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Development Of Adaptive Mesh Refinement Scheme And Conjugate Heat Transfer Model For Engine Simulations
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Book Synopsis Development of Adaptive Mesh Refinement Scheme and Conjugate Heat Transfer Model for Engine Simulations by : Qingluan Xue
Download or read book Development of Adaptive Mesh Refinement Scheme and Conjugate Heat Transfer Model for Engine Simulations written by Qingluan Xue and published by . This book was released on 2009 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Development of Adaptive Mesh Refinement Scheme and Conjugate Heat Transfer Model for Engine Simulations by :
Download or read book Development of Adaptive Mesh Refinement Scheme and Conjugate Heat Transfer Model for Engine Simulations written by and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spray modeling is a critical component to engine combustion and emissions simulations. Accurate spray modeling often requires a fine computational mesh for better numerical resolutions. This, in turn, will require extensive computer time. A major concern for the successful application of computational methods in an industrial environment is its capability to handle complex configurations with acceptable accuracy at reasonable human and computational costs. To assure the accuracy and reliability of the solution, grid modification and grid refinement studies are often necessary within an iterative process. Adaptive algorithms are a promising approach to realize discretizations that are able to automatically resolve the physically relevant phenomena at reduced costs. The first goal of the dissertation work is to developed a methodology that uses a locally dynamically refined mesh in the spray region for engine spray simulations. An h-refinement adaptive scheme is developed and implemented into an existing computer code. It is a dynamic process that adapts an initial mesh by employing local cell division and recovery. Adaptation of the cells is composed of isotropic division of one hexahedron into eight sub-cells in three dimensions. The concept of polyhedral elements is implemented to treat any possible hanging node configuration that occurs at the interface between the divided and undivided zones in a natural way. This flexibility of this method was demonstrated to handle successive grid adaptation and efficient data management when it is extended to multi-level refinement process. A special data structure based on octree has been developed for high storage efficiency. The solid-cone and hollow-cone sprays under direct-injection gasoline engine conditions were simulated. Predicted spray characteristics using different mesh densities with various refinement levels were compared. Results show that the present mesh refinement scheme can accurately predict spray structure
Book Synopsis Adaptive Mesh Refinement - Theory and Applications by : Tomasz Plewa
Download or read book Adaptive Mesh Refinement - Theory and Applications written by Tomasz Plewa and published by Springer Science & Business Media. This book was released on 2005-12-20 with total page 550 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced numerical simulations that use adaptive mesh refinement (AMR) methods have now become routine in engineering and science. Originally developed for computational fluid dynamics applications these methods have propagated to fields as diverse as astrophysics, climate modeling, combustion, biophysics and many others. The underlying physical models and equations used in these disciplines are rather different, yet algorithmic and implementation issues facing practitioners are often remarkably similar. Unfortunately, there has been little effort to review the advances and outstanding issues of adaptive mesh refinement methods across such a variety of fields. This book attempts to bridge this gap. The book presents a collection of papers by experts in the field of AMR who analyze past advances in the field and evaluate the current state of adaptive mesh refinement methods in scientific computing.
Book Synopsis Adaptive Mesh Refinement Method for CFD Applications by : Oscar Luis Antepara Zambrano
Download or read book Adaptive Mesh Refinement Method for CFD Applications written by Oscar Luis Antepara Zambrano and published by . This book was released on 2019 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main objective of this thesis is the development of an adaptive mesh refinement (AMR) algorithm for computational fluid dynamics simulations using hexahedral and tetrahedral meshes. This numerical methodology is applied in the context of large-eddy simulations (LES) of turbulent flows and direct numerical simulations (DNS) of interfacial flows, to bring new numerical research and physical insight. For the fluid dynamics simulations, the governing equations, the spatial discretization on unstructured grids and the numerical schemes for solving Navier-Stokes equations are presented. The equations follow a discretization by conservative finite-volume on collocated meshes. For the turbulent flows formulation, the spatial discretization preserves symmetry properties of the continuous differential operators and the time integration follows a self-adaptive strategy, which has been well tested on unstructured grids. Moreover, LES model consisting of a wall adapting local-eddy-viscosity within a variational multi-scale formulation is used for the applications showed in this thesis. For the two-phase flow formulation, a conservative level-set