cratering by liquid drops follows the same energy scaling and reproduces the same crater morphology as that of asteroid impact craters. Inspired by this similarity, we integrate the physical insight from planetary sciences, the liquid marble model from fluid mechanics, and the concept of jamming transition from granular physics into a simple theoretical framework that quantitatively describes all of the main features of liquid-drop imprints in granular media. Our study sheds light on the mechanisms governing raindrop impacts on granular surfaces and reveals a remarkable analogy between familiar phenomena of raining and catastrophic asteroid strikes. PMID:25548187

Dynamic Deformation and Collapse of Granular Columns

NASA Astrophysics Data System (ADS)

Uenishi, K.; Tsuji, K.; Doi, S.

2009-12-01

Large dynamic deformation of granular materials may be found in nature not only in the failure of slopes and cliffs — due to earthquakes, rock avalanches, debris flows and landslides — but also in earthquake faulting itself. Granular surface flows often consist of solid grains and intergranular fluid, but the effect of the fluid may be usually negligible because the volumetric concentration of grains is in many cases high enough for interparticle forces to dominate momentum transport. Therefore, the investigation of dry granular flow of a mass might assist in further understanding of the above mentioned geophysical events. Here, utilizing a high-speed digital video camera system, we perform a simple yet fully-controlled series of laboratory experiments related to the collapse of granular columns. We record, at an interval of some microseconds, the dynamic transient granular mass flow initiated by abrupt release of a tube that contains dry granular materials. The acrylic tube is partially filled with glass beads and has a cross-section of either a fully- or semi-cylindrical shape. Upon sudden removal of the tube, the granular solid may fragment under the action of its own weight and the particles spread on a rigid horizontal plane. This study is essentially the extension of the previous ones by Lajeunesse et al. (Phys. Fluids 2004) and Uenishi and Tsuji (JPGU 2008), but the striped layers of particles in a semi-cylindrical tube, newly introduced in this contribution, allow us to observe the precise particle movement inside the granular column: The development of slip lines inside the column and the movement of particles against each other can be clearly identified. The major controlling parameters of the spreading dynamics are the initial aspect ratio of the granular (semi-)cylindrical column, the frictional properties of the horizontal plane (substrate) and the size of beads. We show the influence of each parameter on the average flow velocity and final radius and height of the deposit, i.e., the fraction of granular mass mobilized by the flow, and the final shape of the deposit.

USE OF CARBON STABLE ISOTOPE FOR THE DECHLORINATION OF TRICHLOROETHYLENE ON GRANULAR-GRAPHITE PACKED ELECTRODES (PRESENTATION)

EPA Science Inventory

Trichloroethylene (TCE) is widely used as a solvent in metal processing and electronic manufacturing industries, but waste and spilled TCE often results in blocks of non-aqueous liquid in vadose and saturated zones which become continuous contamination sources for groundwater. El...

Stick-slip instabilities in sheared granular flow: The role of friction and acoustic vibrations.

PubMed

Lieou, Charles K C; Elbanna, Ahmed E; Langer, J S; Carlson, J M

2015-08-01

We propose a theory of shear flow in dense granular materials. A key ingredient of the theory is an effective temperature that determines how the material responds to external driving forces such as shear stresses and vibrations. We show that, within our model, friction between grains produces stick-slip behavior at intermediate shear rates, even if the material is rate strengthening at larger rates. In addition, externally generated acoustic vibrations alter the stick-slip amplitude, or suppress stick-slip altogether, depending on the pressure and shear rate. We construct a phase diagram that indicates the parameter regimes for which stick-slip occurs in the presence and absence of acoustic vibrations of a fixed amplitude and frequency. These results connect the microscopic physics to macroscopic dynamics and thus produce useful information about a variety of granular phenomena, including rupture and slip along earthquake faults, the remote triggering of instabilities, and the control of friction in material processing.

Slow dynamics and strength recovery in unconsolidated granular earth materials: a mechanistic theory

DOE PAGES

Lieou, Charles Ka Cheong; Daub, Eric G.; Ecke, Robert E.; ...

2017-09-08

Rock materials often display long-time relaxation, commonly termed aging or “slow dynamics”, after the cessation of acoustic perturbations. In this paper, we focus on unconsolidated rock materials and propose to explain such nonlinear relaxation through the Shear-Transformation-Zone (STZ) theory of granular media, adapted for small stresses and strains. The theory attributes the observed relaxation to the slow, irreversible change of positions of constituent grains, and posits that the aging process can be described in three stages: fast recovery before some characteristic time associated with the subset of local plastic events or grain rearrangements with a short time scale, log-linear recoverymore » of the elastic modulus at intermediate times, and gradual turnover to equilibrium steady-state behavior at long times. Here we demonstrate good agreement with experiments on aging in granular materials such as simulated fault gouge after an external disturbance. These results may provide insights into observed modulus recovery after strong shaking in the near surface region of earthquake zones.« less

Slow Dynamics and Strength Recovery in Unconsolidated Granular Earth Materials: A Mechanistic Theory

NASA Astrophysics Data System (ADS)

Lieou, Charles K. C.; Daub, Eric G.; Ecke, Robert E.; Johnson, Paul A.

2017-10-01

Rock materials often display long-time relaxation, commonly termed aging or "slow dynamics," after the cessation of acoustic perturbations. In this paper, we focus on unconsolidated rock materials and propose to explain such nonlinear relaxation through the shear-transformation-zone theory of granular media, adapted for small stresses and strains. The theory attributes the observed relaxation to the slow, irreversible change of positions of constituent grains and posits that the aging process can be described in three stages: fast recovery before some characteristic time associated with the subset of local plastic events or grain rearrangements with a short time scale, log linear recovery of the elastic modulus at intermediate times, and gradual turnover to equilibrium steady state behavior at long times. We demonstrate good agreement with experiments on aging in granular materials such as simulated fault gouge after an external disturbance. These results may provide insights into observed modulus recovery after strong shaking in the near surface region of earthquake zones.

A new experimental material for modeling relief dynamics and interactions between tectonics and surface processes

NASA Astrophysics Data System (ADS)

Graveleau, F.; Hurtrez, J.-E.; Dominguez, S.; Malavieille, J.

2011-12-01

We developed a new granular material (MatIV) to study experimentally landscape evolution in active mountain belt piedmonts. Its composition and related physical properties have been determined using empirical criteria derived from the scaling of deformation, erosion-transport and sedimentation natural processes. MatIV is a water-saturated composite material made up with 4 granular components (silica powder, glass microbeads, plastic powder and graphite) whose physical, mechanical and erosion-related properties were measured with different laboratory tests. Mechanical measurements were made on a modified Hubbert-type direct shear apparatus. Erosion-related properties were determined using an experimental set-up that allows quantifying the erosion/sedimentation budget from tilted relaxation topographies. For MatIV, we also investigated the evolution of mean erosion rates and stream power erosion law exponents in 1D as a function of slope. Our results indicate that MatIV satisfies most of the defined criteria. It deforms brittlely according to the linear Mohr-Coulomb failure criterion and localizes deformation along discrete faults. Its erosion pattern is characterized by realistic hillslope and channelized processes (slope diffusion, mass wasting, channel incision). During transport, eroded particles are sorted depending on their density and shape, which results in stratified alluvial deposits displaying lateral facies variations. To evaluate the degree of similitude between model and nature, we used a new experimental device that combines accretionary wedge deformation mechanisms and surface runoff erosion processes. Results indicate that MatIV succeeded in producing detailed morphological and sedimentological features (drainage basin, channel network, terrace, syntectonic alluvial fan). Geometric, kinematic and dynamic similarity criteria have been investigated to compare precisely model to nature. Although scaling is incomplete, it yields particularly informative orders of magnitude. With all these characteristics, MatIV appears as a very promising material to investigate experimentally a wide range of scientific questions dealing with relief dynamics and interactions between tectonics, erosion and sedimentation processes.

An Analytical Model of Tribocharging in Regolith

NASA Astrophysics Data System (ADS)

Carter, D. P.; Hartzell, C. M.

2015-12-01

Nongravitational forces, including electrostatic forces and cohesion, can drive the behavior of regolith in low gravity environments such as the Moon and asteroids. Regolith is the 'skin' of solid planetary bodies: it is the outer coating that is observed by orbiters and the first material contacted by landers. Triboelectric charging, the phenomenon by which electrical charge accumulates during the collision or rubbing of two surfaces, has been found to occur in initially electrically neutral granular mixtures. Although charge transfer is often attributed to chemical differences between the different materials, charge separation has also been found to occur in mixtures containing grains of a single material, but with a variety of grain sizes. In such cases, the charge always separates according to grain size; typically the smaller grains acquire a more negative charge than the larger grains. Triboelectric charging may occur in a variety of planetary phenomena (including mass wasting and dust storms) as well as during spacecraft-surface interactions (including sample collection and wheel motion). Interactions between charged grains or with the solar wind plasma could produce regolith motion. However, a validated, predictive model of triboelectric charging between dielectric grains has not yet been developed. A model for such size-dependent charge separation will be presented, demonstrating how random collisions between initially electrically neutral grains lead to net migration of electrons toward the smaller grains. The model is applicable to a wide range of single-material granular mixtures, including those with unusual or wildly varying size distributions, and suggests a possible mechanism for the reversal of the usual size-dependent charge polarity described above. This is a significant improvement over existing charge exchange models, which are restricted to two discrete grains sizes and provide severely limited estimates for charge magnitude. We will also discuss the design of an experiment planned to test the charging estimates provided by the model presented and the potential implications for our understanding of regolith behavior.

Heavy metal removal mechanisms of sorptive filter materials for road runoff treatment and remobilization under de-icing salt applications.

PubMed

Huber, Maximilian; Hilbig, Harald; Badenberg, Sophia C; Fassnacht, Julius; Drewes, Jörg E; Helmreich, Brigitte

2016-10-01

The objective of this research study was to elucidate the removal and remobilization behaviors of five heavy metals (i.e., Cd, Cu, Ni, Pb, and Zn) that had been fixed onto sorptive filter materials used in decentralized stormwater treatment systems receiving traffic area runoff. Six filter materials (i.e., granular activated carbon, a mixture of granular activated alumina and porous concrete, granular activated lignite, half-burnt dolomite, and two granular ferric hydroxides) were evaluated in column experiments. First, a simultaneous preloading with the heavy metals was performed for each filter material. Subsequently, the remobilization effect was tested by three de-icing salt experiments in duplicate using pure NaCl, a mixture of NaCl and CaCl2, and a mixture of NaCl and MgCl2. Three layers of each column were separated to specify the attenuation of heavy metals as a function of depth. Cu and Pb were retained best by most of the selected filter materials, and Cu was often released the least of all metals by the three de-icing salts. The mixture of NaCl and CaCl2 resulted in a stronger effect upon remobilization than the other two de-icing salts. For the material with the highest retention, the effect of the preloading level upon remobilization was measured. The removal mechanisms of all filter materials were determined by advanced laboratory methods. For example, the different intrusions of heavy metals into the particles were determined. Findings of this study can result in improved filter materials used in decentralized stormwater treatment systems. Copyright © 2016 Elsevier Ltd. All rights reserved.

Nonlinear softening of unconsolidated granular earth materials

NASA Astrophysics Data System (ADS)

Lieou, Charles K. C.; Daub, Eric G.; Guyer, Robert A.; Johnson, Paul A.

2017-09-01

Unconsolidated granular earth materials exhibit softening behavior due to external perturbations such as seismic waves, namely, the wave speed and elastic modulus decrease upon increasing the strain amplitude above dynamics strains of about 10-6 under near-surface conditions. In this letter, we describe a theoretical model for such behavior. The model is based on the idea that shear transformation zones—clusters of grains that are loose and susceptible to contact changes, particle displacement, and rearrangement—are responsible for plastic deformation and softening of the material. We apply the theory to experiments on simulated fault gouge composed of glass beads and demonstrate that the theory predicts nonlinear resonance shifts, reduction of the P wave modulus, and attenuation, in agreement with experiments. The theory thus offers insights on the nature of nonlinear elastic properties of a granular medium and potentially into phenomena such as triggering on earthquake faults.

A two-phase micromorphic model for compressible granular materials

NASA Astrophysics Data System (ADS)

Paolucci, Samuel; Li, Weiming; Powers, Joseph

2009-11-01

We introduce a new two-phase continuum model for compressible granular material based on micromorphic theory and treat it as a two-phase mixture with inner structure. By taking an appropriate number of moments of the local micro scale balance equations, the average phase balance equations result from a systematic averaging procedure. In addition to equations for mass, momentum and energy, the balance equations also include evolution equations for microinertia and microspin tensors. The latter equations combine to yield a general form of a compaction equation when the material is assumed to be isotropic. When non-linear and inertial effects are neglected, the generalized compaction equation reduces to that originally proposed by Bear and Nunziato. We use the generalized compaction equation to numerically model a mixture of granular high explosive and interstitial gas. One-dimensional shock tube and piston-driven solutions are presented and compared with experimental results and other known solutions.

Meso-scale framework for modeling granular material using computed tomography

DOE PAGES

Turner, Anne K.; Kim, Felix H.; Penumadu, Dayakar; ...

2016-03-17

Numerical modeling of unconsolidated granular materials is comprised of multiple nonlinear phenomena. Accurately capturing these phenomena, including grain deformation and intergranular forces depends on resolving contact regions several orders of magnitude smaller than the grain size. Here, we investigate a method for capturing the morphology of the individual particles using computed X-ray and neutron tomography, which allows for accurate characterization of the interaction between grains. The ability of these numerical approaches to determine stress concentrations at grain contacts is important in order to capture catastrophic splitting of individual grains, which has been shown to play a key role in themore » plastic behavior of the granular material on the continuum level. Discretization approaches, including mesh refinement and finite element type selection are presented to capture high stress concentrations at contact points between grains. The effect of a grain’s coordination number on the stress concentrations is also investigated.« less

Spreading granular material with a blade

NASA Astrophysics Data System (ADS)

Dressaire, Emilie; Singh, Vachitar; Grimaldi, Emma; Sauret, Alban

2015-11-01

The spreading of a complex fluid with a blade is encountered in applications that range from the bulldozing of granular material in construction projects to the coating of substrates with fluids in industrial applications. This spreading process is also present in everyday life, when we use a knife to turn a lump of peanut butter into a thin layer over our morning toast. In this study, we rely on granular media in a model experiment to describe the three-dimensional spreading of the material. Our experimental set-up allows tracking the spreading of a sandpile on a translating flat surface as the blade remains fixed. We characterize the spreading dynamics and the shape of the spread fluid layer when varying the tilt of the blade, its spacing with the surface and its speed. Our findings suggest that it is possible to tune the spreading parameters to optimize the coating.

Breakage mechanics for granular materials in surface-reactive environments

NASA Astrophysics Data System (ADS)

Zhang, Yida; Buscarnera, Giuseppe

2018-03-01

It is known that the crushing behaviour of granular materials is sensitive to the state of the fluids occupying the pore space. Here, a thermomechanical theory is developed to link such macroscopic observations with the physico-chemical processes operating at the microcracks of individual grains. The theory relies on the hypothesis that subcritical fracture propagation at intra-particle scale is the controlling mechanism for the rate-dependent, water-sensitive compression of granular specimens. First, the fracture of uniaxially compressed particles in surface-reactive environments is studied in light of irreversible thermodynamics. Such analysis recovers the Gibbs adsorption isotherm as a central component linking the reduction of the fracture toughness of a solid to the increase of vapour concentration. The same methodology is then extended to assemblies immersed in wet air, for which solid-fluid interfaces have been treated as a separate phase. It is shown that this choice brings the solid surface energy into the dissipation equations of the granular matrix, thus providing a pathway to (i) integrate the Gibbs isotherm with the continuum description of particle assemblies and (ii) reproduce the reduction of their yield strength in presence of high relative humidity. The rate-effects involved in the propagation of cracks and the evolution of breakage have been recovered by considering non-homogenous dissipation potentials associated with the creation of surface area at both scales. It is shown that the proposed model captures satisfactorily the compression response of different types of granular materials subjected to varying relative humidity. This result was achieved simply by using parameters based on the actual adsorption characteristics of the constituting minerals. The theory therefore provides a physically sound and thermodynamically consistent framework to study the behaviour of granular solids in surface-reactive environments.

Calculation of energy recovery and greenhouse gas emission reduction from palm oil mill effluent treatment by an anaerobic granular-sludge process.

PubMed

Show, K Y; Ng, C A; Faiza, A R; Wong, L P; Wong, L Y

2011-01-01

Conventional aerobic and low-rate anaerobic processes such as pond and open-tank systems have been widely used in wastewater treatment. In order to improve treatment efficacy and to avoid greenhouse gas emissions, conventional treatment can be upgraded to a high performance anaerobic granular-sludge system. The anaerobic granular-sludge systems are designed to capture the biogas produced, rendering a potential for claims of carbon credits under the Kyoto Protocol for reducing emissions of greenhouse gases. Certified Emission Reductions (CERs) would be issued, which can be exchanged between businesses or bought and sold in international markets at the prevailing market prices. As the advanced anaerobic granular systems are capable of handling high organic loadings concomitant with high strength wastewater and short hydraulic retention time, they render more carbon credits than other conventional anaerobic systems. In addition to efficient waste degradation, the carbon credits can be used to generate revenue and to finance the project. This paper presents a scenario on emission avoidance based on a methane recovery and utilization project. An example analysis on emission reduction and an overview of the global emission market are also outlined.

Self-organized magnetic particles to tune the mechanical behavior of a granular system

NASA Astrophysics Data System (ADS)

Cox, Meredith; Wang, Dong; Barés, Jonathan; Behringer, Robert P.

2016-09-01

Above a certain density a granular material jams. This property can be controlled by either tuning a global property, such as the packing fraction or by applying shear strain, or at the micro-scale by tuning grain shape, inter-particle friction or externally controlled organization. Here, we introduce a novel way to change a local granular property by adding a weak anisotropic magnetic interaction between particles. We measure the evolution of the pressure, P, and coordination number, Z, for a packing of 2D photo-elastic disks, subject to uniaxial compression. A fraction R m of the particles have embedded cuboidal magnets. The strength of the magnetic interactions between particles is too weak to have a strong direct effect on P or Z when the system is jammed. However, the magnetic interactions play an important role in the evolution of latent force networks when systems containing a large enough fraction of the particles with magnets are driven through unjammed to jammed states. In this case, a statistically stable network of magnetic chains self-organizes before jamming and overlaps with force chains once jamming occurs, strengthening the granular medium. This property opens a novel way to control mechanical properties of granular materials.

Stationary bubble formation and cavity collapse in wedge-shaped hoppers

PubMed Central

Yagisawa, Yui; Then, Hui Zee; Okumura, Ko

2016-01-01

The hourglass is one of the apparatuses familiar to everyone, but reveals intriguing behaviors peculiar to granular materials, and many issues are remained to be explored. In this study, we examined the dynamics of falling sand in a special form of hourglass, i.e., a wedge-shaped hopper, when a suspended granular layer is stabilized to a certain degree. As a result, we found remarkably different dynamic regimes of bubbling and cavity. In the bubbling regime, bubbles of nearly equal size are created in the sand at a regular time interval. In the cavity regime, a cavity grows as sand beads fall before a sudden collapse of the cavity. Bubbling found here is quite visible to a level never discussed in the physics literature and the cavity regime is a novel phase, which is neither continuous, intermittent nor completely blocked phase. We elucidate the physical conditions necessary for the bubbling and cavity regimes and develop simple theories for the regimes to successfully explain the observed phenomena by considering the stability of a suspended granular layer and clogging of granular flow at the outlet of the hopper. The bubbling and cavity regimes could be useful for mixing a fluid with granular materials. PMID:27138747

Modelling polymeric deformable granular materials - from experimental data to numerical models at the grain scale

NASA Astrophysics Data System (ADS)

Teil, Maxime; Harthong, Barthélémy; Imbault, Didier; Peyroux, Robert

2017-06-01

Polymeric deformable granular materials are widely used in industry and the understanding and the modelling of their shaping process is a point of interest. This kind of materials often presents a viscoelasticplastic behaviour and the present study promotes a joint approach between numerical simulations and experiments in order to derive the behaviour law of such granular material. The experiment is conducted on a polystyrene powder on which a confining pressure of 7MPa and an axial pressure reaching 30MPa are applied. Between different steps of the in-situ test, the sample is scanned in an X-rays microtomograph in order to know the structure of the material depending on the density. From the tomographic images and by using specific algorithms to improve the images quality, grains are automatically identified, separated and a finite element mesh is generated. The long-term objective of this study is to derive a representative sample directly from the experiments in order to run numerical simulations using a viscoelactic or viscoelastic-plastic constitutive law and compare numerical and experimental results at the particle scale.

Granular compaction and the topology of pore deformation

NASA Astrophysics Data System (ADS)

Saadatfar, Mohammad; Takeuchi, Hiroshi; Hanifpour, Maryam; Robins, Vanessa; Francois, Nicolas; Hiraoka, Yasuaki

2017-06-01

The mechanism of crystallisation in highly dissipative materials such as foams or granular materials is still widely unknown. In macroscopic granular materials high levels of energy need to be injected to overcome the natural propensity of these dissipative materials to form amorphous structures [1, 2]. The transition from disordered to ordered packings in such systems triggers a wide range of geometrical, topological and mechanical changes at multi length scales [3]. Formation of cavities and patterns by aggregates of grains and their evolution during this transition requires a complete topological description of the system. Here, crystallisation of three-dimensional packings of frictional spheres is studied at the grain scale with x-ray tomography. Using a novel and powerful topological tool, Persistent Homology, we describe the complete formation process of perfect tetrahedral and octahedral patterns: the two building blocks of FCC and HCP crystalline arrangements. Additionally we present possible and allowable deformations of these components that accurately reproduce the main topological features of the system. These results give new insights into the crystallisation of these highly dissipative materials.

Shear flow of angular grains: acoustic effects and nonmonotonic rate dependence of volume.

PubMed

Lieou, Charles K C; Elbanna, Ahmed E; Langer, J S; Carlson, J M

2014-09-01

Naturally occurring granular materials often consist of angular particles whose shape and frictional characteristics may have important implications on macroscopic flow rheology. In this paper, we provide a theoretical account for the peculiar phenomenon of autoacoustic compaction-nonmonotonic variation of shear band volume with shear rate in angular particles-recently observed in experiments. Our approach is based on the notion that the volume of a granular material is determined by an effective-disorder temperature known as the compactivity. Noise sources in a driven granular material couple its various degrees of freedom and the environment, causing the flow of entropy between them. The grain-scale dynamics is described by the shear-transformation-zone theory of granular flow, which accounts for irreversible plastic deformation in terms of localized flow defects whose density is governed by the state of configurational disorder. To model the effects of grain shape and frictional characteristics, we propose an Ising-like internal variable to account for nearest-neighbor grain interlocking and geometric frustration and interpret the effect of friction as an acoustic noise strength. We show quantitative agreement between experimental measurements and theoretical predictions and propose additional experiments that provide stringent tests on the new theoretical elements.

Visualization of particle interactions in granular media.

PubMed

Meier, Holger A; Schlemmer, Michael; Wagner, Christian; Kerren, Andreas; Hagen, Hans; Kuhl, Ellen; Steinmann, Paul

2008-01-01

Interaction between particles in so-called granular media, such as soil and sand, plays an important role in the context of geomechanical phenomena and numerous industrial applications. A two scale homogenization approach based on a micro and a macro scale level is briefly introduced in this paper. Computation of granular material in such a way gives a deeper insight into the context of discontinuous materials and at the same time reduces the computational costs. However, the description and the understanding of the phenomena in granular materials are not yet satisfactory. A sophisticated problem-specific visualization technique would significantly help to illustrate failure phenomena on the microscopic level. As main contribution, we present a novel 2D approach for the visualization of simulation data, based on the above outlined homogenization technique. Our visualization tool supports visualization on micro scale level as well as on macro scale level. The tool shows both aspects closely arranged in form of multiple coordinated views to give users the possibility to analyze the particle behavior effectively. A novel type of interactive rose diagrams was developed to represent the dynamic contact networks on the micro scale level in a condensed and efficient way.

Low-resistive vibratory penetration in granular media.

PubMed

Darbois Texier, Baptiste; Ibarra, Alejandro; Melo, Francisco

2017-01-01

Non-cohesive materials such as sand, dry snow or cereals are encountered in various common circumstances, from everyday situations to industry. The process of digging into these materials remains a challenge to most animals and machines. Within the animal kingdom, different strategies are employed to overcome this issue, including excavation methods used by ants, the two-anchor strategy employed by soft burrowers such as razor-clams, and undulatory motions exhibited by sandfish lizards. Despite the development of technology to mimic these techniques in diggers and robots, the limitations of animals and machines may differ, and mimicry of natural processes is not necessarily the most efficient technological strategy. This study presents evidence that the resisting force for the penetration of an intruder into a dry granular media can be reduced by one order of magnitude with small amplitude (A ≃ 10 μm) and low frequency (f = 50 - 200 Hz) mechanical vibrations. This observed result is attributed to the local fluidization of the granular bed which induces the rupture of force chains. The drop in resistive force on entering dry granular materials may be relevant in technological development in order to increase the efficiency of diggers and robots.

Granular material flow in two-dimensional hoppers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brennen, C.; Pearce, J.C.

To aid in improving the transport of granular media for industrial purposes, the California Institute of Technology presents a comparison of experimental data with analytical results for the flow of dry granular media (such as coal) through a two-dimensional or wedge-shaped hopper. The analytical solution, which is based on the constitutive postulates (suggested by A.W. Jenike and R.T. Shield) of intergrain Coulomb friction and isotropy, produces results that are in good agreement with the experimental measurements.

In situ grain fracture mechanics during uniaxial compaction of granular solids

NASA Astrophysics Data System (ADS)

Hurley, R. C.; Lind, J.; Pagan, D. C.; Akin, M. C.; Herbold, E. B.

2018-03-01

Grain fracture and crushing are known to influence the macroscopic mechanical behavior of granular materials and be influenced by factors such as grain composition, morphology, and microstructure. In this paper, we investigate grain fracture and crushing by combining synchrotron x-ray computed tomography and three-dimensional x-ray diffraction to study two granular samples undergoing uniaxial compaction. Our measurements provide details of grain kinematics, contacts, average intra-granular stresses, inter-particle forces, and intra-grain crystal and fracture plane orientations. Our analyses elucidate the complex nature of fracture and crushing, showing that: (1) the average stress states of grains prior to fracture vary widely in their relation to global and local trends; (2) fractured grains experience inter-particle forces and stored energies that are statistically higher than intact grains prior to fracture; (3) fracture plane orientations are primarily controlled by average intra-granular stress and contact fabric rather than the orientation of the crystal lattice; (4) the creation of new surfaces during fracture accounts for a very small portion of the energy dissipated during compaction; (5) mixing brittle and ductile grain materials alters the grain-scale fracture response. The results highlight an application of combined x-ray measurements for non-destructive in situ analysis of granular solids and provide details about grain fracture that have important implications for theory and modeling.

The self-propulsion of a helix in granular matter

NASA Astrophysics Data System (ADS)

Valdes, Rogelio; Angeles, Veronica; de La Calleja, Elsa; Zenit, Roberto

2017-11-01

The effect of the shape of helicoidal on the displacement of magnetic robots in granular media is studied experimentally. We quantify the influences of three main parameters of the shape of the helicoidal swimmers: body diameter, step, and the angle. We compare the experimental measurements with an empirically modified resistive force theory prediction that accounts for the static friction coefficient of the particles of the granular material, leading to good agreement. Comparisons are also made with the granular resistive force theory proposed by Goldman and collaborators. We found an optimal helix angle to produce movement and determined a relationship between the swimmer size and speed.

Drag force scaling for penetration into granular media.

PubMed

Katsuragi, Hiroaki; Durian, Douglas J

2013-05-01

Impact dynamics is measured for spherical and cylindrical projectiles of many different densities dropped onto a variety non-cohesive granular media. The results are analyzed in terms of the material-dependent scaling of the inertial and frictional drag contributions to the total stopping force. The inertial drag force scales similar to that in fluids, except that it depends on the internal friction coefficient. The frictional drag force scales as the square-root of the density of granular medium and projectile, and hence cannot be explained by the combination of granular hydrostatic pressure and Coulomb friction law. The combined results provide an explanation for the previously observed penetration depth scaling.

Numerical insight into the micromechanics of jet erosion of a cohesive granular material

NASA Astrophysics Data System (ADS)

Cuéllar, Pablo; Benseghier, Zeyd; Luu, Li-Hua; Bonelli, Stéphane; Delenne, Jean-Yves; Radjaï, Farhang; Philippe, Pierre

2017-06-01

Here we investigate the physical mechanisms behind the surface erosion of a cohesive granular soil induced by an impinging jet by means of numerical simulations coupling fluid and grains at the microscale. The 2D numerical model combines the Discrete Element and Lattice Boltzmann methods (DEM-LBM) and accounts for the granular cohesion with a contact model featuring a paraboloidal yield surface. Here we review first the hydrodynamical conditions imposed by the fluid jet on a solid granular packing, turning then the attention to the impact of cohesion on the erosion kinetics. Finally, the use of an additional subcritical debonding damage model based on the work of Silvani and co-workers provides a novel insight into the internal solicitation of the cohesive granular sample by the impinging jet.

Nitrate removal from high strength nitrate-bearing wastes in granular sludge sequencing batch reactors.

PubMed

Krishna Mohan, Tulasi Venkata; Renu, Kadali; Nancharaiah, Yarlagadda Venkata; Satya Sai, Pedapati Murali; Venugopalan, Vayalam Purath

2016-02-01

A 6-L sequencing batch reactor (SBR) was operated for development of granular sludge capable of denitrification of high strength nitrates. Complete and stable denitrification of up to 5420 mg L(-1) nitrate-N (2710 mg L(-1) nitrate-N in reactor) was achieved by feeding simulated nitrate waste at a C/N ratio of 3. Compact and dense denitrifying granular sludge with relatively stable microbial community was developed during reactor operation. Accumulation of large amounts of nitrite due to incomplete denitrification occurred when the SBR was fed with 5420 mg L(-1) NO3-N at a C/N ratio of 2. Complete denitrification could not be achieved at this C/N ratio, even after one week of reactor operation as the nitrite levels continued to accumulate. In order to improve denitrification performance, the reactor was fed with nitrate concentrations of 1354 mg L(-1), while keeping C/N ratio at 2. Subsequently, nitrate concentration in the feed was increased in a step-wise manner to establish complete denitrification of 5420 mg L(-1) NO3-N at a C/N ratio of 2. The results show that substrate concentration plays an important role in denitrification of high strength nitrate by influencing nitrite accumulation. Complete denitrification of high strength nitrates can be achieved at lower substrate concentrations, by an appropriate acclimatization strategy. Copyright © 2015 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

ULTRASTRUCTURE OF THE NUCLEOLUS DURING THE CHINESE HAMSTER CELL CYCLE

PubMed Central

Noel, J. S.; Dewey, W. C.; Abel, J. H.; Thompson, R. P.

1971-01-01

Changes in the structure of the nucleolus during the cell cycle of the Chinese hamster cell in vitro were studied. Quantitative electron microscopic techniques were used to establish the size and volume changes in nucleolar structures. In mitosis, nucleolar remnants, "persistent nucleoli," consisting predominantly of ribosome-like granular material, and a granular coating on the chromosomes were observed. Persistent nucleoli were also observed in some daughter nuclei as they were leaving telophase and entering G1. During very early G1, a dense, fibrous material characteristic of interphase nucleoli was noted in the nucleoplasm of the cells. As the cells progressed through G1, a granular component appeared which was intimately associated with the fibrous material. By the middle of G1, complete, mature nucleoli were present. The nucleolar volume enlarged by a factor of two from the beginning of G1 to the middle of S primarily due to the accumulation of the granular component. During the G2 period, there was a dissolution or breakdown of the nucleolus prior to the entry of the cells into mitosis. Correlations between the quantitative aspects of this study and biochemical and cytochemical data available in the literature suggest the following: nucleolar reformation following division results from the activation of the nucleolar organizer regions which transcribe for RNA first appearing in association with protein as a fibrous component (45S RNA) and then later as a granular component (28S and 32S RNA). PMID:4933472

Reconsolidated Salt as a Geotechnical Barrier

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansen, Francis D.; Gadbury, Casey

Salt as a geologic medium has several attributes favorable to long-term isolation of waste placed in mined openings. Salt formations are largely impermeable and induced fractures heal as stress returns to equilibrium. Permanent isolation also depends upon the ability to construct geotechnical barriers that achieve nearly the same high-performance characteristics attributed to the native salt formation. Salt repository seal concepts often include elements of reconstituted granular salt. As a specific case in point, the Waste Isolation Pilot Plant recently received regulatory approval to change the disposal panel closure design from an engineered barrier constructed of a salt-based concrete to onemore » that employs simple run-of-mine salt and temporary bulkheads for isolation from ventilation. The Waste Isolation Pilot Plant is a radioactive waste disposal repository for defense-related transuranic elements mined from the Permian evaporite salt beds in southeast New Mexico. Its approved shaft seal design incorporates barrier components comprising salt-based concrete, bentonite, and substantial depths of crushed salt compacted to enhance reconsolidation. This paper will focus on crushed salt behavior when applied as drift closures to isolate disposal rooms during operations. Scientific aspects of salt reconsolidation have been studied extensively. The technical basis for geotechnical barrier performance has been strengthened by recent experimental findings and analogue comparisons. The panel closure change was accompanied by recognition that granular salt will return to a physical state similar to the halite surrounding it. Use of run-of-mine salt ensures physical and chemical compatibility with the repository environment and simplifies ongoing disposal operations. Our current knowledge and expected outcome of research can be assimilated with lessons learned to put forward designs and operational concepts for the next generation of salt repositories. Mined salt repositories have the potential to isolate permanently vast inventories of radioactive and hazardous wastes.« less

Adsorption of Methyl Tertiary Butyl Ether on Granular Zeolites: Batch and Column Studies

PubMed Central

Abu-Lail, Laila; Bergendahl, John A.; Thompson, Robert W.

2010-01-01

Methyl tertiary butyl ether (MTBE) has been shown to be readily removed from water with powdered zeolites, but the passage of water through fixed beds of very small powdered zeolites produces high friction losses not encountered in flow through larger sized granular materials. In this study, equilibrium and kinetic adsorption of MTBE onto granular zeolites, a coconut shell granular activated carbon (CS-1240), and a commercial carbon adsorbent (CCA) sample was evaluated. In addition, the effect of natural organic matter (NOM) on MTBE adsorption was evaluated. Batch adsorption experiments determined that ZSM-5 was the most effective granular zeolite for MTBE adsorption. Further equilibrium and kinetic experiments verified that granular ZSM-5 is superior to CS-1240 and CCA in removing MTBE from water. No competitive-adsorption effects between NOM and MTBE were observed for adsorption to granular ZSM-5 or CS-1240, however there was competition between NOM and MTBE for adsorption onto the CCA granules. Fixed-bed adsorption experiments for longer run times were performed using granular ZSM-5. The bed depth service time model (BDST) was used to analyze the breakthrough data. PMID:20153106

The Microstructural Response of Granular Soil Under Uniaxial Strain

DTIC Science & Technology

1993-10-01

under uniaxial strains of up to 10 percent. The material tested was a poorly graded ottowa sand with specimens consisting of either 0.5- or 0.75-mm...microstructural effects in granular material under uniaxial strain of up to 10.0 percent. The relative influence of several microstructural effects (such as...uniaxial strain. The confinement vessel consisted of a base plate, four walls, and a loading cap. The sidewalls extended up beyond the specimen and served

Solvent extraction of diatomite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, W.

1984-07-24

There is provided a method of extracting hydrocarbons from a diatomite ore. The particle size of the ore is first reduced to form a processed ore. The processed ore is then mixed with a substantially irregular granular material to form an unstratified ore mixture having increased permeability to an extracting solvent. The unstratified ore mixture is then permeated with an extracting solvent to obtain a hydrocarbon-solvent stream from which hydrocarbons are subsequently separated. The irregular granular material may be sand.

