Article
Physics, Fluids & Plasmas
M. Buzzicotti, F. Bonaccorso, P. Clark Di Leoni, L. Biferale
Summary: The study investigates the use of computer vision tools for data reconstruction, specifically examining the application of convolutional neural networks and deep generative adversarial models in turbulent data. Two methods based on context encoders are proposed to improve the quality of reconstructed fields. A comparison with a different data assimilation tool, based on Nudging, is presented, offering new research directions in the study of turbulence.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Mechanics
Oleg Bogoyavlenskij
Summary: A new effect has been discovered in viscous fluid dynamics that satisfies the three-dimensional Navier-Stokes equations without external forces. This effect consists of oscillations of the total angular momentum vector. Exact solutions for viscous flows obeying the no-slip boundary condition are derived, with an arbitrary number of oscillations of the total angular momentum vector on any given interval of time. The stability of these oscillations under small perturbations of the exact solutions has been proven.
Article
Mechanics
Chuong V. Tran, Xinwei Yu, David G. Dritschel
Summary: Incompressible fluid flows are characterized by high correlations between velocity and pressure, as well as between vorticity and pressure. This correlation plays a significant role in maintaining regularity in Navier-Stokes flows. The study suggests that as long as global pressure minimum (or minima) and velocity maximum (or maxima) are mutually exclusive, regularity is likely to persist.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mathematics, Applied
Yanghai Yu, Jinlu Li, Zhaoyang Yin
Summary: In this paper, a new smallness hypothesis of initial data for the three-dimensional incompressible Navier-Stokes equations is derived and used to prove the existence of a unique global solution. Additionally, two examples of initial data satisfying the smallness condition are constructed, demonstrating that the norm of the initial data can be arbitrarily large.
APPLIED MATHEMATICS LETTERS
(2022)
Article
Computer Science, Interdisciplinary Applications
C. De Michele, G. Coppola
Summary: In this study, the conservation properties of various discretizations of the compressible Euler equations for shock-free flows were analyzed. The treatment of the energy equation and the induced discrete equations for other thermodynamic quantities were given special focus. The analysis was done both theoretically and numerically, considering the choice of energy equation and the splitting used in the discretization of the convective terms. The performances of different schemes were evaluated using two widely used test cases, and new and potentially useful formulations were also analyzed.
COMPUTERS & FLUIDS
(2023)
Article
Mathematics, Applied
Yanqing Wang, Yulin Ye
Summary: In this paper, an energy conservation criterion is derived for weak solutions of both the incompressible and compressible Navier-Stokes equations. The criterion is based on a combination of velocity and its gradient. For the incompressible case, it extends known results on periodic domain, including the famous Lions' energy conservation criterion. For the compressible case, it improves recent results and extends criteria for energy conservation from incompressible to compressible flow.
MATHEMATICAL METHODS IN THE APPLIED SCIENCES
(2023)
Article
Mathematics, Applied
Yanghai Yu, Xiaolei Yang, Xing Wu
Summary: In this paper, the Cauchy problem for the tri-dimensional compressible Navier-Stokes-Korteweg system is considered. The global solutions to the tri-dimensional Navier-Stokes-Korteweg equations are established with a specific choice on the Korteweg tensor in the whole space. These solutions are applicable to a class of large initial data whose L-2 norm can be arbitrarily large.
MATHEMATICAL METHODS IN THE APPLIED SCIENCES
(2022)
Article
Physics, Fluids & Plasmas
L. M. Yang, Z. H. Li, C. Shu, Y. Y. Liu, W. Liu, J. Wu
Summary: This work proposes a discrete unified gas-kinetic wave-particle (DUGKWP) method for simulation of flows in all flow regimes. The DUGKWP combines the advantages of the discrete velocity method (DVM) and the direct simulation Monte Carlo (DSMC) method. It accurately predicts flow properties in all flow regimes and enjoys superior efficiency with less memory consumption.
Article
Physics, Fluids & Plasmas
Candi Zheng, Yang Wang, Shiyi Chen
Summary: Finding extended hydrodynamics equations that can be applied from the dense gas region to the rarefied gas region is a difficult task. Accurate constitutive relations for stress and heat flux are crucial for success. Data-driven models offer a new approach to learning these relations, but the choice of derivatives in these models is arbitrary and lacks a physical explanation.
Article
Engineering, Multidisciplinary
Xuejian Li, Elizabeth V. Hawkins, Leo G. Rebholz, Duygu Vargun
Summary: This paper explores the improvement of Picard and Newton iterative solvers for the Navier-Stokes equations by incorporating data measurements or solution observations. The authors propose adapted iterations that integrate known solution data into the solvers using continuous data assimilation (CDA) style nudging. The results demonstrate improved convergence rate and contractive properties for CDA-Picard, as well as an enlarged domain of convergence for CDA-Newton with increased measurement data. The paper also highlights the possibility of implementing CDA by directly enforcing measurement data into the solution.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2023)
Article
Mechanics
Siddharth Gupta, Namshad Thekkethil, Amit Agrawal, Kerry Hourigan, Mark C. Thompson, Atul Sharma
Summary: This study investigates the energy efficiency of self-propelled hydrofoils for different modes and kinematics of swimming among various body-caudal fin fish. It is found that intermittent burst-and-coast (B&C) swimming can save energy, albeit with increased travel time. Additionally, the research shows that B&C swimming is effective for carangiform and thunniform tail-like kinematics but not for anguilliform body-like kinematics of the hydrofoil.