method is applied for capturing the interface between two fluids and is implemented with a variable density projection scheme to simulate incompressible two-phase flows on unstructured meshes. The AMR algorithm developed in this thesis is based on a quad/octree data structure and keeps a relation of 1:2 between levels of refinement. In the case of tetrahedral meshes, a geometrical criterion is followed to keep the quality metric of the mesh on a reasonable basis. The parallelization strategy consists mainly in the creation of mesh elements in each sub-domain and establishes a unique global identification number, to avoid duplicate elements. Load balance is assured at each AMR iteration to keep the parallel performance of the CFD code. Moreover, a mesh multiplication algorithm (02) is reported to create large meshes, with different kind of mesh elements, but preserving the topology from a coarser original mesh. This thesis focuses on the study of turbulent flows and two-phase flows using an AMR framework. The cases studied for LES of turbulent flows applications are the flow around one and two separated square cylinders, and the flow around a simplified car model. In this context, a physics-based refinement criterion is developed, consisting of the residual velocity calculated from a multi-scale decomposition of the instantaneous velocity. This criteria ensures grid adaptation following the main vortical structures and giving enough mesh resolution on the zones of interest, i.e., flow separation, turbulent wakes, and vortex shedding. The cases studied for the two-phase flows are the DNS of 2D and 3D gravity-driven bubble, with a particular focus on the wobbling regime. A study of rising bubbles in the wobbling regime and the effect of dimensionless numbers on the dynamic behavior of the bubbles are presented. Moreover, the use of tetrahedral AMR is applied for the numerical simulation of gravity-driven bubbles in complex domains. On this topic, the methodology is validated on bubbles rising in cylindrical channels with different topology, where the study of these cases contributed to having new numerical research and physical insight in the development of a rising bubble with wall effects.
Book Synopsis Commencement by : Iowa State University
Download or read book Commencement written by Iowa State University and published by . This book was released on 2008 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Adaptive Mesh Refinement for Finite Element Flow Modeling in Complex Geometries by : Sujata Prakash
Download or read book Adaptive Mesh Refinement for Finite Element Flow Modeling in Complex Geometries written by Sujata Prakash and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Adaptive mesh refinement is a powerful tool for obtaining the highest solution accuracy for a given computational effort. Over the past decade, many adaptive techniques have been developed and applied to a variety of fluid flow problems. Results obtained for compressible flows, and to an extent, 2D incompressible flows have been impressive, however, similar progress has not been noted for 3D incompressible flows, particularly in complicated geometries. The objective of this thesis was to develop and test an adaptive solution methodology for 3D incompressible flow simulations in domains of arbitrary complexity. To characterize the finite element solution error, the Zienkiewicz-Zhu patch recovery error estimator (LPR) was adopted. An enhanced version of the LPR error estimator was formulated and implemented using 10-noded tetrahedral elements. The enhanced estimator (LPRC) resulted in significantly improved gradient recovery (and consequently, improved error estimates) at virtually no additional computational cost. For mesh refinement, an elemental subdivision procedure was implemented. To enable refinement in complex geometries, a procedure for preserving the boundary integrity of a refined mesh was developed. This methodology can be used for geometric data from any solid modeling (CAD) system provided the data can be exported in the IGES format. A benchmark study of the AMR procedure, in which steady flow over a three-dimensional backward-facing step was simulated, showed that the cumulative computational effort required in the adaptive analysis was lower than that required in a non-adaptive analysis of the same problem. In the second phase of this work, the AMR procedure was applied to modeling flow through two arterial geometries. Specifically, flows in an idealized end-to-side anastomosis and in a human right coronary artery were examined. Both studies assessed whether an AMR analysis could achieve more accurate solutions than conventional analyses that utilize high-resolution meshes whose gradation is based on 'a priori' knowledge of the flow field. It was noted that mesh-independent velocity fields were not very difficult to obtain even in the absence of an adaptive methodology. However, wall shear stress fields were much more difficult to absolutely resolve non-adaptively. Given that shear stresses occurring on arterial walls are widely believed to be a key factor governing the development of arterial disease, it is very important to accurately resolve wall shear stress fields if confidence can be placed in the results of numerical simulations of arterial flow phenomena. These results indicate that wall shear stress is an extremely sensitive measure of spatial resolution, and that the systematic solution-adaptive methodology developed in this thesis is very effective in producing accurately resolved wall shear stress fields.
