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Modeling and simulation

About: Modeling and simulation is a research topic. Over the lifetime, 10273 publications have been published within this topic receiving 111550 citations.


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DissertationDOI
01 Sep 2002
TL;DR: In this article, the authors use the proper orthogonal decomposition (POD) and Galerkin projection to reduce the Navier-Stokes equations to a lowdimensional system of ordinary differential equations (ODEs).
Abstract: This thesis involves the modeling of self-sustained oscillations in the flow past a rectangular cavity. The emphasis is on developing low-dimensional models that are suitable for analysis using tools from dynamical systems and control theory. Two-dimensional direct numerical simulations are performed, and indicate the presence of a “wake mode,” which has been observed previously in experiments, but which is much less well understood than the “shear-layer mode” usually observed. We characterize the flow in both shear-layer mode and wake mode, and provide a criterion for predicting the onset of wake mode, as a function of the various geometrical and flow-related parameters. We focus on the modeling of shear-layer mode, and employ two distinct modeling approaches: first, we use the method of Proper Orthogonal Decomposition (POD) and Galerkin projection to reduce the Navier-Stokes equations to a lowdimensional system of ordinary differential equations (ODEs). We extend the method to compressible flows, using approximations that are valid for cold flows at moderate Mach number. In a compressible flow, both the kinematic and thermodynamic variables contribute to the total energy, and an inner product is introduced which respects this, and allows one to use vector-valued POD modes for the Galerkin projection. We obtain models in the form of ODEs with between 2 and 60 states, and compare models based on scalar-valued and vector-valued POD modes. All of the models work well for short times (a few periods of oscillation), but the models based on scalar-valued modes deviate for longer times, while in general the models based on vector-valued modes retain qualitatively correct dynamical behavior. In the second modeling approach, we model the underlying physical mechanisms separately (shear-layer amplification, acoustic scattering, acoustic propagation), and obtain linear models that are suitable for control design and analysis. We design a controller which stabilizes the model, and implement a similar control law on an experiment, demonstrating significant reduction in the amplitude of the oscillations, but revealing some limitations of feedback control.

115 citations

Proceedings ArticleDOI
22 Apr 2002
TL;DR: An alternative representation of computational simulations, which includes the influence of the probability theory significantly underestimates the environment on the system, is applied and is found that a traditional application of the system is considered nonlikelihood of a hypothetical unsafe region.
Abstract: tional simulation, computer simulations can appear most In the recent mathematical and risk assessment convincing Terminology such as “virtual prototyping”, literature on uncertainty estimation, it has been argued “virtual testing”, “full physics simulation”, and that the traditional application of probability theory “modeling and simulation based acquisition” are provides an inadequate model to capture the full scope of extremely appealing when budgets are highly constrainepistemic uncertainty Epistemic uncertainty is also ed, competitors are taking market share, or when referred to as subjective uncertainty, reducible political constraints do not allow testing of certain uncertainty, or uncertainty due to lack of knowledge systems To assess the accuracy and usefulness of This paper applies an alternative representation of computational simulations, three key aspects are needed uncertainty, evidence theory (also referred to as in the analysis and experimental process: code and Dempster-Shafer theory), to a simple example The solution verification, experimental validation of the example system involves an algebraic equation with two mathematical models of the process being simulated, and uncertain input parameters and one system response estimation of the uncertainty of both the inputs and variable The information for each of the uncertain outputs of the simulation The topics of verification and parameters is given by multiple sources of intervalvalidation are not addressed here, but these are covered at valued data, so that large epistemic uncertainty exists in length in the literature A number of fields have the parameters The example is solved with traditional contributed to the development of uncertainty estimation probability theory and evidence theory The discussion techniques and procedures, such as, nuclear reactor safety, stresses the mathematical and procedural steps needed to underground storage of radioactive and toxic wastes, and compute uncertainty bounds in the system response structural dynamics (see, for example, Refs 1-15) using evidence theory, as well as the similarities and Uncertainty estimation for engineered systems is differences between evidence theory and the traditional sometimes referred to as the simulation of approach Given the nature of the specified uncertainty nondeterministic systems The mathematical model of information, it is found that a traditional application of the system, which includes the influence of the probability theory significantly underestimates the environment on the system, is considered nonlikelihood of a hypothetical unsafe region as compared to deterministic in the sense that: a) the model can produce evidence theory Strengths and weaknesses of evidence nonunique system responses because of the existence of theory are discussed, and several important open issues uncertainty in the input data for the model, or b) there are are identified that must be addressed before evidence multiple alternative mathematical models for the system theory can be used confidently and productively in The mathematical models, however, are assumed to be engineering applications deterministic in the sense that when all necessary input data for the model are specified, the model produces only

115 citations

Journal ArticleDOI
TL;DR: This Review focuses on the modeling- and simulation-guided development and implementation of solar-driven water-splitting prototypes from a holistic viewpoint that explores the various interplays between the components.
Abstract: An integrated cell for the solar-driven splitting of water consists of multiple functional components and couples various photoelectrochemical (PEC) processes at different length and time scales. The overall solar-to-hydrogen (STH) conversion efficiency of such a system depends on the performance and materials properties of the individual components as well as on the component integration, overall device architecture, and system operating conditions. This Review focuses on the modeling- and simulation-guided development and implementation of solar-driven water-splitting prototypes from a holistic viewpoint that explores the various interplays between the components. The underlying physics and interactions at the cell level is are reviewed and discussed, followed by an overview of the use of the cell model to provide target properties of materials and guide the design of a range of traditional and unique device architectures.

113 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202333
202291
2021268
2020332
2019450
2018442