Mechanics of Granular Materials (MGM) Flight Hardware

NASA Technical Reports Server (NTRS)

1997-01-01

A test cell for the Mechanics of Granular Materials (MGM) experiment is shown in its on-orbit configuration in Spacehab during preparations for STS-89. The twin locker to the left contains the hydraulic system to operate the experiment. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Note: Because the image on the screen was muted in the original image, its brightness and contrast are boosted in this rendering to make the test cell more visible. Credit: NASA/Marshall Space Flight Center (MSFC)

Promoting Interspecies Electron Transfer with Biochar

PubMed Central

Chen, Shanshan; Rotaru, Amelia-Elena; Shrestha, Pravin Malla; Malvankar, Nikhil S.; Liu, Fanghua; Fan, Wei; Nevin, Kelly P.; Lovley, Derek R.

2014-01-01

Biochar, a charcoal-like product of the incomplete combustion of organic materials, is an increasingly popular soil amendment designed to improve soil fertility. We investigated the possibility that biochar could promote direct interspecies electron transfer (DIET) in a manner similar to that previously reported for granular activated carbon (GAC). Although the biochars investigated were 1000 times less conductive than GAC, they stimulated DIET in co-cultures of Geobacter metallireducens with Geobacter sulfurreducens or Methanosarcina barkeri in which ethanol was the electron donor. Cells were attached to the biochar, yet not in close contact, suggesting that electrons were likely conducted through the biochar, rather than biological electrical connections. The finding that biochar can stimulate DIET may be an important consideration when amending soils with biochar and can help explain why biochar may enhance methane production from organic wastes under anaerobic conditions. PMID:24846283

Scaling behavior of immersed granular flows

NASA Astrophysics Data System (ADS)

Amarsid, L.; Delenne, J.-Y.; Mutabaruka, P.; Monerie, Y.; Perales, F.; Radjai, F.

2017-06-01

The shear behavior of granular materials immersed in a viscous fluid depends on fluid properties (viscosity, density), particle properties (size, density) and boundary conditions (shear rate, confining pressure). Using computational fluid dynamics simulations coupled with molecular dynamics for granular flow, and exploring a broad range of the values of parameters, we show that the parameter space can be reduced to a single parameter that controls the packing fraction and effective friction coefficient. This control parameter is a modified inertial number that incorporates viscous effects.

Pecan shell-based granular activated carbon for treatment of chemical oxygen demand (COD) in municipal wastewater.

PubMed

Bansode, R R; Losso, J N; Marshall, W E; Rao, R M; Portier, R J

2004-09-01

The present investigation was undertaken to compare the adsorption efficiency of pecan shell-based granular activated carbon with the adsorption efficiency of the commercial carbon Filtrasorb 200 with respect to uptake of the organic components responsible for the chemical oxygen demand (COD) of municipal wastewater. Adsorption efficiencies for these two sets of carbons (experimental and commercial) were analyzed by the Freundlich adsorption model. The results indicate that steam-activated and acid-activated pecan shell-based carbons had higher adsorption for organic matter measured as COD, than carbon dioxide-activated pecan shell-based carbon or Filtrasorb 200 at all the carbon dosages used during the experiment. The higher adsorption may be related to surface area as the two carbons with the highest surface area also had the highest organic matter adsorption. These results show that granular activated carbons made from agricultural waste (pecan shells) can be used with greater effectiveness for organic matter removal from municipal wastewater than a coal-based commercial carbon. Copyright 2004 Elsevier Ltd.

LABORATORY EVALUATION OF ZERO-VALENT IRON TO TREAT WATER IMPACTED BY ACID MINE DRAINAGE

EPA Science Inventory

This study examines the applicability and limitations of granular zero-valent iron for the treatment of water impacted by mine wastes. Rates of acid neutralization and of metal (Cu, Cd, Ni, Zn, Hg, Al, and Mn) and metalloid (As) uptake were determined in batch systems using simu...

Probing Dynamics in Granular Media of Contrasting Geometries via X-Ray Phase Contrast Imaging and PDV

NASA Astrophysics Data System (ADS)

Crum, Ryan; Pagan, Darren; Lind, Jon; Homel, Michael; Hurley, Ryan; Herbold, Eric; Akin, Minta

Granular systems are ubiquitous in our everyday world and play a central role in many dynamic scientific problems including mine blasting, projectile penetration, astrophysical collisions, explosions, and dynamic compaction. An understanding of granular media's behavior under various loading conditions is an ongoing scientific grand challenge. This is partly due to the intricate interplay between material properties, loading conditions, grain geometry, and grain connectivity. Previous dynamic studies in granular media predominantly utilize the macro-scale analyses VISAR or PDV, diagnostics that are not sensitive to the many degrees of freedom and their interactions, focusing instead on their aggregate effect. Results of a macro-scale analysis leave the principal interactions of these degrees of freedom too entangled to elucidate. To isolate the significance of grain geometry, this study probes various geometries of granular media subjected to gas gun generated waves via in-situ X-ray analysis. Analyses include evaluating displacement fields, grain fracture, inter- and intra-granular densification, and wave front motion. Phase Contrast Imaging (PCI) and PDV analyses feed directly into our concurrent meso-scale granular media modeling efforts to enhance our predictive capabilities.

Instabilities and the Development of Density Waves in Gas-Particle and Granular Flows

NASA Astrophysics Data System (ADS)

Glasser, Benjamin J.; Liss, Elizabeth D.; Conway, Stephen L.; Johri, Jayati

2002-11-01

The dynamics of gas-particle and granular flows impact numerous technologies related to the local utilization of Lunar and Martian soils and the Martian atmosphere. On earth, such flows occur in a large number of industries including the chemical, pharmaceutical, materials, mining and food industries.

Plastic deformation in a metallic granular chain

NASA Astrophysics Data System (ADS)

Musson, Ryan W.; Carlson, William

2016-03-01

Solitary wave response was investigated in a metallic granular chain-piston system using LS-DYNA. A power law hardening material model was used to show that localized plastic deformation is present in a metallic granular chain for an impact velocity of 0.5 m/s. This loss due to plastic deformation was quantified via impulse, and it was shown that the loss scales nearly linearly with impact velocity. Therefore, metallic grains may not be suitable for devices that require high-amplitude solitary waves. There would be too much energy lost to plastic deformation. One can assume that ceramics will behave elastically; therefore, the response of an aluminum oxide granular chain was compared to that of a steel chain.

Impact of projectiles of different geometries on dry granular media using DEM simulations

NASA Astrophysics Data System (ADS)

Vajrala, Spandana; Bagheri, Hosain; Emady, Heather; Marvi, Hamid; Particulate Process; Product Design Group Team; Birth Lab Collaboration

Recently, several studies involving numerical and experimental methods have focused on the study of impact dynamics in both dry and wet granular media. Most of these studies considered the impact of spherical projectiles under different conditions, while representative models could involve more complex shapes. Examples include such things as an animal's foot impacting sand or an asteroid hitting the ground. Dropping different shaped geometries with conserved density, volume and velocity on a granular bed may experience contrasting drag forces upon penetration. This is the result of the difference in the surface areas coming in contact with the granular media. Therefore, this work will utilize three-dimensional Discrete Element Modelling (DEM) simulations to observe and compare the impact of different geometries like cylinder and cuboid of same material properties and volume. These geometries will be impacted on a loosely packed non-cohesive dry granular bed with the same impact velocities where the effect of surface area in contact with the granular media will be analyzed upon impact and penetration.

Synthesis of Biodiesel in Batch and Packed-Bed Reactors Using Powdered and Granular Sugar Catalyst

NASA Astrophysics Data System (ADS)

Janaun, J.; Lim, P. M.; Balan, W. S.; Yaser, A. Z.; Chong, K. P.

2017-06-01

Increasing world production of palm oil warrants effective utilization of its waste. In particular, conversion of waste cooking oil into biodiesel has obtained global interest because of renewable energy need and reduction of CO2 emission. In this study, oleic acid used as a model compound for waste cooking oil conversion using esterification reaction catalysed by sugar catalyst (SC) in powdered (P-SC) and granular (G-SC) forms. The catalysts were synthesized via incomplete carbonization of D-glucose followed by functionalization with concentrated sulphuric acid. Catalysts characterizations were done for their physical and chemical properties using modern tools. Batch and packed-bed reactor systems were used to evaluate the reactivity of the catalysts. The results showed that G-SC had slightly higher total acidity and more porous than P-SC. The experimental conditions for batch reaction were temperature of 60°C, molar ratio of 1:20 (Oleic Acid:Methanol) and 2 wt. catalyst with respect to oleic acid. The results showed the maximum oleic acid conversion using G-SC and P-SC were 52 and 48, respectively. Whereas, the continuous reaction with varying feed flow rate as a function of retention time was studied by using 3 g of P-SC in 60 °C and 1:20 molar ratio in a packed-bed reactor. The results showed that a longer retention time which was 6.48 min and feed flow rate 1.38 ml/min, achieved higher average conversion of 9.9 and decreased with further increasing flow rate. G-SC showed a better average conversion of 10.8 at lowest feed flow rate of 1.38 ml/min in continuous reaction experiments. In a broader perspective, large scale continuous biodiesel production is feasible using granular over powdered catalyst mainly due to it lower pressure drop.

Inhibitory effect of high NH{sub 4}{sup +}–N concentration on anaerobic biotreatment of fresh leachate from a municipal solid waste incineration plant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Zhao; Dang, Yan; Li, Caihua

2015-09-15

Highlights: • High NH{sub 4}{sup +}–N concentrations inhibit anaerobic treatment of leachate. • Inhibitory effect of NH{sub 4}{sup +}–N concentrations on anaerobic granular sludge is reversible. • High NH{sub 4}{sup +}–N concentrations inhibit bioactivities of microorganisms instead of survival. - Abstract: Fresh leachate from municipal solid waste (MSW) incineration plants generally contains extremely high NH{sub 4}{sup +}–N concentration which could inhibit the bioactivity of microorganisms. The inhibitory effect of high NH{sub 4}{sup +}–N concentration on anaerobic biotreatment of fresh leachate from a MSW incineration plant in China has been investigated in this study. The inhibition processes was studied by bothmore » static tests and a laboratory-scale expanded granular sludge bed (EGSB) reactor. The specific methanogenic activity (SMA) of the microorganisms in anaerobic granular sludge was inhibited with the NH{sub 4}{sup +}–N concentration increasing to 1000 mg/L in static tests. As well the chemical oxygen demand (COD) removal efficiency and the methane yield decreased in the EGSB reactor, while the volatile fatty acids (VFAs) accumulated and extracellular polymeric substances (EPS) of the anaerobic granular sludge increased with NH{sub 4}{sup +}–N concentration rising to 1000 mg/L, without any rebounding during 30 days of operation. Decreasing NH{sub 4}{sup +}–N concentration to 500 mg/L in influent, the COD removal efficiency recovered to about 85% after 26 days. 1000 mg/L of NH{sub 4}{sup +}–N in leachate was suggested to be the inhibition threshold in EGSB reactor. High-throughput sequencing results showed little changes in microbial communities of the sludge for a high NH{sub 4}{sup +}–N concentration, indicating that the survival of most microorganisms was not affected under such a condition. It inhibited the bioactivity of the microorganisms, resulting in decrease of the COD removal efficiency.« less

An experimental study of ultrasonic vibration and the penetration of granular material

PubMed Central

Firstbrook, David; Worrall, Kevin; Timoney, Ryan; Suñol, Francesc; Gao, Yang

2017-01-01

This work investigates the potential use of direct ultrasonic vibration as an aid to penetration of granular material. Compared with non-ultrasonic penetration, required forces have been observed to reduce by an order of magnitude. Similarly, total consumed power can be reduced by up to 27%, depending on the substrate and ultrasonic amplitude used. Tests were also carried out in high-gravity conditions, displaying a trend that suggests these benefits could be leveraged in lower gravity regimes. PMID:28293134

Deformation profiles of elastic cylindrical tubes filled with granular media under an overload

NASA Astrophysics Data System (ADS)

Álvarez Salazar, V. Salomón; Medina, Abraham; Klapp, Jaime

2017-06-01

The deformation of a thin-walled vertical tube, filled with a liquid or a cohesionless granular material is investigated theoretically and experimentally. Experiments with an overload and without it were made with latex tubes filled with water or spherical glass beads and the results were compared with the theoretical profile derived from the Janssen model. The results suggest that the soft elastic tubes could provide a simple and convenient means to investigate the forces that arise in different materials.

Contact force structure and force chains in 3D sheared granular systems

NASA Astrophysics Data System (ADS)

Mair, Karen; Jettestuen, Espen; Abe, Steffen

2010-05-01

Faults often exhibit accumulations of granular debris, ground up to create a layer of rock flour or fault gouge separating the rigid fault walls. Numerical simulations and laboratory experiments of sheared granular materials, suggest that applied loads are preferentially transmitted across such systems by transient force networks that carry enhanced forces. The characterisation of such features is important since their nature and persistence almost certainly influence the macroscopic mechanical stability of these systems and potentially that of natural faults. 3D numerical simulations of granular shear are a valuable investigation tool since they allow us to track individual particle motions, contact forces and their evolution during applied shear, that are difficult to view directly in laboratory experiments or natural fault zones. In characterising contact force distributions, it is important to use global structure measures that allow meaningful comparisons of granular systems having e.g. different grain size distributions, as may be expected at different stages of a fault's evolution. We therefore use a series of simple measures to characterise the structure, such as distributions and correlations of contact forces that can be mapped onto a force network percolation problem as recently proposed by Ostojic and coworkers for 2D granular systems. This allows the use of measures from percolation theory to both define and characterise the force networks. We demonstrate the application of this method to 3D simulations of a sheared granular material. Importantly, we then compare our measure of the contact force structure with macroscopic frictional behaviour measured at the boundaries of our model to determine the influence of the force networks on macroscopic mechanical stability.

Conceptual design of a bioregenerative life support system containing crops and silkworms

NASA Astrophysics Data System (ADS)

Hu, Enzhu; Bartsev, Sergey I.; Liu, Hong

2010-04-01

This article summarizes a conceptual design of a bioregenerative life support system for permanent lunar base or planetary exploration. The system consists of seven compartments - higher plants cultivation, animal rearing, human habitation, water recovery, waste treatment, atmosphere management, and storages. Fifteen kinds of crops, such as wheat, rice, soybean, lettuce, and mulberry, were selected as main life support contributors to provide the crew with air, water, and vegetable food. Silkworms fed by crop leaves were designated to produce partial animal nutrition for the crew. Various physical-chemical and biological methods were combined to reclaim wastewater and solid waste. Condensate collected from atmosphere was recycled into potable water through granular activated carbon adsorption, iodine sterilization, and trace element supplementation. All grey water was also purified though multifiltration and ultraviolet sterilization. Plant residue, human excrement, silkworm feces, etc. were decomposed into inorganic substances which were finally absorbed by higher plants. Some meat, ingredients, as well as nitrogen fertilizer were prestored and resupplied periodically. Meanwhile, the same amount and chemical composition of organic waste was dumped to maintain the steady state of the system. A nutritional balanced diet was developed by means of the linear programming method. It could provide 2721 kcal of energy, 375.5 g of carbohydrate, 99.47 g of protein, and 91.19 g of fat per capita per day. Silkworm powder covered 12.54% of total animal protein intakes. The balance of material flows between compartments was described by the system of stoichiometric equations. Basic life support requirements for crews including oxygen, food, potable and hygiene water summed up to 29.68 kg per capita per day. The coefficient of system material closure reached 99.40%.

Experimental study on the heat transfer characteristics of waste printed circuit boards pyrolysis.

PubMed

Ma, Hongting; Du, Na; Lin, Xueyin; Li, Chen; Lai, Junwen; Li, Zihao

2018-08-15

In order to study the appropriate and advanced technology for recycling waste printed circuit boards (PCBs), a fixed bed pyrolysis device with stirring function has been designed and developed. The effect of rotating speed on the temperature distribution and mass change in the pyrolysis process of FR-4 PCB has been analyzed. The heat transfer and pyrolysis characteristics of different granular layers with and without stirring have been investigated. The results indicate that the stirring can change the main way of heat transfer from conduction to convection in the PCB layers. As the increase of rotating speed, the temperature rising rate of material at the bottom of the pyrolysis furnace gradually decreases, while the heating rate is increasing at the upper layer, and the temperature difference between the upper and bottom layers is gradually reduced. When the rotating speed varies from 0r/min to 18r/min, the weight loss of the material increases from 3.97% to 6.76%, and the overall pyrolysis degree is improved. During the pyrolysis process, the material layer can be divided into three zones along the vertical direction, namely complete pyrolysis zone, partial pyrolysis zone and non-pyrolysis zone. As the rotating speed is 0r/min, the thickness of each zones is 6cm, 6cm and 3cm, respectively. However, when the rotating speed is increased to 18r/min, the non-pyrolysis zone disappears, and the thickness of complete pyrolysis zone and partial pyrolysis zone increase to 9cm and 6cm, respectively. Copyright © 2018 Elsevier B.V. All rights reserved.

Method and apparatus for filtering gas with a moving granular filter bed

DOEpatents

Brown, Robert C.; Wistrom, Corey; Smeenk, Jerod L.

2007-12-18

A method and apparatus for filtering gas (58) with a moving granular filter bed (48) involves moving a mass of particulate filter material (48) downwardly through a filter compartment (35); tangentially introducing gas into the compartment (54) to move in a cyclonic path downwardly around the moving filter material (48); diverting the cyclonic path (58) to a vertical path (62) to cause the gas to directly interface with the particulate filter material (48); thence causing the gas to move upwardly through the filter material (48) through a screened partition (24, 32) into a static upper compartment (22) of a filter compartment for exodus (56) of the gas which has passed through the particulate filter material (48).

Granular Crater Formation

NASA Astrophysics Data System (ADS)

Clark, Abe; Behringer, Robert; Brandenburg, John

2009-11-01

This project characterizes crater formation in a granular material by a jet of gas impinging on a granular material, such as a retro-rocket landing on the moon. We have constructed a 2D model of a planetary surface, which consists of a thin, clear box partially filled with granular materials (sand, lunar and Mars simulants...). A metal pipe connected to a tank of nitrogen gas via a solenoid valve is inserted into the top of the box to model the rocket. The results are recorded using high-speed video. We process these images and videos in order to test existing models and develop new ones for describing crater formation. A similar set-up has been used by Metzger et al.footnotetextP. T. Metzger et al. Journal of Aerospace Engineering (2009) We find that the long-time shape of the crater is consistent with a predicted catenary shape (Brandenburg). The depth and width of the crater both evolve logarithmically in time, suggesting an analogy to a description in terms of an activated process: dD/dt = A (-aD) (D is the crater depth, a and A constants). This model provides a useful context to understand the role of the jet speed, as characterized by the pressure used to drive the flow. The box width also plays an important role in setting the width of the crater.

Avalanches, and evolution of stress and fabric for a cyclically sheared granular material

NASA Astrophysics Data System (ADS)

Wang, Dengming; Bares, Jonathan; Wang, Dong; Behringer, Bob

2015-03-01

Granular materials yield for large enough shear stress, leading to avalanches. We seek to understand the relation between macroscopic avalanches and the the microscopic granular structure. We present an experimental study of a 2D granular material subjected to cyclic pure shear, which we visualized by a photo-elastic technique. We start from a stress-free sample of frictional particles in the shear-jamming regime (ϕS <= ϕ <=ϕJ). We apply multiple cycles of pure shear: shear in one direction, followed by a reversal to the original boundary configuration. The strain is made in small quasi-static steps: after each small step, we obtain polarized and unpolarized images yielding particle-scale forces and locations. Statistical measures of the avalanches are in reasonable agreement with recent mean-field avalanche models by Dahmen et al. (Nature Physics 7, 554 (2011)) The system structure evolves slowly to reduce the stress at the extrema of strain, similar to the relaxation observed by Ren et al. (Phys. Rev. Lett. 110, 018302 (2013)) in a simple shear experiment. To understand how this relaxation occurs, we track the stress and fabric tensors and measures of the strain field over many cycles of shear. Supported by NASA Grant NNX10AU01G, and NSF Grants DMR1206351 and DMS1248071.

Adsorptive removal of heavy metals from water using sodium titanate nanofibres loaded onto GAC in fixed-bed columns.

PubMed

Sounthararajah, D P; Loganathan, P; Kandasamy, J; Vigneswaran, S

2015-04-28

Heavy metals are serious pollutants in aquatic environments. A study was undertaken to remove Cu, Cd, Ni, Pb and Zn individually (single metal system) and together (mixed metals system) from water by adsorption onto a sodium titanate nanofibrous material. Langmuir adsorption capacities (mg/g) at 10(-3)M NaNO3 ionic strength in the single metal system were 60, 83, 115 and 149 for Ni, Zn, Cu, and Cd, respectively, at pH 6.5 and 250 for Pb at pH 4.0. In the mixed metals system they decreased at high metals concentrations. In column experiments with 4% titanate material and 96% granular activated carbon (w/w) mixture at pH 5.0, the metals breakthrough times and adsorption capacities (for both single and mixed metals systems) decreased in the order Pb>Cd, Cu>Zn>Ni within 266 bed volumes. The amounts adsorbed were up to 82 times higher depending on the metal in the granular activated carbon+titanate column than in the granular activated carbon column. The study showed that the titanate material has high potential for removing heavy metals from polluted water when used with granular activated carbon at a very low proportion in fixed-bed columns. Copyright © 2015 Elsevier B.V. All rights reserved.

Performance and microbial diversity of an expanded granular sludge bed reactor for high sulfate and nitrate waste brine treatment.

PubMed

Liao, Runhua; Li, Yan; Yu, Xuemin; Shi, Peng; Wang, Zhu; Shen, Ke; Shi, Qianqian; Miao, Yu; Li, Wentao; Li, Aimin

2014-04-01

The disposal of waste brines has become a major challenge that hinders the wide application of ion-exchange resins in the water industry in recent decades. In this study, high sulfate removal efficiency (80%-90%) was achieved at the influent sulfate concentration of 3600 mg/L and 3% NaCl after 145 days in an expanded granular sludge bed (EGSB) reactor. Furthermore, the feasibility of treating synthetic waste brine containing high levels of sulfate and nitrate was investigated in a single EGSB reactor during an operation period of 261 days. The highest nitrate and sulfate loading rate reached 6.38 and 5.78 kg/(m(3)·day) at SO(2-)4-S/NO(-)3-N mass ratio of 4/3, and the corresponding removal efficiency was 99.97% and 82.26% at 3% NaCl, respectively. Meanwhile, 454-pyrosequencing technology was used to analyze the bacterial diversity of the sludge on the 240th day for stable operation of phase X. Results showed that a total of 9194 sequences were obtained, which could be affiliated to 14 phyla, including Proteobacteria, Firmicutes, Chlorobi, Bacteroidetes, Synergistetes and so on. Proteobacteria (77.66%) was the dominant microbial population, followed by Firmicutes (12.23%) and Chlorobi (2.71%). Copyright © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Microgravity and Hypogravity Compatible Methods for the Destruction of Solid Wastes by Magnetically Assisted Gasification

NASA Technical Reports Server (NTRS)

Atwater, James E.; Akse, James R.; Wheeler, Richard R., Jr.; Jovanovic, Goran N.; Pinto-Espinoza, Joaquin; Reed, Brian; Sornchamni, Thana

2003-01-01

This report summarizes a three-year collaborative effort between researchers at UMPQUA Research Company (URC) and the Chemical Engineering Department at Oregon State University (OSU). The Magnetically Assisted Gasification (MAG) concept was originally conceived as a microgravity and hypogravity compatible means for the decomposition of solid waste materials generated aboard spacecraft, lunar and planetary habitations, and for the recovery of potentially valuable resources. While a number of methods such as supercritical water oxidation (SCW0), fluidized bed incineration, pyrolysis , composting and related biological processes have been demonstrated for the decomposition of solid wastes, none of these methods are particularly well- suited for employment under microgravity or hypogravity conditions. For example, fluidized bed incineration relies upon a balance between drag forces which the flowing gas stream exerts upon the fluidization particles and the opposing force of gravity. In the absence of gravity, conventional fluidization cannot take place. Hypogravity operation can also be problematic for conventional fluidized bed reactors, because the various factors which govern fluidization phenomena do not all scale linearly with gravity. For this reason it may be difficult to design and test fluidized bed reactors in lg, which are intended to operate under different gravitational conditions. However, fluidization can be achieved in microgravity (and hypogravity) if a suitable replacement force to counteract the forces between fluid and particles can be found. Possible alternatives include: centripetal force, electric fields, or magnetic fields. Of these, magnetic forces created by the action of magnetic fields and magnetic field gradients upon ferromagnetic media offer the most practical approach. The goal of this URC-OSU collaborative effort was to develop magnetic hardware and methods to control the degree of fluidization (or conversely consolidation) of granular ferromagnetic media and to employ these innovations in sequential filtration and fluidized bed processes for the segregation and decomposition of solid waste materials, and for the concentration and collection of inorganic residue (ash). This required the development of numerous enabling technologies and tools.

The influence of slope-angle ratio on the dynamics of granular flows: insights from laboratory experiments

NASA Astrophysics Data System (ADS)

Sulpizio, R.; Castioni, D.; Rodriguez-Sedano, L. A.; Sarocchi, D.; Lucchi, F.

2016-11-01

Laboratory experiments on granular flows using natural material were carried out in order to investigate the behaviour of granular flows passing over a break in slope. Sensors in the depositional area recorded the flow kinematics, while video footage permitted reconstruction of the deposit formation, which allowed investigation of the deposit shape as a function of the change in slope. We defined the slope-angle ratio as the proportion between slope angle in the depositional area and that of the channel. When the granular flow encounters the break in slope part of the flow front forms a bouncing clast zone due to elastic impact with the expansion box floor. During this process, part of the kinetic energy of the dense granular flow is transferred to elutriating fine ash, which subsequently forms turbulent ash cloud accompanying the granular flow until it comes to rest. Morphometric analysis of the deposits shows that they are all elliptical, with an almost constant minor axis and a variable major axis. The almost constant value of the minor axis relates to the spreading angle of flow at the end of the channel, which resembles the basal friction angle of the material. The variation of the major axis is interpreted to relate to the effect of competing inertial and frictional forces. This effect also reflects the partitioning of centripetal and tangential velocities, which changes as the flow passes over the break in slope. After normalization, morphometric data provided empirical relationships that highlight the dependence of runout from the product of slope-angle ratio and the difference in height between granular material release and deposit. The empirical relationships were tested against the runouts of hot avalanches formed during the 1944 ad eruption at Vesuvius, with differences among actual and calculated values are between 1.7 and 15 %. Velocity measurements of laboratory granular flows record deceleration paths at different breaks in slope. When normalized, the velocity data show third-order polynomial fit, highlighting a complex behaviour involving interplay between inertial and frictional forces. The theoretical velocity decays were tested against the data published for volcaniclastic debris flows of the 5-6 May 1998 event in the Sarno area. The comparison is very good for non-channelized debris flows, with significant differences between actual and calculated velocities for the channelized debris flows.

Stochastic clustering of material surface under high-heat plasma load

NASA Astrophysics Data System (ADS)

Budaev, Viacheslav P.

2017-11-01

The results of a study of a surface formed by high-temperature plasma loads on various materials such as tungsten, carbon and stainless steel are presented. High-temperature plasma irradiation leads to an inhomogeneous stochastic clustering of the surface with self-similar granularity - fractality on the scale from nanoscale to macroscales. Cauliflower-like structure of tungsten and carbon materials are formed under high heat plasma load in fusion devices. The statistical characteristics of hierarchical granularity and scale invariance are estimated. They differ qualitatively from the roughness of the ordinary Brownian surface, which is possibly due to the universal mechanisms of stochastic clustering of material surface under the influence of high-temperature plasma.

Controlled Viscosity in Dense Granular Materials

NASA Astrophysics Data System (ADS)

Gnoli, A.; de Arcangelis, L.; Giacco, F.; Lippiello, E.; Ciamarra, M. Pica; Puglisi, A.; Sarracino, A.

2018-03-01

We experimentally investigate the fluidization of a granular material subject to mechanical vibrations by monitoring the angular velocity of a vane suspended in the medium and driven by an external motor. On increasing the frequency, we observe a reentrant transition, as a jammed system first enters a fluidized state, where the vane rotates with high constant velocity, and then returns to a frictional state, where the vane velocity is much lower. While the fluidization frequency is material independent, the viscosity recovery frequency shows a clear dependence on the material that we rationalize by relating this frequency to the balance between dissipative and inertial forces in the system. Molecular dynamics simulations well reproduce the experimental data, confirming the suggested theoretical picture.

Anaerobic bioremediation of hexavalent uranium in groundwater by reductive precipitation with methanogenic granular sludge.

PubMed

Tapia-Rodriguez, Aida; Luna-Velasco, Antonia; Field, Jim A; Sierra-Alvarez, Reyes

2010-04-01

Uranium has been responsible for extensive contamination of groundwater due to releases from mill tailings and other uranium processing waste. Past evidence has confirmed that certain bacteria can enzymatically reduce soluble hexavalent uranium (U(VI)) to insoluble tetravalent uranium (U(IV)) under anaerobic conditions in the presence of appropriate electron donors. This paper focuses on the evaluation of anaerobic granular sludge as a source of inoculum for the bioremediation of uranium in water. Batch experiments were performed with several methanogenic anaerobic granular sludge samples and different electron donors. Abiotic controls consisting of heat-killed inoculum and non-inoculated treatments confirmed the biological removal process. In this study, unadapted anaerobic granular sludge immediately reduced U(VI), suggesting an intrinsic capacity of the sludge to support this process. The high biodiversity of anaerobic granular sludge most likely accounts for the presence of specific microorganisms capable of reducing U(VI). Oxidation by O(2) was shown to resolubilize the uranium. This observation combined with X-ray diffraction evidence of uraninite confirmed that the removal during anaerobic treatment was due to reductive precipitation. The anaerobic removal activity could be sustained after several respikes of U(VI). The U(VI) removal was feasible without addition of electron donors, indicating that the decay of endogenous biomass substrates was contributing electron equivalents to the process. Addition of electron donors, such as H(2) stimulated the removal of U(VI) to varying degrees. The stimulation was greater in sludge samples with lower endogenous substrate levels. The present work reveals the potential application of anaerobic granular sludge for continuous bioremediation schemes to treat uranium-contaminated water. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

A theoretical and numerical study of the flow of granular materials down an inclined plane. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajagopal, K.R.

The mechanics of the flowing granular materials such as coal, agricultural products, at deal of attention as it has fertilizers, dry chemicals, metal ores, etc. have received a great deal of attention as it has relevance to several important technological problems. Despite wide interest and more than five decades of experimental and theoretical investigations, most aspects of the behavior of flowing granular materials are still not well understood. So Experiments have to be devised which quantify and describe the non-linear behavior of the modular materials, and theories developed which can explain the experimentally observed facts. As many models have beenmore » suggested for describing the behavior of granular materials, from both continuum and kinetic theory viewpoints, we proposed to investigate the validity and usefulness of representative models from both the continuum and kinetic theory points of view, by determining the prediction of such a theory, in a representative flow, with respect to existence, non-existence, multiplicity and stability of solutions. The continuum model to be investigated is an outgrowth of a model due to Goodman and Cowin (1971, 1972) and the kinetic theory models being those due to Jenkins and Richman (1985) and Boyle and Massoudi (1989). In this report we present detailed results regarding the same. Interestingly, we find that the predictions of all the theories, in certain parameter space associated with these models, are qualitatively similar. This ofcourse depends on the values assumed for various material parameters in the models, which as yet are unknown, as reliable experiments have not been carried out as yet for their determination.« less

The distribution of saturated clusters in wetted granular materials

NASA Astrophysics Data System (ADS)

Li, Shuoqi; Hanaor, Dorian; Gan, Yixiang

2017-06-01

The hydro-mechanical behaviour of partially saturated granular materials is greatly influenced by the spatial and temporal distribution of liquid within the media. The aim of this paper is to characterise the distribution of saturated clusters in granular materials using an optical imaging method under different water drainage conditions. A saturated cluster is formed when a liquid phase fully occupies the pore space between solid grains in a localized region. The samples considered here were prepared by vibrating mono-sized glass beads to form closely packed assemblies in a rectangular container. A range of drainage conditions were applied to the specimen by tilting the container and employing different flow rates, and the liquid pressure was recorded at different positions in the experimental cell. The formation of saturated clusters during the liquid withdrawal processes is governed by three competing mechanisms arising from viscous, capillary, and gravitational forces. When the flow rate is sufficiently large and the gravity component is sufficiently small, the viscous force tends to destabilize the liquid front leading to the formation of narrow fingers of saturated material. As the water channels along these liquid fingers break, saturated clusters are formed inside the specimen. Subsequently, a spatial and temporal distribution of saturated clusters can be observed. We investigated the resulting saturated cluster distribution as a function of flow rate and gravity to achieve a fundamental understanding of the formation and evolution of such clusters in partially saturated granular materials. This study serves as a bridge between pore-scale behavior and the overall hydro-mechanical characteristics in partially saturated soils.

Microgravity Experiments to Evaluate Electrostatic Forces in Controlling Cohesion and Adhesion of Granular Materials

NASA Technical Reports Server (NTRS)

Marshall, J.; Weislogel, M.; Jacobson, T.

1999-01-01

The bulk behavior of dispersed, fluidized, or undispersed stationary granular systems cannot be fully understood in terms of adhesive/cohesive properties without understanding the role of electrostatic forces acting at the level of the grains themselves. When grains adhere to a surface, or come in contact with one another in a stationary bulk mass, it is difficult to measure the forces acting on the grains, and the forces themselves that induced the cohesion and adhesion are changed. Even if a single grain were to be scrutinized in the laboratory, it might be difficult, perhaps impossible, to define the distribution and character of surface charging and the three-dimensional relationship that charges (electrons, holes) have to one another. The hypothesis that we propose to test in microgravity (for dielectric materials) is that adhesion and cohesion of granular matter are mediated primarily by dipole forces that do not require the presence of a net charge; in fact, nominally electrically neutral materials should express adhesive and cohesive behavior when the neutrality results from a balance of positive and negative charge carriers. Moreover, the use of net charge alone as a measure of the electrical nature of grain-to-grain relationships within a granular mass may be misleading. We believe that the dipole forces arise from the presence of randomly-distributed positive and negative fixed charge carriers on grains that give rise to a resultant dipole moment. These dipole forces have long-range attraction. Random charges are created whenever there is triboelectrical activity of a granular mass, that is, whenever the grains experience contact/separation sequences or friction.

Monodisperse granular flows in viscous dispersions in a centrifugal acceleration field

NASA Astrophysics Data System (ADS)

Cabrera, Miguel Angel; Wu, Wei

2016-04-01

Granular flows are encountered in geophysical flows and innumerable industrial applications with particulate materials. When mixed with a fluid, a complex network of interactions between the particle- and fluid-phase develops, resulting in a compound material with a yet unclear physical behaviour. In the study of granular suspensions mixed with a viscous dispersion, the scaling of the stress-strain characteristics of the fluid phase needs to account for the level of inertia developed in experiments. However, the required model dimensions and amount of material becomes a main limitation for their study. In recent years, centrifuge modelling has been presented as an alternative for the study of particle-fluid flows in a reduced scaled model in an augmented acceleration field. By formulating simple scaling principles proportional to the equivalent acceleration Ng in the model, the resultant flows share many similarities with field events. In this work we study the scaling principles of the fluid phase and its effects on the flow of granular suspensions. We focus on the dense flow of a monodisperse granular suspension mixed with a viscous fluid phase, flowing down an inclined plane and being driven by a centrifugal acceleration field. The scaled model allows the continuous monitoring of the flow heights, velocity fields, basal pressure and mass flow rates at different Ng levels. The experiments successfully identify the effects of scaling the plastic viscosity of the fluid phase, its relation with the deposition of particles over the inclined plane, and allows formulating a discussion on the suitability of simulating particle-fluid flows in a centrifugal acceleration field.

Finite Element Studies of Solitary Waves in Granular Chains

NASA Astrophysics Data System (ADS)

Musson, Ryan W.

