Application of Mechanics to Plant Seeds as a Granular or Particulate Material

The mechanical behavior of plant seeds as a granular or particulate material dramatically differs from the mechanical behavior of solid materials. This difference is caused by the possibility of partially autonomous movement and rotation of seeds, their mutual contacts, or due to the occurrence of the second fluid phase among the seeds at the stage of their moving or processing. For obtaining the economic effects from the seeds (energy, nutrients, livestock, etc.), seeds must often be subjected to mechanical treatment. In this context application of mechanics as science concerned with the behavior of physical bodies when subjected to forces or displacements is very important and needed. One of the goals of this chapter is therefore to provide an overview for readers who are not primarily concerned with mechanics but who are interested in the behavior of seeds in the context of biology, agriculture, and pharmacy or food industry. This chapter is therefore focused on both an overview of the principles of mechanics of granular or particulate materials and the presentation of experimental results particularly in the area of mechanical extraction of oil from seeds

Shear stress distribution within narrowly constrained structured grains and granulated powder beds

An experimental study is presented here to understand the stress transmission characteristics under different geometrical arrangements of particulates inside a narrow chamber subjected to axial compression loading. The multi-grain systems considered here are face-centred, simple cubic and poly-dispersed structures, as well as inclusions embedded inside seeded, unseeded and cohesive powder bed of Durcal (calcium carbonate). The distribution of the maximum shear stress, direction of the major principal stress and shear stress concentration factor were obtained using photo stress analysis tomography (PSAT). The results show that the maximum shear stress distribution in the simple cubic structure is chain-like and self-repetitive, i.e, a single grain behaviour is representative of the whole system. This is not the case in the case of other granular packing. In the case of the inclusion surrounded by powder media, the maximum shear stress distribution in the inclusion occurs through ring-like structures, which are different from those observed in the structured granular packing. This tendency increases for an increase in the cohesivity of the surrounding particulates. In the granular systems, the direction of the major principal stress is mostly orthogonal to the direction of loading except in some particles in the random granular packing. In the case of inclusion surrounded by Durcal particulates, the directional of the major principal stress acts along the direction of the axial loading except in the ring region where this tends to be oblique to the direction of axial loading. Estimates of the shear stress concentration factor (k) show that, k tends to be independent of the structural arrangement of granular packing at higher load levels. In the case of inclusion surrounded by powder bed, k for the seeded granulated particulate bed is mostly independent of the external load levels. In the case of unseeded particulate (granulated) bed, a fluctuation in k is observed with the loading level. This suggests that the seeded granules could distribute stresses in a stable manner without much change in the nature of shear stress-transmitting fabric of the particulate contacts under external loading. An increase in the cohesion of particulate bed results in more plastic deformation as shown by the differential shear stress concentration factor. The results reported in this study show the usefulness of optical stress analysis to shed some scientific lights on unravelling some of the complexities of particulate systems under different structural arrangements of grains and surrounding conditions of the inclusions in particulate media

A review of the meteorological parameters which affect aerial application

The ambient wind field and temperature gradient were found to be the most important parameters. Investigation results indicated that the majority of meteorological parameters affecting dispersion were interdependent and the exact mechanism by which these factors influence the particle dispersion was largely unknown. The types and approximately ranges of instrumented capabilities for a systematic study of the significant meteorological parameters influencing aerial applications were defined. Current mathematical dispersion models were also briefly reviewed. Unfortunately, a rigorous dispersion model which could be applied to aerial application was not available

Discrete element modelling of the dynamic behaviour of non-spherical particulate materials

PhD ThesisA numerical model based on the discrete element (DE) method, for modelling the flow of irregularly shaped, smooth-surfaced particles in a 3-D system is presented. An existing DE program for modelling the contact between spherical particles in periodic space (without real walls or boundaries) was modified to model non-spherical particles in a system with containing walls. The new model was validated against analytical calculations of single particle movements and also experimentally against data from physical experiments using synthetic non-spherical particles at both a particle and bulk scale. It was then used to study the effect of particle shape on the flow behaviour of assemblies of particles with various aspect ratios discharging from a flat-bottomed hopper. The particles were modelled using the Multi-Sphere Method (MSM) which is based on the CSG (Constructive Solid Geometry) technique for construction of complex solids by combining primitive shapes. In this method particle geometry is approximated using overlapping spheres of arbitrary diameter which are fixed in position relative to each other. The contact mechanics and contact detection method are the same as those used for spheres, except that translation and rotation of element spheres are calculated with respect to the motion of the whole particle....Numerical simulations of packing and flow of particles from a flat-bottomed hopper with a range of aspect ratios were performed to investigate the effect of particle shape on packing and flow behaviour of a particulate assembly. It was found that the particle shape influenced both bed structure and flow characteristics such as flow pattern, shear band strength and the occurrence of bridging. The flow of the bed of spherical particles was smoother than the flow of beds of elongated particles in which flow was fluctuating and there was more resistance to shear.Ministry of Culture and Higher Education of IRAN: University of Mashhad

CFD Simulation of Mixing And Segregation in a Tapered Fluidized Bed

Fluidization of different materials results either in a well-mixed or a segregated bed. Depending upon the operating conditions, smaller particles (floatsam) tend to rise to the bed, and larger particles (jetsam) tend to sink to the bottom of the bed. The tapered fluidized bed can be used to overcome certain draw backs of the gas-solid system because of the fact that a velocity gradient exists along the axial direction of the bed with increase in cross-sectional area. To study the dynamic characteristics of the homogenous mixture of regular and irregular particles several experiments have been carried out with varying compositions.The particle flow pattern and granule segregation in tapered fluidized bed have been studied by first fluidizing the beds of varying total mass and granule fractions and then defluidize them suddenly to freeze the composition, section the bed in layers, and determine the composition in each layer by sieving. A series of unsteady, three-fluid CFD simulations were performed using FLUENTTM 6.2. Simulation parameters viz. solution technique, grid, maximum packing fraction and operating conditions like gas velocity were each investigated for the relative effects on particle mixing and segregation. Good agreement of solid volume fraction profile was obtained between the experimental results and simulation results for regular particle

