Development of a Numerical Simulation Method for Rocky Body Impacts and Theoretical Analysis of Asteroidal Shapes

Development of a Numerical Simulation Method for Rocky Body Impacts and Theoretical Analysis of Asteroidal Shapes PDF

Author: Keisuke Sugiura

Publisher: Springer Nature

Published: 2020-03-17

Total Pages: 143

ISBN-13: 9811537224

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This book describes numerical simulations of collisions between asteroids, based on a unique numerical code developed by the author. The code accurately solves the elastic dynamic equations and describes the effects of fracture and friction, which makes it possible to investigate the shapes of impact outcomes produced by asteroid collisions and subsequent gravitational accumulation of fragments. The author parallelizes the code with high parallelization efficiency; accordingly, it can be used to conduct high-resolution simulations with the aid of supercomputers and clarify the shapes of small remnants produced through the catastrophic destruction of asteroids. The author demonstrates that flat asteroids can only be produced by impacts involving objects with similar mass and low velocity, which suggests that the flat asteroids in our solar system were created in the planet formation era and have kept their shapes until today. The author also shows that asteroid collisions under certain conditions can produce the extremely elongated shape of an interstellar minor body, 1I/‘Oumuamua. In brief, the book offers a comprehensive investigation of asteroid impacts and shapes, making it a uniquely valuable resource.

Literature 1997, Part 1

Literature 1997, Part 1 PDF

Author: Astronomisches Rechen-InstitutARI

Publisher: Springer Science & Business Media

Published: 2013-11-11

Total Pages: 1746

ISBN-13: 3642517587

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Astronomy and Astrophysics Abstracts is devoted to the recording, summarizing and indexing of astronomical publications throughout the world. Two volumes are scheduled to appear per year. Volume 67 records 10,903 papers covering besides the classical fields of astronomy and astrophysics such matters as space flights related to astronomy, lunar and planetary probes and satellites, meteorites and interplanetary matter, X rays and cosmic rays, quasars and pulsars. The abstracts are classified under more than one hundred subject categories thus permitting quick surveying of the bulk of material published on the same topic within six months. For instance, this volume records 119 papers on minor planets, 155 papers on supernovae, and 554 papers on cosmology.

Scientific and Technical Aerospace Reports

Scientific and Technical Aerospace Reports PDF

Author:

Publisher:

Published: 1994

Total Pages: 1028

ISBN-13:

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Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.

Application of Rigid Body Impact Mechanics and Discrete Element Modeling to Rockfall Simulation

Application of Rigid Body Impact Mechanics and Discrete Element Modeling to Rockfall Simulation PDF

Author: Parham Ashayer

Publisher:

Published: 2007

Total Pages: 410

ISBN-13: 9780494393994

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Numerical modeling can assist in predicting falling rock trajectories and reducing the destruction caused by rockfalls. The majority of existing rockfall simulations are based on particle or lumped-mass models that consider the falling rock as an infinitesimal particle with a concentrated mass. Hybrid models usually find the rock-slope contact point using techniques similar to those used in particle models, while incorporating some aspects of the rigid body collisions for bouncing. There are also some rigid body models that employ simplified mathematical impact models. In the framework of this thesis, the applications of rigid body theory and discrete element modeling to rockfall simulation are investigated. A modified version of the discrete element model (MDEM), which can model impacts using methods similar to low-compliance impact models, is offered. In this model, the normal linear dashpot is replaced by a nonlinear dashpot which dissipates the impact velocity based on the contact normal velocity. A mono-direction sliding unit is added to model low-compliance impacts and the tangential dashpot is removed. Several numerical tests strongly indicate that if shape geometries can be sufficiently approximated by a group of particles, the proposed MDEM can replicate the rebound velocities that are predicted by the application of low compliance rigid body impact models. Application of rigid body impact mechanics (RBIM), originally developed by Stronge, in rockfall simulation is studied and compared with other classical rockfall impact models. The effects of several parameters on widely-used coefficients of restitution are investigated including: rock geometry and slenderness, angle of impact, rock orientation, and slope material properties. A new geometrical rockfall simulation program, GeoRFS, based on rigid body mechanics in two-dimensional space, is developed, where rock geometry can vary from prisms with a randomly generated polygonal cross section to superellipsoids. The trajectories of different rock geometries (e.g., roll-out distances, bounce heights, velocities, and energies) during multiple impacts on flat and inclined impact surfaces are studied. The results strongly suggest that the provided simulation program can satisfactorily replicate the roll-out distances obtained from the in-situ tests performed by the Oregon Department of Transportation using different rock geometries. It is expected that the geometrical simulation tools introduced in this work will replace the particle impact model currently used in rockfall programs.