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 694 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Parallel Adaptive Mesh Refinement by :
Download or read book Parallel Adaptive Mesh Refinement written by and published by . This book was released on 2005 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: As large-scale, parallel computers have become more widely available and numerical models and algorithms have advanced, the range of physical phenomena that can be simulated has expanded dramatically. Many important science and engineering problems exhibit solutions with localized behavior where highly-detailed salient features or large gradients appear in certain regions which are separated by much larger regions where the solution is smooth. Examples include chemically-reacting flows with radiative heat transfer, high Reynolds number flows interacting with solid objects, and combustion problems where the flame front is essentially a two-dimensional sheet occupying a small part of a three-dimensional domain. Modeling such problems numerically requires approximating the governing partial differential equations on a discrete domain, or grid. Grid spacing is an important factor in determining the accuracy and cost of a computation. A fine grid may be needed to resolve key local features while a much coarser grid may suffice elsewhere. Employing a fine grid everywhere may be inefficient at best and, at worst, may make an adequately resolved simulation impractical. Moreover, the location and resolution of fine grid required for an accurate solution is a dynamic property of a problem's transient features and may not be known a priori. Adaptive mesh refinement (AMR) is a technique that can be used with both structured and unstructured meshes to adjust local grid spacing dynamically to capture solution features with an appropriate degree of resolution. Thus, computational resources can be focused where and when they are needed most to efficiently achieve an accurate solution without incurring the cost of a globally-fine grid. Figure 1.1 shows two example computations using AMR; on the left is a structured mesh calculation of a impulsively-sheared contact surface and on the right is the fuselage and volume discretization of an RAH-66 Comanche helicopter [35]. Note the ability of both meshing methods to resolve simulation details by varying the local grid spacing.
Book Synopsis A Framework for Mesh Refinement Suitable for Finite-Volume and Discontinuous-Galerkin Schemes with Application to Multiphase Flow Prediction by : Andrée-Anne Dion-Dallaire
Download or read book A Framework for Mesh Refinement Suitable for Finite-Volume and Discontinuous-Galerkin Schemes with Application to Multiphase Flow Prediction written by Andrée-Anne Dion-Dallaire and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Modelling multiphase flow, more specifically particle-laden flow, poses multiple challenges. These difficulties are heightened when the particles are differentiated by a set of "internal" variables, such as size or temperature. Traditional treatments of such flows can be classified in two main categories, Lagrangian and Eulerian methods. The former approaches are highly accurate but can also lead to extremely expensive computations and challenges to load balancing on parallel machines. In contrast, the Eulerian models offer the promise of less expensive computations but often introduce modelling artifacts and can become more complicated and expensive when a large number of internal variables are treated. Recently, a new model was proposed to treat such situations. It extends the ten-moment Gaussian model for viscous gases to the treatment of a dilute particle phase with an arbitrary number of internal variables. In its initial application, the only internal variable chosen for the particle phase was the particle diameter. This new polydisperse Gaussian model (PGM) comprises 15 equations, has an eigensystem that can be expressed in closed form and also possesses a convex entropy. Previously, this model has been tested in one dimension. The PGM was developed with the detonation of radiological dispersal devices (RDD) as an immediate application. The detonation of RDDs poses many numerical challenges, namely the wide range of spatial and temporal scales as well as the high computational costs to accurately resolve solutions. In order to address these issues, the goal of this current project is to develop a block-based adaptive mesh refinement (AMR) implementation that can be used in conjunction with a parallel computer. Another goal of this project is to obtain the first three-dimensional results for the PGM. In this thesis, the kinetic theory of gases underlying the development of the PGM is studied. Different numerical schemes and adaptive mesh refinement methods are described. The new block-based adaptive mesh refinement algorithm is presented. Finally, results for different flow problems using the new AMR algorithm are shown, as well as the first three-dimensional results for the PGM.
Book Synopsis An Adaptive Mesh Refinement Technique for Dynamics of Solids by : Abhishek Trivedi
Download or read book An Adaptive Mesh Refinement Technique for Dynamics of Solids written by Abhishek Trivedi and published by . This book was released on 2007 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: Simulation of dynamics problems generally is heavily dependent on mesh size for convergence and accuracy. In many cases, the requirement of mesh size reaches to such proportions that the problem becomes unsolvable for the available computational resources. We perceive that such problems can be solved by refining and unrefining mesh adaptively during time stepping. Adaptive mesh refinement techniques available in popular literature are marred by various limitations, such as element-specific techniques, algorithm-specific techniques, etc. We utilize Conforming Hierarchical Refinement Methods (CHARMS) [32] for our purpose since it relies on the refinement of finite element basis instead of geometric sub-division of elements. Refinement in this fashion produces conforming meshes during adaptive mesh refinement for a wide range of elements. We improve CHARMS to incorporate time stepping problems. In order to show the effectiveness of such an algorithm, we modify an explicit Newmark solver to incorporate it within the adaptive mesh refinement framework. We perform the analysis of conservation properties of the modified algorithm to understand its limitations. Later, we demonstrate application of such development with a very practical example, simulation of an NDE experiment using ultrasonic guided waves. Details presented in [76] has shown that such a simulation would otherwise not have been possible. We further study the guided wave experiment and optimize various parameters of the algorithm to validate experimental results.