Article
Mechanics
Milad Azari, Arman Sadeghi
Summary: The paper theoretically studies the unsteady dispersion of a solute band in a semicircular microchannel under a steady pressure-driven flow. Analytical solutions are obtained for the exchange, convection, and dispersion coefficients as well as the solute concentration and mean solute concentration. The study investigates the influences of the initial concentration distribution and the reaction rate on the transport coefficients.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mathematics, Applied
Animikh Biswas, Zachary Bradshaw, Michael Jolly
Summary: This paper introduces a localized version of the nudging data assimilation algorithm for the periodic 2D Navier-Stokes equations, in which observations are confined to a moving window across the entire domain. It is proven that the algorithm perfectly synchronizes with a reference solution if the movement is fast enough. The analysis suggests that moving the subdomain according to a region where the error is dominant is optimal. Numerical simulations are presented to compare the efficacy of regular pattern movement, error-guided movement, and random movement.
DISCRETE AND CONTINUOUS DYNAMICAL SYSTEMS
(2023)
Article
Mathematics, Applied
Ke Chen, Ly Kim Ha, Ruilin Hu, Hung Nguyen
Summary: In this paper, the global well-posedness problem for the 1d compressible Navier-Stokes systems (cNSE) in gas dynamics with rough initial data is studied. The existing global well-posedness results for the 1d isentropic cNSE and the 1d full cNSE are improved, and new ideas are proposed based on establishing various end-point smoothing estimates for the 1d parabolic equation.
JOURNAL DE MATHEMATIQUES PURES ET APPLIQUEES
(2023)
Article
Engineering, Aerospace
Yuanwei Bin, George Huang, Xiang I. A. Yang
Summary: In this study, we recalibrate the standard Spalart-Allmaras model using experimental and simulation data. Our approach, which employs Bayesian optimization and feedforward neural networks, focuses on free-shear flow, the buffer layer, the log layer, and flows with adverse pressure gradients. The recalibrated model is then implemented and tested in 11 flows, demonstrating improvements while preserving the model's existing good behavior.
Article
Engineering, Mechanical
E. Saredi, A. Sciacchitano, F. Scarano
Summary: This study proposes a novel approach for detecting outliers in PIV measurements by comparing the ratio between local advection and turbulent kinetic energy (TKE) production, and shows that it outperforms the state-of-the-art method in terms of accuracy.
EXPERIMENTS IN FLUIDS
(2022)
Editorial Material
Engineering, Multidisciplinary
Andrea Sciacchitano, Stefano Discetti
MEASUREMENT SCIENCE AND TECHNOLOGY
(2022)
Article
Engineering, Multidisciplinary
Dimitris K. Iakovidis, Melanie Ooi, Ye Chow Kuang, Serge Demidenko, Alexandr Shestakov, Vladimir Sinitsin, Manus Henry, Andrea Sciacchitano, Stefano Discetti, Silvano Donati, Michele Norgia, Andreas Menychtas, Ilias Maglogiannis, Selina C. Wriessnegger, Luis Alberto Barradas Chacon, George Dimas, Dimitris Filos, Anthony H. Aletras, Johannes Toger, Feng Dong, Shangjie Ren, Andreas Uhl, Jacek Paziewski, Jianghui Geng, Francesco Fioranelli, Ram M. Narayanan, Carlos Fernandez, Christoph Stiller, Konstantina Malamousi, Spyros Kamnis, Konstantinos Delibasis, Dong Wang, Jianjing Zhang, Robert X. Gao
Summary: Signal processing plays a crucial role in sensor-enabled systems and has various applications. The advancement in artificial intelligence and machine learning has shifted research focus towards intelligent, data-driven signal processing. This roadmap provides a critical overview of current methods and applications, aiming to identify future challenges and research opportunities for next generation measurement systems.
MEASUREMENT SCIENCE AND TECHNOLOGY
(2022)
Article
Green & Sustainable Science & Technology
Ming Huang, Carlos Ferreira, Andrea Sciacchitano, Fulvio Scarano
Summary: This study investigates wake recovery from planar porous actuators that simulate the effect of wind turbines, proposing an effective mixing diameter for scaling streamwise momentum recovery and validating this concept through wind tunnel experiments and numerical simulations.
Article
Engineering, Aerospace
Hasse N. J. Dekker, Daniele Ragni, Woutijn J. Baars, Fulvio Scarano, Marthijn Tuinstra
Summary: This study experimentally investigates the aerodynamic behavior of a two-rotor system in ground proximity. It is found that the wake deflection due to the ground and the formation of separated flow regions below each rotor significantly affect the flow field. Additionally, flow re-ingestion occurs when the rotors are sufficiently far apart.
