Digital Packing Research Articles

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Validation of a stochastic digital packing algorithm for porosity prediction in fluvial gravel deposits

Porosity as one of the key properties of sediment mixtures is poorly understood. Most of the existing porosity predictors based upon grain size characteristics have been unable to produce satisfying results for fluvial sediment porosity, due to the lack of consideration of other porosity-controlling factors like grain shape and depositional condition. Considering this, a stochastic digital packing algorithm was applied in this work, which provides an innovative way to pack particles of arbitrary shapes and sizes based on digitization of both particles and packing space. The purpose was to test the applicability of this packing algorithm in predicting fluvial sediment porosity by comparing its predictions with outcomes obtained from laboratory measurements. Laboratory samples examined were two natural fluvial sediments from the Rhine River and Kall River (Germany), and commercial glass beads (spheres). All samples were artificially combined into seven grain size distributions: four unimodal distributions and three bimodal distributions. Our study demonstrates that apart from grain size, grain shape also has a clear impact on porosity. The stochastic digital packing algorithm successfully reproduced the measured variations in porosity for the three different particle sources. However, the packing algorithm systematically overpredicted the porosity measured in random dense packing conditions, mainly because the random motion of particles during settling introduced unwanted kinematic sorting and shape effects. The results suggest that the packing algorithm produces loose packing structures, and is useful for trend analysis of packing porosity.

A Meso-scale Model for Fluid-microstructure Interactions

Particle-fluid and fluid-structure interactions are important areas in particle technology. Typical processes where such interactions are prevalent include fluidized beds, filtration and sedimentation. In addition, fluid-structure interactions are significant in applications such as nuclear waste management, for example in the cementation process used to store radioactive materials, as well as in carbon capture and storage applications where the leakage of gas injected in underground geological reservoirs must be considered in hazard and risk assessments. Given the difficulties in directly measuring the propagation of cracks in solid structures, their permeability or the internal build-up of any gases, for example, numerical techniques in conjunction with non-destructive measurements are important tools of value in assessing and predicting the behavior of fluid-structure interactions. In this work, coupling between the lattice Boltzmann method and a digital packing algorithm based on the discrete element method is used to provide a basis for predicting such coupled interactions. The development of the coupled algorithm is described, with the calculations performed on a regular lattice grid and based on the momentum exchange method to evaluate the force exerted by the fluid on a solid boundary. A number of test cases are reported to allow assessment of the coupled model's capabilities. Overall, these test cases demonstrate reasonable quantitative agreement with available analytical and experimental results for the case of a sphere settling in a liquid, and the expected qualitative behavior for the case of different orientation cylinders settling in a fluid, and for three dynamic packing processes.

Effect of flake shape on packing characteristics of popped popcorn

The purpose of this study was to determine to role of flake shape on the packing characteristics of popped popcorn. Unilateral, bilateral, and multilateral popcorn flakes, named for the direction of expansion of the popcorn flake, were digitized and packed into a virtual conical frustum-shaped container using a digital packing algorithm to simulate particle packing. Corresponding laboratory experiments were also conducted. Number of flakes required to fill the container agreed between simulated and laboratory experiments (r=0.996; p<0.0001) and ranged from about 340 for 50% bilateral +50% multilateral to >600 for 100% unilateral. Statistical modeling revealed 36.9% bilateral +63.1% multilateral would minimize the number of flakes required to fill the container. Packing fraction varied from ρ=0.14 for 10% unilateral +75% bilateral +15% multilateral to ρ=0.28 for 100% unilateral shape. These results offer insights into the packing characteristics of irregularly-shaped materials.

Predictions of porosity and fluid distribution through nonspherical‐packed columns

AbstractFor beds comprised randomly arranged nonspherical particles, the prediction and understanding of the packing characteristics and subsequent fluid flow through the resulting porous media is a longstanding problem for chemical and process engineers. This paper presents the application of a digital modeling approach to particle packing, in which no more than elementary physical concepts are used, with the model using collision points to predict trends in bed structures of particles of different geometry. Lattice Boltzmann modeling (LBM), coupled to the output of the packing model, is used to subsequently assess velocity distribution through the generated structures. Simulation results are compared with data available from the literature, as a means of model validation, where it is demonstrated that the combined approach of the digital packing algorithm and LBM provide a modeling capability that is of value to a range of engineering applications. © 2011 American Institute of Chemical Engineers AIChE J, 2012