Dynamic Simulation of Multibody Systems in Simultaneous, Indeterminate Contact and Impact with Friction

Dynamic Simulation of Multibody Systems in Simultaneous, Indeterminate Contact and Impact with Friction PDF

Author: Adrian Rodriguez

Publisher:

Published: 2014

Total Pages: 138

ISBN-13:

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This research is focused on improving the solutions obtained using theory in contact and impact modeling. A theoretical framework is developed which can simulate the performance of dynamic systems within a real world environment. This environment involves conditions, such as contact, impact and friction. Numerical simulation provides an easy way to perform numerous iterations with varying conditions, which is more cost effective than building equivalent experimental setups. The developed framework will serve as a tool for engineers and scientists to gain some insight on predicting how a system may behave. The current field of research in multibody system dynamics lacks a framework for modeling simultaneous, indeterminate contact and impact with friction. This special class of contact and impact problems is the major focus of this research. This research develops a framework, which contributes to the existing literature. The contact and impact problems examined in this work are indeterminate with respect to the impact forces. This is problematic because the impact forces are needed to determine the slip-state of contact and impact points. The novelty of the developed approach relies on the formation of constraints among the velocities of the impact points. These constraints are used to address the indeterminate nature of the collisions encountered. This approach strictly adheres to the assumptions of rigid body modeling in conjunction with the notion that the configuration of the system does not change in the short time span of the collision. These assumptions imply that the impact Jacobian is constant during the collision, which enforces a kinematic relationship between the impact points. The developed framework is used to address simultaneous, indeterminate contact and impact problems with friction. In the preliminary stages of this research, an iterative method, which incorporated an optimization function was used obtain the solutions for numerical solution to the collision. In an effort to improve the time and accuracy of the results, the iterative method was replaced with an analytical approach and implemented with the constraint formulation to achieve more energetically consistent solutions (i.e. there are no unusual gains in energy after the impact). The details of why this claim is valid will be discussed in more detail in this dissertation. The analytical framework was developed for planar contact and impact problems, while a numerical framework is developed for three-dimensional (3D) problems. The modeling of friction in 3D presents some challenging issues that are well documented in the literature, which make it difficult to apply an analytical framework. Simulations are conducted for a planar ball, planar rocking block problem, Newton's Cradle, 3D sphere, and 3D rocking block. Some examples serve as benchmark problems, in which the results are validated using experimental data.

Development of an Explicit Numerical Manifold Method for Dynamic Stability Analysis of Rock Slope

Development of an Explicit Numerical Manifold Method for Dynamic Stability Analysis of Rock Slope PDF

Author: Xiaolei Qu

Publisher:

Published: 2013

Total Pages: 226

ISBN-13:

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In this thesis, an explicit version of the numerical manifold method (NMM) has been developed for dynamic stability analysis of rock slope. Firstly, Newmark integration scheme used in the NMM is brief introduced and derived in detail to further deepen understanding of the NMM and its implementations. The numerical results present the explicit scheme is more efficient in solving the nonlinear dynamic systems and such problems compared to implicit scheme. Then, an explicit time integration scheme for the NMM is proposed to improve the computational efficiency. The developed explicit NMM (ENMM) is validated by several examples. The calibration study of the ENMM on P-wave propagation across a rock bar has been conducted. Various considerations in the numerical simulations are discussed and parametric studies have been carried out to obtain an insight into the influencing factors in wave propagation simulation. The numerical results from the ENMM and NMM modelling are accordant well with the theoretical solutions, but the ENMM is more efficient than the original NMM. The temporal and spatial coupled explicit-implicit (E-I) algorithms for the numerical manifold method (NMM) are proposed. The time integration schemes, transfer algorithm, contact algorithm and damping algorithm are studied in the temporal coupled E-I algorithm to merge both merits of the explicit and implicit algorithms in terms of efficiency and accuracy. In particular, onefold cover system is drawn into the coupled spatial E-I algorithm, in which the contact algorithm based on the onefold cover system is discussed and derived in detail. The simulated results are well agreement with the implicit and explicit algorithms simulations, but the efficiency is improved evidently. The dynamic stability analysis of rock slope failure using the NMM is studied. Conservational pseudo-static methods (PSMs), Newmark method and numerical methods applying into the seismic stability analyses are investigated, the advantages and limitations of which are studied by contrast of the NMM. An alternative ENMM and coupled E-I algorithms are applied to study the seismic stability of rock slope. Furthermore, parallel computing with OpenMP is evaluated to improve efficiency of the NMM. To reveal the validity and applicability of the developed ENMM, some numerical examples of rock slope stability analysis are investigated, in which one example of rock slope is taken into account to present the coupled ENMM with discontinuous deformation analysis (DDA) in terms of efficiency. Simulated results of the NMM will compare with the field measurements to illustrate the applicability of the NMM. The present study showed the developed ENMM is more efficient while without losing the accuracy, comparing to the original implicit version of the NMM. Therefore, it can be predicted that the proposed ENMM is promising and can be extend applied to larger scale project of rock slope with dynamic stability analysis.

Numerical Simulation of Fracture Pattern Development and Implications for Fuid Flow

Numerical Simulation of Fracture Pattern Development and Implications for Fuid Flow PDF

Author: Adriana Paluszny Rodriguez

Publisher:

Published: 2009

Total Pages:

ISBN-13:

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Simulations are instrumental to understanding flow through discrete fracturegeometric representations that capture the large-scale permeability structure offractured porous media. The contribution of this thesis is threefold: an efficient finite-element finite-volume discretisation of the advection/diffusion flow equations, ageomechanical fracture propagation algorithm to create fractured rock analogues, and a study of the effect of growth on hydraulic conductivity. We describe aniterative geomechanics-based finite-element model to simulate quasi-static crackpropagation in a linear elastic matrix from an initial set of random flaws. Thecornerstones are a failure and propagation criterion as well as a geometric kernel fordynamic shape housekeeping and automatic remeshing. Two-dimensional patternsexhibit connectivity, spacing, and density distributions reproducing en echelon cracklinkage, tip hooking, and polygonal shrinkage forms. Differential stresses at theboundaries yield fracture curving. A stress field study shows that curvature can besuppressed by layer interaction effects. Our method is appropriate to model layeredmedia where interaction with neighbouring layers does not dominate deformation. Geomechanically generated fracture patterns are the input to single-phase flowsimulations through fractures and matrix. Thus, results are applicable to fracturedporous media in addition to crystalline rocks. Stress state and deformation historycontrol emergent local fracture apertures. Results depend on the number of initialflaws, their initial random distribution, and the permeability of the matrix. Straightpathfracture pattern simplifications yield a lower effective permeability in comparisonto their curved counterparts. Fixed apertures overestimate the conductivity ofthe rock by up to six orders of magnitude. Local sample percolation effectsare representative of the entire model flow behaviour for geomechanical apertures. Effective permeability in fracture dataset subregions are higher than the overallconductivity of the system. The presented methodology captures emerging patternsdue to evolving geometric and flow properties essential to the realistic simulation ofsubsurface processes.

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