Homogeneity assessment of multi-element heterogeneous granular mixtures by using Multivariate Analysis of Variance

Rad se bavi analizom homogenosti heterogenih zrnatih smjesa s više sastojaka. U tu se svrhu primijenila multivarijantna analiza variance. Istraživanje je provedeno u pogonu za proizvodnju krme koristeći vertikalni mikser s pužnom miješalicom u koji staje masa materijala od 2,1 ÷ 2,2 tone. Analizirale su se krmne smjese sastavljene od desetak vrsta raznog sjemena s različitim dimenzijama zrna, različitih gustoća i oblika. Homogenost smjese određena je uzimanjem uzoraka tijekom punjenja vreća. Pokazalo se – na osnovu statističkih ispitivanja – da je koncentracija pojedinačnih multi-elemenata, heterogenih zrnatih mješavina ista u čitavoj količini krmne smjese. Smjese su homogene (jednolike), što je od bitne važnosti, kada se procjenjuje kvaliteta dobivenih smjesa. U tom stadiju proizvodnje nije bilo nikakvog razdvajanja smjese i sastojci su bili dobro izmiješani. Nadalje, verificirana je hipoteza da skraćivanje vremena miješanja od standardnih 30 na 20 minuta nema utjecaja na homogenost smjese.The article presents a homogeneity analysis of multi–element heterogeneous granular mixtures. For this purpose, multivariate analysis of variance was used. The research study was conducted in an industrial feed production plant using a vertical mixer equipped with a worm agitator and with the mass of materials of 2,1 ÷ 2,2 tones being put into it. Fodders comprising a dozen of whole seed components varying in grain diameter dimensions, densities and shapes were the subject of the research material. Homogeneity of fodder was determined based on samples taken during the bagging process. It was demonstrated – on the basis of statistical tests – that concentration of individual multi-elements, the heterogeneous granular mixtures is the same in the whole volume of the fodder. The mixtures are homogeneous (uniform), which is of vital significance, when considering the quality of mixtures being obtained. At this stage of production, there was no dissection of the mixture, and components were well–mixed. Furthermore, the hypothesis stating that shortening of the mixing time from standard mixing time of 30 to 20 minutes would not adversely affect the homogeneity of the mixture was verified

Regression model of sunflower seed separation and the investigation of it’s germination in corona field

Seed separation and cleaning is one of the important processes in obtaining pure high quality seed. The main characteristics that influence the ability to separation seeds are seed size (length, width, and thickness), shape, density, surface texture, terminal velocity, resilience, color, and electrical conductivity. Electrostatic separation is based on differences in the ability of particles to develop and maintain electric charges. In this study, a high tension roll‐type electrostatic separator was constructed to separation of sunflower’s seed in order to extraction of pure seed and remove impurities. An extended corona discharge field was generated by three wire type electrodes in the roll-type separator. The experiment was performed in the form of factorial analysis based on a randomized complete block design with three replications. The pure sunflower’s seed was measured in the treatment combinations of the rotational speed (40, 50 and 60 rpm), electrode distance from roll (4, 5 and 6 cm) and the power supply voltage (20, 30 and 40 kV). The linear regression model carried out for investigation of the impact of effective factors on sunflower separation. The result showed that rotational speed had the greatest impact on ideal separation. The germination experiment showed that the electric field of this separator had no significant effects on improving the germination of sunflower see

Examining the Relationship Between Lignocellulosic Biomass Structural Constituents and Its Flow Behavior

Lignocellulosic biomass material sourced from plants and herbaceous sources is a promising substrate of inexpensive, abundant, and potentially carbon-neutral energy. One of the leading limitations of using lignocellulosic biomass as a feedstock for bioenergy products is the flow issues encountered during biomass conveyance in biorefineries. In the biorefining process, the biomass feedstock undergoes flow through a variety of conveyance systems. The inherent variability of the feedstock materials, as evidenced by their complex microstructural composition and non-uniform morphology, coupled with the varying flow conditions in the conveyance systems, gives rise to flow issues such as bridging, ratholing, and clogging. These issues slow down the conveyance process, affect machine life, and potentially lead to partial or even complete shutdown of the biorefinery. Hence, we need to improve our fundamental understanding of biomass feedstock flow physics and mechanics to address the flow issues and improve biorefinery economics. This dissertation research examines the fundamental relationship between structural constituents of diverse lignocellulosic biomass materials, i.e., cellulose, hemicellulose, and lignin, their morphology, and the impact of the structural composition and morphology on their flow behavior. First, we prepared and characterized biomass feedstocks of different chemical compositions and morphologies. Then, we conducted our fundamental investigation experimentally, through physical flow characterization tests, and computationally through high-fidelity discrete element modeling. Finally, we statistically analyzed the relative influence of the properties of lignocellulosic biomass assemblies on flow behavior to determine the most critical properties and the optimum values of flow parameters. Our research provides an experimental and computational framework to generalize findings to a wider portfolio of biomass materials. It will help the bioenergy community to design more efficient biorefining machinery and equipment, reduce the risk of failure, and improve the overall commercial viability of the bioenergy industry