Book Synopsis Patch-based Adaptive Mesh Refinement for Multimaterial Hydrodynamics by : B. Liu
Download or read book Patch-based Adaptive Mesh Refinement for Multimaterial Hydrodynamics written by B. Liu and published by . This book was released on 2005 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a patch-based direct Eulerian adaptive mesh refinement (AMR) algorithm for modeling real equation-of-state, multimaterial compressible flow with strength. Our approach to AMR uses a hierarchical, structured grid approach first developed by (Berger and Oliger 1984), (Berger and Oliger 1984). The grid structure is dynamic in time and is composed of nested uniform rectangular grids of varying resolution. The integration scheme on the grid hierarchy is a recursive procedure in which the coarse grids are advanced, then the fine grids are advanced multiple steps to reach the same time, and finally the coarse and fine grids are synchronized to remove conservation errors during the separate advances. The methodology presented here is based on a single grid algorithm developed for multimaterial gas dynamics by (Colella et al. 1993), refined by(Greenough et al. 1995), and extended to the solution of solid mechanics problems with significant strength by (Lomov and Rubin 2003). The single grid algorithm uses a second-order Godunov scheme with an approximate single fluid Riemann solver and a volume-of-fluid treatment of material interfaces. The method also uses a non-conservative treatment of the deformation tensor and an acoustic approximation for shear waves in the Riemann solver. This departure from a strict application of the higher-order Godunov methodology to the equation of solid mechanics is justified due to the fact that highly nonlinear behavior of shear stresses is rare. This algorithm is implemented in two codes, Geodyn and Raptor, the latter of which is a coupled rad-hydro code. The present discussion will be solely concerned with hydrodynamics modeling. Results from a number of simulations for flows with and without strength will be presented.
Book Synopsis Future Directions for Adaptive Mesh Refinement in ASCI and Other LLNL Simulation Projects by :
Download or read book Future Directions for Adaptive Mesh Refinement in ASCI and Other LLNL Simulation Projects written by and published by . This book was released on 1997 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1986 with total page 1362 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book AMRSim written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Adaptive mesh refinement is complicated by both the algorithms and the dynamic nature of the computations. In parallel the complexity of getting good performance is dependent upon the architecture and the application. Most attempts to address the complexity of AMR have lead to the development of library solutions, most have developed object-oriented libraries or frameworks. All attempts to date have made numerous and sometimes conflicting assumptions which make the evaluation of performance of AMR across different applications and architectures difficult or impracticable. The evaluation of different approaches can alternatively be accomplished through simulation of the different AMR processes. In this paper we outline our research work to simulate the processing of adaptive mesh refinement grids using a distributed array class library (P++). This paper presents a combined analytic and empirical approach, since details of the algorithms can be readily predicted (separated into specific phases), while the performance associated with the dynamic behavior must be studied empirically. The result, AMRSim, provides a simple way to develop bounds on the expected performance of AMR calculations subject to constraints given by the algorithms, frameworks, and architecture.
Book Synopsis International Aerospace Abstracts by :
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1999 with total page 1020 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1987 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Numerical Initial Value Problems in Ordinary Differential Equations by : Charles William Gear
Download or read book Numerical Initial Value Problems in Ordinary Differential Equations written by Charles William Gear and published by Prentice Hall. This book was released on 1971 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: Introduction -- Higher order one-step methods -- Systems of equations and equations of order greater than one -- Convergence, error bounds, and error estimates for one-step methods -- The choice of step size and order -- Extrapolation methods -- Multivalue or multistep methods - introduction -- General multistep methods, order and stability -- Multivalue methods -- Existence, convergence, and error estimates for multivalue methods -- Special methods for special problems -- Choosing a method.
