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The effective radius of Lucas-Washburn dynamics in periodically constricted tubes

MICROFLUIDICS AND NANOFLUIDICS 2025年第5期29卷 1-9页

作者： Urteaga, Raul Berli, Claudio L. A. Univ Nacl Litoral CONICET IFIS Litoral Guemes 3450 RA-3000 Santa Fe Argentina Univ Nacl Litoral INTEC CONICET Gnuemes 3450 RA-3000 Santa Fe Argentina

Capillary imbibition in periodically constricted tubes (PCTs) plays a critical role in multiple natural and technological processes, where the control of autonomous flows is intrinsically linked to the geometric architecture of the imbibition space. Here we present analytical expressions for the effective radius (r(eff)) of PCTs with different wave shapes and analyze how geometric parameters influence the infiltration dynamics. Our analysis reveals that r(eff) is strongly dependent on the ratio of maximum to minimum radii (alpha) and, for stepped geometries, on the relative segment length proportion (gamma). Increasing alpha enhances r(eff) up to a critical value, beyond which a strong reduction is observed: for alpha>> 2, approximately, the infiltration velocity progressively decreases. This counterintuitive behavior arises from the interplay between hydrodynamic resistance and capillary driving forces. We evaluated the effect on different geometries, achieving different r(eff) that can be analytically predicted by closed-form expressions. The model was also validated against previously reported experimental data. These findings underline the potential of geometric design to optimize capillary-driven flows, providing a framework for tailoring PCTs to specific applications in microfluidics, porous media, and related fields.

关键词： Capillary filling Non-uniform tubes Effective radius probability density functions

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Estimation of the Parameters of a Three-Dimensional Gust Model with a Wind Lidar

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AIAA JOURNAL 2025年第4期63卷 1568-1579页

作者： Musso, Christian Boulant, Thibault Valla, Matthieu Lefebvre, Sidonie Michel, David T. French Aerosp Lab Opt & Tech Associees ONERA F-91120 Palaiseau France

Reducing fuel consumption for future airplanes is a critical issue. One solution is to design airplanes with a large wing aspect ratio to increase the lift. However, such wings are sensitive to loads induced by gusts. A technique consists of using adaptive wings that modify their shape according to the gust measured ahead of the airplane (the so-called feed-forward gust load alleviation). The gust is typically measured using a wind lidar at the nose of the airplane. To determine the three-dimensional wind field, the lidar is addressed along different axes to obtain the projections of the wind along each of them. In this paper, we present a methodology for reconstructing a gust immersed in wind turbulence from the lidar measurements. The proposed estimation methods are based on the Bayesian filtering theory. Considering simplified models, numerical simulations show the feasibility of such a reconstruction.

关键词： Light Detection and Ranging Aeroplane Wing Planforms Numerical Simulation Aircraft Wing Design Loads Alleviation Energy Economics Turbulence Models probability density functions Wind Field Reconstruction

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

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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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Statistical Analysis of the Surface Roughness on Aircraft Icing

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JOURNAL OF AIRCRAFT 2024年第1期61卷 245-256页

作者： Sotomayor-Zakharov, Denis Radenac, Emmanuel Gallia, Mariachiara Guardone, Alberto Knop, Inken Tech Univ Carolo Wilhelmina Braunschweig Inst Fluid Mech Hermann Blenk Str 37 D-38106 Braunschweig Germany Univ Toulouse ONERA DMPE 2 Ave Edouard Belin F-31055 Toulouse France Polytech Univ Milan Dept Aerosp Sci & Technol Via Masa 34 I-20156 Milan Italy Tech Univ Carolo Wilhelmina Braunschweig Inst Fluid Mech Multiphase Flows & Icing Workgrp Hermann Blenk Str 37 D-38106 Braunschweig Germany

A statistical analysis of the surface roughness is performed on experimentally obtained ice shapes on an asymmetrical airfoil at Rec approximate to 2 & sdot;106. The ice shapes were generated in the Icing Wind Tunnel of the Technical University of Braunschweig under Appendix C and O conditions of the EASA airplane certification standards as part of the ICE GENESIS project. The photogrammetry method is used for the digitization of the experimental ice shapes, while statistical parameters such as the mean ice shape and the local root mean square (RMS) of the ice geometry are extracted using a traditional surface projection method, as well as a self-organizing maps approach. Results show the evolution of the statistical parameters over time and the influence of the freestream static temperature on these parameters. A comparison between the experimental values of the local RMS of the ice geometry and a correlation for roughness prediction is presented, showing a good match with the original formulation of the correlation for cases under Appendix C conditions while having a good match with Appendix O conditions when a temperature correction factor is applied to the formulation. Additionally, results show an almost linear growth of roughness over the whole accretion time.