Solitary wave propagation in a monodisperse metallic granular chain was simulated using the finite element method. The model was built to address a discrepancy between numerical and experimental results from Lazaridi and Nesterenko (J. Appl. Mech. Tech. Phys., 26 [3] 405-408 1985). In their work, solitary waves were generated in a chain of particles through impact of a piston, and results were quantified by comparing the chains' reactions to a rigid wall. Their numerical calculations resulted in a solitary wave with a force amplitude of 83 N, while it was measured experimentally to be 71 N. In the present work, the configuration of the granular chain and piston was duplicated from Lazaridi and Nesterenko (J. Appl. Mech. Tech. Phys., 26 [3] 405-408 1985). Qualitatively similar solitary waves were produced, and von Mises stress values indicated that localized plastic deformation is possible, even at low piston impact velocities. These results show that localized plastic deformation was a likely source of dissipation in experiments performed by Lazaridi and Nesterenko. Solitary wave response was investigated in the same metallic granular chain-piston system using LS-DYNA. A power-law hardening material model was used to show that localized plastic deformation is present in the metallic granular chain, even for an impact velocity of 0.5 m/s. This loss due to plastic deformation was quantified via impulse, and it was shown that the loss scales nearly linearly with impact velocity. Therefore, metallic grains may not be suitable for devices that require high amplitude solitary waves. There would be too much energy lost to plastic deformation. The response of an aluminum oxide granular chain was subsequently compared to that of a steel chain because ceramics are inherently elastic. It was shown that solitary waves travel faster and the initial peak is slightly lower when compared to a steel chain. The response of granular chains to impulse loading was investigated as a function of material properties. COMSOL Multiphysics was used to study the effect of density and elastic modulus on a granular chain with fixed Poisson's ratio. Solitary wave velocity and amplitude increased with elastic modulus. Increasing density caused a decrease in wave velocity and an increase in amplitude. In addition, higher density granular chains exhibited a decrease in the number of solitary waves in their respective solitary wave trains. LS-DYNA was then used to explore the response of a variety of ceramic and metallic granular chains. Density, elastic modulus, and Poisson's ratio were all set to representative values for the respective material. It was shown that solitary wave development and decay occur at different rates for different materials. In addition, the kinetic energy decay of the impactor was slower for glass compared with tungsten. Finally, it was shown that a single solitary wave with no train could be produced by impacting a high density, high modulus chain such as tungsten with a glass piston, which has relatively low density and elastic modulus. Increasing impact velocity for this case resulted in a single high-amplitude solitary wave with no train.

Pattern palette for complex fluid flows

NASA Astrophysics Data System (ADS)

Sandnes, B.

2012-04-01

From landslides to oil and gas recovery to the squeeze of a toothpaste tube, flowing complex fluids are everywhere around us in nature and engineering. That is not to say, though, that they are always well understood. The dissipative interactions, through friction and inelastic collisions, often give rise to nonlinear dynamics and complexity manifested in pattern formation on large scales. The images displayed on this poster illustrate the diverse morphologies found in multiphase flows involving wet granular material: Air is injected into a generic mixture of granular material and fluid contained in a 500 µm gap between two parallel glass plates. At low injection rates, friction between the grains - glass beads averaging 100 µm in diameter - dominates the rheology, producing "stick-slip bubbles" and labyrinthine frictional fingering. A transition to various other morphologies, including "corals" and viscous fingers, emerges for increasing injection rate. At sufficiently high granular packing fractions, the material behaves like a deformable, porous solid, and the air rips through in sudden fractures.

Rate Dependence in Force Networks of Sheared Granular Materials

NASA Astrophysics Data System (ADS)

Hartley, Robert; Behringer, Robert P.

2003-03-01

We describe experiments that explore rate dependence in force networks of dense granular materials undergoing slow deformation by shear and by compression. The experiments were carried out using 2D photoelastic particles so that it was possible to visualize forces at the grain scale. Shear experiments were carried out in a Couette geometry with a rate Ω. Compression experiments were carried out by repetitive compaction via a piston in a rigid chamber at comparable rates to the shear experiments. Under shearing the mean stress/force grew logarithmically with Ω for at least four decades. For compression, no dependence of the mean stress on rate was observed. In related measurements, we observed relaxation of stress in static samples that had been sheared and where the shearing was abruptly stopped. Relaxation of the force network occured over time scales of days. No relaxation of the force network was observable for uniformly compressed static samples. These results are of particular interest because they provide insight into creep and failure in granular materials.

Machanics of Granular Materials (MGM) Investigator

NASA Technical Reports Server (NTRS)

2000-01-01

Key persornel in the Mechanics of Granular Materials (MGM) experiment include Khalid Alshibli, project scientist at NASA's Marshall Space Flight Center (MSFC). Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that cannot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (Credit: MSFC).

Microgravity

NASA Image and Video Library

1998-01-25

Astronaut James Reilly uses a laptop computer monitor the Mechanics of Granular Materials (MGM) experiment during STS-89. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: NASA/Marshall Space Flight Center (MSFC)

Microgravity

NASA Image and Video Library

1996-09-18

Astronaut Carl Walz installs Mechanics of Granular Materials (MGM) test cell on STS-79. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: NASA/John Space Center

Numerical modeling of the tensile strength of a biological granular aggregate: Effect of the particle size distribution

NASA Astrophysics Data System (ADS)

Heinze, Karsta; Frank, Xavier; Lullien-Pellerin, Valérie; George, Matthieu; Radjai, Farhang; Delenne, Jean-Yves

2017-06-01

Wheat grains can be considered as a natural cemented granular material. They are milled under high forces to produce food products such as flour. The major part of the grain is the so-called starchy endosperm. It contains stiff starch granules, which show a multi-modal size distribution, and a softer protein matrix that surrounds the granules. Experimental milling studies and numerical simulations are going hand in hand to better understand the fragmentation behavior of this biological material and to improve milling performance. We present a numerical study of the effect of granule size distribution on the strength of such a cemented granular material. Samples of bi-modal starch granule size distribution were created and submitted to uniaxial tension, using a peridynamics method. We show that, when compared to the effects of starch-protein interface adhesion and voids, the granule size distribution has a limited effect on the samples' yield stress.

Moving Bed Granular Bed Filter Development Program. Topical report, September 1994

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haas, J.C.; Prudhomme, J.W.; Wilson, K.W.

1994-09-01

Five test arrangements have been designed to support the Granular Bed Filter Development Program as defined in the Test Plan. The first arrangement is a 3.6 ft. diameter half filter, with a glass covering along the cross section to allow visual examination of the granular alumina material passing through the filter. The second test arrangement is a 3.6 ft diameter full size filter having refractory lining to simulate actual surface roughness conditions. The third test arrangement will examine filter geometry scale up by testing a 6.0 ft. diameter full size filter. The fourth Test Arrangement consists of a small 12more » inch diameter fluidizer to measure the minimum fluidization velocity of the 7 m (approx. size) alumina material to be used in the filter assemblies. The last Test Unit is used to evaluation relative abrasion characteristics of potential refractory and ceramic materials to be installed in high abrasion areas in the pneumatic transport piping.« less

Installing Mechanics of Granular Materials (MGM) experiment Test Cell

NASA Technical Reports Server (NTRS)

1996-01-01

Astronaut Jay Apt installs Mechanics of Granular Materials (MGM0 test cell on STS-79. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (Credit: NASA/John Space Center).

Mechanics of Granular Materials labeled hardware

NASA Technical Reports Server (NTRS)

2000-01-01

Mechanics of Granular Materials (MGM) flight hardware takes two twin double locker assemblies in the Space Shuttle middeck or the Spacehab module. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (Credit: NASA/MSFC).

LITERATURE REVIEWS TO SUPPORT ION EXCHANGE TECHNOLOGY SELECTION FOR MODULAR SALT PROCESSING

DOE Office of Scientific and Technical Information (OSTI.GOV)

King, W

2007-11-30

This report summarizes the results of literature reviews conducted to support the selection of a cesium removal technology for application in a small column ion exchange (SCIX) unit supported within a high level waste tank. SCIX is being considered as a technology for the treatment of radioactive salt solutions in order to accelerate closure of waste tanks at the Savannah River Site (SRS) as part of the Modular Salt Processing (MSP) technology development program. Two ion exchange materials, spherical Resorcinol-Formaldehyde (RF) and engineered Crystalline Silicotitanate (CST), are being considered for use within the SCIX unit. Both ion exchange materials havemore » been studied extensively and are known to have high affinities for cesium ions in caustic tank waste supernates. RF is an elutable organic resin and CST is a non-elutable inorganic material. Waste treatment processes developed for the two technologies will differ with regard to solutions processed, secondary waste streams generated, optimum column size, and waste throughput. Pertinent references, anticipated processing sequences for utilization in waste treatment, gaps in the available data, and technical comparisons will be provided for the two ion exchange materials to assist in technology selection for SCIX. The engineered, granular form of CST (UOP IE-911) was the baseline ion exchange material used for the initial development and design of the SRS SCIX process (McCabe, 2005). To date, in-tank SCIX has not been implemented for treatment of radioactive waste solutions at SRS. Since initial development and consideration of SCIX for SRS waste treatment an alternative technology has been developed as part of the River Protection Project Waste Treatment Plant (RPP-WTP) Research and Technology program (Thorson, 2006). Spherical RF resin is the baseline media for cesium removal in the RPP-WTP, which was designed for the treatment of radioactive waste supernates and is currently under construction in Hanford, WA. Application of RF for cesium removal in the Hanford WTP does not involve in-riser columns but does utilize the resin in large scale column configurations in a waste treatment facility. The basic conceptual design for SCIX involves the dissolution of saltcake in SRS Tanks 1-3 to give approximately 6 M sodium solutions and the treatment of these solutions for cesium removal using one or two columns supported within a high level waste tank. Prior to ion exchange treatment, the solutions will be filtered for removal of entrained solids. In addition to Tanks 1-3, solutions in two other tanks (37 and 41) will require treatment for cesium removal in the SCIX unit. The previous SCIX design (McCabe, 2005) utilized CST for cesium removal with downflow supernate processing and included a CST grinder following cesium loading. Grinding of CST was necessary to make the cesium-loaded material suitable for vitrification in the SRS Defense Waste Processing Facility (DWPF). Because RF resin is elutable (and reusable) and processing requires conversion between sodium and hydrogen forms using caustic and acidic solutions more liquid processing steps are involved. The WTP baseline process involves a series of caustic and acidic solutions (downflow processing) with water washes between pH transitions across neutral. In addition, due to resin swelling during conversion from hydrogen to sodium form an upflow caustic regeneration step is required. Presumably, one of these basic processes (or some variation) will be utilized for MSP for the appropriate ion exchange technology selected. CST processing involves two primary waste products: loaded CST and decontaminated salt solution (DSS). RF processing involves three primary waste products: spent RF resin, DSS, and acidic cesium eluate, although the resin is reusable and typically does not require replacement until completion of multiple treatment cycles. CST processing requires grinding of the ion exchange media, handling of solids with high cesium loading, and handling of liquid wash and conditioning solutions. RF processing requires handling and evaporation of cesium eluates, disposal of spent organic resin, and handling of the various liquid wash and regenerate solutions used. In both cases, the DSS will be immobilized in a low activity waste form. It appears that both technologies are mature, well studied, and generally suitable for this application. Technology selection will likely be based on downstream impacts or preferences between the various processing options for the two materials rather than on some unacceptable performance property identified for one material. As a result, the following detailed technical review and summary of the two technologies should be useful to assist in technology selection for SCIX.« less

Multi-scale mechanics of granular solids from grain-resolved X-ray measurements

NASA Astrophysics Data System (ADS)

Hurley, R. C.; Hall, S. A.; Wright, J. P.

2017-11-01

This work discusses an experimental technique for studying the mechanics of three-dimensional (3D) granular solids. The approach combines 3D X-ray diffraction and X-ray computed tomography to measure grain-resolved strains, kinematics and contact fabric in the bulk of a granular solid, from which continuum strains, grain stresses, interparticle forces and coarse-grained elasto-plastic moduli can be determined. We demonstrate the experimental approach and analysis of selected results on a sample of 1099 stiff, frictional grains undergoing multiple uniaxial compression cycles. We investigate the inter-particle force network, elasto-plastic moduli and associated length scales, reversibility of mechanical responses during cyclic loading, the statistics of microscopic responses and microstructure-property relationships. This work serves to highlight both the fundamental insight into granular mechanics that is furnished by combined X-ray measurements and describes future directions in the field of granular materials that can be pursued with such approaches.

76 FR 47147 - Pure Magnesium in Granular Form From the People's Republic of China: Rescission of Antidumping...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-04

.... SUPPLEMENTARY INFORMATION: Background On November 1, 2010, the Department published a notice of opportunity to... granular materials of which the Department is aware used to make such excluded reagents are: lime, calcium metal, calcium silicon, calcium carbide, calcium carbonate, carbon, slag coagulants, fluorspar...

Is Sulfur Limiting Maize Grown on Eroded Midwestern U.S. Soils?

USDA-ARS?s Scientific Manuscript database

The importance of adequate sulfur (S) for maize (Zea mays L.) production has been recognized for many years and recently confirmed by positive yield responses. We compared a granular S-enhanced fertilizer material [SEF (13-33-0-15S)], granular ammonium sulfate [AMS (21-0-0-24S)], and liquid ammonium...

Granular Gas in a Periodic Lattice

ERIC Educational Resources Information Center

Dorbolo, S.; Brandenbourger, M.; Damanet, F.; Dister, H.; Ludewig, F.; Terwagne, D.; Lumay, G.; Vandewalle, N.

2011-01-01

Glass beads are placed in the compartments of a horizontal square grid. This grid is then vertically shaken. According to the reduced acceleration [image omitted] of the system, the granular material exhibits various behaviours. By counting the number of beads in each compartment after shaking, it is possible to define three regimes. At low…

Electromagnetic phenomena in granular flows in the laboratory and dusty plasmas in geophysics and astrophysics

NASA Astrophysics Data System (ADS)

Lathrop, Daniel; Eiskowitz, Skylar; Rojas, Ruben

2017-11-01

In clouds of suspended particles, collisions electrify particles and the clouds produce electric potential differences over large scales. This is seen in the atmosphere as lightning in thunderstorms, thundersnow, dust storms, and volcanic ash plumes, but it is a general phenomena in granular systems. The electrification process is not well understood. To investigate the relative importance of particle material properties and collective phenomena in granular and atmospheric electrification, we used several tabletop experiments that excite particle-laden flows. Various electromagnetic phenomena ensue. Measured electric fields result from capacitive and direct charge transfer to electrodes. These results suggest that while particle properties do matter (as previous investigations have shown), macroscopic electrification of granular flows is somewhat material independent and large-scale collective phenomena play a major role. As well, our results on charge separation and Hall effects suggest a very different view of the dynamics of clouds, planetary rings, and cold accretion disks in proto-planetary systems. We gratefully acknowledge past funding from the Julian Schwinger Foundation as well as the Ph.D. work of Freja Nordsiek.

Advances in the simulation and automated measurement of well-sorted granular material: 1. Simulation

USGS Publications Warehouse

Daniel Buscombe,; Rubin, David M.

2012-01-01

1. In this, the first of a pair of papers which address the simulation and automated measurement of well-sorted natural granular material, a method is presented for simulation of two-phase (solid, void) assemblages of discrete non-cohesive particles. The purpose is to have a flexible, yet computationally and theoretically simple, suite of tools with well constrained and well known statistical properties, in order to simulate realistic granular material as a discrete element model with realistic size and shape distributions, for a variety of purposes. The stochastic modeling framework is based on three-dimensional tessellations with variable degrees of order in particle-packing arrangement. Examples of sediments with a variety of particle size distributions and spatial variability in grain size are presented. The relationship between particle shape and porosity conforms to published data. The immediate application is testing new algorithms for automated measurements of particle properties (mean and standard deviation of particle sizes, and apparent porosity) from images of natural sediment, as detailed in the second of this pair of papers. The model could also prove useful for simulating specific depositional structures found in natural sediments, the result of physical alterations to packing and grain fabric, using discrete particle flow models. While the principal focus here is on naturally occurring sediment and sedimentary rock, the methods presented might also be useful for simulations of similar granular or cellular material encountered in engineering, industrial and life sciences.

Universal robotic gripper based on the jamming of granular material

PubMed Central

Brown, Eric; Rodenberg, Nicholas; Amend, John; Mozeika, Annan; Steltz, Erik; Zakin, Mitchell R.; Lipson, Hod; Jaeger, Heinrich M.

2010-01-01

Gripping and holding of objects are key tasks for robotic manipulators. The development of universal grippers able to pick up unfamiliar objects of widely varying shape and surface properties remains, however, challenging. Most current designs are based on the multifingered hand, but this approach introduces hardware and software complexities. These include large numbers of controllable joints, the need for force sensing if objects are to be handled securely without crushing them, and the computational overhead to decide how much stress each finger should apply and where. Here we demonstrate a completely different approach to a universal gripper. Individual fingers are replaced by a single mass of granular material that, when pressed onto a target object, flows around it and conforms to its shape. Upon application of a vacuum the granular material contracts and hardens quickly to pinch and hold the object without requiring sensory feedback. We find that volume changes of less than 0.5% suffice to grip objects reliably and hold them with forces exceeding many times their weight. We show that the operating principle is the ability of granular materials to transition between an unjammed, deformable state and a jammed state with solid-like rigidity. We delineate three separate mechanisms, friction, suction, and interlocking, that contribute to the gripping force. Using a simple model we relate each of them to the mechanical strength of the jammed state. This advance opens up new possibilities for the design of simple, yet highly adaptive systems that excel at fast gripping of complex objects.

Active earth pressure model tests versus finite element analysis

NASA Astrophysics Data System (ADS)

Pietrzak, Magdalena

2017-06-01

The purpose of the paper is to compare failure mechanisms observed in small scale model tests on granular sample in active state, and simulated by finite element method (FEM) using Plaxis 2D software. Small scale model tests were performed on rectangular granular sample retained by a rigid wall. Deformation of the sample resulted from simple wall translation in the direction `from the soil" (active earth pressure state. Simple Coulomb-Mohr model for soil can be helpful in interpreting experimental findings in case of granular materials. It was found that the general alignment of strain localization pattern (failure mechanism) may belong to macro scale features and be dominated by a test boundary conditions rather than the nature of the granular sample.

Perspective: Evolutionary design of granular media and block copolymer patterns

NASA Astrophysics Data System (ADS)

Jaeger, Heinrich M.; de Pablo, Juan J.

2016-05-01

The creation of new materials "by design" is a process that starts from desired materials properties and proceeds to identify requirements for the constituent components. Such process is challenging because it inverts the typical modeling approach, which starts from given micro-level components to predict macro-level properties. We describe how to tackle this inverse problem using concepts from evolutionary computation. These concepts have widespread applicability and open up new opportunities for design as well as discovery. Here we apply them to design tasks involving two very different classes of soft materials, shape-optimized granular media and nanopatterned block copolymer thin films.

Breaking of rod-shaped model material during compression

NASA Astrophysics Data System (ADS)

Lukas, Kulaviak; Vera, Penkavova; Marek, Ruzicka; Miroslav, Puncochar; Petr, Zamostny; Zdenek, Grof; Frantisek, Stepanek; Marek, Schongut; Jaromir, Havlica

2017-06-01

The breakage of a model anisometric dry granular material caused by uniaxial compression was studied. The bed of uniform rod-like pasta particles (8 mm long, aspect ratio 1:8) was compressed (Gamlen Tablet Press) and their size distribution was measured after each run (Dynamic Image Analysing). The compression dynamics was recorded and the effect of several parameters was tested (rate of compression, volume of granular bed, pressure magnitude and mode of application). Besides the experiments, numerical modelling of the compressed breakable material was performed as well, employing the DEM approach (Discrete Element Method). The comparison between the data and the model looks promising.

Inhibitory effect of high NH4(+)-N concentration on anaerobic biotreatment of fresh leachate from a municipal solid waste incineration plant.

PubMed

Liu, Zhao; Dang, Yan; Li, Caihua; Sun, Dezhi

2015-09-01

Fresh leachate from municipal solid waste (MSW) incineration plants generally contains extremely high NH4(+)-N concentration which could inhibit the bioactivity of microorganisms. The inhibitory effect of high NH4(+)-N concentration on anaerobic biotreatment of fresh leachate from a MSW incineration plant in China has been investigated in this study. The inhibition processes was studied by both static tests and a laboratory-scale expanded granular sludge bed (EGSB) reactor. The specific methanogenic activity (SMA) of the microorganisms in anaerobic granular sludge was inhibited with the NH4(+)-N concentration increasing to 1000mg/L in static tests. As well the chemical oxygen demand (COD) removal efficiency and the methane yield decreased in the EGSB reactor, while the volatile fatty acids (VFAs) accumulated and extracellular polymeric substances (EPS) of the anaerobic granular sludge increased with NH4(+)-N concentration rising to 1000mg/L, without any rebounding during 30days of operation. Decreasing NH4(+)-N concentration to 500mg/L in influent, the COD removal efficiency recovered to about 85% after 26days. 1000mg/L of NH4(+)-N in leachate was suggested to be the inhibition threshold in EGSB reactor. High-throughput sequencing results showed little changes in microbial communities of the sludge for a high NH4(+)-N concentration, indicating that the survival of most microorganisms was not affected under such a condition. It inhibited the bioactivity of the microorganisms, resulting in decrease of the COD removal efficiency. Copyright © 2015 Elsevier Ltd. All rights reserved.

Modeling of the processes of natural and waste water purification in the reactor-clarifier

NASA Astrophysics Data System (ADS)

Primak, O. D.; Skolubovich, Yu. L.; Fedorova, N. N.; Voitov, E. L.

2018-03-01

The results of the filtration process simulation in a reactor-clarifier installation using a suspended loading layer are presented. Calculations were carried out in ANSYS Fluent on the basis of the Navier-Stokes equations supplemented by the equations of the Eulerian model of multiphase taking into account granularity of the particle phase. The unsteady picture of the formation of a fluidized («boiling») layer of particles is obtained. The results of parametric calculations allowing to estimate the effect of the flow velocity, the loading layer thickness, the thickness of sand and other parameters on the fluidized bed structure are presented. The liquid flow rate at which the loading grains are not washed out is determined. The diameter of particles and the height of the loading layer, at which the filter material is suspended and thus normal operation of the plant is ensured, are defined.

Application of the base catalyzed decomposition process to treatment of PCB-contaminated insulation and other materials associated with US Navy vessels. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmidt, A.J.; Zacher, A.H.; Gano, S.R.

1996-09-01

The BCD process was applied to dechlorination of two types of PCB-contaminated materials generated from Navy vessel decommissioning activities at Puget Sound Naval Shipyard: insulation of wool felt impregnated with PCB, and PCB-containing paint chips/debris from removal of paint from metal surfaces. The BCD process is a two-stage, low-temperature chemical dehalogenation process. In Stage 1, the materials are mixed with sodium bicarbonate and heated to 350 C. The volatilized halogenated contaminants (eg, PCBs, dioxins, furans), which are collected in a small volume of particulates and granular activated carbon, are decomposed by the liquid-phase reaction (Stage 2) in a stirred-tank reactor,more » using a high-boiling-point hydrocarbon oil as the reaction medium, with addition of a hydrogen donor, a base (NaOH), and a catalyst. The tests showed that treating wool felt insulation and paint chip wastes with Stage 2 on a large scale is feasible, but compared with current disposal costs for PCB-contaminated materials, using Stage 2 would not be economical at this time. For paint chips generated from shot/sand blasting, the solid-phase BCD process (Stage 1) should be considered, if paint removal activities are accelerated in the future.« less

Role of hydraulic retention time and granular medium in microbial removal in tertiary treatment reed beds.

PubMed

García, Joan; Vivar, Joan; Aromir, Maria; Mujeriego, Rafael

2003-06-01

The main objective of this paper is to evaluate the role of hydraulic retention time (HRT) and granular medium in faecal coliform (FC) and somatic coliphage (SC) removal in tertiary reed beds. Experiments were carried out in a pilot plant with four parallel reed beds (horizontal subsurface flow constructed wetlands), each one containing a different type of granular medium. This pilot plant is located in a wastewater treatment plant in Montcada i Reixac, near Barcelona, in northeastern Spain. The microbial inactivation ratios obtained in the different beds are compared as a function of three selected HRTs. Secondary effluent from the wastewater treatment plant was used as the influent of the pilot system. The microbial inactivation ratio ranged between 0.1 and 2.7 log-units for FC and from 0.5 to 1.7 log-units for SC in beds with coarser granular material (5-25mm), while it ranged between 0.7 and 3.4 log-units for FC and from 0.9 to 2.6 log-units for SC in the bed with finer material (2-13mm). HRT and granular medium are both key factors in microbial removal in the tertiary reed beds. The microbial inactivation ratio rises as the HRT increases until it reaches a saturation value (in general at an HRT of 3 days). The value of the microbial inactivation ratio at the saturation level depends on the granular medium contained in the bed. The specific surface area necessary to reach 2-3 log-units of FC and SC is approximately 3m(2)/person-equivalent.

Energy Content & Spectral Energy Representation of Wave Propagation in a Granular Chain

NASA Astrophysics Data System (ADS)

Shrivastava, Rohit; Luding, Stefan

2017-04-01

A mechanical wave is propagation of vibration with transfer of energy and momentum. Studying the energy as well as spectral energy characteristics of a propagating wave through disordered granular media can assist in understanding the overall properties of wave propagation through materials like soil. The study of these properties is aimed at modeling wave propagation for oil, mineral or gas exploration (seismic prospecting) or non-destructive testing for the study of internal structure of solids. Wave propagation through granular materials is often accompanied by energy attenuation which is quantified by Quality factor and this parameter has often been used to characterize material properties, hence, determining the Quality factor (energy attenuation parameter) can also help in determining the properties of the material [3], studied experimentally in [2]. The study of Energy content (Kinetic, Potential and Total Energy) of a pulse propagating through an idealized one-dimensional discrete particle system like a mass disordered granular chain can assist in understanding the energy attenuation due to disorder as a function of propagation distance. The spectral analysis of the energy signal can assist in understanding dispersion as well as attenuation due to scattering in different frequencies (scattering attenuation). The selection of one-dimensional granular chain also helps in studying only the P-wave attributes of the wave and removing the influence of shear or rotational waves. Granular chains with different mass distributions have been studied, by randomly selecting masses from normal, binary and uniform distributions and the standard deviation of the distribution is considered as the disorder parameter, higher standard deviation means higher disorder and lower standard deviation means lower disorder [1]. For obtaining macroscopic/continuum properties, ensemble averaging has been invoked. Instead of analyzing deformation-, velocity- or stress-signals, interpreting information from a Total Energy signal turned out to be much easier in comparison to displacement, velocity or acceleration signals of the wave, hence, indicating a better analysis method for wave propagation through granular materials. Increasing disorder decreases the Energy of higher frequency signals transmitted, but at the same time the energy of spatially localized high frequencies increases. Brian P. Lawney and Stefan Luding. Mass-disorder effects on the frequency filtering in one-dimensional discrete particle systems. AIP Conference Proceedings, 1542(1), 2013. Ibrahim Guven. Hydraulical and acoustical properties of porous sintered glass bead systems: experiments, theory and simulations (Doctoral dissertation). Rainer Tonn. Comparison of seven methods for the computation of Q. Physics of the Earth and Planetary Interiors, 55(3):259 - 268, 1989. Rohit Kumar Shrivastava and Stefan Luding.: Effect of Disorder on Bulk Sound Wave Speed : A Multiscale Spectral Analysis, Nonlin. Processes Geophys. Discuss., doi:10.5194/npg-2016-83, in review, 2017.

Two-Piece Screens for Decontaminating Granular Material

NASA Technical Reports Server (NTRS)

Backes, Douglas; Poulter, Clay; Godfrey, Max; Dutton, Melinda; Tolman, Dennis

2009-01-01

Two-piece screens have been designed specifically for use in filtering a granular material to remove contaminant particles that are significantly wider or longer than are the desired granules. In the original application for which the twopiece screens were conceived, the granular material is ammonium perchlorate and the contaminant particles tend to be wires and other relatively long, rigid strands. The basic design of the twopiece screens can be adapted to other granular materials and contaminants by modifying critical dimensions to accommodate different grain and contaminant- particle sizes. A two-piece screen of this type consists mainly of (1) a top flat plate perforated with circular holes arranged in a hexagonal pattern and (2) a bottom plate that is also perforated with circular holes (but not in a pure hexagonal pattern) and is folded into an accordion structure. Fabrication of the bottom plate begins with drilling circular holes into a flat plate in a hexagonal pattern that is interrupted, at regular intervals, by parallel gaps. The plate is then folded into the accordion structure along the gaps. Because the folds are along the gaps, there are no holes at the peaks and valleys of the accordion screen. The top flat plate and the bottom accordion plate are secured within a metal frame. The resulting two-piece screen is placed at the bottom opening of a feed hopper containing the granular material to be filtered. Tests have shown that such long, rigid contaminant strands as wires readily can pass through a filter consisting of the flat screen alone and that the addition of the accordion screen below the flat screen greatly increases the effectiveness of removal of wires and other contaminant strands. Part of the reason for increased effectiveness is in the presentation of the contaminant to the filter surface. Testing has shown that wire type contamination will readily align itself parallel to the material direction flow. Since this direction of flow is nearly always perpendicular to the filter surface holes, the contamination is automatically aligned to pass through. The two-filter configuration reduces the likelihood that a given contaminant strand will be aligned with the flow of material by eliminating the perpendicular presentation angle. Thus, for wires of a certain diameter, a two-piece screen is 20 percent more effective than is the corresponding flat perforated plate alone, even if the holes in the flat plate are narrower. An accordion screen alone is similarly effective in catching contaminants, but lumps of agglomerated granules of the desired material often collect in the valleys and clog the screen. The addition of a flat screen above the accordion screen prevents clogging of the accordion screen. Flat wire screens have often been used to remove contaminants from granular materials, and are about as effective as are the corresponding perforated flat plates used alone.

Numerical simulation of granular flows : comparison with experimental results

NASA Astrophysics Data System (ADS)

Pirulli, M.; Mangeney-Castelnau, A.; Lajeunesse, E.; Vilotte, J.-P.; Bouchut, F.; Bristeau, M. O.; Perthame, B.

2003-04-01

Granular avalanches such as rock or debris flows regularly cause large amounts of human and material damages. Numerical simulation of granular avalanches should provide a useful tool for investigating, within realistic geological contexts, the dynamics of these flows and of their arrest phase and for improving the risk assessment of such natural hazards. Validation of debris avalanche numerical model on granular experiments over inclined plane is performed here. The comparison is performed by simulating granular flow of glass beads from a reservoir through a gate down an inclined plane. This unsteady situation evolves toward the steady state observed in the laboratory. Furthermore simulation exactly reproduces the arrest phase obtained by suddenly closing the gate of the reservoir once a thick flow has developped. The spreading of a granular mass released from rest at the top of a rough inclined plane is also investigated. The evolution of the avalanche shape, the velocity and the characteristics of the arrest phase are compared with experimental results and analysis of the involved forces are studied for various flow laws.

Taming the complexity of granular materials with vector calculus

DTIC Science & Technology

2009-07-29

by 13 c c jk k ke l l or 1 3ˆ c cl l x , where eijk is the Levi - Civita symbol, defi ned by: 0 for , or 1 for , , 1, 2, 3 , 2, 3,1 , 3,1, 2 1...the assumption that the body is continuous and comprises material points that bear only translational degrees of freedom. By contrast, a granular...a continuous body gives rise to a combination of rigid body motion and a change in shape of the body . The change in shape is called deformation

Influence of particle shape on the microstructure evolution and the mechanical properties of granular materials

NASA Astrophysics Data System (ADS)

Tian, Jianqiu; Liu, Enlong; Jiang, Lian; Jiang, Xiaoqiong; Sun, Yi; Xu, Ran

2018-06-01

In order to study the influence of particle shape on the microstructure evolution and the mechanical properties of granular materials, a two-dimensional DEM analysis of samples with three particle shapes, including circular particles, triangular particles, and elongated particles, is proposed here to simulate the direct shear tests of coarse-grained soils. For the numerical test results, analyses are conducted in terms of particle rotations, fabric evolution, and average path length evolution. A modified Rowe's stress-dilatancy equation is also proposed and successfully fitted onto simulation data.

A comprehensive study of MPI parallelism in three-dimensional discrete element method (DEM) simulation of complex-shaped granular particles

NASA Astrophysics Data System (ADS)

Yan, Beichuan; Regueiro, Richard A.

2018-02-01

A three-dimensional (3D) DEM code for simulating complex-shaped granular particles is parallelized using message-passing interface (MPI). The concepts of link-block, ghost/border layer, and migration layer are put forward for design of the parallel algorithm, and theoretical scalability function of 3-D DEM scalability and memory usage is derived. Many performance-critical implementation details are managed optimally to achieve high performance and scalability, such as: minimizing communication overhead, maintaining dynamic load balance, handling particle migrations across block borders, transmitting C++ dynamic objects of particles between MPI processes efficiently, eliminating redundant contact information between adjacent MPI processes. The code executes on multiple US Department of Defense (DoD) supercomputers and tests up to 2048 compute nodes for simulating 10 million three-axis ellipsoidal particles. Performance analyses of the code including speedup, efficiency, scalability, and granularity across five orders of magnitude of simulation scale (number of particles) are provided, and they demonstrate high speedup and excellent scalability. It is also discovered that communication time is a decreasing function of the number of compute nodes in strong scaling measurements. The code's capability of simulating a large number of complex-shaped particles on modern supercomputers will be of value in both laboratory studies on micromechanical properties of granular materials and many realistic engineering applications involving granular materials.

Novel Discrete Element Method for 3D non-spherical granular particles.

NASA Astrophysics Data System (ADS)

Seelen, Luuk; Padding, Johan; Kuipers, Hans

2015-11-01

Granular materials are common in many industries and nature. The different properties from solid behavior to fluid like behavior are well known but less well understood. The main aim of our work is to develop a discrete element method (DEM) to simulate non-spherical granular particles. The non-spherical shape of particles is important, as it controls the behavior of the granular materials in many situations, such as static systems of packed particles. In such systems the packing fraction is determined by the particle shape. We developed a novel 3D discrete element method that simulates the particle-particle interactions for a wide variety of shapes. The model can simulate quadratic shapes such as spheres, ellipsoids, cylinders. More importantly, any convex polyhedron can be used as a granular particle shape. These polyhedrons are very well suited to represent non-rounded sand particles. The main difficulty of any non-spherical DEM is the determination of particle-particle overlap. Our model uses two iterative geometric algorithms to determine the overlap. The algorithms are robust and can also determine multiple contact points which can occur for these shapes. With this method we are able to study different applications such as the discharging of a hopper or silo. Another application the creation of a random close packing, to determine the solid volume fraction as a function of the particle shape.

Erosion of a wet/dry granular interface

NASA Astrophysics Data System (ADS)

Jop, Pierre; Lefebvre, Gautier

2013-04-01

To model the dynamic of landslides, the evolution of the interface between the erodible ground and the flowing material is still studied experimentally or numerically (ie. Mangeney et al. 2010, Iverson 2012). In some cases, the basal material is more cohesive than the flowing one. Such situation arises for example due to cementation or humidity. What are the exchange rates between these phases? What is the coupling between the evolution of the interface and the flow? We studied the erosion phenomenon and performed laboratory experiments to focus on the interaction between a cohesive unsaturated granular material and a dry granular flow. Both materials were spherical grains, the cohesion being induced by adding a given mass of liquid to the grains. Two configurations were explored: a circular aggregate submitted to a dry flow in a rotating drum, and a granular flow eroding a wet granular pile. First, we focused on the influence of the cohesion, controlled by the liquid properties, such as the surface tension and the viscosity. Then the flow characteristics were modified by varying the grain size and density. These results allowed us to present a model for the erosion mechanisms, based on the flow and fluid properties. The main results are the need to take into account the whole probability distribution the stress applied on the wet grains and that both the surface tension and the viscosity are important since they play a different roles. The latter is mainly responsible of the time scale of the dynamic of a wet grain, while the former acts as a threshold on the force distribution. In the second configuration, we could also control the inclination of the slope. This system supported the previous model and moreover revealed an interface instability, leading the formation of steep steps, which is a reminiscence of the cyclic-steps observed during river-channel incision (Parker and Izumi 2000). We will present the dynamics of such granular steps. [1] Mangeney, A., O. Roche, O. Hungr, N. Mangold, G. Faccanoni, and A. Lucas (2010), Erosion and mobility in granular collapse over sloping beds, J. Geophys. Res., 115, F03040, doi:10.1029/2009JF001462. [2] Iverson, R. M. (2012), Elementary theory of bed-sediment entrainment by debris flows and avalanches, J. Geophys. Res., 117, F03006, doi:10.1029/2011JF002189. [3] Parker G.and Izumi N., Purely erosional cyclic and solitary steps created by flow over a cohesive bed, J. Fluid Mech. (2000), vol. 419, pp. 203-238.

