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Data-Driven Approach to the Development of an Aeroelastic Flutter Precursor

AIAA JOURNAL 2025年第1期63卷 174-183页

作者： Meivar, Boaz Karpel, Moti Technion Israel Inst Technol IL-32000 H_efa Israel

This paper presents a novel algorithm for aeroelastic flutter early detection. Two new features for flutter onset detection are presented. Flutter early warning is accomplished using only measured signals, with essentially no prior knowledge needed about the aircraft or the flutter mechanism involved. The algorithm consists of three stages: 1) extraction of regularity features, 2) calibration by addition of white noise to nominal measurements, and 3) thresholding. Four types of datasets were used: a) synthetic data, b) simulated data generated using aeroelastic response simulations to stochastic gusts, c) measured data from a wind tunnel experiment, and d) flight test data including actual flutter onsets. The algorithm was shown to be able to flag an impending flutter event before critical onset occurs. (The Python code for paper is available at https://***/bmeivar/flutter.)

关键词： Flight Testing Wind Tunnels Aeroelastic Modeling probability density functions Power Spectral density Gaussian Mixture Models Flutter Analysis Aircraft Flutter Data Science

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Thorough assessment of a crucial element pertaining to the distribution and average dimensions of droplet sizes in a solvent extraction column

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SEPARATION SCIENCE AND TECHNOLOGY 2025年第3-5期60卷 438-466页

作者： Asadollahzadeh, Mehdi Torkaman, Rezvan Nucl Sci & Technol Res Inst Nucl Fuel Cycle Res Sch Tehran 113658486 Iran

Designing and optimizing solvent extraction columns requires careful consideration of the determination and distribution of drop diameters. The size of droplets is influenced by the equilibrium state of breakage and coalescence. The interfacial area in the dispersed phase plays a vital role in determining the reaction rates, mass transfer, and diffusion between two immiscible liquids. To ascertain the variety of droplet sizes and the average size of drops (known as the Sauter mean), one needs to consider a range of factors such as system characteristics, column configuration, agitation speed and pulsation intensity. Although several correlations have been proposed to estimate the mean drop size in solvent extraction columns during steady-state conditions, many of them are only applicable to systems without reactions. This study aims to provide a comprehensive analysis of current literature on the average droplet size and size distribution in pulsed and agitated extraction columns. Additionally, it explores the influence of materials, system characteristics, column structure, and hydrodynamic behavior. Furthermore, an evaluation of existing correlations for Sauter mean drop diameter and size distribution is presented for different pulsed and agitated extraction columns.

关键词： Extraction columns sauter mean drop diameter drop size distribution empirical correlations probability density functions

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Neural controller for targeting a desired stationary distribution in stochastic systems

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INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS 2025年 174卷

作者： Jia, Wantao Jiao, Zhe Jin, Zhengrong Northwestern Polytech Univ Sch Math & Stat Xian 710129 Peoples R China Northwestern Polytech Univ MOE Key Lab Complex Sci Aerosp Xian 710129 Peoples R China

One of the major missions in the field of stochastic control is to design efficient control policies that guarantee the stochastic systems stabilize within some specified stationary distribution. In this paper, we propose a neural controller based on the stochastic asymptotic stability theory and the condition of detailed balance. A novel physics-informed learning procedure is introduced to update the parameters in a multi-output neural network which is utilized to approximate the controller. We also prove rigorously that the proposed controller is unique if it exists, which is essential in applications. Furthermore, several representative stochastic systems are used to illustrate the usefulness of this neural controller for the stabilization of these dynamical systems in distribution.

关键词： probability density functions Stochastic control Neural networks Detailed balance Stable in distribution

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Multilayer Graphene and Graphite Oxidation Using Kinetic Monte Carlo

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2025年第2期39卷 436-441页

作者： Schmitt, Simon Fu, Rui Martin, Alexandre Univ Kentucky Mech & Aerosp Engn Lexington KY 40506 USA

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Progressive failure analysis and open-hole compressive (OHC) strength prediction of laminates

Progressive failure analysis and open-hole compressive (OHC)...