关键词： probability density functions Surface Properties Freestream Velocity Surface Roughness Distributed Roughness Aircraft Icing Icing Wind Tunnel Photogrammetry Supercooled Large Droplets Asymmetric Airfoil

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In Situ Imaging of Parachute Textile Micromechanics Under Tensile Load

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AIAA JOURNAL 2024年第12期62卷 4691-4700页

作者： Phillippe, Cutler A. Panerai, Francesco Roca, Laura Villafane Univ Illinois Dept Aerosp Engn 104 S Wright St Urbana IL 61801 USA

Micromechanics of parachute fabrics under tensile loads are studied using in situ x-ray microtomography. Results are presented for two nylon textiles commonly used in parachute systems, MIL-C-7020H Type III and MIL-C-44378(GL) Type II. Textiles are subjected to incremental tension using a custom apparatus that loads the fabric radially, and the microstructure is imaged sequentially at steady load conditions. Microtomography images are processed using learning-aided segmentation and a custom processing pipeline that tracks the locations and morphological properties of individual tows on 3D datasets. Results are used to reconstruct tow microscale properties and meso-scale strains. Our findings reveal a direct relation between the fabric architecture and the meso-scale mechanics. Warp tow pretensioning during manufacturing is found to affect decrimping and the anisotropy of the textile strains. Areal porosity increase with tension is quantified, and a geometric model for pore opening under incremental load is validated.

关键词： Microstructure Permeability Fluid Structure Interaction Mechanical Properties Image Segmentation Wing Planforms probability density functions Plastic Deformation Mechanical Testing Data Analysis

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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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Semi-Intrusive Stochastic Galerkin Finite Element Method for Adjoint-Based Optimization Under Uncertainty

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JOURNAL OF AEROSPACE INFORMATION SYSTEMS 2024年第9期21卷 684-697页

作者： Boopathy, Komahan Kennedy, Graeme J. Georgia Inst Technol Sch Aerosp Engn 270 Ferst Dr Atlanta GA 30332 USA Fluent High Performance Comp Lebanon NH 03766 USA

The stochastic Galerkin method for the propagation of probabilistically modeled uncertainties can be difficult to apply in practice due to its formulation and the challenge of creating a computational infrastructure to support it. To address these challenges, this work proposes a sampling-based stochastic Galerkin method that leverages existing deterministic analysis and adjoint-based derivative implementations. The proposed formulation is semi-intrusive since it is implemented using an existing deterministic framework, requiring only the numerical sampling of the deterministic residuals, Jacobians, boundary conditions, and adjoint implementations at nodes in the probabilistic domain. The software architectures to support stochastic generalizations of the deterministic finite element frameworks are presented. This proposed approach is demonstrated using a finite element framework for flexible multibody dynamics problems. Finally, the semi-intrusive implementation of the stochastic Galerkin method is used to demonstrate gradient-based optimizations of flexible multibody dynamics systems in the presence of probabilistically modeled uncertainties.

关键词： Galerkin Finite Element Method Uncertainty Quantification Software Architecture Multibody Dynamics Robotic Manipulators Mechanism and Machines probability density functions

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Robust Trajectory Control for Multitarget Tracking in Proximity Operations

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2024年第10期47卷 2194-2203页

作者： Zhang, Jingrui Xue, Zhirun Cai, Han Houssineau, Jeremie Li, Lincheng Nanyang Technol Univ Sch Aerosp Engn Singapore 639798 Singapore Nanyang Technol Univ Div Math Sci Singapore 639798 Singapore Nanyang Technol Univ Sch Elect & Elect Engn Singapore 639798 Singapore Nanyang Technol Univ Sch Astronaut Singapore 639798 Singapore

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Effects of Liquid Film Instability on Spray Features of Liquid-Liquid Pintle Injectors

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AIAA JOURNAL 2024年第11期62卷 4247-4264页

作者： Zhao, Fan Zhang, Haibin Zhao, Liang Bai, Bofeng Xi An Jiao Tong Univ Xian 710049 Peoples R China State Key Lab Multiphase Flow Power Engn Xian Peoples R China Sch Chem Engn & Technol State Key Lab Multiphase Flow Power Engn Xian Peoples R China

As one of the crucial structural parameters for the pintle injectors, the design of the skip distance ratio is still heavily empirical-dependent in engineering, and the intrinsic correlations between the skip distance ratio and spray characteristics of liquid-liquid pintle injectors are also unclear. Inspired by the observations that the instability of axial liquid film exerts significant influence on the downstream spray behaviors of a liquid-liquid pintle injector, the influence of the skip distance ratio on the instability of the axial liquid film and the subsequent spray characteristics of the pintle injector was experimentally investigated. The spray steadiness of the pintle injector was evaluated based on the instantaneous images using the proper orthogonal decomposition technique, and the effects of the skip distance ratio and the momentum ratio on the spray features were analyzed. Furthermore, a proactive strategy was proposed to adjust the liquid film instability by modifying the outer wall morphology of the pintle post, and the verification experiments were carried out based on three different wall morphologies. It was discovered that the rough wall enhances the axial liquid film instability and promotes the liquid sheet breakup and atomization of the pintle injector. These results provide new insights and valuable references for the optimization design of pintle injectors.

关键词： Pintle Injector Bipropellants probability density functions Spray Visualization Image Analysis Doublet Impinging Injectors Twin-Fluid Atomization Kelvin-Helmholtz Instability Boundary Layer Instability

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