Computational Modeling of Interfacial Behaviors in Nanocomposite Materials

PubMed Central

Lin, Liqiang; Wang, Xiaodu; Zeng, Xiaowei

2017-01-01

Towards understanding the bulk material response in nanocomposites, an interfacial zone model was proposed to define a variety of material interface behaviors (e.g. brittle, ductile, rubber-like, elastic-perfectly plastic behavior etc.). It also has the capability to predict bulk material response though independently control of the interface properties (e.g. stiffness, strength, toughness). The mechanical response of granular nanocomposite (i.e. nacre) was investigated through modeling the “relatively soft” organic interface as an interfacial zone among “hard” mineral tablets and simulation results were compared with experimental measurements of stress-strain curves in tension and compression tests. Through modeling varies material interfaces, we found out that the bulk material response of granular nanocomposite was regulated by the interfacial behaviors. This interfacial zone model provides a possible numerical tool for qualitatively understanding of structure-property relationships through material interface design. PMID:28983123

Tuning ligament shape in dealloyed nanoporous tin and the impact of nanoscale morphology on its applications in Na-ion alloy battery anodes

NASA Astrophysics Data System (ADS)

Detsi, Eric; Petrissans, Xavier; Yan, Yan; Cook, John B.; Deng, Ziling; Liang, Yu-Lun; Dunn, Bruce; Tolbert, Sarah H.

2018-05-01

Control over the morphology of nanostructured materials is of primary importance in structure-property relationship studies. Although the size of ligaments and pores in dealloyed nanoporous metals can be controlled by thermal and/or (electro)chemical treatments, tuning the shape of those ligaments is much harder. In the present work, we use corroding media with different reactivity to effectively tailor the ligament shape in nanoporous tin (NP-Sn) during dealloying by free corrosion. NP-Sn architectures with nanowire and granular ligament shapes were made by controlling the pH of the corroding solution, and thus the rate of Sn oxidation relative to the etching rate of the sacrificial component. The standard nanowire structure was formed under acidic conditions where oxidation was slow, but a hierarchical granular structure was formed when fusion of the Sn nanocrystals was inhibited by surface oxidation. To demonstrate the advantages of this architectural control, these two materials systems were investigated as electrodes for Na-ion battery anodes. Similar initial Na storage capacities of ˜500 and 550 mAh/g were achieved in the nanowire and granular materials, respectively, but the cycle life of the two materials was quite different. NP-Sn with a granular ligament shape showed enhanced stability with a capacity retention of ˜55 % over 95 cycles at a specific current of 40 mA/g. By contrast, NP-Sn with a nanowire ligament shape showed very fast capacity fading within the first 10 cycles. This work thus demonstrates the dramatic impact of the nanoscale morphology on the electrochemical performance of nanoporous materials and highlights the need for both shape and size control in dealloyed nanoporous metals.

Predicting Thermal Conductivity

NASA Technical Reports Server (NTRS)

Penn, B.; Ledbetter, F. E., III; Clemons, J.

1984-01-01

Empirical equation predicts thermal conductivity of composite insulators consisting of cellular, granular or fibrous material embedded in matrix of solid viscoelastic material. Application in designing custom insulators for particular environments.

The formation of granular fronts in debris flow - A combined experimental-numerical study

NASA Astrophysics Data System (ADS)

Leonardi, Alessandro; Cabrera, Miguel; Wittel, Falk K.; Kaitna, Roland; Mendoza, Miller; Wu, Wei; Herrmann, Hans J.

2015-04-01

Granular fronts are amongst the most spectacular features of debris flows, and are also one of the reasons why such events are associated with a strong destructive power. They are usually believed to be the result of the convective mechanism of the debris flow, combined with internal size segregation of the grains. However, the knowledge about the conditions leading to the formation of a granular front is not up to date. We present a combined study with experimental and numerical features that aims at providing insight into the phenomenon. A stationary, long-lived avalanche is created within a rotating drum. In order to mimic the composition of an actual debris flow, the material is composed by a mixture of a plastic fluid, obtained with water and kaolin powder, and a collection of monodisperse spherical particles heavier than the fluid. Tuning the material properties and the drum settings, we are able to reproduce and control the formation of a granular front. To gain insight into the internal mechanism, the same scenario is replicated in a numerical environment, using a coupling technique between a discrete solver for the particles, the Discrete Element Method, and a continuum solver for the plastic fluid, the Lattice-Boltzmann Method. The simulations compare well with the experiments, and show the internal reorganization of the material transport. The formation of a granular front is shown to be favored by a higher drum rotational speed, which in turn forces a higher shear rate on the particles, breaks their internal organization, and contrasts their natural tendency to settle. Starting from dimensional analysis, we generalize the obtained results and are able to draw implications for debris flow research.

Optimization of the dynamic behavior of strongly nonlinear heterogeneous materials

NASA Astrophysics Data System (ADS)

Herbold, Eric B.

New aspects of strongly nonlinear wave and structural phenomena in granular media are developed numerically, theoretically and experimentally. One-dimensional chains of particles and compressed powder composites are the two main types of materials considered here. Typical granular assemblies consist of linearly elastic spheres or layers of masses and effective nonlinear springs in one-dimensional columns for dynamic testing. These materials are highly sensitive to initial and boundary conditions, making them useful for acoustic and shock-mitigating applications. One-dimensional assemblies of spherical particles are examples of strongly nonlinear systems with unique properties. For example, if initially uncompressed, these materials have a sound speed equal to zero (sonic vacuum), supporting strongly nonlinear compression solitary waves with a finite width. Different types of assembled metamaterials will be presented with a discussion of the material's response to static compression. The acoustic diode effect will be presented, which may be useful in shock mitigation applications. Systems with controlled dissipation will also be discussed from an experimental and theoretical standpoint emphasizing the critical viscosity that defines the transition from an oscillatory to monotonous shock profile. The dynamic compression of compressed powder composites may lead to self-organizing mesoscale structures in two and three dimensions. A reactive granular material composed of a compressed mixture of polytetrafluoroethylene (PTFE), tungsten (W) and aluminum (Al) fine-grain powders exhibit this behavior. Quasistatic, Hopkinson bar, and drop-weight experiments show that composite materials with a high porosity and fine metallic particles exhibit a higher strength than less porous mixtures with larger particles, given the same mass fraction of constituents. A two-dimensional Eulerian hydrocode is implemented to investigate the mechanical deformation and failure of the compressed powder samples in simulated drop-weight tests. The calculations indicate that the dynamic formation of mesoscale force chains increase the strength of the sample. This is also apparent in three-dimensional finite element calculations of drop-weight test simulations using LS-Dyna despite a higher granular bulk coordination number, and an increased mobility of individual grains.

Hydrogen sulfide removal from sediment and water in box culverts/storm drains by iron-based granules.

PubMed

Sun, J L; Shang, C; Kikkert, G A

2013-01-01

A renewable granular iron-based technology for hydrogen sulfide removal from sediment and water in box culverts and storm drains is discussed. Iron granules, including granular ferric hydroxide (GFH), granular ferric oxide (GFO) and rusted waste iron crusts (RWIC) embedded in the sediment phase removed aqueous hydrogen sulfide formed from sedimentary biological sulfate reduction. The exhausted iron granules were exposed to dissolved oxygen and this regeneration process recovered the sulfide removal capacities of the granules. The recovery is likely attributable to the oxidation of the ferrous iron precipitates film and the formation of new reactive ferric iron surface sites on the iron granules and sand particles. GFH and RWIC showed larger sulfide removal capacities in the sediment phase than GFO, likely due to the less ordered crystal structures on their surfaces. This study demonstrates that the iron granules are able to remove hydrogen sulfide from sediment and water in box culverts and storm drains and they have the potential to be regenerated and reused by contacting with dissolved oxygen.

Torsional rheometer for granular materials slurries and gas-solid mixtures and related methods

DOEpatents

Rajagopal, C.; Rajagopal, K.R.; Yalamanchili, R.C.

1997-03-11

A torsional rheometer apparatus for determining rheological properties of a specimen is provided. A stationary plate and a rotatable plate are in generally coaxial position and structured to receive a specimen there between. In one embodiment, at least one of the plates and preferably both have roughened specimen engaging surfaces to serve to reduce undesired slippage between the plate and the specimen. A motor is provided to rotate the rotatable plate and a transducer for monitoring forces applied to the stationary plate and generating output signals to a computer which determines the desired rheological properties are provided. In one embodiment, the roughened surfaces consist of projections extending toward the specimen. Where granular material is being evaluated, it is preferred that the roughness of the plate is generally equal to the average size of the granular material being processed. In another embodiment, an air-solid mixture is processed and the roughened portions are pore openings in the plates. Air flows through the region between the two pore containing plates to maintain the solid materials in suspension. In yet another embodiment, the base of the stationary plate is provided with a deformable capacitance sensor and associated electronic means. 17 figs.

Torsional rheometer for granular materials slurries and gas-solid mixtures and related methods

DOEpatents

Rajagopal, Chandrika; Rajagopal, Kumbakonam R.; Yalamanchili, Rattaya C.

1997-01-01

A torsional rheometer apparatus for determining rheological properties of a specimen is provided. A stationary plate and a rotatable plate are in generally coaxial position and structured to receive a specimen therebetween. In one embodiment, at least one of the plates and preferably both have roughened specimen engaging surfaces to serve to reduce undesired slippage between the plate and the specimen. A motor is provided to rotate the rotatable plate and a transducer for monitoring forces applied to the stationary plate and generating output signals to a computer which determines the desired rheological properties are provided. In one embodiment, the roughened surfaces consist of projections extending toward the specimen. Where granular material is being evaluated, it is preferred that the roughness of the plate is generally equal to the average size of the granular material being processed. In another embodiment, an air-solid mixture is processed and the roughened portions are pore openings in the plates. Air flows through the region between the two pore containing plates to maintain the solid materials in suspension. In yet another embodiment, the base of the stationary plate is provided with a deformable capacitance sensor and associated electronic means.

A new data-processing approach to study particle motion using ultrafast X-ray tomography scanner: case study of gravitational mass flow

NASA Astrophysics Data System (ADS)

Waktola, Selam; Bieberle, Andre; Barthel, Frank; Bieberle, Martina; Hampel, Uwe; Grudzień, Krzysztof; Babout, Laurent

2018-04-01

In most industrial products, granular materials are often required to flow under gravity in various kinds of silo shapes and usually through an outlet in the bottom. There are several interrelated parameters which affect the flow, such as internal friction, bulk and packing density, hopper geometry, and material type. Due to the low-spatial resolution of electrical capacitance tomography or scanning speed limitation of standard X-ray CT systems, it is extremely challenging to measure the flow velocity and possible centrifugal effects of granular materials flow effectively. However, ROFEX (ROssendorf Fast Electron beam X-ray tomography) opens new avenues of granular flow investigation due to its very high temporal resolution. This paper aims to track particle movements and evaluate the local grain velocity during silo discharging process in the case of mass flow. The study has considered the use of the Seramis material, which can also serve as a type of tracer particles after impregnation, due to its porous nature. The presented novel image processing and analysis approach allows satisfyingly measuring individual particle velocities but also tracking their lateral movement and three-dimensional rotations.

Effectiveness of an anaerobic granular activated carbon fluidized-bed bioreactor to treat soil wash fluids: a proposed strategy for remediating PCP/PAH contaminated soils.

PubMed

Koran, K M; Suidan, M T; Khodadoust, A P; Sorial, G A; Brenner, R C

2001-07-01

An integrated system has been developed to remediate soils contaminated with pentachlorophenol (PCP) and polycyclic aromatic hydrocarbons (PAHs). This system involves the coupling of two treatment technologies, soil-solvent washing and anaerobic biotreatment of the extract. Specifically, this study evaluated the effectiveness of a granular activated carbon (GAC) fluidized-bed reactor to treat a synthetic-waste stream of PCP and four PAHs (naphthalene, acenaphthene, pyrene, and benzo(b)fluoranthene) under anaerobic conditions. This waste stream was intended to simulate the wash fluids from a soil washing process treating soils from a wood-preserving site. The reactor achieved a removal efficiency of greater than 99.8% for PCP with conversion to its dechlorination intermediates averaging 46.5%. Effluent, carbon extraction, and isotherm data also indicate that naphthalene and acenaphthene were removed from the liquid phase with efficiencies of 86 and 93%, respectively. Effluent levels of pyrene and benzo(b)fluoranthene were extremely low due to the high-adsorptive capacity of GAC for these compounds. Experimental evidence does not suggest that the latter two compounds were biochemically transformed within the reactor.

Density waves in granular flow

NASA Astrophysics Data System (ADS)

Herrmann, H. J.; Flekkøy, E.; Nagel, K.; Peng, G.; Ristow, G.

Ample experimental evidence has shown the existence of spontaneous density waves in granular material flowing through pipes or hoppers. Using Molecular Dynamics Simulations we show that several types of waves exist and find that these density fluctuations follow a 1/f spectrum. We compare this behaviour to deterministic one-dimensional traffic models. If positions and velocities are continuous variables the model shows self-organized criticality driven by the slowest car. We also present Lattice Gas and Boltzmann Lattice Models which reproduce the experimentally observed effects. Density waves are spontaneously generated when the viscosity has a nonlinear dependence on density which characterizes granular flow.

Granular Rayleigh-Taylor instability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vinningland, Jan Ludvig; Johnsen, Oistein; Flekkoey, Eirik G.

2009-06-18

A granular instability driven by gravity is studied experimentally and numerically. The instability arises as grains fall in a closed Hele-Shaw cell where a layer of dense granular material is positioned above a layer of air. The initially flat front defined by the grains subsequently develops into a pattern of falling granular fingers separated by rising bubbles of air. A transient coarsening of the front is observed right from the start by a finger merging process. The coarsening is later stabilized by new fingers growing from the center of the rising bubbles. The structures are quantified by means of Fouriermore » analysis and quantitative agreement between experiment and computation is shown. This analysis also reveals scale invariance of the flow structures under overall change of spatial scale.« less

Scaled experiments to determine the role of density on granular flows behavior: preliminary results

NASA Astrophysics Data System (ADS)

Rodriguez Sedano, L. A.; Sarocchi, D.; Borselli, L.; Segura, O.

2013-12-01

Geological granular flows are very complex, gravity driven phenomena which can show different behaviors depending on its origin and the characteristics of the constituent material. Due to their dangerous nature, and multiple scientific and technological applications, these phenomena has being studied deeply in order to have a better comprehension, however, after more than one century of scientific research it remains as an open topic with more questions than answers. One of the aspects that still need exhaustive research is the effect of clast density on the flowing granular material, as pointed out by previous laboratory and field studies. There are anyway few studies which have tried to explain the role of bulk density, as well the density of different phases, as it increasing or decreasing on the kinematic and the rheological characteristics of geological granular flows. The content of low density juvenile material seems to condition the processes of transformations of debris flows to more diluted phases, as well the transport and emplacing mechanisms. It is well known that the content of clay in debris flows has great influence on its behavior, physical processes and the deposits characteristics for this reason lahars has being subdivided in base of this parameter. Our hypothesis is that, in like manner, the presence of low density material inside the granular flows (dry and wet) could conditioning its physical characteristics and its behavior. In order to put this to the test, we made some laboratory experiments using a five meter long and 0.3 m wide experimental flume equipped with a wide range of sensors and laser barriers to precisely measure the rheological properties and kinematic of the sliding avalanches. A special effort was devoted to determine a threshold or critical level in the amount of low density material at which the avalanche behavior suffer appreciable changes. The obtained preliminary results confirm our hypothesis and encouraged to perform further experiments. Such studies are important because they could provide useful information for developing analog models that take into account this important physical property.

"EGM" (Electrostatics of Granular Matter): A Space Station Experiment to Examine Natural Particulate Systems

NASA Astrophysics Data System (ADS)

Marshall, J.; Sauke, T.; Buehler, M.; Farrell, W.; Green, R.; Birchenough, A.

1999-09-01

A granular-materials experiment is being developed for a 2002 launch for Space Station deployment. The experiment is funded by NASA HQ and managed through NASA Lewis Research Center. The experiment will examine electrostatic aggregation of coarse granular materials with the goals of (a) obtaining proof for an electrostatic dipole model of grain interactions, and (b) obtaining knowledge about the way aggregation affects the behavior of natural particulate masses: (1) in unconfined dispersions (clouds such as nebulae, aeolian dust palls, volcanic plumes), (2) in semi-confined, self-loaded masses as in fluidized flows (pyroclastic surges, avalanches) and compacted regolith, or (3) in semi-confined non-loaded masses as in dust layers adhering to solar cells or space suits on Mars. The experiment addresses both planetary/astrophysical issues as well as practical concerns for human exploration of Mars or other solar system bodies. Additional information is contained in the original.

Rheology of wet granular materials under continuous shear: experiments and simulations

NASA Astrophysics Data System (ADS)

Badetti, Michel; Fall, Abdoulaye; Roux, Jean-Noël

2017-06-01

The behaviour of wet granular media in shear flow is characterized by the dependence of apparent friction μ* and solid fraction Φs on the reduced pressure P* and the inertia number I. Reduced pressure, P* = σ22a2/F0, compares the applied normal stress σ22 on grains of diameter a to the tensile strength of contact F0 (proportional to the surface tension D of the liquid and the beads diameter). A specifically modified rotational rheometer is used to characterize the response of model wet granular material to applied shear rate \\dot γ under controlled normal stress σ22. Discrete Element Method (DEM) simulations in 3D are carried out in parallel and numerical results are compared with experimental ones. Cohesive, inertia, saturation and viscous effects on macroscopic coefficient of friction μ* and solid fraction Φs are discussed.

Influence of dry cohesion on the micro- and macro-mechanical properties of dense polydisperse powders & grains

NASA Astrophysics Data System (ADS)

Kievitsbosch, Robert; Smit, Hendrik; Magnanimo, Vanessa; Luding, Stefan; Taghizadeh, Kianoosh

2017-06-01

Understanding how cohesive granular materials behave is of interest for many industrial applications, such as pharmaceutical or food and civil engineering. Models of the behaviour of granular materials on the microscopic scale can be used to obtain macroscopic continuum relations by a micro-macro transition approach. The Discrete Element Method (DEM) is used to inspect the influence of cohesion on the micro and macro behaviour of granular assemblies by using an elasto-plastic cohesive contact model. Interestingly, we observe that frictional samples prepared with different cohesion values show a significant difference in pressure and coordination number in the jammed regime; the differences become more pronounced when packings are closer to the jamming density, i.e. the lowest density where the system is mechanically stable. Furthermore, we observe that cohesion has an influence on the jamming density for frictional samples, but there is no influence on the jamming density for frictionless samples.

Motion Imagery and Robotics Application (MIRA): Standards-Based Robotics

NASA Technical Reports Server (NTRS)

Martinez, Lindolfo; Rich, Thomas; Lucord, Steven; Diegelman, Thomas; Mireles, James; Gonzalez, Pete

2012-01-01

This technology development originated from the need to assess the debris threat resulting from soil material erosion induced by landing spacecraft rocket plume impingement on extraterrestrial planetary surfaces. The impact of soil debris was observed to be highly detrimental during NASA s Apollo lunar missions and will pose a threat for any future landings on the Moon, Mars, and other exploration targets. The innovation developed under this program provides a simulation tool that combines modeling of the diverse disciplines of rocket plume impingement gas dynamics, granular soil material liberation, and soil debris particle kinetics into one unified simulation system. The Unified Flow Solver (UFS) developed by CFDRC enabled the efficient, seamless simulation of mixed continuum and rarefied rocket plume flow utilizing a novel direct numerical simulation technique of the Boltzmann gas dynamics equation. The characteristics of the soil granular material response and modeling of the erosion and liberation processes were enabled through novel first principle-based granular mechanics models developed by the University of Florida specifically for the highly irregularly shaped and cohesive lunar regolith material. These tools were integrated into a unique simulation system that accounts for all relevant physics aspects: (1) Modeling of spacecraft rocket plume impingement flow under lunar vacuum environment resulting in a mixed continuum and rarefied flow; (2) Modeling of lunar soil characteristics to capture soil-specific effects of particle size and shape composition, soil layer cohesion and granular flow physics; and (3) Accurate tracking of soil-borne debris particles beginning with aerodynamically driven motion inside the plume to purely ballistic motion in lunar far field conditions.

A test of the double-shearing model of flow for granular materials

USGS Publications Warehouse

Savage, J.C.; Lockner, D.A.

1997-01-01

The double-shearing model of flow attributes plastic deformation in granular materials to cooperative slip on conjugate Coulomb shears (surfaces upon which the Coulomb yield condition is satisfied). The strict formulation of the double-shearing model then requires that the slip lines in the material coincide with the Coulomb shears. Three different experiments that approximate simple shear deformation in granular media appear to be inconsistent with this strict formulation. For example, the orientation of the principal stress axes in a layer of sand driven in steady, simple shear was measured subject to the assumption that the Coulomb failure criterion was satisfied on some surfaces (orientation unspecified) within the sand layer. The orientation of the inferred principal compressive axis was then compared with the orientations predicted by the double-shearing model. The strict formulation of the model [Spencer, 1982] predicts that the principal stress axes should rotate in a sense opposite to that inferred from the experiments. A less restrictive formulation of the double-shearing model by de Josselin de Jong [1971] does not completely specify the solution but does prescribe limits on the possible orientations of the principal stress axes. The orientations of the principal compression axis inferred from the experiments are probably within those limits. An elastoplastic formulation of the double-shearing model [de Josselin de Jong, 1988] is reasonably consistent with the experiments, although quantitative agreement was not attained. Thus we conclude that the double-shearing model may be a viable law to describe deformation of granular materials, but the macroscopic slip surfaces will not in general coincide with the Coulomb shears.

An experimental study of low velocity impacts into granular material in reduced gravity

NASA Astrophysics Data System (ADS)

Murdoch, Naomi; Avila Martinez, Iris; Sunday, Cecily; Cherrier, Olivier; Zenou, Emanuel; Janin, Tristan; Cadu, Alexandre; Gourinat, Yves; Mimoun, David

2016-04-01

The granular nature of asteroid surfaces, in combination with the low surface gravity, makes it difficult to predict lander - surface interactions from existing theoretical models. Nonetheless, an understanding of such interactions is particularly important for the deployment of a lander package. This was demonstrated by the Philae lander, which bounced before coming to rest roughly 1 kilometer away from its intended landing site on the surface of comet 67P/Churyumov-Gerasimenko before coming to rest (Biele et al., 2015). In addition to being important for planning the initial deployment, information about the acceleration profile upon impact is also important in the choice of scientific payloads that want to exploit the initial landing to study the asteroid surface mechanical properties (e.g., Murdoch et al., 2016). Using the ISAE-SUPAERO drop tower, we have performed a series of low-velocity collisions into granular material in low gravity. Reduced-gravity is simulated by releasing a free-falling projectile into a surface container with a downward acceleration less than that of Earth's gravity. The acceleration of the surface is controlled through the use an Atwood machine, or a system of pulleys and counterweights. In reducing the effective surface acceleration of the granular material, the confining pressure will be reduced, and the properties of the granular material will become more representative of those on an asteroid's surface. In addition, since both the surface and projectile are falling, the projectile requires a minimum amount of time to catch the surface before the collision begins. This extended free-fall increases the experiment duration, making it easier to use accelerometers and high-speed cameras for data collection. The experiment is built into an existing 5.5 m drop-tower frame and has required the custom design of all components, including the projectile, surface sample container, release mechanism and deceleration system (Sunday et al., 2016). Previous experiments using similar methods have demonstrated the important role of gravity in the peak accelerations and collision timescales during low velocity granular impacts (Goldman and Umbanhower, 2007; Alsthuler et al., 2013). The design of our experiment accommodates collision velocities and effective accelerations that are lower than in previous experiments (<20 cm/s and ˜0.1 - 1.0 m/s2, respectively), allowing us to come closer to the conditions that may be encountered by current and future small body missions. [1] Altshuler, E., et al., "Extraterrestrial sink dynamics in granular matter", arXiv 1305.6796, 2013. [2] Biele, J., et al., "The landing(s) of Philae and inferences about comet surface mechanical properties", Science, 349 (6247), 2015. [3] Goldman, D. I., Umbanhowar, P., Scaling and dynamics of sphere and disk impact into granular media, Physics Review E 77 (2), (2008) 021308. [4] Murdoch, N., et al. "Investigating the surface and subsurface properties of the Didymos binary asteroid with a landed CubeSat", EGU, 2016. [5] Sunday, C., et al., "An original facility for reduced-gravity testing: a set-up for studying low-velocity collisions into granular surfaces", Submitted to the Review of Scientific Instruments, 2016.

Nonlocal approach to the analysis of the stress distribution in granular systems. II. Application to experiment

NASA Astrophysics Data System (ADS)

Scott, J. E.; Kenkre, V. M.; Hurd, A. J.

1998-05-01

A theory of stress propagation in granular materials developed recently [Kenkre, Scott, Pease, and Hurd, preceding paper, Phys. Rev. E 57, 5841 (1998)] is applied to the compaction of ceramic and metal powders in pipes with previously unexplained experimental features such as nonmonotonic density and stress variation along the axis of cylindrical compacts.

Increasing the formability of ferritic stainless steel tube by granular medium-based hot forming

NASA Astrophysics Data System (ADS)

Chen, H.; Staupendahl, D.; Hiegemann, L.; Tekkaya, A. E.

2017-09-01

Ferritic stainless steel without the alloy constituent nickel is an economical substitution for austenitic stainless steel in the automotive industry. Its lower formability, however, oftentimes prevents the direct material substitution in forming processes such as hydroforming, necessitating new forming strategies. To extend the forming capacity of ferritic stainless steel tube, the approach of forming at elevated temperatures is proposed. Utilizing granular material as forming medium, high forming temperatures up to 900°C are realized. The forming process works by moving punches axially into the granular medium, thereby, compressing it and causing axial as well as radial pressure. In experimental and numerical investigations it is shown that interfacial friction between the granular medium and the tube inherently causes tube feed, resulting in stain states in the tension-compression region of the FLD. Formability data for this region are gained by notched tensile tests, which are performed at room temperature as well as at elevated temperatures. The measured data show that the formability is improved at forming temperatures higher than 700°C. This observed formability increase is experimentally validated using a demonstrator geometry, which reaches expansion ratios that show fracture in specimens formed at room temperature.

Microgravity

NASA Image and Video Library

2000-05-05

A test cell for Mechanics of Granular Materials (MGM) experiment is tested for long-term storage with water in the system as plarned for STS-107. This view shows the top of the sand column with the metal platten removed. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that cannot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: University of Colorado at Boulder

Microgravity

NASA Image and Video Library

2000-05-05

A test cell for Mechanics of Granular Materials (MGM) experiment is tested for long-term storage with water in the system as plarned for STS-107. This view shows the compressed sand column with the protective water jacket removed. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that cannot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: University of Colorado at Boulder

Microgravity

NASA Image and Video Library

1998-01-25

A test cell for Mechanics of Granular Materials (MGM) experiment is shown approximately 20 and 60 minutes after the start of an experiment on STS-89. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: NASA/Marshall Space Flight Center (MSFC)

Evaluation of an up-flow anaerobic sludge bed (UASB) reactor containing diatomite and maifanite for the improved treatment of petroleum wastewater.

PubMed

Chen, Chunmao; Liang, Jiahao; Yoza, Brandon A; Li, Qing X; Zhan, Yali; Wang, Qinghong

2017-11-01

Novel diatomite (R1) and maifanite (R2) were utilized as support materials in an up-flow anaerobic sludge bed (UASB) reactor for the treatment of recalcitrant petroleum wastewater. At high organic loadings (11kg-COD/m 3 ·d), these materials were efficient at reducing COD (92.7% and 93.0%) in comparison with controls (R0) (88.4%). Higher percentages of large granular sludge (0.6mm or larger) were observed for R1 (30.3%) and R2 (24.6%) compared with controls (22.6%). The larger portion of granular sludge provided a favorable habitat that resulted in greater microorganism diversity. Increased filamentous bacterial communities are believed to have promoted granular sludge formation promoting a conductive environment for stimulation methanogenic Archaea. These communities had enhanced pH tolerance and produced more methane. This study illustrates a new potential use of diatomite and maifanite as support materials in UASB reactors for increased efficiency when treating refractory wastewaters. Copyright © 2017 Elsevier Ltd. All rights reserved.

Temperature scaling in a dense vibrofluidized granular material.

PubMed

Sunthar, P; Kumaran, V

1999-08-01

The leading order "temperature" of a dense two-dimensional granular material fluidized by external vibrations is determined. The grain interactions are characterized by inelastic collisions, but the coefficient of restitution is considered to be close to 1, so that the dissipation of energy during a collision is small compared to the average energy of a particle. An asymptotic solution is obtained where the particles are considered to be elastic in the leading approximation. The velocity distribution is a Maxwell-Boltzmann distribution in the leading approximation. The density profile is determined by solving the momentum balance equation in the vertical direction, where the relation between the pressure and density is provided by the virial equation of state. The temperature is determined by relating the source of energy due to the vibrating surface and the energy dissipation due to inelastic collisions. The predictions of the present analysis show good agreement with simulation results at higher densities where theories for a dilute vibrated granular material, with the pressure-density relation provided by the ideal gas law, are in error.

Mechanics of Granular Materials (MGM) Investigators

NASA Technical Reports Server (NTRS)

2000-01-01

Key persornel in the Mechanics of Granular Materials (MGM) experiment at the University of Colorado at Boulder include Tawnya Ferbiak (software engineer), Susan Batiste (research assistant), and Christina Winkler (graduate research assistant). Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that cannot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (Credit: University of Colorado at Boulder).

Mechanic of Granular Materials (MGM) Investigator

NASA Technical Reports Server (NTRS)

2000-01-01

Key persornel in the Mechanics of Granular Materials (MGM) experiment are Mark Lankton (Program Manager at University Colorado at Boulder), Susan Batiste (research assistance, UCB), and Stein Sture (principal investigator). Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that cannot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (Credit: University of Colorado at Boulder).

Destabilization of confined granular packings due to fluid flow

NASA Astrophysics Data System (ADS)

Monloubou, Martin; Sandnes, Bjørnar

2016-04-01

Fluid flow through granular materials can cause fluidization when fluid drag exceeds the frictional stress within the packing. Fluid driven failure of granular packings is observed in both natural and engineered settings, e.g. soil liquefaction and flowback of proppants during hydraulic fracturing operations. We study experimentally the destabilization and flow of an unconsolidated granular packing subjected to a point source fluid withdrawal using a model system consisting of a vertical Hele-Shaw cell containing a water-grain mixture. The fluid is withdrawn from the cell at a constant rate, and the emerging flow patterns are imaged in time-lapse mode. Using Particle Image Velocimetry (PIV), we show that the granular flow gets localized in a narrow channel down the center of the cell, and adopts a Gaussian velocity profile similar to those observed in dry grain flows in silos. We investigate the effects of the experimental parameters (flow rate, grain size, grain shape, fluid viscosity) on the packing destabilization, and identify the physical mechanisms responsible for the observed complex flow behaviour.

Stopping dynamics of a steady uniform granular flow over a rough incline

NASA Astrophysics Data System (ADS)

Deboeuf, Stéphanie; Saingier, Guillaume; Thiruvalluvar, Nitharshini; Lagrée, Pierre-Yves; Popinet, Stéphane; Staron, Lydie

2017-06-01

Granular material flowing on complex topographies are ubiquitous in industrial and geophysical situations. Even model granular flows are difficult to understand and predict. Recently, the frictional rheology μ(I) -describing the ratio of the shear stress to the normal stress as a function of the inertial number I, that compares inertial and confinement effects- allows unifying different configurations of granular flows. However it does not succeed in describing some phenomenologies, such as creep flow, deposit height, … Is it attributable to the rheology, to non-local effects, ...? Here, we consider a thin layer of grains flowing steadily and uniformly on a rough incline, when the input mass flow rate is suddenly stopped. We focus on the arrest dynamics by using both experimental and numerical approaches. We measure the height and surface velocities of the granular layer during the long-time stopping dynamics and we compare our experimental results with computations of depthaveraged equations for a fluid of rheology μ(I).

Scaling laws in granular flow and pedestrian flow

NASA Astrophysics Data System (ADS)

Chen, Shumiao; Alonso-Marroquin, Fernando; Busch, Jonathan; Hidalgo, Raúl Cruz; Sathianandan, Charmila; Ramírez-Gómez, Álvaro; Mora, Peter

2013-06-01

We use particle-based simulations to examine the flow of particles through an exit. Simulations involve both gravity-driven particles (representing granular material) and velocity-driven particles (mimicking pedestrian dynamics). Contact forces between particles include elastic, viscous, and frictional forces; and simulations use bunker geometry. Power laws are observed in the relation between flow rate and exit width. Simulations of granular flow showed that the power law has little dependence on the coefficient of friction. Polydisperse granular systems produced higher flow rates than those produced by monodisperse ones. We extend the particle model to include the main features of pedestrian dynamics: thoracic shape, shoulder rotation, and desired velocity oriented towards the exit. Higher desired velocity resulted in higher flow rate. Granular simulations always give higher flow rate than pedestrian simulations, despite the values of aspect ratio of the particles. In terms of force distribution, pedestrians and granulates share similar properties with the non-democratic distribution of forces that poses high risks of injuries in a bottleneck situation.

Simultaneous Cr(VI) bio-reduction and methane production by anaerobic granular sludge.

PubMed

Hu, Qian; Sun, Jiaji; Sun, Dezhi; Tian, Lan; Ji, Yanan; Qiu, Bin

2018-08-01

Wastewater containing toxic hexavalent chromium (Cr(VI)) were treated with well-organized anaerobic granular sludge in this study. Results showed that the anaerobic granular sludge rapidly removed Cr(VI), and 2000 µg·L -1 Cr(VI) was completely eliminated within 6 min, which was much faster than the reported duration of removal by reported artificial materials. Sucrose added as a carbon source acted as an initial electron donor to reduce Cr(VI) to Cr(III). This process was considered as the main mechanism of Cr(VI) removal. Methane production by anaerobic granular sludge was improved by the addition of Cr(VI) at a concentration lower than 500 µg·L -1 . Anaerobic granular sludge had a well-organized structure, which presented good resistance against toxic Cr(VI). Trichoccus accelerated the degradation of organic substances to generate acetates with a low Cr(VI) concentration, thereby enhancing methane production by acetotrophic methanogens. Copyright © 2018 Elsevier Ltd. All rights reserved.

Thermodynamic limitations on the resolution obtainable with metal replicas.

PubMed

Woodward, J T; Zasadzinski, J A

1996-12-01

The major factor limiting resolution of metal-shadowed surfaces for electron and scanning tunnelling microscopy is the granularity of the metal film. This granularity had been believed to result from a recrystallization of the evaporated film, and hence could be limited by use of higher melting point materials for replication, or inhibited by adding carbon or other impurities to the film. However, evaporated and sputtered films of amorphous metal alloys that do not crystallize also show a granularity that decreases with increasing alloy melting point. A simple thermodynamic analysis shows that the granularity results from a dewetting of the typically low surface energy sample by the high surface energy metal film, similar to the beading up of drops of spilled mercury. The metal granularity and the resulting resolution of the metal-coated surface is proportional to the mobility of the metal on the surface after evaporation, which is related to the difference in temperature between the melting point of the metal and the sample surface temperature.