Digital CS1 study pack based on Moodle and Python

We believe that CS1 courses can be made more attractive to students: by teaching a highly interactive scripting language - Python by using an open source course management system - such as Moodle - to make all course resources available in a comprehensive digital study pack, and by offering detailed self-guided online labs . We have used Moodle [1] and Python [2] to develop a "Python First" digital study pack [3] which comprises a wealth of new, original learning modules: extensive e-texts, detailed self-guided labs, numerous sample programs, quizzes, and slides. Our digital study pack pedagogy is described in recent ITiCSE and SIGCSE papers [4, 5]. "Python First" digital packs instances have already been adopted by instructors at several universities. This demonstration reveals instructor and student perspectives to the "Python First" digital pack. In particular, we demonstrate how instructors can use standard Moodle functionality to customize and manage digital packs. We also demonstrate several Moodle-supported, Python-based self-guided labs.

Digital predictions of complex cylinder packed columns

A digital computational approach has been developed to simulate realistic structures of packed beds. The underlying principle of the method is digitisation of the particles and packing space, enabling the generation of realistic structures. Previous publications [Caulkin, R., Fairweather, M., Jia, X., Gopinathan, N., & Williams, R.A. (2006). An investigation of packed columns using a digital packing algorithm. Computers & Chemical Engineering, 30, 1178–1188; Caulkin, R., Ahmad, A., Fairweather, M., Jia, X., & Williams, R. A. (2007). An investigation of sphere packed shell-side columns using a digital packing algorithm. Computers & Chemical Engineering, 31, 1715–1724] have demonstrated the ability of the code in predicting the packing of spheres. For cylindrical particles, however, the original, random walk-based code proved less effective at predicting bed structure. In response to this, the algorithm has been modified to make use of collisions to guide particle movement in a way which does not sacrifice the advantage of simulation speed. Results of both the original and modified code are presented, with bulk and local voidage values compared with data derived by experimental methods. The results demonstrate that collisions and their impact on packing structure cannot be disregarded if realistic packing structures are to be obtained.

クロム化成皮膜中クロム（ＶＩ）の簡易高感度分析法

The chromate conversion coatings treatment of aluminum was treated with 90 cm3 of boiling water for 5 min. The resultant solution was poured into solid phase extraction column (IBC Advanced Technologies Inc., Cr-02 type) and eluted with 2 cm3 of 3 mol/dm3 hydrochloric acid solution. The resultant solution was measured with Digital pack test for Cr (VI) (Kyoritsu Chemical-Check. Lab., Corp). The required time for total analytical procedure was faster than 10 min. The solid phase extraction column could be used repeatedly about 300 times or more. The minimum limit of determination of chromium (VI) was 0.004 mg/dm3.

An investigation of sphere packed shell-side columns using a digital packing algorithm

This paper on the fundamental structural properties of shell-side packed columns presents an investigative study using a novel packing algorithm with the aim of validation against experimental results. The novel contribution in the predictive approach employed is the digitalisation of particles, container and packing space to generate complex life-like stochastic packing structures of particulate systems at relatively high speed (when compared to traditional vector-based approaches) which are comparable with experimentally packed beds without need for further conversion of numerical data. A variety of packed column simulations, comprising more complex beds than often seen in the literature, namely shell-side beds with increasing complexity of internal structure and packed with spherical particles, have been undertaken and the resulting averaged numerical data compared like-for-like with experimental results with key trends reproduced. The overall aim of this work is to demonstrate the usefulness of the technique and associated computer code as an engineering aide for research, design and optimisation of the performance of packed bed systems of any geometric complexity in terms of packing structure, as well as to highlight possible areas for further development of the code.

Validation of a digital packing algorithm in predicting powder packing densities

DigiPac is a particle packing algorithm based on a digital approach to represent particle shape, packing space and particle movements. It is capable of packing particles of arbitrary shapes and sizes in a container of arbitrary geometry. A number of case studies have been performed to validate this digital approach, some of which are reported in this paper to show that with DigiPac shape factors used by many traditional models for predicting packing density become redundant. It also demonstrates that for polydisperse mixtures of non-spherical particles, a single size distribution measured using conventional means (e.g. light scattering) is inadequate for the purpose of predicting packing properties. [Display omitted]

"Python first"

The emphasis on Java and other commercial languages in CS1 has established the perception of computer science as a dry and technically difficult discipline among undecided students who are still seeking careers. This may not be a big problem during an enrolment boom, but in times of decreased enrolment such negative perception may have a devastating effect on computer science programs and therefore should not be ignored. We have made our CS1 course offerings more attractive to students (1) by introducing an easy to learn yet effective scripting language - Python, (2) by making all course resources available in a comprehensive online study pack, and (3) by offering an extensive set of detailed and easy to follow self-guided labs. Our custom-designed online study pack comprises a wealth of new, original learning modules: extensive e-texts, detailed self-guided labs, numerous sample programs, quizzes, and slides. Our recent student survey demonstrates that students like and prefer Python as a first language and that they also percept the online study pack as very beneficial. Our "Python First" course, originally required for computer science majors, has been so well received that it has been recently approved as a general education science elective, thus opening new recruitment opportunities for the computer science major. Our "Python First" digital pack is published online at http://studypack.com.

