Numerical modelling of rainfall-induced internal erosion process within vegetated deposited slopes

Internal erosion is a common form of damage in geomaterial structures that is caused by the migration of soil particles under a seepage flow. The geometrical characteristics of soil particles is regarded as the intrinsic factor for internal instability; thus, in this study, a network modelling technique is formulated for this purpose. The soil particles and pores are generalised into a network model according to their fractal gradations; thereafter, the percolation theory is applied to analyse this conceptual probabilistic model. The percolation and erosion backbones are simulated in the direct square bond percolation model through the extended Hoshen–Kopelman algorithm and direct electrifying algorithm. Monte Carlo experiments are conducted to analyse the internal erosion process in this network model. The extent of internal instability can be calculated quantitatively, and the deposition rate of transported particles in the mass conservation equation can be evaluated for further analysis. Compared with internal erosion tests, the percolation analytical method is in accordance with experimental results. This method provides fresh insights on the nature of internal erosion from a statistical perspective.

This paper deals with the issue of numerical modelling of the piercing process of thick-walled tube shell in two-rolls skew rolling mill, which is equipped with guiding devices of Diescher type. After a short characteristic of the process, the worked out numerical model of this process is described. The numerical model considers e.g. thermal phenomena taking place in the metal during forming. Moreover, in this model tools were assumed as rigid bodies apart from the piercing plug which could be deformed in the elastic range. Applying the worked out FEM model, simulations of the piercing process in the skew rolling mill were made. The results of calculations were presented in the form of maps of: strains, stresses, temperatures and surface pressures.

TIG welding is an important process, which is commonly used in the aircraft industry. A number of elements of airplane bodies or shields of engines are made using this technique. Numerical models of this process are needed to understand better phenomena involved in the TIG welding and to design the optimal process parameters. In the present paper numerical simulations were performed and the possibilities of modeling heat transfer in the investigated process were evaluated. Comparison of results of numerical simulations with the experimental data confirmed good predictive capabilities of the model, as far as realistic description of the phenomena involved in this process are considered. Correctness of the Goldak model, which describes density of the energy in the heat source, was confirmed as well.

Shear coefficient determination in linear friction welding of aluminum alloys

A two-dimensional numerical model of the steam-assisted gravity drainage process with a pair of horizontal wells (SAGD) is developed for heterogeneous, layered tar sand reservoirs. As a case study, this model is applied to Ugnu reservoir to study the effect of heterogeneity on the growth of steam chamber and the process performance. A detailed simulation study is conducted to determine the effect of various reservoir parameters such as porosity, permeability, initial mobile water saturation, Dykstra-Parson’s permeability variation, reservoir anisotropy and shale barriers on the SAGD process performance in Ugnu reservoir. Also, the effect of process parameters such as steam injectivity, steam quality, steam temperature, horizontal well length, vertical and lateral well spacing is studied.

Internal erosion processes in soils play an important role on the instability analyses of hillslopes and embankment dams. Field observations support the assumption that the internal fine particles may migrate among the channels formed by coarser particles under the high hydraulic gradient condition, where the enrichment of fine particles has great potential on the increase of local pore-water pressure due to their low permeability. Although a number of traditional seepage experiments in laboratory have provided data showing the effect of soil properties on the macroscopic permeability, however, much remains unknown particularly for microscopic erosion processes. Therefore, in the current study, a series of one-dimensional soil seepage tests were firstly conducted by controlling the coarse to fine particle size ratio, and then the X-ray tomography tests were carried out at beamline BL13W1 at the Shanghai Synchrotron Radiation Facility (SSRF) to obtain the particle distributions and three-dimensional pore structures. By coupling discrete element method (DEM) with Darcy’s law, the internal particle erosion processes were back-analyzed. The results reveal that the preferential erosion can occur in the top and bottom regions of the soil specimen, and the migrated fine particles can be supplied when the pore size is large enough along the seepage path.

The productivity of the feed preparation line and its technical and economic efficiency are affected by the design and technological parameters of the equipment. The geometry of the expander screw and its operating modes are no exception. To reduce the specific energy consumption of the expander, it is necessary to establish its rational design and operating parameters. This can be done using analytical calculation methods that consider the mechanisms of movement and destruction of solid substances. Modelling using the discrete element method is becoming increasingly common to describe the movement of solid components in granulators, extruders, or expanders. The purpose of the study is to improve the physical and mathematical apparatus of movement of solid feed components in the screw channel of the feed expander and develop a method for its numerical modelling. Numerical modelling was performed using a model of the movement of a multiphase Euler mixture with a split flow in three-dimensional space. In this case, the motion was subject to an admissible two-layer k-ε model of turbulence and the multiphase equation of state. The physical and mathematical apparatus for the movement of solid feed components in the screw channel of the feed expander was improved, which is the basis for the numerical modelling technique in the Star-CCM+ software suite, based on the fact that the conglomerate of feed components is represented as a package of spherical particles. In this case, the pressure force must be compensated by the total force of contact interaction of particles with each other and the wall. Preliminary numerical modelling of the process of expanded feed preparation was performed in the Star-CCM+ software suite. The practical significance lies in the fact that the improved physical and mathematical apparatus and the developed method of numerical modelling of the feed expander operation process allow substantiating its design and regime parameters to ensure low specific energy consumption without losing the quality of the technological process