Simplified greywater treatment systems: Slow filters of sand and slate waste followed by granular activated carbon.

PubMed

Zipf, Mariah Siebert; Pinheiro, Ivone Gohr; Conegero, Mariana Garcia

2016-07-01

One of the main actions of sustainability that is applicable to residential, commercial, and public buildings is the rational use of water that contemplates the reuse of greywater as one of the main options for reducing the consumption of drinking water. Therefore, this research aimed to study the efficiencies of simplified treatments for greywater reuse using slow sand and slow slate waste filtration, both followed by granular activated carbon filters. The system monitoring was conducted over 28 weeks, using analyses of the following parameters: pH, turbidity, apparent color, biochemical oxygen demand (BOD), chemical oxygen demand (COD), surfactants, total coliforms, and thermotolerant coliforms. The system was run at two different filtration rates: 6 and 2 m(3)/m(2)/day. Statistical analyses showed no significant differences in the majority of the results when filtration rate changed from 6 to 2 m(3)/m(2)/day. The average removal efficiencies with regard to the turbidity, apparent color, COD and BOD were 61, 54, 56, and 56%, respectively, for the sand filter, and 66, 61, 60, and 51%, respectively, for the slate waste filter. Both systems showed good efficiencies in removing surfactants, around 70%, while the pH reached values of around 7.80. The average removal efficiencies of the total and thermotolerant coliforms were of 61 and 90%, respectively, for the sand filter, and 67 and 80%, respectively, for the slate waste filter. The statistical analysis found no significant differences between the responses of the two systems, which attest to the fact that the slate waste can be a substitute for sand. The maximum levels of efficiency were high, indicating the potential of the systems, and suggesting their optimization in order to achieve much higher average efficiencies. Copyright © 2016 Elsevier Ltd. All rights reserved.

Role of 3D force networks in linking grain scale to macroscale processes in sheared granular debris

NASA Astrophysics Data System (ADS)

Mair, K.; Jettestuen, E.; Abe, S.

2013-12-01

Active faults, landslides and subglacial tills contain accumulations of granular debris that evolve during sliding. The macroscopic motion in these environments is at least to some extent determined by processes operating in this sheared granular material. A valid question is how the local behavior at the individual granular contacts actually sums up to influence macroscopic sliding. Laboratory experiments and numerical modeling can potentially help elucidate this. Observations of jamming (stick) and unjamming (flow) as well as concentrated shear bands on the scale of 5-10 grains suggest that a simple continuum description may be insufficient to capture important elements of the behavior. We therefore seek a measure of the organization of the granular fabric and the 3D structure of the load bearing skeleton that effectively demonstrates how the individual grain interactions are manifested in the macroscopic sliding behavior we observe. Contact force networks are an expression of this. Here we investigate the structure and variability of the most connected system spanning force networks produced in 3D discrete element models of granular layers under shear. We use percolation measures to identify, characterize, compare and track the evolution of these strongly connected contact force networks. We show that specific topological measures used in describing the networks, such as number of contacts and coordination number, are sensitive to grain size distribution (and likely the grain shape) of the material as well as loading conditions. Hence, faults of different maturity would be expected to accommodate shear in different ways. Distinct changes in the topological characteristics i.e. the geometry of strong force networks with accumulated strain are directly correlated to fluctuations in macroscopic shearing resistance. This suggests that 3D force networks play an important bridging role between individual grain scale processes and macroscopic sliding behavior.

Feasibility studies for the treatment and reuse of contaminated marine sediments.

PubMed

Bonomoa, L; Careghini, A; Dastoli, S; De Propris, L; Ferrari, G; Gabellini, M; Saponaro, S

2009-07-01

This paper presents preliminary results of laboratory tests aimed at evaluating the easibility of the remediation of marine sediments, which are polluted by mercury and petroleum hydrocarbons, dredged at the bay of Augusta (SR, Italy). The treatment is composed of two sequential steps: in the first, a cement-based granular material is produced (based on a high performance concrete approach); then, the volatile and the semi-volatile compounds in the granular material are removed by a thermal desorption step. Treated materials could be reused or put into caissons, according to their mechanical properties and environmental compatibility. The experiments were focused on evaluating the effect of the process parameter values on: (i) the evolution of cement hydration reactions, (ii) thermal desorption removal efficiencies, (iii) leaching behaviour of the treated material.

Two-Phase Solid/Fluid Simulation of Dense Granular Flows With Dilatancy Effects

NASA Astrophysics Data System (ADS)

Mangeney, Anne; Bouchut, Francois; Fernandez-Nieto, Enrique; Narbona-Reina, Gladys; Kone, El Hadj

2017-04-01

Describing grain/fluid interaction in debris flows models is still an open and challenging issue with key impact on hazard assessment [1]. We present here a two-phase two-thin-layer model for fluidized debris flows that takes into account dilatancy effects. It describes the velocity of both the solid and the fluid phases, the compression/ dilatation of the granular media and its interaction with the pore fluid pressure [2]. The model is derived from a 3D two-phase model proposed by Jackson [3] and the mixture equations are closed by a weak compressibility relation. This relation implies that the occurrence of dilation or contraction of the granular material in the model depends on whether the solid volume fraction is respectively higher or lower than a critical value. When dilation occurs, the fluid is sucked into the granular material, the pore pressure decreases and the friction force on the granular phase increases. On the contrary, in the case of contraction, the fluid is expelled from the mixture, the pore pressure increases and the friction force diminishes. To account for this transfer of fluid into and out of the mixture, a two-layer model is proposed with a fluid or a solid layer on top of the two-phase mixture layer. Mass and momentum conservation are satisfied for the two phases, and mass and momentum are transferred between the two layers. A thin-layer approximation is used to derive average equations. Special attention is paid to the drag friction terms that are responsible for the transfer of momentum between the two phases and for the appearance of an excess pore pressure with respect to the hydrostatic pressure. Interestingly, when removing the role of water, our model reduces to a dry granular flow model including dilatancy. We first compare experimental and numerical results of dilatant dry granular flows. Then, by quantitatively comparing the results of simulation and laboratory experiments on submerged granular flows, we show that our model contains the basic ingredients making it possible to reproduce the interaction between the granular and fluid phases through the change in pore fluid pressure. In particular, we analyse the different time scales in the model and their role in granular/fluid flow dynamics. References [1] R. Delannay, A. Valance, A. Mangeney, O. Roche, P. Richard, J. Phys. D: Appl. Phys., in press (2016). [2] F. Bouchut, E. D. Fernández-Nieto, A. Mangeney, G. Narbona-Reina, J. Fluid Mech., 801, 166-221 (2016). [3] R. Jackson, Cambridges Monographs on Mechanics (2000).

Internal and surface waves in vibrofluidized granular materials: Role of cohesion

NASA Astrophysics Data System (ADS)

Huang, Kai

2018-05-01

Wave phenomena in vibrofluidized dry and partially wet granular materials confined in a quasi-two-dimensional geometry are investigated with numerical simulations considering individual particles as hard spheres. Short-ranged cohesive interactions arising from the formation of liquid bridges between adjacent particles are modeled by changing the velocity-dependent coefficient of restitution. Such a change effectively suppresses the formation of surface waves, in agreement with previous experimental observations. The difference in pattern creation arises from the suppressed momentum transfer due to wetting and it can be quantitatively understood from an analysis of binary impacts.

Experiments, Theory, and Simulation on the Evolution of Fabric in Granular Materials

DTIC Science & Technology

1992-07-27

Evolution of Fabric in Granular- Materials "I S ELECTE AU 27 199Z A 60 0 1C cb t H" Thi f, : :,ent h,- beo:n approved t f,:,z p, L~i- an-. .,!,’c d ...Hall 6.1102F Ithaca, New York 14853-1503 SPONSORING/MOYITORI G AGENCY NAME( S ) AND ADDRESS(ES) 10. SPONSORING/MONITORING LFOSR / / V . AGENCY REPORT...else loop j (1,jgp) xvel(l,j) = svel xvel(igp,j) = - s -vel end-loop end .if end ;--- analysis function --- def analyse d -vol = 0.0 loop i (1,izones

Secondary Waste Form Screening Test Results—THOR® Fluidized Bed Steam Reforming Product in a Geopolymer Matrix

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pires, Richard P.; Westsik, Joseph H.; Serne, R. Jeffrey

2011-07-14

Screening tests are being conducted to evaluate waste forms for immobilizing secondary liquid wastes from the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Plans are underway to add a stabilization treatment unit to the Effluent Treatment Facility to provide the needed capacity for treating these wastes from WTP. The current baseline is to use a Cast Stone cementitious waste form to solidify the wastes. Through a literature survey, DuraLith alkali-aluminosilicate geopolymer, fluidized-bed steam reformation (FBSR) granular product encapsulated in a geopolymer matrix, and a Ceramicrete phosphate-bonded ceramic were identified both as candidate waste forms and alternatives to the baseline.more » These waste forms have been shown to meet waste disposal acceptance criteria, including compressive strength and universal treatment standards for Resource Conservation and Recovery Act (RCRA) metals (as measured by the toxicity characteristic leaching procedure [TCLP]). Thus, these non-cementitious waste forms should also be acceptable for land disposal. Information is needed on all four waste forms with respect to their capability to minimize the release of technetium. Technetium is a radionuclide predicted to be in the secondary liquid wastes in small quantities, but the Integrated Disposal Facility (IDF) risk assessment analyses show that technetium, even at low mass, produces the largest contribution to the estimated IDF disposal impacts to groundwater.« less

Maisotsenko cycle applications in multi-stage ejector recycling module for chemical production

NASA Astrophysics Data System (ADS)

Levchenko, D. O.; Artyukhov, A. E.; Yurko, I. V.

2017-08-01

The article is devoted to the theoretical bases of multistage (multi-level) utilization modules as part of chemical plants (on the example of the technological line for obtaining nitrogen fertilizers). The possibility of recycling production waste (ammonia vapors, dust and substandard nitrogen fertilizers) using ejection devices and waste heat using Maisotsenko cycle technology (Maisotsenko heat and mass exchanger (HMX), Maisotsenko power cycles and recuperators, etc.) is substantiated. The principle of operation of studied recycling module and prospects for its implementation are presented. An improved technological scheme for obtaining granular fertilizers and granules with porous structure with multistage (multi-level) recycling module is proposed.

Experimental observations of root growth in a controlled photoelastic granular material

NASA Astrophysics Data System (ADS)

Barés, Jonathan; Mora, Serge; Delenne, Jean-Yves; Fourcaud, Thierry

2017-06-01

We present a novel root observation apparatus capable of measuring the mechanical evolution of both the root network and the surrounding granular medium. The apparatus consists of 11 parallel growth frames, two of them being shearable, where the roots grow inside a photo-elastic or glass granular medium sandwiched between two pieces of glass. An automated system waters the plant and image each frame periodically in white light and between crossed polarisers. This makes it possible to follow (i) the root tips and (ii) the grain displacements as well as (iii) their inner pressure. We show how a root networks evolve in a granular medium and how it can mechanically stabilize it. This constitutes a model experiment to move forward in the understanding of the complex interaction between root growth and surrounding soil mechanical evolution.

Magnetic testing for inter-granular crack defect of tubing coupling

NASA Astrophysics Data System (ADS)

Hu, Bo; Yu, Runqiao

2018-04-01

This study focused on the inter-granular crack defects of tubing coupling wherein a non-destructive magnetic testing technique was proposed to determine the magnetic flux leakage features on coupling surface in the geomagnetic field using a high-precision magnetic sensor. The abnormal magnetic signatures of defects were analysed, and the principle of the magnetic test was explained based on the differences in the relative permeability of defects and coupling materials. Abnormal fluctuations of the magnetic signal were observed at the locations of the inter-granular crack defects. Imaging showed the approximate position of defects. The test results were proven by metallographic phase.

Rupture in cemented granular media: application to wheat endosperm

NASA Astrophysics Data System (ADS)

Topin, V.; Delenne, J.-Y.; Radjai, F.

2009-06-01

The mechanical origin of the wheat hardness used to classify wheat flours is an open issue. Wheat endosperm can be considered as a cemented granular material, consisting of densely packed solid particles (the starch granules) and a pore-filling solid matrix (the protein) sticking to the particles. We use the lattice element method to investigate cemented granular materials with a texture close to that of wheat endosperm and with variable matrix volume fraction and particle-matrix adherence. From the shape of the probability density of vertical stresses we distinguish weak, intermediate and strong stresses. The large stresses occur mostly at the contact zones as in noncohesive granular media with a decreasing exponential distribution. The weak forces reflect the arching effect. The intermediate stresses belong mostly to the bulk of the particles and their distribution is well fit to a Gaussian distribution. We also observe that the stress chains are essentially guided by the cementing matrix in tension and by the particulate backbone in compression. Crack formation is analyzed in terms of particle damage as a function of matrix volume fraction and particle-matrix adherence. Our data provide evidence for three regimes of crack propagation depending on the crack path through the material. We find that particle damage scales well with the relative toughness of the particle-matrix interface. The interface toughness appears therefore to be strongly correlated with particle damage and determines transition from soft to hard behavior in wheat endosperm.

The recovery of polyphenols from olive mill waste using two adsorbing vegetable matrices.

PubMed

Ena, Alba; Pintucci, Cristina; Carlozzi, Pietro

2012-02-20

Olive mill wastewater (OMW) is considered one of the most pollutive waste materials in the Mediterranean basin. However, its phenolic fraction should be recovered, since it has been shown to have incredible benefits for health. In the present study, the adsorbent and desorbent capacities of Azolla and granular activated carbon (GAC) were investigated. The GAC was found to be more efficient than Azolla in both the adsorption and the desorption of phenols. The total characterization of two powder products obtained from Azolla and GAC desorption is reported, together with their antioxidant and antiradical activities. In the Azolla powder product, total polyphenols were more than twice as numerous as those found in the GAC powder product. The GAC powder contained hydroxytyrosol in concentrations that were 3.5 times higher than those of Azolla. On the other hand, both powder products showed great antiradical activities: the IC₅₀ was found to be 102 mg ml⁻¹ for the Azolla and 199 mg ml⁻¹ for the GAC powders respectively. The oxygen radical absorbance capacity was very high: 4097 μmol TE g⁻¹ Azolla powder product and 1277 μmol TE g⁻¹ of GAC powder products. Copyright © 2011 Elsevier B.V. All rights reserved.

Effects of coarse aggregate on the physical properties of Florida concrete mixes.

DOT National Transportation Integrated Search

2015-10-01

Portland cement concrete is a heterogeneous, composite material composed of coarse and fine granular material : embedded in a matrix of hardened paste. The coarse material is aggregate, which is primarily used as inexpensive filler : and comprises th...

Quantifying Void Ratio in Granular Materials Using Voronoi Tessellation

NASA Technical Reports Server (NTRS)

Alshibli, Khalid A.; El-Saidany, Hany A.; Rose, M. Franklin (Technical Monitor)

2000-01-01

Voronoi technique was used to calculate the local void ratio distribution of granular materials. It was implemented in an application-oriented image processing and analysis algorithm capable of extracting object edges, separating adjacent particles, obtaining the centroid of each particle, generating Voronoi polygons, and calculating the local void ratio. Details of the algorithm capabilities and features are presented. Verification calculations included performing manual digitization of synthetic images using Oda's method and Voronoi polygon system. The developed algorithm yielded very accurate measurements of the local void ratio distribution. Voronoi tessellation has the advantage, compared to Oda's method, of offering a well-defined polygon generation criterion that can be implemented in an algorithm to automatically calculate local void ratio of particulate materials.

Microgravity Experiments to Evaluate Electrostatic Forces in Controlling Cohesion and Adhesion of Granular Materials

NASA Technical Reports Server (NTRS)

Marshall, J.; Weislogel, M.; Jacobson, T.

1999-01-01

The bulk behavior of dispersed, fluidized, or undispersed stationary granular systems cannot be fully understood in terms of adhesive/cohesive properties without understanding the role of electrostatic forces acting at the level of the grains themselves. When grains adhere to a surface, or come in contact with one another in a stationary bulk mass, it is difficult to measure the forces acting on the grains, and the forces themselves that induced the cohesion and adhesion are changed. Even if a single gain were to be scrutinized in the laboratory, it might be difficult, perhaps impossible, to define the distribution and character of surface charging and the three- dimensional relationship that charges (electrons, holes) have to one another. The hypothesis that we propose to test in microgravity (for dielectric materials) is that adhesion and cohesion of granular matter are mediated primarily by dipole forces that do not require the presence of a net charge; in fact, nominally electrically neutral materials should express adhesive and cohesive behavior when the neutrality results from a balance of positive and negative charge carriers. Moreover, the use of net charge alone as a measure of the electrical nature of grain-to-grain relationships within a granular mass may be misleading. We believe that the dipole forces arise from the presence of randomly-distributed positive and negative fixed charge carriers on grains that give rise to a resultant dipole moment. These dipole forces have long-range attraction. Random charges are created whenever there is triboelectrical activity of a granular mass, that is, whenever the grains experience contact/separation sequences or friction. Electrostatic forces are generally under-estimated for their role in causing agglomeration of dispersed grains in particulate clouds, or their role in affecting the internal frictional relationships in packed granular masses. We believe that electrostatic, in particular dipole-mediated processes, are pervasive and probably affect, at some level, everything from astrophysical-scale granular systems such as interstellar nebulae, protoplanetary dust and debris disks, planetary-scale systems such as debris palls from meteorite impact, volcanic eruptions, and aeolian dust storms, all the way to industrial-scale systems in mining, powder and grain processing, pharmaceuticals, and smoke-stack technologies. NASA must concern itself with the electrostatic behavior of dust and sand on Mars because of its potentially critical importance to human exploration. The motion and adhesion of martian surface materials will affect the design and performance of spacesuits, habitats, processing plants, solar panels, and any externally exposed equipment such as surface rovers or communication and weather stations. Additionally, the adhesion of dust and sand could greatly enhance contact with the potentially toxic components of the martian soil.

Dynamic and impact contact mechanics of geologic materials: Grain-scale experiments and modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cole, David M.; Hopkins, Mark A.; Ketcham, Stephen A.

2013-06-18

High fidelity treatments of the generation and propagation of seismic waves in naturally occurring granular materials is becoming more practical given recent advancements in our ability to model complex particle shapes and their mechanical interaction. Of particular interest are the grain-scale processes that are activated by impact events and the characteristics of force transmission through grain contacts. To address this issue, we have developed a physics based approach that involves laboratory experiments to quantify the dynamic contact and impact behavior of granular materials and incorporation of the observed behavior indiscrete element models. The dynamic experiments do not involve particle damagemore » and emphasis is placed on measured values of contact stiffness and frictional loss. The normal stiffness observed in dynamic contact experiments at low frequencies (e.g., 10 Hz) are shown to be in good agreement with quasistatic experiments on quartz sand. The results of impact experiments - which involve moderate to extensive levels of particle damage - are presented for several types of naturally occurring granular materials (several quartz sands, magnesite and calcium carbonate ooids). Implementation of the experimental findings in discrete element models is discussed and the results of impact simulations involving up to 5 Multiplication-Sign 105 grains are presented.« less

Ottawa Sand for Mechanics of Granular Materials (MGM) Experiment

NASA Technical Reports Server (NTRS)

2000-01-01

What appear to be boulders fresh from a tumble down a mountain are really grains of Ottawa sand, a standard material used in civil engineering tests and also used in the Mechanics of Granular Materials (MGM) experiment. The craggy surface shows how sand grans have faces that can cause friction as they roll and slide against each other, or even causing sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM uses the microgravity of space to simulate this behavior under conditions that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. These images are from an Electron Spectroscopy for Chemical Analysis (ESCA) study conducted by Dr. Binayak Panda of IITRI for Marshall Space Flight Center (MSFC). (Credit: NASA/MSFC)

Radionuclide and contaminant immobilization in the fluidized bed steam reforming waste products

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neeway, James J.; Qafoku, Nikolla; Westsik, Joseph H.

2012-05-01

The goal of this chapter is to introduce the reader to the Fluidized Bed Steam Reforming (FBSR) process and resulting waste form. The first section of the chapter gives an overview of the potential need for FBSR processing in nuclear waste remediation followed by an overview of the engineering involved in the process itself. This is followed by a description of waste form production at a chemical level followed by a section describing different process streams that have undergone the FBSR process. The third section describes the resulting mineral product in terms of phases that are present and the abilitymore » of the waste form to encapsulate hazardous and radioactive wastes from several sources. Following this description is a presentation of the physical properties of the granular and monolith waste form product including and contaminant release mechanisms. The last section gives a brief summary of this chapter and includes a section on the strengths associated with this waste form and the needs for additional data and remaining questions yet to be answered. The reader is directed elsewhere for more information on other waste forms such as Cast Stone (Lockrem, 2005), Ceramicrete (Singh et al., 1997, Wagh et al., 1999) and geopolymers (Kyritsis et al., 2009; Russell et al., 2006).« less

Analysis of the Angle of Maximal Stability and Flow Regime Transitions in Different Proportions of Bi-phasic Granular Matter Mixtures

NASA Astrophysics Data System (ADS)

Maquiling, Joel Tiu; Visaga, Shane Marie

This study investigates the dependence of the critical angle θc of stability on different mass ratios γ of layered bi-phasic granular matter mixtures and on the critical angle of its mono-disperse individual components. It also aims to investigate and explain regime transitions of granular matter flowing down a tilted rough inclined plane. Critical angles and flow regimes for a bi-phasic mixture of sago spheres and bi-phasic pepper mixture of fine powder and rough spheres were observed and measured using video analysis. The critical angles θc MD of mono-disperse granular matter and θc BP of biphasic granular matter mixtures were observed and compared. All types of flow regimes and a supramaximal critical angle of stability exist at mass ratio γ = 0.5 for all biphasic granular matter mixtures. The θc BP of sago spheres was higher than the θc MD of sago spheres. Moreover, the θc BP of the pepper mixture was in between the θc MD of fine pepper and θc MD of rough pepper spheres. Comparison of different granular material shows that θc MD is not simply a function of particle diameter but of particle roughness as well. Results point to a superposition mechanism of the critical angles of biphasic sphere mixtures.

The Stability Analysis Method of the Cohesive Granular Slope on the Basis of Graph Theory.

PubMed

Guan, Yanpeng; Liu, Xiaoli; Wang, Enzhi; Wang, Sijing

2017-02-27

This paper attempted to provide a method to calculate progressive failure of the cohesivefrictional granular geomaterial and the spatial distribution of the stability of the cohesive granular slope. The methodology can be divided into two parts: the characterization method of macro-contact and the analysis of the slope stability. Based on the graph theory, the vertexes, the edges and the edge sequences are abstracted out to characterize the voids, the particle contact and the macro-contact, respectively, bridging the gap between the mesoscopic and macro scales of granular materials. This paper adopts this characterization method to extract a graph from a granular slope and characterize the macro sliding surface, then the weighted graph is analyzed to calculate the slope safety factor. Each edge has three weights representing the sliding moment, the anti-sliding moment and the braking index of contact-bond, respectively, . The safety factor of the slope is calculated by presupposing a certain number of sliding routes and reducing Weight repeatedly and counting the mesoscopic failure of the edge. It is a kind of slope analysis method from mesoscopic perspective so it can present more detail of the mesoscopic property of the granular slope. In the respect of macro scale, the spatial distribution of the stability of the granular slope is in agreement with the theoretical solution.

The effectiveness of resistive force theory in granular locomotiona)

NASA Astrophysics Data System (ADS)

Zhang, Tingnan; Goldman, Daniel I.

2014-10-01

Resistive force theory (RFT) is often used to analyze the movement of microscopic organisms swimming in fluids. In RFT, a body is partitioned into infinitesimal segments, each of which generates thrust and experiences drag. Linear superposition of forces from elements over the body allows prediction of swimming velocities and efficiencies. We show that RFT quantitatively describes the movement of animals and robots that move on and within dry granular media (GM), collections of particles that display solid, fluid, and gas-like features. RFT works well when the GM is slightly polydisperse, and in the "frictional fluid" regime such that frictional forces dominate material inertial forces, and when locomotion can be approximated as confined to a plane. Within a given plane (horizontal or vertical) relationships that govern the force versus orientation of an elemental intruder are functionally independent of the granular medium. We use the RFT to explain features of locomotion on and within granular media including kinematic and muscle activation patterns during sand-swimming by a sandfish lizard and a shovel-nosed snake, optimal movement patterns of a Purcell 3-link sand-swimming robot revealed by a geometric mechanics approach, and legged locomotion of small robots on the surface of GM. We close by discussing situations to which granular RFT has not yet been applied (such as inclined granular surfaces), and the advances in the physics of granular media needed to apply RFT in such situations.

Analytical and Computational Modeling of Mechanical Waves in Microscale Granular Crystals: Nonlinearity and Rotational Dynamics

NASA Astrophysics Data System (ADS)

Wallen, Samuel P.

Granular media are one of the most common, yet least understood forms of matter on earth. The difficulties in understanding the physics of granular media stem from the fact that they are typically heterogeneous and highly disordered, and the grains interact via nonlinear contact forces. Historically, one approach to reducing these complexities and gaining new insight has been the study of granular crystals, which are ordered arrays of similarly-shaped particles (typically spheres) in Hertzian contact. Using this setting, past works explored the rich nonlinear dynamics stemming from contact forces, and proposed avenues where such granular crystals could form designer, dynamically responsive materials, which yield beneficial functionality in dynamic regimes. In recent years, the combination of self-assembly fabrication methods and laser ultrasonic experimental characterization have enabled the study of granular crystals at microscale. While our intuition may suggest that these microscale granular crystals are simply scaled-down versions of their macroscale counterparts, in fact, the relevant physics change drastically; for example, short-range adhesive forces between particles, which are negligible at macroscale, are several orders of magnitude stronger than gravity at microscale. In this thesis, we present recent advances in analytical and computational modeling of microscale granular crystals, in particular concerning the interplay of nonlinearity, shear interactions, and particle rotations, which have previously been either absent, or included separately at macroscale. Drawing inspiration from past works on phononic crystals and nonlinear lattices, we explore problems involving locally-resonant metamaterials, nonlinear localized modes, amplitude-dependent energy partition, and other rich dynamical phenomena. This work enhances our understanding of microscale granular media, which may find applicability in fields such as ultrasonic wave tailoring, signal processing, shock and vibration mitigation, and powder processing.

A numerical study of granular dam-break flow

NASA Astrophysics Data System (ADS)

Pophet, N.; Rébillout, L.; Ozeren, Y.; Altinakar, M.

2017-12-01

Accurate prediction of granular flow behavior is essential to optimize mitigation measures for hazardous natural granular flows such as landslides, debris flows and tailings-dam break flows. So far, most successful models for these types of flows focus on either pure granular flows or flows of saturated grain-fluid mixtures by employing a constant friction model or more complex rheological models. These saturated models often produce non-physical result when they are applied to simulate flows of partially saturated mixtures. Therefore, more advanced models are needed. A numerical model was developed for granular flow employing a constant friction and μ(I) rheology (Jop et al., J. Fluid Mech. 2005) coupled with a groundwater flow model for seepage flow. The granular flow is simulated by solving a mixture model using Finite Volume Method (FVM). The Volume-of-Fluid (VOF) technique is used to capture the free surface motion. The constant friction and μ(I) rheological models are incorporated in the mixture model. The seepage flow is modeled by solving Richards equation. A framework is developed to couple these two solvers in OpenFOAM. The model was validated and tested by reproducing laboratory experiments of partially and fully channelized dam-break flows of dry and initially saturated granular material. To obtain appropriate parameters for rheological models, a series of simulations with different sets of rheological parameters is performed. The simulation results obtained from constant friction and μ(I) rheological models are compared with laboratory experiments for granular free surface interface, front position and velocity field during the flows. The numerical predictions indicate that the proposed model is promising in predicting dynamics of the flow and deposition process. The proposed model may provide more reliable insight than the previous assumed saturated mixture model, when saturated and partially saturated portions of granular mixture co-exist.

Height-dependent Velocity Structure of Photospheric Convection in Granules and Intergranular Lanes with Hinode /SOT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oba, T.; Iida, Y.; Shimizu, T., E-mail: oba.takayoshi@ac.jaxa.jp

The solar photosphere is the visible surface of the Sun, where many bright granules, surrounded by narrow dark intergranular lanes, are observed everywhere. The granular pattern is a manifestation of convective motion at the photospheric level, but its velocity structure in the height direction is poorly understood observationally. Applying bisector analysis to a photospheric spectral line recorded by the Hinode Solar Optical Telescope, we derived the velocity structure of the convective motion in granular regions and intergranular lanes separately. The amplitude of motion of the convective material decreases from 0.65 to 0.40 km s{sup −1} as the material rises inmore » granules, whereas the amplitude of motion increases from 0.30 to 0.50 km s{sup −1} as it descends in intergranular lanes. These values are significantly larger than those obtained in previous studies using bisector analysis. The acceleration of descending materials with depth is not predicted from the convectively stable condition in a stratified atmosphere. Such convective instability can be developed more efficiently by radiative cooling and/or a gas pressure gradient, which can control the dynamical behavior of convective material in intergranular lanes. Our analysis demonstrated that bisector analysis is a useful method for investigating the long-term dynamic behavior of convective material when a large number of pixels is available. In addition, one example is the temporal evolution of granular fragmentation, in which downflowing material develops gradually from a higher layer downward.« less

Slip-localization within confined gouge powder sheared at moderate to high slip-velocity

NASA Astrophysics Data System (ADS)

Reches, Zeev; Chen, Xiaofeng; Morgan, Chance; Madden, Andrew

2015-04-01

Slip along faults in the upper crust is always associated with comminution and formation of non-cohesive gouge powder that can be lithified to cataclasite. Typically, the fine-grained powders (grain-size < 1 micron) build a 1-10 cm thick inner-core of a fault-zone. The ubiquitous occurrence of gouge powder implies that gouge properties may control the dynamic weakening of faults. Testing these properties is the present objective. We built a Confined ROtary Cell, CROC, with a ring-shape, ~3 mm thick gouge chamber, with 62.5 and 81.2 mm of inner and outer diameters. The sheared powder is sealed by two sets of seals pressurized by nitrogen. In CROC, we can control the pore-pressure and to inject fluids, and to monitor CO2 and H2O concentration; in addition, we monitor the standard mechanical parameters (slip velocity, stresses, dilation, and temperature). We tested six types of granular materials (starting grain-size in microns): Talc (<250), Kasota dolomite (125-250), ooides grains (125-250), San Andreas fault zone powder (< 840), montmorillonite powder (1-2), kaolinite powder and gypsum. The experimental slip-velocity ranged 0.001-1 m/s, slip distances from a few tens of cm to tens of m, effective normal stress up to 6.1 MPa. The central ultra-microscopic (SEM) observation is that almost invariably the slip was localized along principal-slip-zone (PSZ) within the granular layer. Even though the starting material was loose, coarse granular material, the developed PSZ was cohesive, hard, smooth and shining. The PSZ is about 1 micron thick, and built of agglomerated, ultra-fine grains (20-50 nm) that were pulverized from the original granular material. We noted that PSZs of the different tested compositions display similar characteristics in terms of structure, grain size, and roughness. Further, we found striking similarities between PSZ in the granular samples and the PZS that developed along experimental faults made of solid rock that were sheared at similar conditions. The ultra-fine grains and extreme slip localization in these experiments are generally similar to ultra-cataclasites found in exhumed faults-zones, and the intensely pulverized gouge found in drilling across active faults.

Dilatancy and compaction effects on the submerged granular column collapse

NASA Astrophysics Data System (ADS)

Wang, Chun; Wang, Yongqi; Peng, Chong; Meng, Xiannan

2017-10-01

The effects of dilatancy on the collapse dynamics of granular materials in air or in a liquid are studied experimentally and numerically. Experiments show that dilatancy has a critical effect on the collapse of granular columns in the presence of an ambient fluid. Two regimes of the collapse, one being quick and the other being slow, are observed from the experiments and the underlying reasons are analyzed. A two-fluid smoothed particle hydrodynamics model, based on the granular-fluid mixture theory and the critical state theory, is employed to investigate the complex interactions between the solid particles and the ambient water. It is found that dilatancy, resulting in large effective stress and large frictional coefficient between solid particles, helps form the slow regime. Small permeability, representing large inter-phase drag force, also retards the collapse significantly. The proposed numerical model is capable of reproducing these effects qualitatively.

Effect of periodic fluctuation of soil particle rotation resistance on interface shear behaviour

NASA Astrophysics Data System (ADS)

Ebrahimian, Babak; Noorzad, Asadollah

2010-06-01

The interface behaviour between infinite extended narrow granular layer and bounding structure is numerically investigated using finite element method. The micro-polar (Cosserat) continuum approach within the framework of elasto-plasticity is employed to remove the numerical difficulties caused by strain-softening of materials in classical continuum mechanics. Mechanical properties of cohesionless granular soil are described with Lade's model enhanced with polar terms including Cosserat rotations, curvatures and couple stresses via mean grain diameter as the internal length. The main attention of paper is laid on the influence of spatial periodic fluctuation of rotation resistance of soil particles interlocked with the surface of bounding structure on evolution and location of shear band developed inside granular body. The finite element results demonstrate that the location and evolution of shear localization in granular body is strongly affected by prescribed non-uniform micro-polar kinematic boundary conditions along the interface.

Biotransformation of RDX and HMX by Anaerobic Granular Sludge with Enriched Sulfate and Nitrate.

PubMed

An, Chunjiang; Shi, Yarong; He, Yanling; Huang, Guohe; Liu, Yonghong; Yang, Shucheng

2017-05-01

  RDX and HMX are widely used energetic materials and they are recognized as environmental contaminants at numerous locations. The present study investigated the biotransformation of RDX and HMX by anaerobic granular sludge under sulfate- and nitrate-enriched conditions. The results showed that RDX and HMX could be transformed by anaerobic granular sludge when nitrate was present. However, the biotransformation of RDX and HMX was negatively influenced, especially with high nitrate concentrations. Sulfate-enriched conditions were more favorable for the removal of ammunition compounds by anaerobic granular sludge than nitrate-enriched conditions. The removal of RDX and HMX under both nitrate- and sulfate-enriched conditions was facilitated by the use of glucose as additional substrate. This knowledge may help identify factors required for rapid removal of RDX and HMX in high-rate bioreactors. These results can also be applied to devise an appropriate and practical biological treatment strategy for explosive contaminated wastewater.

Scaling laws for the mechanics of loose and cohesive granular materials based on Baxter's sticky hard spheres

NASA Astrophysics Data System (ADS)

Gaume, Johan; Löwe, Henning; Tan, Shurun; Tsang, Leung

2017-09-01

We have conducted discrete element simulations (pfc3d) of very loose, cohesive, granular assemblies with initial configurations which are drawn from Baxter's sticky hard sphere (SHS) ensemble. The SHS model is employed as a promising auxiliary means to independently control the coordination number zc of cohesive contacts and particle volume fraction ϕ of the initial states. We focus on discerning the role of zc and ϕ for the elastic modulus, failure strength, and the plastic consolidation line under quasistatic, uniaxial compression. We find scaling behavior of the modulus and the strength, which both scale with the cohesive contact density νc=zcϕ of the initial state according to a power law. In contrast, the behavior of the plastic consolidation curve is shown to be independent of the initial conditions. Our results show the primary control of the initial contact density on the mechanics of cohesive granular materials for small deformations, which can be conveniently, but not exclusively explored within the SHS-based assembling procedure.

Comparison of a 3-D DEM simulation with MRI data

NASA Astrophysics Data System (ADS)

Ng, Tang-Tat; Wang, Changming

2001-04-01

This paper presents a comparison of a granular material studied experimentally and numerically. Simple shear tests were performed inside the magnetic core of magnetic resonance imaging (MRI) equipment. Spherical pharmaceutical pills were used as the granular material, with each pill's centre location determined by MRI. These centre locations in the initial assembly were then used as the initial configuration in the numerical simulation using the discrete element method. The contact properties between pharmaceutical pills used in the numerical simulation were obtained experimentally. The numerical predication was compared with experimental data at both macroscopic and microscopic levels. Good agreement was found at both levels.

