首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到10条相似文献,搜索用时 140 毫秒
1.
Despite a steady increase in computing power, the complexity of engineering analyses seems to advance at the same rate. Traditional parametric design analysis is inadequate for the analysis of large-scale engineering systems because of its computational inefficiency; therefore, a departure from the traditional parametric design approach is required. In addition, the existence of legacy data for complex, large-scale systems is commonplace. Approximation techniques may be applied to build computationally inexpensive surrogate models for large-scale systems to replace expensive-to-run computer analysis codes or to develop a model for a set of nonuniform legacy data. Response-surface models are frequently utilized to construct surrogate approximations; however, they may be inefficient for systems having with a large number of design variables. Kriging, an alternative method for creating surrogate models, is applied in this work to construct approximations of legacy data for a large-scale system. Comparisons between response surfaces and kriging are made using the legacy data from the High Speed Civil Transport (HSCT) approximation challenge. Since the analysis points already exist, a modified design-of-experiments technique is needed to select the appropriate sample points. In this paper, a method to handle this problem is presented, and the results are compared against previous work.  相似文献   

2.
Large scale, multidisciplinary, engineering designs are always difficult due to the complexity and dimensionality of these problems. Direct coupling between the analysis codes and the optimization routines can be prohibitively time consuming due to the complexity of the underlying simulation codes. One way of tackling this problem is by constructing computationally cheap(er) approximations of the expensive simulations that mimic the behavior of the simulation model as closely as possible. This paper presents a data driven, surrogate-based optimization algorithm that uses a trust region-based sequential approximate optimization (SAO) framework and a statistical sampling approach based on design of experiment (DOE) arrays. The algorithm is implemented using techniques from two packages—SURFPACK and SHEPPACK that provide a collection of approximation algorithms to build the surrogates and three different DOE techniques—full factorial (FF), Latin hypercube sampling, and central composite design—are used to train the surrogates. The results are compared with the optimization results obtained by directly coupling an optimizer with the simulation code. The biggest concern in using the SAO framework based on statistical sampling is the generation of the required database. As the number of design variables grows, the computational cost of generating the required database grows rapidly. A data driven approach is proposed to tackle this situation, where the trick is to run the expensive simulation if and only if a nearby data point does not exist in the cumulatively growing database. Over time the database matures and is enriched as more and more optimizations are performed. Results show that the proposed methodology dramatically reduces the total number of calls to the expensive simulation runs during the optimization process.  相似文献   

3.
Newton-Krylov-FAC methods for problems discretized on locally refined grids   总被引:1,自引:0,他引:1  
Many problems in computational science and engineering are nonlinear and time-dependent. The solutions to these problems may include spatially localized features, such as boundary layers or sharp fronts, that require very fine grids to resolve. In many cases, it is impractical or prohibitively expensive to resolve these features with a globally fine grid, especially in three dimensions. Adaptive mesh refinement (AMR) is a dynamic gridding approach that employs a fine grid only where necessary to resolve such features. Numerous AMR codes exist for solving hyperbolic problems with explicit time stepping and some classes of linear elliptic problems. Researchers have paid much less attention to the development of AMR algorithms for the implicit solution of systems of nonlinear equations. Recent efforts encompassing a variety of applications demonstrate that Newton-Krylov methods are effective when combined with multigrid preconditioners. This suggests that hierarchical methods, such as the Fast Adaptive Composite grid (FAC) method of McCormick and Thomas, can provide effective preconditioning for problems discretized on locally refined grids. In this paper, we address algorithm and implementation issues for the use of Newton-Krylov-FAC methods on structured AMR grids. In our software infrastructure, we combine nonlinear solvers from KINSOL and PETSc with the SAMRAI AMR library, and include capabilities for implicit time stepping. We have obtained convergence rates independent of the number of grid refinement levels for simple, nonlinear, Poisson-like, problems. Additional efforts to employ this infrastructure in new applications are underway. Communicated by: G. Wittum  相似文献   

4.
5.
Currently available small computer systems and their potential use in the design and analysis of structures are summarized. The use of expensive main-frame computers in structural analysis is being challenged by the availability of inexpensive minicomputers and microprocessors. However, the use of this new equipment has not been fully exploited due to the lack of software which must be tailored for small computers.The development of interactive, computer assisted, structural design has not progressed significantly in the past due to expensive computer hardware or remote time-sharing costs. The availability of powerful inexpensive computer systems within small design firms will allow the design engineer to gradually integrate interactive computer assisted design into the design process without a major investment in computer hardware.The total cost of a small computer with extended BASIC and FORTRAN IV languages is less than $10,000. In addition to the ability to perform engineering computations the same computer system can be used for administration functions such as accounting, inventory, cost estimates and word processing associated with the writing of specifications and engineering reports. The total cost of a small microcomputer may be completely justified by its use as a high or low speed remote terminal to a larger computer.  相似文献   

