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Mesh-Sequenced Realizations for Evaluation of Subgrid-Scale Models for Turbulent Combustion

AIAA JOURNAL 2020年第11期58卷 4878-4892页

作者： Edwards, Jack R. Nielsen, Tanner B. North Carolina State Univ Dept Mech & Aerosp Engn Raleigh NC 27695 USA Los Alamos Natl Lab Los Alamos NM 87545 USA

This paper develops a new approach for analysis of subgrid closures for turbulent combustion as modeled using direct quadrature (finite-rate chemistry) techniques. The approach, termed multiresolution analysis through mesh-sequenced realizations (MRA-MSR), conducts simultaneous, constrained large-eddy simulations on a set of hierarchically coarsened meshes. The availability of underlying fine-mesh (subgrid) data corresponding to coarse-mesh locations allows a clearer assessment of the effects of unresolved fluctuations on apparent reactivity. A key to MRA-MSR is the correlation of eddy structures at coarser mesh levels, which is facilitated by the transfer of filtered fine-mesh velocity information. A seven-mesh MRA-MSR hierarchy using three resolution levels is applied to one of the Sydney bluff-body stabilized methane-hydrogen flames. Analysis of the simultaneously evolved data at different resolution levels reveals several interesting trends. First, at high Damkohler numbers, there is clear evidence of attenuation of apparent reactivity due to the effects of unresolved fluctuations. Secondly, single-point, single-time filtered density functions of a normalized subgrid Damkohler number show a characteristic beta probability density function (PDF) form and display evidence of scale similarity. Interrogation of the MRA-MSR database also shows that the recently-proposed least-squares minimization (LSM) turbulence-chemistry interaction model can account for the observed diminishment in reactivity at high Damkohler numbers but cannot reduce scatter significantly. A new form of the LSM model, which makes use of the normalized subgrid Damkohler number beta PDF distribution, performs slightly better than the original model, illustrating the potential of MRA-MSR both in assessing existing closure concepts and in developing new ones.

关键词： Turbulent Combustion Direct Numerical Simulation Turbulence Length Scale probability density functions Turbulence Kinetic Energy Neutral Point Stress Distribution Shear Layers Mach Numbers Conservation Equations

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Use of Relevance Vector Machine in Structural Reliability Analysis

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JOURNAL OF AIRCRAFT 2013年第6期50卷 1726-1733页

作者： Zhou, Changcong Lu, Zhenzhou Yuan, Xiukai Northwestern Polytech Univ Sch Aeronaut Xian 710072 Shaanxi Peoples R China Xiamen Univ Sch Phys & Mech & Elect Engn Xiamen 361005 Fujian Peoples R China

The applicability of a relevance vector machine to structural reliability analysis is introduced in this work. Samples covering the important domains in the input space are first generated and selected by a modified Metropolis algorithm. Then, the samples are employed to build a surrogate model with the help of a relevance vector machine to approximate the real performance function. The surrogate model is further used for reliability analysis as a substitution of the real one, as calls to the real performance function may be time consuming or cumbersome, especially in engineering cases. In this work, the relevance vector machine and the Metropolis algorithm are combined in an iterated learning process, constantly updating the samples used according to the convergence trend of the failure probabilities. Both numerical and engineering examples have been analyzed and discussed with the proposed method, as well as comparisons to some other classical reliability methods. The research in this work shows that the proposed method based on the relevance vector machine is a viable alternative for structural reliability analysis.

关键词： Structural Reliability Surrogate Model Finite Element Modeling Support Vector Machine probability density functions Cantilever Beam Artificial Neural Network Young's Modulus Wing Box Monte Carlo Simulation

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Self-Sustained Oscillations of Turbulent Flow in an Open Cavity

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JOURNAL OF AIRCRAFT 2010年第3期47卷 820-834页

作者： Lee, Sang Bong Seena, Abu Sung, Hyung Jin Korea Adv Inst Sci & Technol Dept Mech Engn Taejon 305701 South Korea

Direct numerical and large eddy simulations of incompressible turbulent flows over deep and shallow cavies were performed in the range of 600 <= Re-D <= 12, 000 to investigate the influence of the incoming turbulent boundary layer on self-sustained oscillations of the shear layer. When the turbulent boundary layer approached the open cavity with Re-D = 3000, the energy spectra of the pressure fluctuations showed spectral peaks in the range of 0.15 <= omega <= 0.3. Conditionally averaged flowfields disclosed that the spectral peaks arise from the separation of high-speed streaky structures rather than from a geometric singularity of the cavity. The same spectral peaks were observed in a backward-facing step flow as well as in deep and shallow cavity flows, despite the different geometries of these systems. In the turbulent cavity flow of Re-D = 12, 000, however, the peak frequencies of the energy spectra cavity lengths of L/D = land 2 were found to correspond to the Nth modes with N = 2 and 3, respectively. These modes were very similar to the frequency characteristics of self-sustained oscillations reported for laminar cavity flows. Inspection of instantaneous pressure fluctuations as well as spanwise-averaged pressure fluctuations reversed that regular shedding of quasi-two-dimensional vortical structures was responsible for the peak frequency in the energy spectra.