Article
Engineering, Mechanical
Fulvio Scarano, Jan F. G. Schneiders, Gabriel Gonzalez Saiz, Andrea Sciacchitano
Summary: The VIC-TSA method introduces a technique for reconstructing flow fields based on time samples of tracer particles, with investigations into the effect of assimilated length on spatial resolution. Numerical exercises and large-scale PIV experiments validate the method's suitability for accurate reconstruction of real data.
EXPERIMENTS IN FLUIDS
(2022)
Article
Mechanics
Lourenco Tercio Lima Pereira, Francesco Avallone, Daniele Ragni, Fulvio Scarano
Summary: A physical description of the flow mechanisms governing the distribution of wall-pressure fluctuations over a serrated trailing edge is proposed. Three main mechanisms defining the variation of pressure fluctuations across the serrated edge are discussed, and semi-empirical models are formulated based on these mechanisms. It is found that the intensity of wall-pressure fluctuations increases at the tips due to increased convective velocity caused by sidewise momentum diffusion. Another factor, the change in impedance across the edge, leads to a reduction in pressure fluctuations near the trailing edge. Additionally, secondary flow patterns induced by non-symmetric flow at different angles of attack result in higher wall-pressure fluctuations over the serration edges.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Engineering, Multidisciplinary
Sagar Adatrao, Simone van der Velden, Mark-Jan van der Meulen, Marc Cruellas Bordes, Andrea Sciacchitano
Summary: This paper introduces a statistical tool called design of experiments (DOEs) for uncertainty quantification in particle image velocimetry (PIV). The tool allows for quantifying both the total and systematic uncertainties arising from various experimental factors. By measuring a quantity multiple times while varying the levels of experimental factors, the total variance and uncertainty can be computed using Analysis of Variances. The approach also provides individual variances for each factor, estimating their contributions to the total uncertainty.
MEASUREMENT SCIENCE AND TECHNOLOGY
(2023)
Article
Engineering, Civil
Constantin Jux, Andrea Sciacchitano, Fulvio Scarano
Summary: The aerodynamic characteristics of a modern road cycling wheel in crosswind were investigated using force- and planar PIV measurements in the TU Delft Open Jet Facility. The performance of a 62 mm deep rim with three tire profiles and yaw angles up to 24 degrees was evaluated. It was found that the rim-tire section of the wheel behaved similar to an airfoil, resulting in a reduction of aerodynamic resistance with increasing yaw angle. This reduction was limited by the stall angle of the tire-rim profile, which was found to depend on the tire's surface structure. Higher stall angles and lower resistance were achieved when the tire profile triggered laminar-to-turbulent boundary layer transition.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2023)
Article
Engineering, Aerospace
Xavier Carrillo Corcoles, Christoph Mertens, Andrea Sciacchitano, Bas W. W. van Oudheusden, Roeland De Breuker, Jurij Sodja
Summary: This study conducted an aeroelastic wind-tunnel experiment to investigate the influence of wing stiffness and hinge release threshold on the gust load alleviation performance of a folding wingtip design. The results showed that the structural properties did not have a significant impact on the peak load alleviation, but the hinge release threshold and timing did. Releasing the hinge at the correct timing significantly reduced peak loads, but also affected the system dynamics, decreasing flutter speed and increasing load oscillations.
JOURNAL OF AIRCRAFT
(2023)
Editorial Material
Engineering, Multidisciplinary
Stefano Discetti, Andrea Sciacchitano
MEASUREMENT SCIENCE AND TECHNOLOGY
(2023)
Article
Acoustics
Lourenco Tercio Lima Pereira, Francesco Avallone, Daniele Ragni, Fulvio Scarano
Summary: This work discusses the physics and design impact of noise reduction achieved from serrated trailing-edges. An experimental campaign is carried out on a 2D model using different trailing-edge serrations to build a complete dataset of acoustic measurements. Systematic modifications of a reference sawtooth serration design are made to its scale and geometry. The results obtained provide guidelines for serration design choices and their impact on broadband noise reduction.
Article
Engineering, Civil
Alexander Spoelstra, Wouter Terra, Andrea Sciacchitano
Summary: An aerodynamic assessment was conducted on two elite skaters in different skating postures using on-site Ring of Fire measurements. The study found that variations in posture lead to changes in airflow and aerodynamic drag. Additionally, similarities were observed in average flow velocity and vorticity fields across all postures. The optimization of the deep sit posture resulted in a 7.5% reduction in aerodynamic drag, while the difference between skating with two loose arms versus one loose arm was not statistically significant.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2023)
Article
Green & Sustainable Science & Technology
Daan van der Hoek, Joeri Frederik, Ming Huang, Fulvio Scarano, Carlos Simao Ferreira, Jan-Willem Van Wingerden
Summary: Dynamic induction control (DIC) is an effective method to increase the power output of wind farms. This study investigates the wake of a wind turbine under periodic excitation using a wind tunnel experiment. The results show that DIC increases the available power in the wake, and enhanced wake recovery contributes to the increased energy.
WIND ENERGY SCIENCE
(2022)