6.
The ability to perform and evaluate the effect of shape changes on the stress and modal responses of components is an important ingredient in the “design” of aircraft engine components. The classical design of experiments (DOE)-based approach that is motivated from statistics (for physical experiments) is one of the possible approaches for the evaluation of the component response with respect to design parameters [Myers, Montgomery. Response surface methodology, process and product optimization using design of experiments. John Wiley and Sons, NY (1995)]. As the underlying physical model used for the component response is deterministic and understood through a computer simulation model, one needs to re-think the use of the classical DOE techniques for this class of problems. In this paper, we explore an alternate sensitivity-analysis-based technique where a deterministic parametric response is constructed using exact derivatives of the complex finite-element (FE)-based computer models to design parameters. The method is based on a discrete sensitivity analysis formulation using semi-automatic differentiation (Griewank, SIAM (2000), ADIFOR, Automatic Differentiation of FORTRAN codes ) to compute the Taylor series or its Pade equivalent for finite-element-based responses. Shape design or optimization in the context of finite element modeling is challenging because the evaluation of the response for different shape requires the need for a meshing consistent with the new geometry. This paper examines the differences in the nature and performance (accuracy and efficiency) of the analytical derivatives approach against other existing approaches with validation on several benchmark structural applications. The use of analytical derivatives for parametric analysis is demonstrated to have accuracy benefits on certain classes of shape applications.  相似文献   

7.
Analogical planning provides a means of solving engineering problems where other machine learning methods fail. Unlike many machine learning paradigms, analogy does not require numerous previous examples or a rich domain theory. Instead, analogical planners adapt knowledge of solved problems in similar domains to the current problem. Unfortunately, the analogical planning task is an expensive one. While the process of forming correspondences between a known problem and a new problem is complex, the problem of selecting a base case for the analogy is virtually intractable.This paper addresses the issue of efficiently forming analogical plans. The Anagram planning system is described, which takes advantage of the massively parallel architecture of the Connection Machine to perform base selection and map formation. Anagram provides a tractable solution to analogical planning, with a complexity that is sublinear in the size of the plans.This paper describes the Anagram system and its parallel algorithms. The paper also presents theoretical analyses and empirical results of testing the system on a large database of plans from the domain of automatic programming.  相似文献   

8.
Mathematical programming provides general tools for engineering design optimization. We present numerical models for simultaneous analysis and design optimization (SAND) and multidisciplinary design optimization (MDO) represented by mathematical programs. These models are solved with numerical techniques based on the feasible arc interior point algorithm (FAIPA) for nonlinear constrained optimization. Even if MDO is a very large optimization problem, our approach reduces considerably the computer effort. Several tools for very large problems are also presented. The present approach is very strong and efficient for real industrial applications and can easily interact with existing simulation engineering codes.  相似文献   

9.
A simulation environment to support engineering design embedded in an enterprise-wide information system is presented. The environment consists of a set of structures and managers housing the problem definition, tools for controlling the simulation model construction and execution, and the interaction of simulation processes with the product data management system. The issues associated with the introduction of automated and adaptive geometry-based simulation processes into the engineering design process are emphasised.  相似文献   

10.
Function in Device Representation   总被引:9,自引:0,他引:9  
We explore the meanings of the terms ‘structure’, ‘behaviour’, and, especially, ‘function’ in engineering practice. Computers provide great assistance in calculation tasks in engineering practice, but they also have great potential for helping with reasoning tasks. However, realising this vision requires precision in representing engineering knowledge, in which the terms mentioned above play a central role. We start with a simple ontology for representing objects and causal interactions between objects. Using this ontology, we investigate a range of meanings for the terms of interest. Specifically, we distinguish between function as effect on the environment, and a device-centred view of device function. In the former view, function is seen as an intended or desired role that an artifact plays in its environment. We identify an important concept called mode of deployment that is often left implicit, but whose explicit representation is necessary for correct and complete reasoning. We discuss the task of design and design verification in this framework. We end with a discussion that relates needs in the world to functions of artifacts created to satisfy the needs.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号