关键词： Incompressible Flow Boundary Layer Thickness Convection Direct Numerical Simulation Vortices Freestream Velocity probability density functions Flow Characteristics Kelvin Helmholtz Instability Particle Image Velocimetry

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A new Probabilistic Active Contour region-based method for multiclass medical image segmentation

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MEDICAL & BIOLOGICAL ENGINEERING & COMPUTING 2019年第3期57卷 565-576页

作者： Arce-Santana, Edgar R. Mejia-Rodriguez, Aldo R. Martinez-Pena, Enrique Alba, Alfonso Mendez, Martin Scalco, Elisa Mastropietro, Alfonso Rizzo, Giovanna Univ Autonoma San Luis Potosi Fac Ciencias San Luis Potosi Mexico CNR Inst Mol Bioimaging & Physiol IBFM Milan Italy

In medical imaging, the availability of robust and accurate automatic segmentation methods is very important for a user-independent and time-saving delineation of regions of interest. In this work, we present a new variational formulation for multiclass image segmentation based on active contours and probability density functions demonstrating that the method is fast, accurate, and effective for MRI brain image segmentation. We define an energy function assuming that the regions to segment are independent. The first term of this function measures how much the pixels belong to each class and forces the regions to be disjoint. In order for this term to be outlier-resistant, probability density functions were used allowing to define the structures to be segmented. The second one is the classical regularization term which constrains the border length of each region removing inhomogeneities and noise. Experiments with synthetic and real images showed that this approach is robust to noise and presents an accuracy comparable to other classical segmentation approaches (in average DICE coefficient over 90% and ASD below one pixel), with further advantages related to segmentation speed.

关键词： Multiclass segmentation Active contours probability density functions

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Survey on stochastic distribution systems: A full probability density function control theory with potential applications

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OPTIMAL CONTROL APPLICATIONS & METHODS 2021年第6期42卷 1812-1839页

作者： Wang, Aiping Wang, Hong Bozhou Univ Dept Elect & Informat Engn Bozhou Peoples R China Anhui Univ Inst Comp Sci Hefei Peoples R China Oak Ridge Natl Lab Energy Sci & Technol Directorate 1 Bethel Valley Rd Oak Ridge TN 37831 USA Univ Manchester Manchester Lancs England

Complex systems seen either in general engineering practice or economics are subjected to ever increased uncertainties that are mostly represented as random variables or parameters, and the characteristics of random variables are represented by their probability density functions (PDFs). Controlling their PDFs means to shape their stochastic distributions and in general it would provide a full treatment for system analysis and operational control and optimization. This leads to the development of stochastic distribution control (SDC) systems theory in the past decades, where the original aim of the controller design is to realize a shape control of the distributions of certain random variables in their PDFs sense for some engineering processes. Indeed, once the PDFs of these random variables or parameters are used to describe their distribution characters, the control task is to obtain control signals so that the output PDFs of stochastic systems are made to follow their target PDFs. The subject of SDC was initially originated for non-Gaussian stochastic control systems design but has found a wide spectrum of applications in general systems in terms of data-driven modeling, analysis, signal processing (filtering), data mining via multivariable statistics, decision-making (optimization) for systems subjected to uncertainties and even in economics. In this context, SDC constitutes an effective primer tool for complex system analysis, control and operational optimizations. In this review paper, a detailed survey of the developments on the research of SDC systems will be made together with their wide spectrum applications and future perspectives.

关键词： fault detection and diagnosis filtering iterative learning mechanisms neural networks optimization probability density functions stochastic distribution control systems

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Joseph Formulation of Unscented and Quadrature Filters with Application to Consider States

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2013年第6期36卷 1871-1874页

作者： Zanetti, Renato DeMars, Kyle J. Charles Stark Draper Lab Inc Houston TX 77058 USA US Air Force Res Lab Space Vehicles Directorate Kirtland AFB NM 87117 USA

The optimal estimator reduces to the consider filter in the case of linear measurements, and it can be approximated by linearization around the conditional mean to obtain the well-known consider filter results. It should be noted that the unscented Kalman filter can employ different weights for the mean and covariance calculations. Three methods for constructing the input sigma points and their associated weights are reviewed: the symmetric, extended symmetric, and scaled extended symmetric sigma-point selection schemes. The symmetric sigma-point selection scheme guarantees matching of the mean and covariance of the input distribution. Two estimation schemes that do not rely on linearization centered at the current estimate are the unscented Kalman filter and quadrature filters. The proposed generalized Joseph formula is necessary to update the estimation error covariance whenever a nonoptimal gain is chosen in the linear unbiased estimator. Various reasons could dictate the need of a nonoptimal gain selection.