Structural stability of rubble-pile asteroids

NASA Astrophysics Data System (ADS)

Sharma, Ishan

2013-03-01

Granular aggregates, like fluids, do not admit all manners of shapes and rotation rates. It is hoped that an analysis of a suspected granular asteroid’s equilibrium shape and its structural stability will help confirm its rubble-pile nature, and, perhaps, even constrain the asteroid’s material parameters. Equilibrium shapes have been analyzed in the past by several investigators (Holsapple, K.A. [2001]. Icarus 154, 432-448; Harris, A.W., Fahnestock, E.G., Pravec, P. [2009]. Icarus 199, 310-318; Sharma, I., Jenkins, J.T., Burns, J.A. [2009]. Icarus 200, 304-322). Here, we extend the classical Lagrange-Dirichlet stability theorem to the case of self-gravitating granular aggregates. This stability test is then applied to probe the stability of several near-Earth asteroids, and explore the influence of material parameters such as internal friction angle and plastic bulk modulus. Finally, we consider their structural stability to close planetary encounters. We find that it is possible for asteroids to be stable to small perturbations, but unstable to strong and/or extended perturbations as experienced during close flybys. Conversely, assuming stability in certain situations, it is possible to estimate material properties of some asteroids like, for example, 1943 Anteros.

Microgravity

NASA Image and Video Library

1996-09-18

One of three Mechanics of Granular Materials (MGM) test cells after flight on STS-79 and before impregnation with resin. Note that the sand column has bulged in the middle, and that the top of the column is several inches lower than the top of the plastic enclosure. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: University of Colorado at Boulder

Mechanics of Granular Materials (MGM0 Flight Hardware in Bench Test

NASA Technical Reports Server (NTRS)

2000-01-01

Engineering bench system hardware for the Mechanics of Granular Materials (MGM) experiment is tested on a lab bench at the University of Colorado in Boulder. This is done in a horizontal arrangement to reduce pressure differences so the tests more closely resemble behavior in the microgravity of space. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (Credit: University of Colorado at Boulder).

Computational domain discretization in numerical analysis of flow within granular materials

NASA Astrophysics Data System (ADS)

Sosnowski, Marcin

2018-06-01

The discretization of computational domain is a crucial step in Computational Fluid Dynamics (CFD) because it influences not only the numerical stability of the analysed model but also the agreement of obtained results and real data. Modelling flow in packed beds of granular materials is a very challenging task in terms of discretization due to the existence of narrow spaces between spherical granules contacting tangentially in a single point. Standard approach to this issue results in a low quality mesh and unreliable results in consequence. Therefore the common method is to reduce the diameter of the modelled granules in order to eliminate the single-point contact between the individual granules. The drawback of such method is the adulteration of flow and contact heat resistance among others. Therefore an innovative method is proposed in the paper: single-point contact is extended to a cylinder-shaped volume contact. Such approach eliminates the low quality mesh elements and simultaneously introduces only slight distortion to the flow as well as contact heat transfer. The performed analysis of numerous test cases prove the great potential of the proposed method of meshing the packed beds of granular materials.

Seismic wave propagation in granular media

NASA Astrophysics Data System (ADS)

Tancredi, Gonzalo; López, Francisco; Gallot, Thomas; Ginares, Alejandro; Ortega, Henry; Sanchís, Johnny; Agriela, Adrián; Weatherley, Dion

2016-10-01

Asteroids and small bodies of the Solar System are thought to be agglomerates of irregular boulders, therefore cataloged as granular media. It is a consensus that many asteroids might be considered as rubble or gravel piles.Impacts on their surface could produce seismic waves which propagate in the interior of these bodies, thus causing modifications in the internal distribution of rocks and ejections of particles and dust, resulting in a cometary-type comma.We present experimental and numerical results on the study of propagation of impact-induced seismic waves in granular media, with special focus on behavior changes by increasing compression.For the experiment, we use an acrylic box filled with granular materials such as sand, gravel and glass spheres. Pressure inside the box is controlled by a movable side wall and measured with sensors. Impacts are created on the upper face of the box through a hole, ranging from free-falling spheres to gunshots. We put high-speed cameras outside the box to record the impact as well as piezoelectic sensors and accelerometers placed at several depths in the granular material to detect the seismic wave.Numerical simulations are performed with ESyS-Particle, a software that implements the Discrete Element Method. The experimental setting is reproduced in the numerical simulations using both individual spherical particles and agglomerates of spherical particles shaped as irregular boulders, according to rock models obtained with a 3D scanner. The numerical experiments also reproduces the force loading on one of the wall to vary the pressure inside the box.We are interested in the velocity, attenuation and energy transmission of the waves. These quantities are measured in the experiments and in the simulations. We study the dependance of these three parameters with characteristics like: impact speed, properties of the target material and the pressure in the media.These results are relevant to understand the outcomes of impacts in rubble/gravel pile asteroids.

The runout of granular material: from analogue to numerical modelling

NASA Astrophysics Data System (ADS)

Longchamp, Celine; Caspar, Olivier; Gygax, Remo; Podladchikov, Yury; Jaboyedoff, Michel

2014-05-01

Rock avalanches are catastrophic events in which important granular rock masses (>106 m3) travel at velocities up to ten meters per second. The mobilized rock mass travel long distances, which in exceptional cases can reach up to tens of kilometers. Those highly destructive and uncontrollable events, give important insight to understand the interactions between the displaced masses and landscape conditions. However, as those events are not frequent, analogue and numerical modelling plays a fundamental role to better understand their behaviour. The objective of the research is to explore the propagation of rock avalanches and to compare a simple numerical model with analogue modelling. The laboratory experiments investigate the fluidlike flow of a granular mass down a slope. The flow is unconfined, following a 45° slope and spreading freely on a horizontal depositional surface. Different grainsize of calibrate material (115, 545 and 2605 μm) and substratum roughness (simulate by aluminium and sandpapers with grainsize from 16 to 425 μm) were used in order to understand their influence on the motion of a granular mass. High speed movies are recorded to analyse the behaviour of the mass during the whole experiment. The numerical model is based on the continuum mechanics approach and solving the shallow water equations. The avalanche is described from an eulerian point of view within a continuum framework as single phase of incompressible granular material following Mohr-Coulomb friction law. The combination of the fluid dynamic equation with the frictional law enables the self-channelization of the mass without any topographic constraints or special border conditions. The results obtained with the numerical model are similar to those observed with the analogue. In both cases, based on similar initial condition (slope, volume, basal friction, height of fall and initial velocity), the runout of the mass is of comparable size and the shape of the deposit matches well. This preliminary version of the code gives encouraging results in agreement with those obtained with laboratory experiments.

Characteristics of undulatory locomotion in granular media

NASA Astrophysics Data System (ADS)

Peng, Zhiwei; Pak, On Shun; Elfring, Gwynn J.

2016-03-01

Undulatory locomotion is ubiquitous in nature and observed in different media, from the swimming of flagellated microorganisms in biological fluids, to the slithering of snakes on land, or the locomotion of sandfish lizards in sand. Despite the similarity in the undulating pattern, the swimming characteristics depend on the rheological properties of different media. Analysis of locomotion in granular materials is relatively less developed compared with fluids partially due to a lack of validated force models but recently a resistive force theory in granular media has been proposed and shown useful in studying the locomotion of a sand-swimming lizard. Here we employ the proposed model to investigate the swimming characteristics of a slender filament, of both finite and infinite length, undulating in a granular medium and compare the results with swimming in viscous fluids. In particular, we characterize the effects of drifting and pitching in terms of propulsion speed and efficiency for a finite sinusoidal swimmer. We also find that, similar to Lighthill's results using resistive force theory in viscous fluids, the sawtooth swimmer is the optimal waveform for propulsion speed at a given power consumption in granular media. The results complement our understanding of undulatory locomotion and provide insights into the effective design of locomotive systems in granular media.

Continuum modeling of rate-dependent granular flows in SPH

DOE PAGES

Hurley, Ryan C.; Andrade, José E.

2016-09-13

In this paper, we discuss a constitutive law for modeling rate-dependent granular flows that has been implemented in smoothed particle hydrodynamics (SPH). We model granular materials using a viscoplastic constitutive law that produces a Drucker–Prager-like yield condition in the limit of vanishing flow. A friction law for non-steady flows, incorporating rate-dependence and dilation, is derived and implemented within the constitutive law. We compare our SPH simulations with experimental data, demonstrating that they can capture both steady and non-steady dynamic flow behavior, notably including transient column collapse profiles. In conclusion, this technique may therefore be attractive for modeling the time-dependent evolutionmore » of natural and industrial flows.« less

Methods of parallel computation applied on granular simulations

NASA Astrophysics Data System (ADS)

Martins, Gustavo H. B.; Atman, Allbens P. F.

2017-06-01

Every year, parallel computing has becoming cheaper and more accessible. As consequence, applications were spreading over all research areas. Granular materials is a promising area for parallel computing. To prove this statement we study the impact of parallel computing in simulations of the BNE (Brazil Nut Effect). This property is due the remarkable arising of an intruder confined to a granular media when vertically shaken against gravity. By means of DEM (Discrete Element Methods) simulations, we study the code performance testing different methods to improve clock time. A comparison between serial and parallel algorithms, using OpenMP® is also shown. The best improvement was obtained by optimizing the function that find contacts using Verlet's cells.

Spontaneous density fluctuations in granular flow and traffic

NASA Astrophysics Data System (ADS)

Herrmann, Hans J.

It is known that spontaneous density waves appear in granular material flowing through pipes or hoppers. A similar phenomenon is known from traffic jams on highways. Using numerical simulations we show that several types of waves exist and find that the density fluctuations follow a power law spectrum. We also investigate one-dimensional traffic models. If positions and velocities are continuous variables the model shows self-organized criticality driven by the slowest car. Lattice gas and lattice Boltzmann models reproduce the experimentally observed effects. Density waves are spontaneously generated when the viscosity has a non-linear dependence on density or shear rate as it is the case in traffic or granular flow.

Two-Phase Solid/Fluid Simulation of Dense Granular Flows With Dilatancy Effects

NASA Astrophysics Data System (ADS)

Mangeney, A.; Bouchut, F.; Fernández-Nieto, E. D.; Kone, E. H.; Narbona-Reina, G.

2016-12-01

Describing grain/fluid interaction in debris flows models is still an open and challenging issue with key impact on hazard assessment [1]. We present here a two-phase two-thin-layer model for fluidized debris flows that takes into account dilatancy effects. It describes the velocity of both the solid and the fluid phases, the compression/ dilatation of the granular media and its interaction with the pore fluid pressure [2]. The model is derived from a 3D two-phase model proposed by Jackson [3] and the mixture equations are closed by a weak compressibility relation. This relation implies that the occurrence of dilation or contraction of the granular material in the model depends on whether the solid volume fraction is respectively higher or lower than a critical value. When dilation occurs, the fluid is sucked into the granular material, the pore pressure decreases and the friction force on the granular phase increases. On the contrary, in the case of contraction, the fluid is expelled from the mixture, the pore pressure increases and the friction force diminishes. To account for this transfer of fluid into and out of the mixture, a two-layer model is proposed with a fluid or a solid layer on top of the two-phase mixture layer. Mass and momentum conservation are satisfied for the two phases, and mass and momentum are transferred between the two layers. A thin-layer approximation is used to derive average equations. Special attention is paid to the drag friction terms that are responsible for the transfer of momentum between the two phases and for the appearance of an excess pore pressure with respect to the hydrostatic pressure. By comparing quantitatively the results of simulation and laboratory experiments on submerged granular flows, we show that our model contains the basic ingredients making it possible to reproduce the interaction between the granular and fluid phases through the change in pore fluid pressure. In particular, we analyse the different time scales in the model and their role in granular/fluid flow dynamics. References[1] R. Delannay, A. Valance, A. Mangeney, O. Roche, P. Richard, J. Phys. D: Appl. Phys., in press (2016). [2] F. Bouchut, E. D. Fernández-Nieto, A. Mangeney, G. Narbona-Reina, J. Fluid Mech., 801, 166-221 (2016). [3] R. Jackson, Cambridges Monographs on Mechanics (2000).

Carbon bed mercury emissions control for mixed waste treatment.

PubMed

Soelberg, Nick; Enneking, Joe

2010-11-01

Mercury has various uses in nuclear fuel reprocessing and other nuclear processes, and so it is often present in radioactive and mixed (radioactive and hazardous) wastes. Compliance with air emission regulations such as the Hazardous Waste Combustor (HWC) Maximum Achievable Control Technology (MACT) standards can require off-gas mercury removal efficiencies up to 99.999% for thermally treating some mixed waste streams. Test programs have demonstrated this level of off-gas mercury control using fixed beds of granular sulfur-impregnated activated carbon. Other results of these tests include (1) the depth of the mercury control mass transfer zone was less than 15-30 cm for the operating conditions of these tests; (2) MERSORB carbon can sorb mercury up to 19 wt % of the carbon mass; and (3) the spent carbon retained almost all (98.3-99.99%) of the mercury during Toxicity Characteristic Leachability Procedure (TCLP) tests, but when even a small fraction of the total mercury dissolves, the spent carbon can fail the TCLP test when the spent carbon contains high mercury concentrations.

Evaluation of aggregate subgrade materials used as pavement subgrade/granular subbase.

DOT National Transportation Integrated Search

2015-07-01

With recent focus on sustainable construction practices and the ever-increasing transportation costs and scarcity of : natural resources, integration of large-size and marginally acceptable aggregates and recycled materials (e.g., : reclaimed asphalt...

Eshelby inclusions in granular matter: Theory and simulations.

PubMed

McNamara, Sean; Crassous, Jérôme; Amon, Axelle

2016-08-01

We present a numerical implementation of an active inclusion in a granular material submitted to a biaxial test. We discuss the dependence of the response to this perturbation on two parameters: the intragranular friction coefficient on one hand, and the degree of the loading on the other hand. We compare the numerical results to theoretical predictions taking into account the change of volume of the inclusion as well as the anisotropy of the elastic matrix.

Can one ``Hear'' the aggregation state of a granular system?

NASA Astrophysics Data System (ADS)

Kruelle, Christof A.; Sánchez, Almudena García

2013-06-01

If an ensemble of macroscopic particles is mechanically agitated the constant energy input is dissipated into the system by multiple inelastic collisions. As a result, the granular material can exhibit, depending on the magnitude of agitation, several physical states - like a gaseous phase for high energy input or a condensed state for low agitation. Here we introduce a new method for quantifying the acoustical response of the granular system. Our experimental system consists of a monodisperse packing of glass beads with a free upper surface, which is confined inside a cylindrical container. An electro-mechanical shaker exerts a sinusoidal vertical vibration at normalized accelerations well above the fluidization threshold for a monolayer of particles. By increasing the number of beads the granular gas suddenly collapses if a critical threshold is exceeded. The transition can be detected easily with a microphone connected to the soundcard of a PC. From the recorded audio track a FFT is calculated in real-time. Depending on either the number of particles at a fixed acceleration or the amount of energy input for a given number of particles, the resulting rattling noise exhibits a power spectrum with either the dominating (shaker) frequency plus higher harmonics for a granular crystal or a high-frequency broad-band noise for a granular gas, respectively. Our new method demonstrates that it is possible to quantify analytically the subjective audio impressions of a careful listener and thus to distinguish easily between different aggregation states of an excited granular system.

Spatiotemporal stick-slip phenomena in a coupled continuum-granular system

NASA Astrophysics Data System (ADS)

Ecke, Robert

In sheared granular media, stick-slip behavior is ubiquitous, especially at very small shear rates and weak drive coupling. The resulting slips are characteristic of natural phenomena such as earthquakes and well as being a delicate probe of the collective dynamics of the granular system. In that spirit, we developed a laboratory experiment consisting of sheared elastic plates separated by a narrow gap filled with quasi-two-dimensional granular material (bi-dispersed nylon rods) . We directly determine the spatial and temporal distributions of strain displacements of the elastic continuum over 200 spatial points located adjacent to the gap. Slip events can be divided into large system-spanning events and spatially distributed smaller events. The small events have a probability distribution of event moment consistent with an M - 3 / 2 power law scaling and a Poisson distributed recurrence time distribution. Large events have a broad, log-normal moment distribution and a mean repetition time. As the applied normal force increases, there are fractionally more (less) large (small) events, and the large-event moment distribution broadens. The magnitude of the slip motion of the plates is well correlated with the root-mean-square displacements of the granular matter. Our results are consistent with mean field descriptions of statistical models of earthquakes and avalanches. We further explore the high-speed dynamics of system events and also discuss the effective granular friction of the sheared layer. We find that large events result from stored elastic energy in the plates in this coupled granular-continuum system.

The Stability Analysis Method of the Cohesive Granular Slope on the Basis of Graph Theory

PubMed Central

Guan, Yanpeng; Liu, Xiaoli; Wang, Enzhi; Wang, Sijing

2017-01-01

This paper attempted to provide a method to calculate progressive failure of the cohesive-frictional granular geomaterial and the spatial distribution of the stability of the cohesive granular slope. The methodology can be divided into two parts: the characterization method of macro-contact and the analysis of the slope stability. Based on the graph theory, the vertexes, the edges and the edge sequences are abstracted out to characterize the voids, the particle contact and the macro-contact, respectively, bridging the gap between the mesoscopic and macro scales of granular materials. This paper adopts this characterization method to extract a graph from a granular slope and characterize the macro sliding surface, then the weighted graph is analyzed to calculate the slope safety factor. Each edge has three weights representing the sliding moment, the anti-sliding moment and the braking index of contact-bond, respectively, E1E2E3E1E2E3. The safety factor of the slope is calculated by presupposing a certain number of sliding routes and reducing Weight E3 repeatedly and counting the mesoscopic failure of the edge. It is a kind of slope analysis method from mesoscopic perspective so it can present more detail of the mesoscopic property of the granular slope. In the respect of macro scale, the spatial distribution of the stability of the granular slope is in agreement with the theoretical solution. PMID:28772596

7 CFR 58.735 - Quality specifications for raw materials.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 3 2011-01-01 2011-01-01 false Quality specifications for raw materials. 58.735 Section 58.735 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING... specifications for raw materials. (a) Cheddar colby, washed or soaked curd, granular or stirred curd cheese...

Processing of oil palm empty fruit bunch as filler material of polymer recycles

NASA Astrophysics Data System (ADS)

Saepulloh, D. R.; Nikmatin, S.; Hardhienata, H.

2017-05-01

Oil palm empty fruit bunches (OPEFB) is waste from crude palm oil (CPO) processing plants. This research aims to process OPEFB to be a reinforcement polymer recycle with the mechanical milling method and identify each establishment molecular with the orbital hybridization theory. OPEFB fibers were synthesized using a mechanical milling until the size shortfiber and microfiber. Then do the biocomposite granular synthesis with single screw extruder. TAPPI chemical test shows levels of α-cellulose fibers amounted 41.68%. Based on density, the most optimum composition contained in the filler amounted 15% with the size is the microfiber. The test results of morphology with SEM showed deployment of filler OPEFB fiber is fairly equitable distributed. Regarding the molecular interaction between matrix with OPEFB fiber, described by the theory of orbital hybridization. But the explanation establishment of the bond for more complex molecules likes this from the side of the molecular orbital theory is necessary complete information of the hybrid levels.

Adsorption characteristics of benzene on biosolid adsorbent and commercial activated carbons.

PubMed

Chiang, Hung-Lung; Lin, Kuo-Hsiung; Chen, Chih-Yu; Choa, Ching-Guan; Hwu, Ching-Shyung; Lai, Nina

2006-05-01

This study selected biosolids from a petrochemical waste-water treatment plant as the raw material. The sludge was immersed in 0.5-5 M of zinc chloride (ZnCl2) solutions and pyrolyzed at different temperatures and times. Results indicated that the 1-M ZnCl2-immersed biosolids pyrolyzed at 500 degrees C for 30 min could be reused and were optimal biosolid adsorbents for benzene adsorption. Pore volume distribution analysis indicated that the mesopore contributed more than the macropore and micropore in the biosolid adsorbent. The benzene adsorption capacity of the biosolid adsorbent was 65 and 55% of the G206 (granular-activated carbon) and BPL (coal-based activated carbon; Calgon, Carbon Corp.) activated carbons, respectively. Data from the adsorption and desorption cycles indicated that the benzene adsorption capacity of the biosolid adsorbent was insignificantly reduced compared with the first-run capacity of the adsorbent; therefore, the biosolid adsorbent could be reused as a commercial adsorbent, although its production cost is high.

Solid-state fermentation of soybean residues for bioflocculant production in a pilot-scale bioreactor system.

PubMed

Zulkeflee, Zufarzaana; Sánchez, Antoni

2014-01-01

An innovative approach using soybean residues for the production of bioflocculants through solid-state fermentation was carried out in 4.5 L near-to-adiabatic bioreactors at pilot-scale level. An added inoculum of the strain Bacillus subtilis UPMB13 was tested in comparison with control reactors without any inoculation after the thermophilic phase of the fermentation. The flocculating performances of the extracted bioflocculants were tested on kaolin suspensions, and crude bioflocculants were obtained from 20 g of fermented substrate through ethanol precipitation. The production of bioflocculants was observed to be higher during the death phase of microbial growth. The bioflocculants were observed to be granular in nature and consisted of hydroxyl, carboxyl and methoxyl groups that aid in their flocculating performance. The results show the vast potential of the idea of using wastes to produce bioactive materials that can replace the current dependence on chemicals, for future prospect in water treatment applications.

Economic evaluation of radiation processing in urban solid wastes treatment

NASA Astrophysics Data System (ADS)

Carassiti, F.; Lacquaniti, L.; Liuzzo, G.

During the last few years, quite a number of studies have been done, or are still in course, on disinfection of urban liquid wastes by means of ionizing radiations. The experience gained by SANDIA pilot plant of irradiation on dried sewage sludge, together with the recently presented conceptual design of another plant handling granular solids, characterized by high efficiency and simple running, have shown the possibility of extending this process to the treatment of urban solid wastes. As a matter of fact, the problems connected to the pathogenic aspects of sludge handling are often similar to those met during the disposal of urban solid wastes. This is even more so in the case of their reuse in agriculture and zootechny. The present paper introduces the results of an analysis carried out in order to evaluate the economical advantage of inserting irradiation treatment in some process scheme for management of urban solid wastes. Taking as an example a comprehensive pattern of urban solid wastes management which has been analysed and estimated economically in previous works, we first evaluated the extra capital and operational costs due to the irradiation and then analysed economical justification, taking into account the increasing commercial value of the by-products.

Shear flow of dense granular materials near smooth walls. I. Shear localization and constitutive laws in the boundary region.

PubMed

Shojaaee, Zahra; Roux, Jean-Noël; Chevoir, François; Wolf, Dietrich E

2012-07-01

We report on a numerical study of the shear flow of a simple two-dimensional model of a granular material under controlled normal stress between two parallel smooth frictional walls moving with opposite velocities ± V. Discrete simulations, which are carried out with the contact dynamics method in dense assemblies of disks, reveal that, unlike rough walls made of strands of particles, smooth ones can lead to shear strain localization in the boundary layer. Specifically, we observe, for decreasing V, first a fluidlike regime (A), in which the whole granular layer is sheared, with a homogeneous strain rate except near the walls, then (B) a symmetric velocity profile with a solid block in the middle and strain localized near the walls, and finally (C) a state with broken symmetry in which the shear rate is confined to one boundary layer, while the bulk of the material moves together with the opposite wall. Both transitions are independent of system size and occur for specific values of V. Transient times are discussed. We show that the first transition, between regimes A and B, can be deduced from constitutive laws identified for the bulk material and the boundary layer, while the second one could be associated with an instability in the behavior of the boundary layer. The boundary zone constitutive law, however, is observed to depend on the state of the bulk material nearby.

Accommodating Ontologies to Biological Reality—Top-Level Categories of Cumulative-Constitutively Organized Material Entities

PubMed Central

Vogt, Lars; Grobe, Peter; Quast, Björn; Bartolomaeus, Thomas

2012-01-01

Background The Basic Formal Ontology (BFO) is a top-level formal foundational ontology for the biomedical domain. It has been developed with the purpose to serve as an ontologically consistent template for top-level categories of application oriented and domain reference ontologies within the Open Biological and Biomedical Ontologies Foundry (OBO). BFO is important for enabling OBO ontologies to facilitate in reliably communicating and managing data and metadata within and across biomedical databases. Following its intended single inheritance policy, BFO's three top-level categories of material entity (i.e. ‘object’, ‘fiat object part’, ‘object aggregate’) must be exhaustive and mutually disjoint. We have shown elsewhere that for accommodating all types of constitutively organized material entities, BFO must be extended by additional categories of material entity. Methodology/Principal Findings Unfortunately, most biomedical material entities are cumulative-constitutively organized. We show that even the extended BFO does not exhaustively cover cumulative-constitutively organized material entities. We provide examples from biology and everyday life that demonstrate the necessity for ‘portion of matter’ as another material building block. This implies the necessity for further extending BFO by ‘portion of matter’ as well as three additional categories that possess portions of matter as aggregate components. These extensions are necessary if the basic assumption that all parts that share the same granularity level exhaustively sum to the whole should also apply to cumulative-constitutively organized material entities. By suggesting a notion of granular representation we provide a way to maintain the single inheritance principle when dealing with cumulative-constitutively organized material entities. Conclusions/Significance We suggest to extend BFO to incorporate additional categories of material entity and to rearrange its top-level material entity taxonomy. With these additions and the notion of granular representation, BFO would exhaustively cover all top-level types of material entities that application oriented ontologies may use as templates, while still maintaining the single inheritance principle. PMID:22253856

Shear dilatancy and acoustic emission in dry and saturated granular materials

NASA Astrophysics Data System (ADS)

Brodsky, E. E.; Siman-Tov, S.

2017-12-01

Shearing of granular materials plays a strong role in naturally sheared systems as landslides and faults. Many works on granular flows have concentrated on dry materials, but relatively little work has been done on water saturated sands. Here we experimentally investigate dry versus saturated quartz-rich sand to understand the effect of the fluid medium on the rheology and acoustic waves emission of the sheared sand. The sand was sheared in a rotary shear rheometer under applied constant normal stress boundary at low (100 µm/s) to high (1 m/s) velocities. Mechanical, acoustic data and deformation were continuously recorded and imaged. For dry and water saturated experiments the granular volume remains constant for low shear velocities ( 10-3 m/s) and increases during shearing at higher velocities ( 1 m/s). Continuous imaging of the sheared sand show that the steady state shear band thickness is thicker during the high velocity steps. No significant change observed in the shear band thickness between dry and water saturated experiments. In contrast, the amount of dilation during water saturated experiments is about half the value measured for dry material. The measured decrease cannot be explained by shear band thickness change as such is not exist. However, the reduced dilation is supported by our acoustic measurements. In general, the event rate and acoustic event amplitudes increase with shear velocity. While isolated events are clearly detected during low velocities at higher the events overlap, resulting in a noisy signal. Although detection is better for saturated experiments, during the high velocity steps the acoustic energy measured from the signal is lower compared to that recorded for dry experiments. We suggest that the presence of fluid suppresses grain motion and particles impacts leading to mild increase in the internal pressure and therefore for the reduced dilation. In addition, the viscosity of fluids may influence the internal pressure via hydrodynamic lubrication which increases the fluid pressure and therefore increases the dilation compared to dry material. The effect is particularly strong for high viscosity fluids, as observed in the silicon oil experiment. Therefore, fluid viscosity can play a crucial role in determining the physics that controls the rheology of the sheared material.

Structural evaluation of asphalt pavements with full-depth reclaimed base.

DOT National Transportation Integrated Search

2012-12-01

Currently, MnDOT pavement design recommends granular equivalency, GE = 1.0 for non-stabilized full-depth : reclamation (FDR) material, which is equivalent to class 5 material. For stabilized full-depth reclamation (SFDR), : there was no guideline for...

DOE Office of Scientific and Technical Information (OSTI.GOV)

James Schondel; Henry S. Chu

Lightweight panels have been designed to protect buildings and vehicles from blast pressures by activating energy dissipation mechanisms under the influence of blast loading. Panels were fabricated which featured a variety of granular materials and hydraulic dissipative deformation mechanisms and the test articles were subjected to full-scale blast loading. The force time-histories transmitted by each technology were measured by a novel method that utilized inexpensive custom-designed force sensors. The array of tests revealed that granular materials can effectively dissipate blast energy if they are employed in a way that they easily crush and rearrange. Similarly, hydraulic dissipation can effectively dissipatemore » energy if the panel features a high fraction of porosity and the panel encasement features low compressive stiffness.« less

Efficient Voronoi volume estimation for DEM simulations of granular materials under confined conditions

PubMed Central

Frenning, Göran

2015-01-01

When the discrete element method (DEM) is used to simulate confined compression of granular materials, the need arises to estimate the void space surrounding each particle with Voronoi polyhedra. This entails recurring Voronoi tessellation with small changes in the geometry, resulting in a considerable computational overhead. To overcome this limitation, we propose a method with the following features:•A local determination of the polyhedron volume is used, which considerably simplifies implementation of the method.•A linear approximation of the polyhedron volume is utilised, with intermittent exact volume calculations when needed.•The method allows highly accurate volume estimates to be obtained at a considerably reduced computational cost. PMID:26150975

Sustainable materials used as stone column filler: A short review

NASA Astrophysics Data System (ADS)

Zukri, Azhani; Nazir, Ramli

2018-04-01

Stone columns (also known as granular piles) are one of the methods for soft soil stabilization and typically used to increase bearing capacity and stability of slope.; Apart from decreasing the compressibility of loose and fine graded soils, it also accelerates the consolidation effect by improving the drainage path for pore water pressure dissipation and reduces the liquefaction potential of soils during earthquake event. Stone columns are probably the most “natural” ground treatment method or foundation system in existence to date. The benefit of stone columns is owing to the partial replacement of compressible soil by more competent materials such as stone aggregate, sand and other granular materials. These substitutes also act as reinforcement material, hence increasing overall strength and stiffness of the soft soil. Nowadays, a number of research has been conducted on the behaviour and performance of stone columns with various materials utilized as column filler replacing the normal aggregate. This paper will review extensively on previously conducted research on some of the materials used as stone column backfill materials, its suitability and the effectiveness as a substitute for regular aggregates in soft soil improvement works.

Physical Properties of Granulates Used in Analogue Experiments of Caprock Failure and Sediment Remobilisation

NASA Astrophysics Data System (ADS)

Kukowski, N.; Warsitzka, M.; May, F.

2014-12-01

Geological systems consisting of a porous reservoir and a low-permeable caprock are prone to hydraulic fracturing, if pore pressure rises to the effective stress. Under certain conditions, hydraulic fracturing is associated with sediment remobilisation, e.g. sand injections or pipes, leading to reduced seal capacity of the caprock. In dynamically scaled analogue experiments using granular materials and air pressure, we intent to investigate strain patterns and deformation mechanisms during caprock failure and fluidisation of shallow over-pressured reservoirs. The aim of this study is to improve the understanding of leakage potential of a sealing formation and the fluidisation potential of a reservoir formation depending on rock properties and effective stress. For reliable interpretation of analogue experiments, physical properties of analogue materials, e.g. frictional strength, cohesion, density, permeability etc., have to be correctly scaled according to those of their natural equivalents. The simulation of caprock requires that the analogue material possess a low permeability and is capable to shear failure and tensional failure. In contrast, materials representing the reservoir have to possess high porosity and low shear strength. In order to find suitable analogue materials, we measured the stress-strain behaviour and the permeability of over 25 different types of natural and artificial granular materials, e.g. glass powder, siliceous microspheres, diatomite powder, loess, or plastic granulate. Here, we present data of frictional parameters, compressibility and permeability of these granular materials characterized as a function of sphericity, grain size, and density. The repertoire of different types of granulates facilitates the adjustment of accurate mechanical properties in the analogue experiments. Furthermore, conditions during seal failure and fluidisation can be examined depending on the wide range of varying physical properties.

Granular rheology: measuring boundary forces with laser-cut leaf springs

NASA Astrophysics Data System (ADS)

Tang, Zhu; Brzinski, Theodore A.; Daniels, Karen E.

2017-06-01

In granular physics experiments, it is a persistent challenge to obtain the boundary stress measurements necessary to provide full a rheological characterization of the dynamics. Here, we describe a new technique by which the outer boundary of a 2D Couette cell both confines the granular material and provides spatially- and temporally- resolved stress measurements. This key advance is enabled by desktop laser-cutting technology, which allows us to design and cut linearly-deformable walls with a specified spring constant. By tracking the position of each segment of the wall, we measure both the normal and tangential stress throughout the experiment. This permits us to calculate the amount of shear stress provided by basal friction, and thereby determine accurate values of μ(I).

Modeling the Collisional-Plastic Stress Transition for Bin Discharge of Granular Material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pannala, Sreekanth; Daw, C Stuart; FINNEY, Charles E A

2009-01-01

We propose a heuristic model for the transition between collisional and frictional/plastic stresses in the flow of granular material. Our approach is based on a physically motivated, nonlinear blending function that produces a weighted average of the limiting stresses, depending on the local void fraction in the flow field. Previously published stress models are utilized to describe the behavior in the collisional (Lun et al., 1984) and quasi-static limits (Schaeffer, 1987 and Syamlal et al., 1993). Sigmoidal and hyperbolic tangent functions are used to mimic the observed smooth yet rapid transition between the collisional and plastic stress zones. We implementmore » our stress transition model in an opensource multiphase flow solver, MFIX (Multiphase Flow with Interphase eXchanges, www.mfix.org) and demonstrate its application to a standard bin discharge problem. The model s effectiveness is illustrated by comparing computational predictions to the experimentally derived Beverloo correlation. With the correct choice of function parameters, the model predicts bin discharge rates within the error margins of the Beverloo correlation and is more accurate than one of the alternative granular stress models proposed in the literature. Although a second granular stress model in the literature is also reasonably consistent with the Beverloo correlation, we propose that our alternative blending function is likely to be more adaptable to situations with more complex solids properties (e.g., sticky solids).« less

Effects of acoustic waves on stick-slip in granular media and implications for earthquakes

USGS Publications Warehouse

Johnson, P.A.; Savage, H.; Knuth, M.; Gomberg, J.; Marone, Chris

2008-01-01

It remains unknown how the small strains induced by seismic waves can trigger earthquakes at large distances, in some cases thousands of kilometres from the triggering earthquake, with failure often occurring long after the waves have passed. Earthquake nucleation is usually observed to take place at depths of 10-20 km, and so static overburden should be large enough to inhibit triggering by seismic-wave stress perturbations. To understand the physics of dynamic triggering better, as well as the influence of dynamic stressing on earthquake recurrence, we have conducted laboratory studies of stick-slip in granular media with and without applied acoustic vibration. Glass beads were used to simulate granular fault zone material, sheared under constant normal stress, and subject to transient or continuous perturbation by acoustic waves. Here we show that small-magnitude failure events, corresponding to triggered aftershocks, occur when applied sound-wave amplitudes exceed several microstrain. These events are frequently delayed or occur as part of a cascade of small events. Vibrations also cause large slip events to be disrupted in time relative to those without wave perturbation. The effects are observed for many large-event cycles after vibrations cease, indicating a strain memory in the granular material. Dynamic stressing of tectonic faults may play a similar role in determining the complexity of earthquake recurrence. ??2007 Nature Publishing Group.

Densified waste form and method for forming

DOEpatents

Garino, Terry J.; Nenoff, Tina M.; Sava Gallis, Dorina Florentina

2015-08-25

Materials and methods of making densified waste forms for temperature sensitive waste material, such as nuclear waste, formed with low temperature processing using metallic powder that forms the matrix that encapsulates the temperature sensitive waste material. The densified waste form includes a temperature sensitive waste material in a physically densified matrix, the matrix is a compacted metallic powder. The method for forming the densified waste form includes mixing a metallic powder and a temperature sensitive waste material to form a waste form precursor. The waste form precursor is compacted with sufficient pressure to densify the waste precursor and encapsulate the temperature sensitive waste material in a physically densified matrix.