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AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2025

作者： Shankar, Vignesh Nguyen, Minh Hoang D’mello, Royan J. Waas, Anthony M. Department of Aerospace Engineering University of Michigan Ann ArborMI48109 United States Arizona State University TempeAZ United States

ISBN: (数字)9781624107238

ISBN: (纸本)9781624107238

This paper presents the enhanced semi-discrete damage modeling (eSD2M) framework based on the finite element method to predict the damage progression and open-hole compressive (OHC) strength of laminates. Accurately predicting the Open-hole compressive strength is highly valued as a design variable in the industry. The enhanced semi-discrete damage model’s capability to capture key failure modes and their interactions with high-fidelity and efficiency are highlighted in this study. The FE model is meshed using the semi-discrete meshing and randomization of the material properties using probabilistic methods. The enhanced semidiscrete damage model (eSD2M) demonstrates its capability to accurately capture significant failure modes and failure loads. This is showcased in this paper through virtual testing of the various stacking sequences for which test data is available. © 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Stress Concentration Mechanical Properties Finite Element Method Stress Strain Curve Fiber Reinforced Composites Abaqus probability density functions Computational Modeling Materials Science

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Test and Evaluation Procedure to Develop a Digital Twin of The Sleeper-sat

Test and Evaluation Procedure to Develop a Digital Twin of T...

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AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2025

作者： Garcia, Mario Rayes Castillo, Jesus Shirin, Afroza El PasoTX79968 United States

ISBN: (数字)9781624107238

ISBN: (纸本)9781624107238

A Digital Twin (DT) is not just a collection of static digital models at the component level of a physical system but a dynamic entity that evolves in parallel with the physical system it mirrors. This evolution starts with physics-based or data-driven physics models representing the physical system and advances to Authoritative Virtualization or DT through continuous data assimilation and ongoing Digital Engineering Test and Evaluation processes. This paper aims to create a mathematical framework for the DE Test and Evaluation Process, which incorporates data assimilation to link physical and digital models, uncertainty quantification, uncertainty propagation, and DT calibration process. This framework will enable the DT to perform operations, control, decision-making, and predictions at scale. The framework will be implemented to develop the DT of the Sleeper-sat to analyze the Sleeper-sat's structural deformation during its deployment in space. The Sleeper-sat will be a variant of previously constructed Sleeper-sats from the Aerospace Center at UTEP. The DT of the Sleeper-sat will be capable of predicting and monitoring structural health during its space operations. © 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Digital Engineering Uncertainty Quantification Space Operations Aerospace Kalman Filter Artificial Neural Network probability density functions CubeSat Data Driven Model Structural Load

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Efficient Hessian Calculations Using Automatic Differentiation and the Adjoint Method with Applications

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AIAA JOURNAL 2010年第10期48卷 2406-2417页

作者： Rumpfkeil, Markus P. Mavriplis, Dimitri J. Univ Wyoming Dept Mech Engn Laramie WY 82071 USA

In this paper an efficient general algorithm to calculate the Hessian of a steady or unsteady functional of interest in the context of computational fluid dynamics is outlined, verified, and applied to an aerodynamic optimization and to an extrapolation example. The successful extrapolation is then applied to approximate Monte Carlo simulations for artificial geometric uncertainty analysis. The presented optimization and extrapolation examples demonstrate that the combination of automatic differentiation and an adjoint method to calculate the Hessian of a steady or unsteady objective function, and thereby obtaining second-order information, can be an efficient tool for optimization and uncertainty quantification.