关键词： Unscented Kalman Filter Schmidt Kalman Filter probability density functions Cholesky Factorization Orbit Determination White Noise Computing

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ESTIMATION OF KALMAN FILTER GAIN FROM OUTPUT RESIDUALS

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1993年第5期16卷 903-908页

作者： JUANG, JN CHEN, CW PHAN, M N CAROLINA STATE UNIV MARS MISSION RES CTRRALEIGHNC 27695 LOCKHEED ENGN & SCI CO HAMPTONVA 23665

This paper presents a procedure to estimate the Kalman filter gain from input-output measurement data with a given system model. The system model can be a finite element model or an experimental model from any identification method. The procedure consists of three basic steps. First, the stochastic portion related to the residuals of the response is computed. Second, the coefficients of a linear difference model for the stochastic portion are estimated by a least-squares solution that minimizes the filter residual. Third, the Kalman filter gain is computed from these model coefficients. Experimental results are presented to illustrate the usefulness of the developed procedure.

关键词： Observer Kalman Filter Identification Finite Element Modeling Trusses Accelerometer probability density functions NASA Langley Research Center Autoregressive Model Mathematical Models Air Jet Thrusters White Noise

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Location-based analysis of car-following behavior during braking using naturalistic driving data

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CANADIAN JOURNAL OF CIVIL ENGINEERING 2020年第5期47卷 498-505页

作者： Tawfeek, Mostafa H. El-Basyouny, Karim Ain Shams Univ Dept Civil Engn Cairo Egypt Univ Alberta Dept Civil & Environm Engn Edmonton AB Canada

This study investigates the car-following behavior during braking at intersections and segments. Car-following events were extracted from a naturalistic driving dataset, mapped using ArcGIS, and analyzed to differentiate between the intersection-and segment-related events. The intersection-related events were identified according to an intersection influence area, which was estimated based on the stopping sight distance and the speed limit. Five behavioral measures were quantified based on exploring the probability density functions (PDF) for intersection- and segment-related events. The results showed that there were significant differences between the PDFs of the measures for both cases. Moreover, it was indicated that drivers tend to be more aggressive at intersections compared with segments. Thus, it is crucial to consider the driver's location when investigating driver behavior. The quantified behavioral measures are a rich data source that can be used for car-following microscopic modeling, surrogate safety analysis, and driver assistance systems development.

关键词： driver behavior naturalistic driving data car following during braking driving aggressiveness intersection influence area probability density functions

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Analytical approach to probabilistic prediction of voltage sags on transmission networks

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IEE PROCEEDINGS-GENERATION TRANSMISSION AND DISTRIBUTION 2002年第1期149卷 7-14页

作者： Lim, YS Strbac, G UMIST Dept Engn & Elect Manchester M60 1QD Lancs England

Quantification of voltage sags at a location of interest is the basic requirement for assessing the compatibility between equipment and electrical supply. An analytical method is described that has been developed to determine the probability density functions of voltage sags caused by three phase faults across the network. The method takes into account the impact of fault positions along transmission circuits and patterns of generation associated with the corresponding load demands on the voltage sag profiles. The developed algorithm is applied to the IEEE 24-bus reliability test system to verify the technique and illustrate its application.

关键词： transmission network calculations transmission network voltage sags prediction load demands power transmission reliability Statistics Network and transmission line calculations equipment-supply compatibility power transmission faults Maintenance and reliability power system transients three phase faults Reliability power system analysis computing probability density functions Other topics in statistics probability computer simulation IEEE 24-bus reliability test system

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Filtered density function for subgrid scale modeling of turbulent combustion

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AIAA JOURNAL 2006年第1期44卷 16-23页

作者： Givi, P Univ Pittsburgh Pittsburgh PA 15261 USA

In the late 1980s, this author was preparing a review paper on large-scalenumerical simulations of turbulent reactive flows. The intent was to provide a survey of thecontributions made in both direct numerical simulation (DNS) and large eddy simulation (LES).However, when that paper was finally published, its content was heavily biased toward DNS. This wasnot intentional; it merely reflected the state of progress on LES of turbulent combustion at thattime. But with all of the enthusiasm for DNS in the combustion community, the limitations of suchsimulations were well recognized (even with the most optimistic predictions of growth insupercomputer technology). It was also clear that the future of large-scale simulations of turbulentcombustion would heavily depend on the development of LES.

关键词： Turbulent Combustion Direct Numerical Simulation Reynolds Averaged Navier Stokes Turbulent Reacting Flow National Science Foundation Convection probability density functions NASA Langley Research Center Diffusion Coefficient Incompressible Flow

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