Numerical modelling of the mesofracture process of sintered 316L steel under tension using microtomography

The control of workpiece properties enables an application-oriented and time-efficient production of components. In reverse flow forming, e.g., the control of the microstructure profile, in contrast to the adjustment of the geometry, is not yet part of the state of the art. This is particularly challenging when forming seamless tubes made of metastable austenitic stainless AISI 304L steel. In this steel, a phase transformation from austenite to martensite can occur due to mechanically and/or thermally induced energy. The α’-martensite has different mechanical and micromagnetic properties, which can be advantageous depending on the application. For the purpose of local property control, the resulting α’-martensite content should be measured and controlled online during the forming process. In this paper, results from an empirical correlation model of process parameter combinations and resulting α’-martensite content as well as geometry will be presented. Based on this, the focus of the paper will be on process modeling by means of FEM in order to create the transition to a numerically supported process model. Furthermore, it will be specified how the numerical process model can be used in a predictive manner for an online closed-loop process control.

The purpose of this report is to present analogue studies and literature reviews designed to provide qualitative and quantitative information to test and provide added confidence in process models abstracted for performance assessment (PA) and model predictions pertinent to PA. This report provides updates to studies presented in the Yucca Mountain Site Description (CRWMS M&O 2000 [151945], Section 13) and new examples gleaned from the literature, along with results of quantitative studies conducted specifically for the Yucca Mountain Site Characterization Project (YMP). The intent of the natural analogue studies was to collect corroborative evidence from analogues to demonstrate additional understanding of processes expected to occur during postclosure at a potential Yucca Mountain repository. The report focuses on key processes by providing observations and analyses of natural and anthropogenic (human-induced) systems to improve understanding and confidence in the operation of these processes under conditions similar to those that could occur in a nuclear waste repository. The process models include those that represent both engineered and natural barrier processes. A second purpose of this report is to document the various applications of natural analogues to geologic repository programs, focusing primarily on the way analogues have been used by the YMP. This report is limited to providing support for PA in a confirmatory manner and to providing corroborative inputs for process modeling activities. Section 1.7 discusses additional limitations of this report. Key topics for this report are analogues to emplacement drift degradation, waste form degradation, waste package degradation, degradation of other materials proposed for the engineered barrier, seepage into drifts, radionuclide flow and transport in the unsaturated zone (UZ), analogues to coupled thermal-hydrologic-mechanical-chemical processes, saturated zone (SZ) transport, impact of radionuclide release on the biosphere, and potentially disruptive events. Results of these studies will be used to corroborate estimates of the magnitude and limitation of operative processes in order to build realism into conceptual and numerical process models used as a foundation for PA in the representative case of postclosure safety.

The purpose of this report is to present analogue studies and literature reviews designed to provide qualitative and quantitative information to test and provide added confidence in process models abstracted for performance assessment (PA) and model predictions pertinent to PA. This report provides updates to studies presented in the ''Yucca Mountain Site Description'' (CRWMS M and O 2000 [151945], Section 13) and new examples gleaned from the literature, along with results of quantitative studies conducted specifically for the Yucca Mountain Site Characterization Project (YMP). The intent of the natural analogue studies was to collect corroborative evidence from analogues to demonstrate additional understanding of processes expected to occur during postclosure at a potential Yucca Mountain repository. The report focuses on key processes by providing observations and analyses of natural and anthropogenic (human-induced) systems to improve understanding and confidence in the operation of these processes under conditions similar to those that could occur in a nuclear waste repository. The process models include those that represent both engineered and natural barrier processes. A second purpose of this report is to document the various applications of natural analogues to geologic repository programs, focusing primarily on the way analogues have been used by the YMP.more » This report is limited to providing support for PA in a confirmatory manner and to providing corroborative inputs for process modeling activities. Section 1.7 discusses additional limitations of this report. Key topics for this report are analogues to emplacement drift degradation, waste form degradation, waste package degradation, degradation of other materials proposed for the engineered barrier, seepage into drifts, radionuclide flow and transport in the unsaturated zone (UZ), analogues to coupled thermal-hydrologic-mechanical-chemical processes, saturated zone (SZ) transport, impact of radionuclide release on the biosphere, and potentially disruptive events. Results of these studies will be used to corroborate estimates of the magnitude and limitation of operative processes in order to build realism into conceptual and numerical process models used as a foundation for PA in the representative case of postclosure safety.« less

Evolving process views

Three dimensional thermo-mechanical simulation of the tube forming process in Diescher's mill

A description is given of a three-dimensional process simulator, named SMART-P, that is based on the finite-difference approach to the supercomputer FACOM VP-100. To simulate the impurity redistribution and nonplanar structure in the Si/SiO/sub 2/ system, this simulator contains a three-dimensional oxidation model, an interaction model of impurities, a numerical model of interstitial-assisted oxidation-enhanced diffusion, and other process models. The numerical process modeling in the Si/SiO/sub 2/ system is described. The three-dimensional process modeling CAD (computer-aided design) has been realized by using efficient numerical algorithms based on the generalized coordinate transformation method. The capabilities of this simulator have been demonstrated in applications relating to both local oxidation of silicon (LOCOS) and trench-isolated 0.5 mu m MOSFET structures.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Numerical modelling of the healing process induced by carbonation of a single crack in concrete structures: Theoretical formulation and Embedded Finite Element Method implementation