关键词： CFD Simulation Monte Carlo Simulation Flow Conditions Lift Coefficient Airfoil Profiles Freestream Mach Number Lagrange Multipliers Finite Difference Approximation probability density functions Arbitrary Lagrangian Eulerian

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Influence of random excitations on acoustic instabilities in combustion chambers

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AIAA JOURNAL 2000年第8期38卷 1403-1410页

作者： Burnley, VS Culick, FEC USAF Res Lab Propuls Directorate Edwards AFB CA 93524 USA CALTECH Pasadena CA 91125 USA

Although flows in combustors contain considerable noise, arising from several kinds of sources, there is a sound basis for treating organized oscillations as distinct motions. That has been an essential assumption incorporated in virtually all treatments of combustion instabilities. However, certain characteristics of the organized or deterministic motions seem to have the nature of stochastic processes. For example, the amplitudes in Limit cycles always exhibit a random character, and even the occurrence of instabilities seems occasionally to possess some statistical features. Analysis of nonlinear coherent motions in the presence of stochastic sources is, therefore, an important part of the theory. We report a few results for organized oscillations in the presence of noise. The most significant deficiency is that, because of the low level of current understanding, the stochastic sources of noise are modeled in ad hoc fashion and are not founded on a solid physical basis appropriate to combustion chambers.

关键词： Cylindrical Combustion Chambers Acoustic Instability probability density functions Gasdynamics White Noise Combustion Instability Combustion Noise Signal Processing Monte Carlo Simulation Rocket Motor

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SCALING OF WALL SHEAR-STRESS FLUCTUATIONS IN A TURBULENT DUCT FLOW

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AIAA JOURNAL 1987年第1期25卷 22-29页

作者： SHAH, DA ANTONIA, RA University of Newcastle Newcastle Australia

Instantaneous fluctuations of the wall shear stress have been measured in a fully developed turbulent duct flow over a factor of 10 variation in the Reynolds number. Distributions for the average frequency of detections obtained using the variable-interval time averaging technique suggest that scaling on outer variables or perhaps a mixture of outer and inner variables is more appropriate than scaling on inner variables when the Reynolds number is sufficiently large. The Reynolds number behavior of the average frequencies of zero crossings and local maxima of the shear stress fluctuation rules out the possibility of outer scaling and indicates a weak Reynolds number dependence when scaled on inner variables. These apparently conflicting trends are discussed in the context of published results on the scaling of wall shear stress fluctuations. © 1987 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.

关键词： Shear Stress Boundary Layer Thickness Band Pass Filter Taylor Microscale Prandtl Number Comparators Kinematic Viscosity probability density functions Thermal Conductivity Thermal Conduction

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The probability density Function Related to Shallow Cumulus Entrainment Rate and Its Influencing Factors in a Large-Eddy Simulation

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Advances in Atmospheric Sciences 2024年第1期41卷 173-187页

作者： Lei ZHU Chunsong LU Xiaoqi XU Xin HE Junjun LI Shi LUO Yuan WANG Fan WANG Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD)and Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration Nanjing University of Information Science and TechnologyNanjing 210044China Nanjing Joint Institute for Atmospheric Sciences Nanjing 210019China College of Aviation Meteorology Civil Aviation Flight University of ChinaGuanghan 618307China Collaborative Innovation Center for Western Ecological Safety Lanzhou UniversityLanzhou 730000China Department of Geography Hong Kong Baptist UniversityHong Kong SAR 999077China

The process of entrainment-mixing between cumulus clouds and the ambient air is important for the development of cumulus *** obtaining the entrainment rate(λ)is particularly important for its parameterization within the overall cumulus parameterization *** this study,an improved bulk-plume method is proposed by solving the equations of two conserved variables simultaneously to calculateλof cumulus clouds in a large-eddy *** results demonstrate that the improved bulk-plume method is more reliable than the traditional bulk-plume method,becauseλ,as calculated from the improved method,falls within the range ofλvalues obtained from the traditional method using different conserved *** probability density functions ofλfor all data,different times,and different heights can be well-fitted by a log-normal distribution,which supports the assumed stochastic entrainment process in previous *** analysis demonstrate that the relationship betweenλand the vertical velocity is better than other thermodynamic/dynamical properties;thus,the vertical velocity is recommended as the primary influencing factor for the parameterization ofλin the *** results of this study enhance the theoretical understanding ofλand its influencing factors and shed new light on the development ofλparameterization.

关键词： large-eddy simulation cumulus clouds entrainment rate probability density functions spatial and temporal distribution

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