An investigation of packed columns using a digital packing algorithm

This paper presents results concerning the validation of a recently developed packing algorithm. The basic ethos of this algorithm is to digitise particle shapes, and to use the digitised shapes to generate digital packing structures. A variety of simulations of packed columns, comprising mono, binary and ternary mixtures of spherical particles, have been undertaken and the results compared to existing experimental data with good agreement. The ultimate aim of this work is to develop the packing algorithm as a design tool for use in optimising the performance of packed bed systems and, as a first step, to enable the characterisation of any particle population and prediction of particle behaviour in packing, segregation and mixing.

Predicting Packing Characteristics of Particles of Arbitrary Shapes

A computer model for particle packing is of importance in both theories and applications. By tak- ing a very different approach from existing packing algorithms, our digital packing algorithm � called DigiPacis able to avoid many of the difficulties normally encountered by the conventional algorithms in dealing with non-spherical particles. Using the digital approach, it is easy to pack par- ticles of arbitrary shapes and sizes into a container of any geometry. This paper brief ly describes the digital packing algorithm, but the focus is on validation of the DigiPac model through several case studies involving mono-sized non-spherical particles and also powders with different size distribu- tions. Packing densities from DigiPac simulations are compared with those measured experimentally by ourselves in some cases and in others with data published in the literature using other models. The results show a good agreement in all the cases, which enhances our confidence in DigiPac that despite being a geometrical packing algorithm with no explicit consideration of particle interactions, it is able to predict quite accurately the packing structure of particulates whose shapes are commonly encountered in both industry and everyday life.

Field evaluation of a novel nitrate sensitive electrode in drainage waters from agricultural grassland

Continuous daily determinations of nitrate were made during a 6 week period with a novel nitrate sensitive electrode deployed in V-notch weirs draining grassland lysimeter plots. The sensor molecule, triallyldecylammonium nitrate was covalently bound to an acrylonitrile–butadiene co-polymer to obtain a robust, rubbery membrane that was incorporated into a commercially obtainable electrode body. A nitrate determination assembly was constructed by interfacing the electrode with a double-junction reference electrode and a temperature probe, through a pre-amplifier to a hand-held digital readout and battery pack. One assembly was positioned in each of two V-notch weirs, receiving drainage water with different nominal ranges of nitrate concentration; set 1, 3–20 ppm and set 2, 0.7–5.1 ppm nitrate-N. Despite conditions conducive to rapid chemical and microbiological degradation, all electrodes remained physically intact, maintained nitrate sensitivity without drift and followed the trends in nitrate concentration well. The electrode performance was compared with laboratory automated chemical determinations made on contemporaneous samples of drainage water.

In Vitro Measurement of Bone-Acrylic Interface Pressure During Femoral Component Insertion

Bone-acrylic interface pressure measurements were recorded at the medial interior rasped surfaces of fresh cadaver femurs during digital packing of acrylic bone cement and during insertion and seating of a Trapezoidal-28 femoral total hip component. Plugging of the femoral canal below the tip of the prosthesis stem was an effective means for increasing pressure in the distal femoral canal when the stem was inserted in the early stages of acrylic polymerization (i.e. immediately after dough time). At surgery, this can be accomplished by inserting a small bolus of acrylic down the canal to a depth below the tip of the seated stem and allowing it to polymerize in place. This forms an effective seal which prevents distal extrusion of the acrylic when the cavity is then packed prior to prosthesis insertion. Elimination of cement in the distal canal also avoids any future difficulty of acrylic removal should revision become necessary due to loosening or infection. No significant pressure differences were observed between one and two millimeter thicknesses of acrylic between the metal and bone. Interface pressures developed during finger packing were of the same order of magnitude as those achieved during seating of the femoral component. Use of a rubber diaphragm stretched tightly over the margins of the rasped femoral cavity helped to contain the acrylic and prevent extrusion during finger packing but was ineffective in increasing interface pressure. When this method is used, the acrylic can be poured or injected into the canal and packed before dough stage and thus facilitate increased cancellous penetration when the acrylic is in a state of low viscosity.