Wave propagation of spectral energy content in a granular chain

NASA Astrophysics Data System (ADS)

Shrivastava, Rohit Kumar; Luding, Stefan

2017-06-01

A mechanical wave is propagation of vibration with transfer of energy and momentum. Understanding the spectral energy characteristics of a propagating wave through disordered granular media can assist in understanding the overall properties of wave propagation through inhomogeneous materials like soil. The study of these properties is aimed at modeling wave propagation for oil, mineral or gas exploration (seismic prospecting) or non-destructive testing of the internal structure of solids. The focus is on the total energy content of a pulse propagating through an idealized one-dimensional discrete particle system like a mass disordered granular chain, which allows understanding the energy attenuation due to disorder since it isolates the longitudinal P-wave from shear or rotational modes. It is observed from the signal that stronger disorder leads to faster attenuation of the signal. An ordered granular chain exhibits ballistic propagation of energy whereas, a disordered granular chain exhibits more diffusive like propagation, which eventually becomes localized at long time periods. For obtaining mean-field macroscopic/continuum properties, ensemble averaging has been used, however, such an ensemble averaged spectral energy response does not resolve multiple scattering, leading to loss of information, indicating the need for a different framework for micro-macro averaging.

Scales and kinetics of granular flows.

PubMed

Goldhirsch, I.

1999-09-01

When a granular material experiences strong forcing, as may be the case, e.g., for coal or gravel flowing down a chute or snow (or rocks) avalanching down a mountain slope, the individual grains interact by nearly instantaneous collisions, much like in the classical model of a gas. The dissipative nature of the particle collisions renders this analogy incomplete and is the source of a number of phenomena which are peculiar to "granular gases," such as clustering and collapse. In addition, the inelasticity of the collisions is the reason that granular gases, unlike atomic ones, lack temporal and spatial scale separation, a fact manifested by macroscopic mean free paths, scale dependent stresses, "macroscopic measurability" of "microscopic fluctuations" and observability of the effects of the Burnett and super-Burnett "corrections." The latter features may also exist in atomic fluids but they are observable there only under extreme conditions. Clustering, collapse and a kinetic theory for rapid flows of dilute granular systems, including a derivation of boundary conditions, are described alongside the mesoscopic properties of these systems with emphasis on the effects, theoretical conclusions and restrictions imposed by the lack of scale separation. (c) 1999 American Institute of Physics.

Granular-flow rheology: Role of shear-rate number in transition regime

USGS Publications Warehouse

Chen, C.-L.; Ling, C.-H.

1996-01-01

This paper examines the rationale behind the semiempirical formulation of a generalized viscoplastic fluid (GVF) model in the light of the Reiner-Rivlin constitutive theory and the viscoplastic theory, thereby identifying the parameters that control the rheology of granular flow. The shear-rate number (N) proves to be among the most significant parameters identified from the GVF model. As N ??? 0 and N ??? ???, the GVF model can reduce asymptotically to the theoretical stress versus shear-rate relations in the macroviscous and graininertia regimes, respectively, where the grain concentration (C) also plays a major role in the rheology of granular flow. Using available data obtained from the rotating-cylinder experiments of neutrally buoyant solid spheres dispersing in an interstitial fluid, the shear stress for granular flow in transition between the two regimes proves dependent on N and C in addition to some material constants, such as the coefficient of restitution. The insufficiency of data on rotating-cylinder experiments cannot presently allow the GVF model to predict how a granular flow may behave in the entire range of N; however, the analyzed data provide an insight on the interrelation among the relevant dimensionless parameters.

Tsunamis generated by long and thin granular landslides in a large flume

NASA Astrophysics Data System (ADS)

Miller, Garrett S.; Andy Take, W.; Mulligan, Ryan P.; McDougall, Scott

2017-01-01

In this experimental study, granular material is released down slope to investigate landslide-generated waves. Starting with a known volume and initial position of the landslide source, detailed data are obtained on the velocity and thickness of the granular flow, the shape and location of the submarine landslide deposit, the amplitude and shape of the near-field wave, the far-field wave evolution, and the wave runup elevation on a smooth impermeable slope. The experiments are performed on a 6.7 m long 30° slope on which gravity accelerates the landslides into a 2.1 m wide and 33.0 m long wave flume that terminates with a 27° runup ramp. For a fixed landslide volume of 0.34 m3, tests are conducted in a range of still water depths from 0.05 to 0.50 m. Observations from high-speed cameras and measurements from wave probes indicate that the granular landslide moves as a long and thin train of material, and that only a portion of the landslide (termed the "effective mass") is engaged in activating the leading wave. The wave behavior is highly dependent on the water depth relative to the size of the landslide. In deeper water, the near-field wave behaves as a stable solitary-like wave, while in shallower water, the wave behaves as a breaking dissipative bore. Overall, the physical model observations are in good agreement with the results of existing empirical equations when the effective mass is used to predict the maximum near-field wave amplitude, the far-field amplitude, and the runup of tsunamis generated by granular landslides.

X-ray tomography system to investigate granular materials during mechanical loading

NASA Astrophysics Data System (ADS)

Athanassiadis, Athanasios G.; La Rivière, Patrick J.; Sidky, Emil; Pelizzari, Charles; Pan, Xiaochuan; Jaeger, Heinrich M.

2014-08-01

We integrate a small and portable medical x-ray device with mechanical testing equipment to enable in situ, non-invasive measurements of a granular material's response to mechanical loading. We employ an orthopedic C-arm as the x-ray source and detector to image samples mounted in the materials tester. We discuss the design of a custom rotation stage, which allows for sample rotation and tomographic reconstruction under applied compressive stress. We then discuss the calibration of the system for 3D computed tomography, as well as the subsequent image reconstruction process. Using this system to reconstruct packings of 3D-printed particles, we resolve packing features with 0.52 mm resolution in a (60 mm)3 field of view. By analyzing the performance bounds of the system, we demonstrate that the reconstructions exhibit only moderate noise.

Collapse of tall granular columns in fluid

NASA Astrophysics Data System (ADS)

Kumar, Krishna; Soga, Kenichi; Delenne, Jean-Yves

2017-06-01

Avalanches, landslides, and debris flows are geophysical hazards, which involve rapid mass movement of granular solids, water, and air as a multi-phase system. In order to describe the mechanism of immersed granular flows, it is important to consider both the dynamics of the solid phase and the role of the ambient fluid. In the present study, the collapse of a granular column in fluid is studied using 2D LBM - DEM. The flow kinematics are compared with the dry and buoyant granular collapse to understand the influence of hydrodynamic forces and lubrication on the run-out. In the case of tall columns, the amount of material destabilised above the failure plane is larger than that of short columns. Therefore, the surface area of the mobilised mass that interacts with the surrounding fluid in tall columns is significantly higher than the short columns. This increase in the area of soil - fluid interaction results in an increase in the formation of turbulent vortices thereby altering the deposit morphology. It is observed that the vortices result in the formation of heaps that significantly affects the distribution of mass in the flow. In order to understand the behaviour of tall columns, the run-out behaviour of a dense granular column with an initial aspect ratio of 6 is studied. The collapse behaviour is analysed for different slope angles: 0°, 2.5°, 5° and 7.5°.

75 FR 65450 - Magnesium Metal From the People's Republic of China: Final Results of the 2008-2009 Antidumping...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-25

... certain non-magnesium granular materials to make magnesium-based reagent mixtures, including lime, calcium..., dolomite lime, and colemanite.\\7\\ \\6\\ The material is already covered by existing antidumping orders. See...

Cooperative dynamics in the penetration of a group of intruders in a granular medium.

PubMed

Pacheco-Vázquez, F; Ruiz-Suárez, J C

2010-11-23

An object moving in a fluid experiences a drag force that depends on its velocity, shape and the properties of the medium. From this simplest case to the motion of a flock of birds or a school of fish, the drag forces and the hydrodynamic interactions determine the full dynamics of the system. Similar drag forces appear when a single projectile impacts and moves through a granular medium, and this case is well studied in the literature. On the other hand, the case in which a group of intruders impact a granular material has never been considered. Here, we study the simultaneous penetration of several intruders in a very low-density granular medium. We find that the intruders move through it in a collective way, following a cooperative dynamics, whose complexity resembles flocking phenomena in living systems or the movement of reptiles in sand, wherein changes in drag are exploited to efficiently move or propel.

Non-Gaussian behavior in jamming / unjamming transition in dense granular materials

NASA Astrophysics Data System (ADS)

Atman, A. P. F.; Kolb, E.; Combe, G.; Paiva, H. A.; Martins, G. H. B.

2013-06-01

Experiments of penetration of a cylindrical intruder inside a bidimensional dense and disordered granular media were reported recently showing the jamming / unjamming transition. In the present work, we perform molecular dynamics simulations with the same geometry in order to assess both kinematic and static features of jamming / unjamming transition. We study the statistics of the particles velocities at the neighborhood of the intruder to evince that both experiments and simulations present the same qualitative behavior. We observe that the probability density functions (PDF) of velocities deviate from Gaussian depending on the packing fraction of the granular assembly. In order to quantify these deviations we consider a q-Gaussian (Tsallis) function to fit the PDF's. The q-value can be an indication of the presence of long range correlations along the system. We compare the fitted PDF's obtained with those obtained using the stretched exponential, and sketch some conclusions concerning the nature of the correlations along a granular confined flow.

A thermodynamically consistent model for granular-fluid mixtures considering pore pressure evolution and hypoplastic behavior

NASA Astrophysics Data System (ADS)

Hess, Julian; Wang, Yongqi

2016-11-01

A new mixture model for granular-fluid flows, which is thermodynamically consistent with the entropy principle, is presented. The extra pore pressure described by a pressure diffusion equation and the hypoplastic material behavior obeying a transport equation are taken into account. The model is applied to granular-fluid flows, using a closing assumption in conjunction with the dynamic fluid pressure to describe the pressure-like residual unknowns, hereby overcoming previous uncertainties in the modeling process. Besides the thermodynamically consistent modeling, numerical simulations are carried out and demonstrate physically reasonable results, including simple shear flow in order to investigate the vertical distribution of the physical quantities, and a mixture flow down an inclined plane by means of the depth-integrated model. Results presented give insight in the ability of the deduced model to capture the key characteristics of granular-fluid flows. We acknowledge the support of the Deutsche Forschungsgemeinschaft (DFG) for this work within the Project Number WA 2610/3-1.

Density-wave fronts on the brink of wet granular condensation

NASA Astrophysics Data System (ADS)

Huang, Kai; Zippelius, Andreas; Sand lab @ University of Bayreuth Team

2017-11-01

From sand dunes to Faraday heaping, driven granular matter, i.e., large agglomeration of macroscopic particles, is rich pattern forming system. When a granular material is partially wet (e.g., wet sand on the beach), a different pattern forming scenario arises due to the cohesive particle-particle interactions. Here, we focus on the formation of density-wave fronts in an oscillated wet granular layer undergoing a gas-liquid-like transition. The threshold of the instability is governed by the amplitude of the vertical vibrations. Fronts, which are curved into a spiral shape, propagate coherently along the circular rim of the container with leading edges. They are stable beyond a critical distance from the container center. Based on the measurement of the critical distance and the rotation frequency, we propose a model for the pattern formation by considering the competition between the time scale for the collapse of cohesive particles and that of the energy injection resisting this process. Deutsche Forschungsgemeinschaft (Grant No. HU1939 4-1).

Dynamic shear jamming in granular suspensions

NASA Astrophysics Data System (ADS)

Peters, Ivo; Majumdar, Sayantan; Jaeger, Heinrich

2014-11-01

Jamming by shear allows a frictional granular packing to transition from an unjammed state into a jammed state while keeping the system volume and average packing fraction constant. Shear jamming of dry granular media can occur quasi-statically, but boundaries are crucial to confine the material. We perform experiments in aqueous starch suspension where we apply shear using a rheometer with a large volume (400 ml) cylindrical Couette cell. In our suspensions the packing fraction is sufficiently low that quasi-static deformation does not induce a shear jammed state. Applying a shock-like deformation however, will turn the suspension into a jammed solid. A fully jammed state is reached within tens of microseconds, and can be sustained for at least several seconds. High speed imaging of the initial process reveals a jamming front propagating radially outward through the suspension, while the suspension near the outer boundary remains quiescent. This indicates that granular suspensions can be shear jammed without the need of confining solid boundaries. Instead, confinement is most likely provided by the dynamics in the front region.

Cooperative dynamics in the penetration of a group of intruders in a granular medium

PubMed Central

Pacheco-Vázquez, F.; Ruiz-Suárez, J.C.

2010-01-01

An object moving in a fluid experiences a drag force that depends on its velocity, shape and the properties of the medium. From this simplest case to the motion of a flock of birds or a school of fish, the drag forces and the hydrodynamic interactions determine the full dynamics of the system. Similar drag forces appear when a single projectile impacts and moves through a granular medium, and this case is well studied in the literature. On the other hand, the case in which a group of intruders impact a granular material has never been considered. Here, we study the simultaneous penetration of several intruders in a very low-density granular medium. We find that the intruders move through it in a collective way, following a cooperative dynamics, whose complexity resembles flocking phenomena in living systems or the movement of reptiles in sand, wherein changes in drag are exploited to efficiently move or propel. PMID:21119636

Micro- and macroscopic study on the porosity of marble as a function of temperature and impregnation

NASA Astrophysics Data System (ADS)

Malaga-Starzec, K.; Akesson, U.; Lindqvist, J. E.; Schouenborg, B.

2003-04-01

The thermal weathering of marble is demonstrated by the progressive granular decohesion that leads to an increased porosity and subsequently to loss of strength. In order to determine how temperature cycling initiates changes in the porosity of fresh and impregnated stones: two chemically and petrographically very different marble types were tested for water absorption and ultrasonic velocity propagation and analysed by fluorescence microscopy and nitrogen adsorption. The influence of the impregnation materials: GypStop P17 and P22, both silica sols with different particle size, on changes of the porosity was also evaluated. A separate long-term study of thermal expansion was additionally performed on fresh unimpregnated samples. The results indicated that inter-granular decohesion was more pronounced for the calictic marble than the dolomitic marble. The impregnation materials had a mitigating effect on the granular decohesion. Use of fluorescence microscopy, among the other methods, appears to give inexpensive and reliable information about internal structure of the marbles. A better understanding of the effect that temperature has on the porosity of marble could be used as a guide for election of suitable stone material for exterior use as well as an indication for appropriate conditioning of the samples before physical properties testing.

Microgravity

NASA Image and Video Library

1997-09-09

A test cell for the Mechanics of Granular Materials (MGM) experiment is shown in its on-orbit configuration in Spacehab during preparations for STS-89. The twin locker to the left contains the hydraulic system to operate the experiment. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Note: Because the image on the screen was muted in the original image, its brightness and contrast are boosted in this rendering to make the test cell more visible. Credit: NASA/Marshall Space Flight Center (MSFC)

Biogas pre-upgrading by adsorption of trace compounds onto granular activated carbons and an activated carbon fiber-cloth.

PubMed

Boulinguiez, B; Le Cloirec, P

2009-01-01

The study assesses the adsorption onto activated carbon materials of selected volatile organic compounds -VOCs- (dichloromethane, 2-propanol, toluene, siloxane D4) in a biogas matrix composed of methane and carbon dioxide (55:45 v/v). Three different adsorbents are tested, two of them are granular activated carbon (GAC), and the last is an activated carbon fiber-cloth (ACFC). The adsorption isotherm data are fitted by different models by nonlinear regression. The Langmuir-Freundlich model appears to be the adequate one to describe the adsorption phenomena independently of the VOC considered or the adsorbent. The adsorbents present attractive adsorption capacity of the undesirable compounds in biogas atmosphere though the maximum adsorption capacities for a VOC are quite different from each other. The adsorption kinetics are characterized through three coefficients: the initial adsorption coefficient, the external film mass transfer coefficient and the internal diffusion coefficient of Weber. The ACFC demonstrates advanced kinetic yields compared to the granular activated carbon materials whatever VOC is considered. Therefore, pre-upgrading of biogas produced from wastewater sludge or co-digestion system by adsorption onto activated carbon appears worth investigating. Especially with ACFC material that presents correct adsorption capacities toward VOCs and concrete regeneration process opportunity to realize such process.

Densified waste form and method for forming

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garino, Terry J.; Nenoff, Tina M.; Sava Gallis, Dorina Florentina

Materials and methods of making densified waste forms for temperature sensitive waste material, such as nuclear waste, formed with low temperature processing using metallic powder that forms the matrix that encapsulates the temperature sensitive waste material. The densified waste form includes a temperature sensitive waste material in a physically densified matrix, the matrix is a compacted metallic powder. The method for forming the densified waste form includes mixing a metallic powder and a temperature sensitive waste material to form a waste form precursor. The waste form precursor is compacted with sufficient pressure to densify the waste precursor and encapsulate themore » temperature sensitive waste material in a physically densified matrix.« less

The dependence of granular plasticity on particle shape

NASA Astrophysics Data System (ADS)

Murphy, Kieran; Jaeger, Heinrich

Granular materials plastically deform through reworking an intricate network of particle-particle contacts. Some particle rearrangements have only a fleeting effect before being forgotten while others set in motion global restructuring. How particle shape affects local interactions and how those, in turn, influence the nature of the aggregate's plasticity is far from clear, especially in three dimensions. Here we investigate the remarkably wide range of behaviors in the yielding regime, from quiescent flow to violent jerks, depending on particle shape. We study this complex dependence via uniaxial compression experiments on aggregates of 3D-printed particles, and complement stress-strain data with simultaneous x-ray videos and volumetric strain measurements. We find power law distributions of the slip magnitudes, and discuss their universality. Our data show that the multitude of small slips serves to gradually dilate the packing whereas the fewer large ones accompany significant compaction events. Our findings provide new insights into general features of granular materials during plastic deformation and highlight how small changes in particle shape can give rise to drastic differences in yielding behavior.

Geometric Mechanics for Continuous Swimmers on Granular Material

NASA Astrophysics Data System (ADS)

Dai, Jin; Faraji, Hossein; Schiebel, Perrin; Gong, Chaohui; Travers, Matthew; Hatton, Ross; Goldman, Daniel; Choset, Howie; Biorobotics Lab Collaboration; LaboratoryRobotics; Applied Mechanics (LRAM) Collaboration; Complex Rheology; Biomechanics Lab Collaboration

Animal experiments have shown that Chionactis occipitalis(N =10) effectively undulating on granular substrates exhibits a particular set of waveforms which can be approximated by a sinusoidal variation in curvature, i.e., a serpenoid wave. Furthermore, all snakes tested used a narrow subset of all available waveform parameters, measured as the relative curvature equal to 5.0+/-0.3, and number of waves on the body equal to1.8+/-0.1. We hypothesize that the serpenoid wave of a particular choice of parameters offers distinct benefit for locomotion on granular material. To test this hypothesis, we used a physical model (snake robot) to empirically explore the space of serpenoid motions, which is linearly spanned with two independent continuous serpenoid basis functions. The empirically derived height function map, which is a geometric mechanics tool for analyzing movements of cyclic gaits, showed that displacement per gait cycle increases with amplitude at small amplitudes, but reaches a peak value of 0.55 body-lengths at relative curvature equal to 6.0. This work signifies that with shape basis functions, geometric mechanics tools can be extended for continuous swimmers.

An automatic granular structure generation and finite element analysis of heterogeneous semi-solid materials

NASA Astrophysics Data System (ADS)

Sharifi, Hamid; Larouche, Daniel

2015-09-01

The quality of cast metal products depends on the capacity of the semi-solid metal to sustain the stresses generated during the casting. Predicting the evolution of these stresses with accuracy in the solidification interval should be highly helpful to avoid the formation of defects like hot tearing. This task is however very difficult because of the heterogeneous nature of the material. In this paper, we propose to evaluate the mechanical behaviour of a metal during solidification using a mesh generation technique of the heterogeneous semi-solid material for a finite element analysis at the microscopic level. This task is done on a two-dimensional (2D) domain in which the granular structure of the solid phase is generated surrounded by an intergranular and interdendritc liquid phase. Some basic solid grains are first constructed and projected in the 2D domain with random orientations and scale factors. Depending on their orientation, the basic grains are combined to produce larger grains or separated by a liquid film. Different basic grain shapes can produce different granular structures of the mushy zone. As a result, using this automatic grain generation procedure, we can investigate the effect of grain shapes and sizes on the thermo-mechanical behaviour of the semi-solid material. The granular models are automatically converted to the finite element meshes. The solid grains and the liquid phase are meshed properly using quadrilateral elements. This method has been used to simulate the microstructure of a binary aluminium-copper alloy (Al-5.8 wt% Cu) when the fraction solid is 0.92. Using the finite element method and the Mie-Grüneisen equation of state for the liquid phase, the transient mechanical behaviour of the mushy zone under tensile loading has been investigated. The stress distribution and the bridges, which are formed during the tensile loading, have been detected.

Numerical Simulation of Rocket Exhaust Interaction with Lunar Soil

NASA Technical Reports Server (NTRS)

Liever, Peter; Tosh, Abhijit; Curtis, Jennifer

2012-01-01

This technology development originated from the need to assess the debris threat resulting from soil material erosion induced by landing spacecraft rocket plume impingement on extraterrestrial planetary surfaces. The impact of soil debris was observed to be highly detrimental during NASA s Apollo lunar missions and will pose a threat for any future landings on the Moon, Mars, and other exploration targets. The innovation developed under this program provides a simulation tool that combines modeling of the diverse disciplines of rocket plume impingement gas dynamics, granular soil material liberation, and soil debris particle kinetics into one unified simulation system. The Unified Flow Solver (UFS) developed by CFDRC enabled the efficient, seamless simulation of mixed continuum and rarefied rocket plume flow utilizing a novel direct numerical simulation technique of the Boltzmann gas dynamics equation. The characteristics of the soil granular material response and modeling of the erosion and liberation processes were enabled through novel first principle-based granular mechanics models developed by the University of Florida specifically for the highly irregularly shaped and cohesive lunar regolith material. These tools were integrated into a unique simulation system that accounts for all relevant physics aspects: (1) Modeling of spacecraft rocket plume impingement flow under lunar vacuum environment resulting in a mixed continuum and rarefied flow; (2) Modeling of lunar soil characteristics to capture soil-specific effects of particle size and shape composition, soil layer cohesion and granular flow physics; and (3) Accurate tracking of soil-borne debris particles beginning with aerodynamically driven motion inside the plume to purely ballistic motion in lunar far field conditions. In the earlier project phase of this innovation, the capabilities of the UFS for mixed continuum and rarefied flow situations were validated and demonstrated for lunar lander rocket plume flow impingement under lunar vacuum conditions. Applications and improvements to the granular flow simulation tools contributed by the University of Florida were tested against Earth environment experimental results. Requirements for developing, validating, and demonstrating this solution environment were clearly identified, and an effective second phase execution plan was devised. In this phase, the physics models were refined and fully integrated into a production-oriented simulation tool set. Three-dimensional simulations of Apollo Lunar Excursion Module (LEM) and Altair landers (including full-scale lander geometry) established the practical applicability of the UFS simulation approach and its advanced performance level for large-scale realistic problems.

RCRA Sustainable Materials Management Information

EPA Pesticide Factsheets

This asset includes a broad variety of documents, descriptive data, technical analyses and guidance materials relative to voluntary improvements in resource conservation, the beneficial use of sustainable materials and the management of non-hazardous wastes and materials. Included in this asset are participant information and outreach materials of various voluntary programs relating to better materials and waste management programs. An example is the WasteWise program and Sustainable Materials Management (SMM) Challenges, which help organizations and businesses apply sustainable materials management practices to reduce municipal and select industrial wastes. Also included in this asset are guidance materials to assist municipalities in recycling and reuse of municipal solid waste, including diverting materials to composting, and the use of conversion methods such as anaerobic digestion. Another component are the data necessary to compile reports on the characterization of municipal solid waste (including such waste streams as food waste, yard and wood waste, discarded electronics, and household non-hazardous waste), the recycled content of manufactured goods, and other analyses performed using such tools as the Waste Assessment Reduction Model (WARM).For industrial non-hazardous waste, this asset includes guidance and outreach materials on industrial materials recycling and waste minimization. Finally, this asset includes research analyses on sustainable materia

Granular convection observed by magnetic resonance imaging.

PubMed

Ehrichs, E E; Jaeger, H M; Karczmar, G S; Knight, J B; Kuperman, V Y; Nagel, S R

1995-03-17

Vibrations in a granular material can spontaneously produce convection rolls reminiscent of those seen in fluids. Magnetic resonance imaging provides a sensitive and noninvasive probe for the detection of these convection currents, which have otherwise been difficult to observe. A magnetic resonance imaging study of convection in a column of poppy seeds yielded data about the detailed shape of the convection rolls and the depth dependence of the convection velocity. The velocity was found to decrease exponentially with depth; a simple model for this behavior is presented here.

Evaluation of geofabric in undercut on MSE wall stability.

DOT National Transportation Integrated Search

2011-04-01

Compaction of granular base materials at sites with fine grained native soils often causes unwanted : material loss due to penetration at the base. In 2007, ODOT began placing geotextile fabrics in the : undercut of MSE walls at the interface of the ...

Cost Reductions for Wastewater Treatment Utilizing Water Management at Holston Army Ammunition Plant

DTIC Science & Technology

1976-05-01

says that the granular carbon used is made from bituminous coal. As the waste stream pass through a bed of carbon granules, com- pounds are adsorbed to...findings of laboratory-scale reactor studies conducted at Purdue University for * Clark, Dietz and Associates. The original recommendations and cost...Pretreatment Denitrification by Submerged Anaerbbic I ilters I ~ Trickling Filters S F ,2al Clarification "•’i Pump - ~ Sludge ,Treatment Dual Media Filh:ration

Biopolymer-based thermoplastic mixture for producing solid biodegradable shaped bodies and its photo degradation stability

NASA Astrophysics Data System (ADS)

Sulong, Nurulsaidatulsyida; Rus, Anika Zafiah M.

2013-12-01

In recent years, biopolymers with controllable lifetimes have become increasingly important for many applications in the areas of agriculture, biomedical implants and drug release, forestry, wild life conservation and waste management. Natural oils are considered to be the most important class of renewable sources. They can be obtained from naturally occurring plants, such as sunflower, cotton, linseed and palm oil. In Malaysia, palm oil is an inexpensive and commodity material. Biopolymer produced from palm oil (Bio-VOP) is a naturally occurring biodegradable polymer and readily available from agriculture. For packaging use however, Bio-VOP is not thermoplastic and its granular form is unsuitable for most uses in the plastics industry, mainly due to processing difficulties during extrusion or injection moulding. Thus, research workers have developed several methods to blend Bio-VOP appropriately for industrial uses. In particular, injections moulding processes, graft copolymerisation, and preparation of blends with thermoplastic polymers have been studied to produce solid biodegradable shaped bodies. HDPE was chosen as commercial thermoplastic materials and was added with 10% Bio-VOP for the preparation of solid biodegradable shaped bodies named as HD-VOP. The UV light exposure of HD-VOP at 12 minutes upon gives the highest strength of this material that is 17.6 MPa. The morphological structure of HD-VOP shows dwi structure surface fracture which is brittle and ductile properties.

Early-state damage detection, characterization, and evolution using high-resolution computed tomography

NASA Astrophysics Data System (ADS)

Grandin, Robert John

Safely using materials in high performance applications requires adequately understanding the mechanisms which control the nucleation and evolution of damage. Most of a material's operational life is spent in a state with noncritical damage, and, for example in metals only a small portion of its life falls within the classical Paris Law regime of crack growth. Developing proper structural health and prognosis models requires understanding the behavior of damage in these early stages within the material's life, and this early-stage damage occurs on length scales at which the material may be considered "granular'' in the sense that the discrete regions which comprise the whole are large enough to require special consideration. Material performance depends upon the characteristics of the granules themselves as well as the interfaces between granules. As a result, properly studying early-stage damage in complex, granular materials requires a means to characterize changes in the granules and interfaces. The granular-scale can range from tenths of microns in ceramics, to single microns in fiber-reinforced composites, to tens of millimeters in concrete. The difficulty of direct-study is often overcome by exhaustive testing of macro-scale damage caused by gross material loads and abuse. Such testing, for example optical or electron microscopy, destructive and further, is costly when used to study the evolution of damage within a material and often limits the study to a few snapshots. New developments in high-resolution computed tomography (HRCT) provide the necessary spatial resolution to directly image the granule length-scale of many materials. Successful application of HRCT with fiber-reinforced composites, however, requires extending the HRCT performance beyond current limits. This dissertation will discuss improvements made in the field of CT reconstruction which enable resolutions to be pushed to the point of being able to image the fiber-scale damage structures and the application of this new capability to the study of early-stage damage.

Analytical modeling of structure-soil systems for lunar bases

NASA Technical Reports Server (NTRS)

Macari-Pasqualino, Jose Emir

1989-01-01

The study of the behavior of granular materials in a reduced gravity environment and under low effective stresses became a subject of great interest in the mid 1960's when NASA's Surveyor missions to the Moon began the first extraterrestrial investigation and it was found that Lunar soils exhibited properties quite unlike those on Earth. This subject gained interest during the years of the Apollo missions and more recently due to NASA's plans for future exploration and colonization of Moon and Mars. It has since been clear that a good understanding of the mechanical properties of granular materials under reduced gravity and at low effective stress levels is of paramount importance for the design and construction of surface and buried structures on these bodies. In order to achieve such an understanding it is desirable to develop a set of constitutive equations that describes the response of such materials as they are subjected to tractions and displacements. This presentation examines issues associated with conducting experiments on highly nonlinear granular materials under high and low effective stresses. The friction and dilatancy properties which affect the behavior of granular soils with low cohesion values are assessed. In order to simulate the highly nonlinear strength and stress-strain behavior of soils at low as well as high effective stresses, a versatile isotropic, pressure sensitive, third stress invariant dependent, cone-cap elasto-plastic constitutive model was proposed. The integration of the constitutive relations is performed via a fully implicit Backward Euler technique known as the Closest Point Projection Method. The model was implemented into a finite element code in order to study nonlinear boundary value problems associated with homogeneous as well as nonhomogeneous deformations at low as well as high effective stresses. The effect of gravity (self-weight) on the stress-strain-strength response of these materials is evaluated. The calibration of the model is performed via three techniques: (1) physical identification, (2) optimized calibration at the constitutive level, and (3) optimized calibration at the finite element level (Inverse Identification). Activities are summarized in graphic and outline form.

Efficiency of a multi-soil-layering system on wastewater treatment using environment-friendly filter materials.

PubMed

Ho, Chia-Chun; Wang, Pei-Hao

2015-03-23

The multi-soil-layering (MSL) system primarily comprises two parts, specifically, the soil mixture layer (SML) and the permeable layer (PL). In Japan, zeolite is typically used as the permeable layer material. In the present study, zeolite was substituted with comparatively cheaper and more environmentally friendly materials, such as expanded clay aggregates, oyster shells, and already-used granular activated carbon collected from water purification plants. A series of indoor tests indicated that the suspended solid (SS) removal efficiency of granular activated carbon was between 76.2% and 94.6%; zeolite and expanded clay aggregates achieved similar efficiencies that were between 53.7% and 87.4%, and oyster shells presented the lowest efficiency that was between 29.8% and 61.8%. Further results show that the oyster shell system required an increase of wastewater retention time by 2 to 4 times that of the zeolite system to maintain similar chemical oxygen demand (COD) removal efficiency. Among the four MSL samples, the zeolite system and granular activated carbon system demonstrated a stable NH3-N removal performance at 92.3%-99.8%. The expanded clay aggregate system present lower removal performance because of its low adsorption capacity and excessively large pores, causing NO3--N to be leached away under high hydraulic loading rate conditions. The total phosphorous (TP) removal efficiency of the MSL systems demonstrated no direct correlation with the permeable layer material. Therefore, all MSL samples achieved a TP efficiency of between 92.1% and 99.2%.

Protocol dependence of mechanical properties in granular systems.

PubMed

Inagaki, S; Otsuki, M; Sasa, S

2011-11-01

We study the protocol dependence of the mechanical properties of granular media by means of computer simulations. We control a protocol of realizing disk packings in a systematic manner. In 2D, by keeping material properties of the constituents identical, we carry out compaction with various strain rates. The disk packings exhibit the strain rate dependence of the critical packing fraction above which the pressure becomes non-zero. The observed behavior contrasts with the well-studied jamming transitions for frictionless disk packings. We also observe that the elastic moduli of the disk packings depend on the strain rate logarithmically. Our results suggest that there exists a time-dependent state variable to describe macroscopic material properties of disk packings, which depend on its protocol.

Steadily oscillating axial bands of binary granules in a nearly filled coaxial cylinder.

PubMed

Inagaki, Shio; Ebata, Hiroyuki; Yoshikawa, Kenichi

2015-01-01

Granular materials often segregate under mechanical agitation such as flowing, shaking, or rotating, in contrast to an expectation of mixing. It is well known that bidisperse mixtures of granular materials in a partially filled rotating cylinder exhibit monotonic coarsening dynamics of segregation. Here we report the steady oscillation of segregated axial bands under the stationary rotation of a nearly filled coaxial cylinder for O(10(3)) revolutions. The axial bands demonstrate steady back-and-forth motion along the axis of rotation. Experimental findings indicated that these axial band dynamics are driven by global convection throughout the system. The essential features of the spatiotemporal dynamics are reproduced with a simple phenomenological equation that incorporates the effect of global convection.

Mechanics of a granular skin

NASA Astrophysics Data System (ADS)

Karmakar, Somnath; Sane, Anit; Bhattacharya, S.; Ghosh, Shankar

2017-04-01

Magic sand, a hydrophobic toy granular material, is widely used in popular science instructions because of its nonintuitive mechanical properties. A detailed study of the failure of an underwater column of magic sand shows that these properties can be traced to a single phenomenon: the system self-generates a cohesive skin that encapsulates the material inside. The skin, consisting of pinned air-water-grain interfaces, shows multiscale mechanical properties: they range from contact-line dynamics in the intragrain roughness scale, to plastic flow at the grain scale, all the way to sample-scale mechanical responses. With decreasing rigidity of the skin, the failure mode transforms from brittle to ductile (both of which are collective in nature) to a complete disintegration at the single-grain scale.

A 2D Fourier tool for the analysis of photo-elastic effect in large granular assemblies

NASA Astrophysics Data System (ADS)

Leśniewska, Danuta

2017-06-01

Fourier transforms are the basic tool in constructing different types of image filters, mainly those reducing optical noise. Some DIC or PIV software also uses frequency space to obtain displacement fields from a series of digital images of a deforming body. The paper presents series of 2D Fourier transforms of photo-elastic transmission images, representing large pseudo 2D granular assembly, deforming under varying boundary conditions. The images related to different scales were acquired using the same image resolution, but taken at different distance from the sample. Fourier transforms of images, representing different stages of deformation, reveal characteristic features at the three (`macro-`, `meso-` and `micro-`) scales, which can serve as a data to study internal order-disorder transition within granular materials.

X-ray tomography system to investigate granular materials during mechanical loading

DOE Office of Scientific and Technical Information (OSTI.GOV)

Athanassiadis, Athanasios G.; Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139; La Rivière, Patrick J.

2014-08-15

We integrate a small and portable medical x-ray device with mechanical testing equipment to enable in situ, non-invasive measurements of a granular material's response to mechanical loading. We employ an orthopedic C-arm as the x-ray source and detector to image samples mounted in the materials tester. We discuss the design of a custom rotation stage, which allows for sample rotation and tomographic reconstruction under applied compressive stress. We then discuss the calibration of the system for 3D computed tomography, as well as the subsequent image reconstruction process. Using this system to reconstruct packings of 3D-printed particles, we resolve packing featuresmore » with 0.52 mm resolution in a (60 mm){sup 3} field of view. By analyzing the performance bounds of the system, we demonstrate that the reconstructions exhibit only moderate noise.« less

Imaging natural materials with a quasi-microscope. [spectrophotometry of granular materials

NASA Technical Reports Server (NTRS)

Bragg, S.; Arvidson, R.

1977-01-01

A Viking lander camera with auxilliary optics mounted inside the dust post was evaluated to determine its capability for imaging the inorganic properties of granular materials. During mission operations, prepared samples would be delivered to a plate positioned within the camera's field of view and depth of focus. The auxiliary optics would then allow soil samples to be imaged with an 11 pm pixel size in the broad band (high resolution, black and white) mode, and a 33 pm pixel size in the multispectral mode. The equipment will be used to characterize: (1) the size distribution of grains produced by igneous (intrusive and extrusive) processes or by shock metamorphism, (2) the size distribution resulting from crushing, chemical alteration, or by hydraulic or aerodynamic sorting; (3) the shape and degree of grain roundness and surface texture induced by mechanical and chemical alteration; and (4) the mineralogy and chemistry of grains.

High-speed imaging of traveling waves in a granular material during silo discharge.

PubMed

Börzsönyi, Tamás; Kovács, Zsolt

2011-03-01

We report experimental observations of sound waves in a granular material during resonant silo discharge called silo music. The grain motion was tracked by high-speed imaging while the resonance of the silo was detected by accelerometers and acoustic methods. The grains do not oscillate in phase at neighboring vertical locations, but information propagates upward in this system in the form of sound waves. We show that the wave velocity is not constant throughout the silo but considerably increases toward the lower end of the system, suggesting increased pressure in this region, where the flow changes from cylindrical to converging flow. In the upper part of the silo the wave velocity matches the sound velocity measured in the same material when standing (in the absence of flow). Grain oscillations show a stick-slip character only in the upper part of the silo.

Physical Explanation of Archie's Porosity Exponent in Granular Materials: A Process-Based, Pore-Scale Numerical Study

NASA Astrophysics Data System (ADS)

Niu, Qifei; Zhang, Chi

2018-02-01

The empirical Archie's law has been widely used in geosciences and engineering to explain the measured electrical resistivity of many geological materials, but its physical basis has not been fully understood yet. In this study, we use a pore-scale numerical approach combining discrete element-finite difference methods to study Archie's porosity exponent m of granular materials over a wide porosity range. Numerical results reveal that at dilute states (e.g., porosity ϕ > 65%), m is exclusively related to the particle shape and orientation. As the porosity decreases, the electric flow in pore space concentrates progressively near particle contacts and m increases continuously in response to the intensified nonuniformity of the local electrical field. It is also found that the increase in m is universally correlated with the volume fraction of pore throats for all the samples regardless of their particle shapes, particle size range, and porosities.

Waste water biological purification plants of dairy products industry and energy management

NASA Astrophysics Data System (ADS)

Stepanov, Sergey; Solkina, Olga; Stepanov, Alexander; Zhukova, Maria

2017-10-01

The paper presents results of engineering and economical comparison of waste water biological purification plants of dairy products industry. Three methods of purification are compared: traditional biological purification with the use of secondary clarifiers and afterpurification through granular-bed filters, biomembrane technology and physical-and-chemical treatment together with biomembrane technology for new construction conditions. The improvement of the biological purification technology using nitro-denitrification and membrane un-mixing of sludge mixture is a promising trend in this area. In these calculations, an energy management which is widely applied abroad was used. The descriptions of the three methods are illustrated with structural schemes. Costs of equipment and production areas are taken from manufacturers’ data. The research is aimed at an engineering and economical comparison of new constructions of waste water purification of dairy products industry. The experiment demonstrates advantages of biomembrane technology in waste water purification. This technology offers prospects of 122 million rubles cost saving during 25 years of operation when compared with of the technology of preparatory reagent flotation and of 13.7 million rubles cost saving compared to the option of traditional biological purification.

Microbial characteristics analysis and kinetic studies on substrate composition to methane after microbial and nutritional regulation of fruit and vegetable wastes anaerobic digestion.

PubMed

Zhao, Chunhui; Mu, Hui; Zhao, Yuxiao; Wang, Liguo; Zuo, Bin

2018-02-01

This study firstly evaluated the microbial role when choosing the acclimated anaerobic granular sludge (AGS) and waste activated sludge (WAS) as microbial and nutritional regulators to improve the biomethanation of fruit and vegetable wastes (FVW). Results showed that the enriched hydrogenotrophic methanogens, and Firmicutes and Spirochaeta in the AGS were responsible for the enhanced methane yield. A synthetic waste representing the mixture of WAS and FVW was then used to investigate the influences of different substrate composition on methane generations. The optimal mass ratio of carbohydrate/protein/cellulose was observed to be 50:45:5, and the corresponding methane yield was 411mL/g-VS added . Methane kinetic studies suggested that the modified Gompertz model fitted better with those substrates of carbohydrate- than protein-predominated. Parameter results indicated that the maximum methane yield and production rate were enhanced firstly and then reduced with the decreasing carbohydrate and increasing protein percentages; the lag phase time however increased continuously. Copyright © 2017 Elsevier Ltd. All rights reserved.

A hierarchy of granular continuum models: Why flowing grains are both simple and complex

NASA Astrophysics Data System (ADS)

Kamrin, Ken

2017-06-01

Granular materials have a strange propensity to behave as either a complex media or a simple media depending on the precise question being asked. This review paper offers a summary of granular flow rheologies for well-developed or steady-state motion, and seeks to explain this dichotomy through the vast range of complexity intrinsic to these models. A key observation is that to achieve accuracy in predicting flow fields in general geometries, one requires a model that accounts for a number of subtleties, most notably a nonlocal effect to account for cooperativity in the flow as induced by the finite size of grains. On the other hand, forces and tractions that develop on macro-scale, submerged boundaries appear to be minimally affected by grain size and, barring very rapid motions, are well represented by simple rate-independent frictional plasticity models. A major simplification observed in experiments of granular intrusion, which we refer to as the `resistive force hypothesis' of granular Resistive Force Theory, can be shown to arise directly from rate-independent plasticity. Because such plasticity models have so few parameters, and the major rheological parameter is a dimensionless internal friction coefficient, some of these simplifications can be seen as consequences of scaling.

Discharge flow of a granular media from a silo: effect of the packing fraction and of the hopper angle

NASA Astrophysics Data System (ADS)

Benyamine, Mebirika; Aussillous, Pascale; Dalloz-Dubrujeaud, Blanche

2017-06-01

Silos are widely used in the industry. While empirical predictions of the flow rate, based on scaling laws, have existed for more than a century (Hagen 1852, translated in [1] - Beverloo et al. [2]), recent advances have be made on the understanding of the control parameters of the flow. In particular, using continuous modeling together with a mu(I) granular rheology seem to be successful in predicting the flow rate for large numbers of beads at the aperture (Staron et al.[3], [4]). Moreover Janda et al.[5] have shown that the packing fraction at the outlet plays an important role when the number of beads at the apeture decreases. Based on these considerations, we have studied experimentally the discharge flow of a granular media from a rectangular silo. We have varied two main parameters: the angle of the hopper, and the bulk packing fraction of the granular material by using bidisperse mixtures. We propose a simple physical model to describe the effect of these parameters, considering a continuous granular media with a dilatancy law at the outlet. This model predicts well the dependance of the flow rate on the hopper angle as well as the dependance of the flow rate on the fine mass fraction of a bidisperse mixture.

Method of moments for the dilute granular flow of inelastic spheres

NASA Astrophysics Data System (ADS)

Strumendo, Matteo; Canu, Paolo

2002-10-01

Some peculiar features of granular materials (smooth, identical spheres) in rapid flow are the normal pressure differences and the related anisotropy of the velocity distribution function f(1). Kinetic theories have been proposed that account for the anisotropy, mostly based on a generalization of the Chapman-Enskog expansion [N. Sela and I. Goldhirsch, J. Fluid Mech. 361, 41 (1998)]. In the present paper, we approach the problem differently by means of the method of moments; previously, similar theories have been constructed for the nearly elastic behavior of granular matter but were not able to predict the normal pressures differences. To overcome these restrictions, we use as an approximation of the f(1) a truncated series expansion in Hermite polynomials around the Maxwellian distribution function. We used the approximated f(1) to evaluate the collisional source term and calculated all the resulting integrals; also, the difference in the mean velocity of the two colliding particles has been taken into account. To simulate the granular flows, all the second-order moment balances are considered together with the mass and momentum balances. In balance equations of the Nth-order moments, the (N+1)th-order moments (and their derivatives) appear: we therefore introduced closure equations to express them as functions of lower-order moments by a generalization of the ``elementary kinetic theory,'' instead of the classical procedure of neglecting the (N+1)th-order moments and their derivatives. We applied the model to the translational flow on an inclined chute obtaining the profiles of the solid volumetric fraction, the mean velocity, and all the second-order moments. The theoretical results have been compared with experimental data [E. Azanza, F. Chevoir, and P. Moucheront, J. Fluid Mech. 400, 199 (1999); T. G. Drake, J. Fluid Mech. 225, 121 (1991)] and all the features of the flow are reflected by the model: the decreasing exponential profile of the solid volumetric fraction, the parabolic shape of the mean velocity, the constancy of the granular temperature and of its components. Besides, the model predicts the normal pressures differences, typical of the granular materials.

Design of adaptive load mitigating materials usingnonlinear stress wave tailoring

DTIC Science & Technology

2016-02-24

for granular material use). 3 • Prof. Trudy Kriven (UIUC, Materials Science) is an expert in ceramic and geopolymer fabrication. • Prof. John...Figure A5.1: Schematic diagram showing the 1D chain of spherical elements in contact with (a) a uniform linear medium and (b) a composite linear...each material point to consisting of one of the given material constituents, we allow each material point to be assigned a composite material that is

Poultry litter-based activated carbon for removing heavy metal ions in water.

PubMed

Guo, Mingxin; Qiu, Guannan; Song, Weiping

2010-02-01

Utilization of poultry litter as a precursor material to manufacture activated carbon for treating heavy metal-contaminated water is a value-added strategy for recycling the organic waste. Batch adsorption experiments were conducted to investigate kinetics, isotherms, and capacity of poultry litter-based activated carbon for removing heavy metal ions in water. It was revealed that poultry litter-based activated carbon possessed significantly higher adsorption affinity and capacity for heavy metals than commercial activated carbons derived from bituminous coal and coconut shell. Adsorption of metal ions onto poultry litter-based carbon was rapid and followed Sigmoidal Chapman patterns as a function of contact time. Adsorption isotherms could be described by different models such as Langmuir and Freundlich equations, depending on the metal species and the coexistence of other metal ions. Potentially 404 mmol of Cu2+, 945 mmol of Pb2+, 236 mmol of Zn2+, and 250-300 mmol of Cd2+ would be adsorbed per kg of poultry litter-derived activated carbon. Releases of nutrients and metal ions from litter-derived carbon did not pose secondary water contamination risks. The study suggests that poultry litter can be utilized as a precursor material for economically manufacturing granular activated carbon that is to be used in wastewater treatment for removing heavy metals.

Effect of granular media on the vibrational response of a resonant structure: theory and experiment.

PubMed

Valenza, John J; Hsu, Chaur-Jian; Johnson, David Linton

2010-11-01

The acoustic response of a structure that contains a cavity filled with a loose granular material is analyzed. The inputs to the theory are the effective masses of each subsystem: that of the empty-cavity resonating structure and that of the granular medium within the cavity. This theory accurately predicts the frequencies, widths, and relative amplitudes of the various flexural mode resonances observed with rectangular bars, each having a cavity filled with loose tungsten granules. Inasmuch as the dominant mechanism for damping is due to adsorbed water at the grain-grain contacts, the significant effects of humidity on both the effective mass of the granular medium as well as on the response of the grain-loaded bars are monitored. Here, depending upon the humidity and the preparation protocol, it is possible to observe one, two, or three distinct resonances in a wide frequency range (1-5 kHz) over which the empty bar has but one resonance. These effects are understood in terms of the theoretical framework, which may simplify in terms of perturbation theories.

Computational study on the behaviors of granular materials under mechanical cycling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xiaoliang; Ye, Minyou; Chen, Hongli, E-mail: hlchen1@ustc.edu.cn

2015-11-07

Considering that fusion pebble beds are probably subjected to the cyclic compression excitation in their future applications, we presented a computational study to report the effect of mechanical cycling on the behaviors of granular matter. The correctness of our numerical experiments was confirmed by a comparison with the effective medium theory. Under the cyclic loads, the fast granular compaction was observed to evolve in a stretched exponential law. Besides, the increasing stiffening in packing structure, especially the decreasing moduli pressure dependence due to granular consolidation, was also observed. For the force chains inside the pebble beds, both the internal forcemore » distribution and the spatial distribution of force chains would become increasingly uniform as the external force perturbation proceeded and therefore produced the stress relief on grains. In this case, the originally proposed 3-parameter Mueth function was found to fail to describe the internal force distribution. Thereby, its improved functional form with 4 parameters was proposed here and proved to better fit the data. These findings will provide more detailed information on the pebble beds for the relevant fusion design and analysis.« less

A Three-Stage Mechanistic Model for Solidification Cracking During Welding of Steel

NASA Astrophysics Data System (ADS)

Aucott, L.; Huang, D.; Dong, H. B.; Wen, S. W.; Marsden, J.; Rack, A.; Cocks, A. C. F.

2018-03-01

A three-stage mechanistic model for solidification cracking during TIG welding of steel is proposed from in situ synchrotron X-ray imaging of solidification cracking and subsequent analysis of fracture surfaces. Stage 1—Nucleation of inter-granular hot cracks: cracks nucleate inter-granularly in sub-surface where maximum volumetric strain is localized and volume fraction of liquid is less than 0.1; the crack nuclei occur at solute-enriched liquid pockets which remain trapped in increasingly impermeable semi-solid skeleton. Stage 2—Coalescence of cracks via inter-granular fracture: as the applied strain increases, cracks coalesce through inter-granular fracture; the coalescence path is preferential to the direction of the heat source and propagates through the grain boundaries to solidifying dendrites. Stage 3—Propagation through inter-dendritic hot tearing: inter-dendritic hot tearing occurs along the boundaries between solidifying columnar dendrites with higher liquid fraction. It is recommended that future solidification cracking criterion shall be based on the application of multiphase mechanics and fracture mechanics to the failure of semi-solid materials.

Low-resistive penetration in granular media

NASA Astrophysics Data System (ADS)

Darbois Texier, Baptiste; Ibarra, Alejandro; Melo, Fransisco

The quasi-static immersion of an intruder into a granular assembly requires a force that is several orders of magnitude larger than necessary in fluids under similar conditions. This occurs as a result of the progressive formation of a network composed of force chains, which simultaneously increase in size with intruder penetration. The present work shows that the resisting force for the immersion of an intruder into a granular material can be reduced by an order of magnitude with mechanical vibrations of small amplitude (A = 10 μm) and low frequency (f = 50-200 Hz). The effect of the vibrations characteristics and the intruder geometry on the drop of the resistive force were inspected experimentally. Thanks to flow visualizations, it has been shown that vibrations induce a local convection into the granular media leading to the modification of the network of force chains. Moreover, scaling arguments are developed in order to rationalize our observations and to predict under which circumstances the resistive force is reduced. Finally, the use of such a phenomenon in the animal kingdom and the technological world will be discussed.

Rock-bed thermocline storage: A numerical analysis of granular bed behavior and interaction with storage tank

NASA Astrophysics Data System (ADS)

Sassine, Nahia; Donzé, Frédéric-Victor; Bruch, Arnaud; Harthong, Barthélemy

2017-06-01

Thermal Energy Storage (TES) systems are central elements of various types of power plants operated using renewable energy sources. Packed bed TES can be considered as a cost-effective solution in concentrated solar power plants (CSP). Such a device is made up of a tank filled with a granular bed through which heat-transfer fluid circulates. However, in such devices, the tank might be subjected to catastrophic failure induced by a mechanical phenomenon known as thermal ratcheting. Thermal stresses are accumulated during cycles of loading and unloading until the failure happens. This paper aims at studying the evolution of tank wall stresses over granular bed thermal cycles, taking into account both thermal and mechanical loads, with a numerical model based on the discrete element method (DEM). Simulations were performed to study two different thermal configurations: (i) the tank is heated homogenously along its height or (ii) with a vertical gradient of temperature. Then, the resulting loading stresses applied on the tank are compared as well the response of the internal granular material.

Regulatory Exclusions and Alternative Standards for the Recycling of Materials, Solid Wastes and Hazardous Wastes

EPA Pesticide Factsheets

Determining the Level of Regulation for Hazardous Waste Recycling, Recycled Materials that are not Subject to RCRA Hazardous Waste Regulation, Materials Subject to Alternative Regulatory Controls, Materials Subject to Full Hazardous Waste Regulations.

Dense granular flow around a rigid or flexible intruder

NASA Astrophysics Data System (ADS)

Kolb, Evelyne; Adda-Bedia, Mokhtar

2012-02-01

We experimentally studied the flow of a dense granular material around an obstacle (rigid cylinder or flexible plate) placed in a 2 dimensional confined cell at a packing fraction near the 2D jamming threshold. In the case of the rigid obstacle, the displacement field of grains as well as the drag force experienced by the obstacle were simultaneously recorded and a parametric study was done by changing the cell size, the intruder diameter or the packing fraction. The drag force experienced by the intruder and the formation of a wake behind the obstacle were very sensitive to the approach to jamming. The same experimental set-up was adapted to a flexible intruder and coupling between the granular flow and fibre deflexion were imaged. The deformation of the fibre could be compared with theoretical predictions from elastica.

Stratification, segregation, and mixing of granular materials in quasi-two-dimensional bounded heaps.

PubMed

Fan, Yi; Boukerkour, Youcef; Blanc, Thibault; Umbanhowar, Paul B; Ottino, Julio M; Lueptow, Richard M

2012-11-01

Segregation and mixing of granular mixtures during heap formation has important consequences in industry and agriculture. This research investigates three different final particle configurations of bidisperse granular mixtures--stratified, segregated and mixed--during filling of quasi-two-dimensional silos. We consider a large number and wide range of control parameters, including particle size ratio, flow rate, system size, and heap rise velocity. The boundary between stratified and unstratified states is primarily controlled by the two-dimensional flow rate, with the critical flow rate for the transition depending weakly on particle size ratio and flowing layer length. In contrast, the transition from segregated to mixed states is controlled by the rise velocity of the heap, a control parameter not previously considered. The critical rise velocity for the transition depends strongly on the particle size ratio.

Mechanics of Granular Materials: Experimentation and Simulations for Determining the Compressive and Shear Behaviors of Sand at Granular and Meso Scales

DTIC Science & Technology

2011-09-30

stresses below 10 MPa . This linear phase is followed by rapid collapse of voids with increase in axial stress. The void ratio curves for different...loading. The vertically applied load on the indenter tip was increased until it reached a user-defined value, followed by unloading. The load...0.425 mm, the P30 Young’s modulus values increase from 97.4 GPa, to 102.1 GPa and 108.9 GPa, respectively. As the grain sizes reduce further, the P30

Three-phase fracturing in granular material

NASA Astrophysics Data System (ADS)

Campbell, James; Sandnes, Bjornar

2015-04-01

There exist numerous geo-engineering scenarios involving the invasion of a gas into a water-saturated porous medium: in fracking, this may occur during the fracking process itself or during subsequent gas penetration into propant beds; the process is also at the heart of carbon dioxide sequestration. We use a bed of water-saturated glass beads confined within a Hele-Shaw cell as a model system to illuminate these processes. Depending on packing density, injection rate and other factors, air injected into this system may invade in a broad variety of patterns, including viscous fingering, capillary invasion, bubble formation and fracturing. Here we focus primarily on the latter case. Fracturing is observed when air is injected into a loosely packed bed of unconsolidated granular material. Our approach allows us to image the complete fracture pattern as it forms, and as such to study both the topographical properties of the resulting pattern (fracture density, braching frequency etc) and the dynamics of its growth. We present an overview of the fracturing phenomenon within the context of pattern formation in granular fluids as a whole. We discuss how fracturing arises from an interplay between frictional, capillary and viscous forces, and demonstrate the influence of various parameters on the result.

Granular statistical mechanics - Building on the legacy of Sir Sam Edwards

NASA Astrophysics Data System (ADS)

Blumenfeld, Raphael

When Sir Sam Edwards laid down the foundations for the statistical mechanics of jammed granular materials he opened a new field in soft condensed matter and many followed. In this presentation we review briefly the Edwards formalism and some of its less discussed consequences. We point out that the formalism is useful for other classes of systems - cellular and porous materials. A certain shortcoming of the original formalism is then discussed and a modification to overcome it is proposed. Finally, a derivation of an equation of state with the new formalism is presented; the equation of state is analogous to the PVT relation for thermal gases, relating the volume, the boundary stress and measures of the structural and stress fluctuations. NUDT, Changsha, China, Imperial College London, UK, Cambridge University, UK.

A thermomechanical constitutive model for cemented granular materials with quantifiable internal variables. Part I-Theory

NASA Astrophysics Data System (ADS)

Tengattini, Alessandro; Das, Arghya; Nguyen, Giang D.; Viggiani, Gioacchino; Hall, Stephen A.; Einav, Itai

2014-10-01

This is the first of two papers introducing a novel thermomechanical continuum constitutive model for cemented granular materials. Here, we establish the theoretical foundations of the model, and highlight its novelties. At the limit of no cement, the model is fully consistent with the original Breakage Mechanics model. An essential ingredient of the model is the use of measurable and micro-mechanics based internal variables, describing the evolution of the dominant inelastic processes. This imposes a link between the macroscopic mechanical behavior and the statistically averaged evolution of the microstructure. As a consequence this model requires only a few physically identifiable parameters, including those of the original breakage model and new ones describing the cement: its volume fraction, its critical damage energy and bulk stiffness, and the cohesion.

Granular Materials and the Risks They Pose for Success on the Moon and Mars

NASA Technical Reports Server (NTRS)

Wilkinson, R. Allen; Behringer, Robert P.; Jenkins, James T.; Louge, Michel Y.

2004-01-01

Working with soil, sand, powders, ores, cement and sintered bricks, excavating, grading construction sites, driving off-road, transporting granules in chutes and pipes, sifting gravel, separating solids from gases, and using hoppers are so routine that it seems straightforward to do it on the Moon and Mars as we do it on Earth. This paper brings to the fore how little these processes are understood and the millennia-long trial-and-error practices that lead to today's massive over-design, high failure rate, and extensive incremental scaling up of industrial processes because of the inadequate predictive tools for design. We present a number of pragmatic scenarios where granular materials play a role, the risks involved, and what understanding is needed to greatly reduce the risks.

Granular Materials and the Risks They Pose for Success on the Moon and Mars

NASA Astrophysics Data System (ADS)

Wilkinson, R. Allen; Behringer, Robert P.; Jenkins, James T.; Louge, Michel Y.

2005-02-01

Working with soil, sand, powders, ores, cement and sintered bricks, excavating, grading construction sites, driving off-road, transporting granules in chutes and pipes, sifting gravel, separating solids from gases, and using hoppers are so routine that it seems straightforward to do it on the Moon and Mars as we do it on Earth. This paper brings to the fore how little these processes are understood and the millennia-long trial-and-error practices that lead to today's massive over-design, high failure rate, and extensive incremental scaling up of industrial processes because of the inadequate predictive tools for design. We present a number of pragmatic scenarios where granular materials play a role, the risks involved, and what understanding is needed to greatly reduce the risks.

Granular activated carbon pilot treatment studies for explosives removal from contaminated groundwater

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wujcik, W.J.; Lowe, W.L.; Marks, P.J.

1992-08-01

Manufacturing activities at Army Ammunition Plants (AAPs) result in the production of organic wastewaters that contain both explosive residues and other organic chemicals. As a result of past waste practices at such plants, explosive residues may leach through the soil and contaminate groundwater. Two pilot studies were performed to evaluate the use of granular activated carbon (GAC) to treat groundwater contaminated with explosives at Badger AAP and Milan AAP. An additional goal of the Badger AAP study was to examine the potential discharge of explosives 2,4-DNT and 2,6-DNT from a packed column air stripper used to remove volatile organic compoundsmore » from groundwater. A laboratory method was developed for the BAAP study to permit lower detection levels for 2,4-DNT and 2,6-DNT (0.46[mu]g/L and 0.017 [mu]g/L, respectively). The studies concluded that removal of explosives from groundwater using continuous flow GAC is feasible. 14 refs., 10 figs., 11 tabs.« less

Leaching behavior of total organic carbon, nitrogen, and phosphorus from banana peel.

PubMed

Jiang, Ruixue; Sun, Shujuan; Xu, Yan; Qiu, Xiudong; Yang, Jili; Li, Xiaochen

2015-01-01

The leaching behavior of organic carbon and nutrient compounds from banana peel (BP) was investigated in batch assays with respect to particle size, contact time, pH value, and temperature. The granularity, contact time, pH, and temperature caused no significant effects on the leaching of total phosphorus (TP) from the BP. The maximum leached total nitrogen (TN) content was found at pH 5.0 and 90 minutes, while no significant effects were caused by the granularity and temperature. The maximum leached total organic carbon (TOC) content was found by using a powder of 40 mesh, 150 minutes and at pH 6.0, while the temperature had no effect on the TOC leaching. The proportions of the TN, TP, and TOC contents leached from the dried BP ranged from 33.6% to 40.9%, 60.4% to 72.7%, and 8.2% to 9.9%, respectively, indicating that BP could be a potential pollution source for surface and ground water if discharged as domestic waste or reutilized without pretreatment.

Roles of magnetite and granular activated carbon in improvement of anaerobic sludge digestion.

PubMed

Peng, Hong; Zhang, Yaobin; Tan, Dongmei; Zhao, Zhiqiang; Zhao, Huimin; Quan, Xie

2018-02-01

Granular activated carbon (GAC) or magnetite could promote methane production from organic wastes, but their roles in enhancing anaerobic sludge digestion have not been clarified. GAC, magnetite and their combination were complemented into sludge digesters, respectively. Experimental results showed that average methane production increased by 7.3% for magnetite, 13.1% for GAC, and 20% for the combination of magnetite and GAC, and the effluent TCOD of the control, magnetite, GAC and magnetite-GAC digesters on day 56 were 53.2, 49.6, 48.0 and 46.6 g/L, respectively. Scanning electron microscope (SEM), nitrogen adsorption, Fourier transform infrared spectroscopy (FTIR) and microbial analysis indicated that magnetite enriched iron-reducing bacteria responsible for sludge hydrolysis while GAC enhanced syntrophic metabolism between iron-reducing bacteria and methanogens due to its high electrical conductivity and large surface area. Supplementing magnetite and GAC together into an anaerobic digester simultaneously accelerated sludge hydrolysis and methane production, resulting in better sludge digestion performance. Copyright © 2017 Elsevier Ltd. All rights reserved.

Upscaling the pollutant emission from mixed recycled aggregates under compaction for civil applications.

PubMed

Galvín, Adela P; Ayuso, Jesús; Barbudo, Auxi; Cabrera, Manuel; López-Uceda, Antonio; Rosales, Julia

2017-12-27

In general terms, plant managers of sites producing construction wastes assess materials according to concise, legally recommended leaching tests that do not consider the compaction stage of the materials when they are applied on-site. Thus, the tests do not account for the real on-site physical conditions of the recycled aggregates used in civil works (e.g., roads or embankments). This leads to errors in estimating the pollutant potential of these materials. For that reason, in the present research, an experimental procedure is designed as a leaching test for construction materials under compaction. The aim of this laboratory test (designed specifically for the granular materials used in civil engineering infrastructures) is to evaluate the release of pollutant elements when the recycled aggregate is tested at its commercial grain-size distribution and when the material is compacted under on-site conditions. Two recycled aggregates with different gypsum contents (0.95 and 2.57%) were used in this study. In addition to the designed leaching laboratory test, the conventional compliance leaching test and the Dutch percolation test were performed. The results of the new leaching method were compared with the conventional leaching test results. After analysis, the chromium and sulphate levels obtained from the newly designed test were lower than those obtained from the conventional leaching test, and these were considered more seriously pollutant elements. This result confirms that when the leaching behaviour is evaluated for construction aggregates without density alteration, crushing the aggregate and using only the finest fraction, as is done in the conventional test (which is an unrealistic situation for aggregates that are applied under on-site conditions), the leaching behaviour is not accurately assessed.

Granular Material Response to Dynamic Shock Compression: A Study of SiO2 in the Form of Sand and Soda Lime Glass Beads

DTIC Science & Technology

2011-06-01

method was used vice more accurate immersion techniques based on Archimedes principle . The initial volume of the technical sand was determined by filling...of Porous Materials In solid materials small stresses and strains are very close to being the same as the shock Hugoniot and the principle isentrope

Incident Waste Decision Support Tool - Waste Materials ...

EPA Pesticide Factsheets

Report This is the technical documentation to the waste materials estimator module of I-WASTE. This document outlines the methodology and data used to develop the Waste Materials Estimator (WME) contained in the Incident Waste Decision Support Tool (I-WASTE DST). Specifically, this document reflects version 6.4 of the I-WASTE DST. The WME is one of four primary features of the I-WASTE DST. The WME is both a standalone calculator that generates waste estimates in terms of broad waste categories, and is also integrated into the Incident Planning and Response section of the tool where default inventories of specific waste items are provided in addition to the estimates for the broader waste categories. The WME can generate waste estimates for both common materials found in open spaces (soil, vegetation, concrete, and asphalt) and for a vast array of items and materials found in common structures.

Acoustics of multiscale sorptive porous materials

NASA Astrophysics Data System (ADS)

Venegas, R.; Boutin, C.; Umnova, O.

2017-08-01

This paper investigates sound propagation in multiscale rigid-frame porous materials that support mass transfer processes, such as sorption and different types of diffusion, in addition to the usual visco-thermo-inertial interactions. The two-scale asymptotic method of homogenization for periodic media is successively used to derive the macroscopic equations describing sound propagation through the material. This allowed us to conclude that the macroscopic mass balance is significantly modified by sorption, inter-scale (micro- to/from nanopore scales) mass diffusion, and inter-scale (pore to/from micro- and nanopore scales) pressure diffusion. This modification is accounted for by the dynamic compressibility of the effective saturating fluid that presents atypical properties that lead to slower speed of sound and higher sound attenuation, particularly at low frequencies. In contrast, it is shown that the physical processes occurring at the micro-nano-scale do not affect the macroscopic fluid flow through the material. The developed theory is exemplified by introducing an analytical model for multiscale sorptive granular materials, which is experimentally validated by comparing its predictions with acoustic measurements on granular activated carbons. Furthermore, we provide empirical evidence supporting an alternative method for measuring sorption and mass diffusion properties of multiscale sorptive materials using sound waves.

Final Report: Design of adaptive load mitigating materials using nonlinear stress wave tailoring

DTIC Science & Technology

2016-02-26

for granular material use). 3 • Prof. Trudy Kriven (UIUC, Materials Science) is an expert in ceramic and geopolymer fabrication. • Prof. John...Figure A5.1: Schematic diagram showing the 1D chain of spherical elements in contact with (a) a uniform linear medium and (b) a composite linear...each material point to consisting of one of the given material constituents, we allow each material point to be assigned a composite material that is

Efficiency of a Multi-Soil-Layering System on Wastewater Treatment Using Environment-Friendly Filter Materials

PubMed Central

Ho, Chia-Chun; Wang, Pei-Hao

2015-01-01

The multi-soil-layering (MSL) system primarily comprises two parts, specifically, the soil mixture layer (SML) and the permeable layer (PL). In Japan, zeolite is typically used as the permeable layer material. In the present study, zeolite was substituted with comparatively cheaper and more environmentally friendly materials, such as expanded clay aggregates, oyster shells, and already-used granular activated carbon collected from water purification plants. A series of indoor tests indicated that the suspended solid (SS) removal efficiency of granular activated carbon was between 76.2% and 94.6%; zeolite and expanded clay aggregates achieved similar efficiencies that were between 53.7% and 87.4%, and oyster shells presented the lowest efficiency that was between 29.8% and 61.8%. Further results show that the oyster shell system required an increase of wastewater retention time by 2 to 4 times that of the zeolite system to maintain similar chemical oxygen demand (COD) removal efficiency. Among the four MSL samples, the zeolite system and granular activated carbon system demonstrated a stable NH3-N removal performance at 92.3%–99.8%. The expanded clay aggregate system present lower removal performance because of its low adsorption capacity and excessively large pores, causing NO3−-N to be leached away under high hydraulic loading rate conditions. The total phosphorous (TP) removal efficiency of the MSL systems demonstrated no direct correlation with the permeable layer material. Therefore, all MSL samples achieved a TP efficiency of between 92.1% and 99.2%. PMID:25809517

How sand grains stop a high speed intruder

NASA Astrophysics Data System (ADS)

Behringer, Robert

When a speeding intruder impacts on a granular material, it comes rapidly to rest after penetrating only a modest distance. Empirical dynamical models, dating to the 19th century (if not earlier), describe the drag on the intruder in terms of two types of depth-dependent forces: one a static force, which also includes gravity, and the other a collisional force proportional to the square of the instantaneous speed of the intruder. What processes occur in the material to so quickly decelerate the intruder? We address this question through experiments and simulations (work of Lou Kondic and collaborators). We first probe the granular response using quasi-two-dimensional granular materials consisting of photoelastic discs. When such a particle experiences a force, it appears bright under cross-polarized illumination. High speed video reveals dynamic force transmission into the material along force chains that form in response to the intruder motion. These chains are nearly normal to the intruder surface, implying that collisional rather than frictional forces dominate the momentum transfer from intruder to grains. These observations allow the formation of a collision-based model that correctly captures the collisional drag force for both 2D and 3D intruders of a variety of shapes. This talk will develop a collisional picture of impact, and also explore the change in the system response as the impact speed increases. Experimental collaborators include Abe Clark, Cacey Stevens Bester, and Alec Petersen. This work supported by DTRA, NSF Grant DMR1206351, NASA Grant NNX15AD38G, and the William M. Keck Foundation.

Granular media in the context of small bodies

NASA Astrophysics Data System (ADS)

Tancredi, G.

2014-07-01

Granular materials of different particle sizes are present on the surface and the interior of several atmosphereless Solar System bodies. The presence of very fine particles on the surface of the Moon, the so-called regolith, was confirmed by the Apollo astronauts. From the polarimetric observations and phase angle curves, it is possible to indirectly infer the presence of fine particles on the surfaces of asteroids and planetary satellites. More recently, the visit of spacecraft to several asteroids and comets has provided us with close pictures of the surface, where particles of a wide size range from cm to hundreds of meters have been directly observed. The presence of even finer particles on the visited bodies can also be inferred from image analysis. Solar System bodies smaller than a few hundred km may have a variety of internal structures: monolithic single bodies, objects with internal fractures, rubble piles maintained as a single object by self-gravity, etc. After the visit of the small asteroid Itokawa, it has been speculated that ''some small asteroids appear to be clumps of gravel glued by a very weak gravity field'' (Asphaug 2007). We still do not know the internal structure of these rubble piles and the size distribution of the interior constituents, but these clumps could have several million meter-sized boulders inside. There are several pieces of evidence that many asteroids are agglomerates of small components, like: - Rotation periods for small asteroids - Tidal disruption of asteroids and comets when they enter the Roche's limit of a massive object - The existence of crater chains like the ones observed in Ganymede - Low density estimates (< 2 gr/cm^3) for many asteroids like Mathilde It has been proposed that several typical processes of granular materials (such as: the size segregation of boulders on Itokawa, the displacement of boulders on Eros, the ejection of dust clouds after impacts) can explain some features observed on these bodies. We review the numerical and experimental studies on granular materials with relevance to the understanding of the physical processes on the interior and the surfaces of minor bodies of the Solar System. In particular, we compare the different codes in use to perform numerical simulations of the physical evolution of these objects. We highlight results of these simulations. Some groups have been involved in laboratory experiments on granular material trying to reproduce the conditions in space: vacuum and low gravity. We describe the experimental set-ups and some results of these experiments. Some open problems and future line of work in this field will be presented.