Article
Mechanics
Bo Jin, Simon J. Illingworth, Richard D. Sandberg
Summary: This study focuses on linear feedback control of two-dimensional flow past a cylinder at low Reynolds numbers, specifically looking at the optimal placement of a single sensor and a single actuator. By calculating the leading resolvent forcing and response modes of the flow, H-2-optimal estimators and controllers are designed. The research investigates optimal estimation, full-state information control, and overall feedback control, highlighting the importance of sensor and actuator placements in determining feedback control performance under varying Reynolds numbers.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Peng Han, Emmanuel de Langre, Mark C. Thompson, Kerry Hourigan, Jisheng Zhao
Summary: This study examines the impact of structural damping on the vortex-induced vibration (VIV) of a circular cylinder when the mass ratio is below its critical value. It is demonstrated through water-channel experiments and a reduced-order model that the previously observed phenomenon of VIV forever, characterized by resonance oscillations at any reduced velocity, remains even in the presence of high structural damping. Interestingly, the results from the reduced-order model indicate that the wake mode for VIV forever is unstable with a positive growth rate that increases with reduced velocity, while experimental data suggests that VIV forever is associated with synchronization between the non-stationary cylinder vibration frequency and the vortex-shedding frequency.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Varghese Mathai, Gali Alon Tzezana, Asimanshu Das, Kenneth S. Breuer
Summary: This study investigates the kinematics, dynamics, and flow fields of an oscillating, compliant membrane hydrofoil for energy extraction from water. The results show that dynamic cambering plays an important role in stabilizing the leading-edge vortices and significantly improves power extraction compared to rigid hydrofoils.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Cecilia Huertas-Cerdeira, Andres Goza, John E. Sader, Tim Colonius, Morteza Gharib
Summary: The dynamics of a cantilever plate at non-zero angles exhibit four distinct regimes, including small and large amplitude flapping motions, with different physical mechanisms at play. The plate enters the deflected regime at a lower flow speed with increasing angle of attack, causing the flapping motion to disappear for angles greater than approximately 28 degrees. Additionally, plates with reduced aspect ratios lack a clear distinction between flapping regimes at angles above 8 degrees.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mathematics, Interdisciplinary Applications
Andrey Ph Kiselev, Igor Lebed
Summary: The study investigates the chaotic distortion of regular regimes in the flow around a solid sphere using multi-moment hydrodynamics equations with stochastic terms. It explores the influence of disordered perturbations, loss of stability, behavioral changes in flow, butterfly effect, adjustment of disordered perturbations, and the relationships between the regular and chaotic components of turbulence in the wake behind the sphere.
CHAOS SOLITONS & FRACTALS
(2021)
Article
Mechanics
Pierre-Emmanuel des Boscs, Hendrik C. Kuhlmann
Summary: This study numerically investigates the linear stability of incompressible flow in an infinitely extended cavity with rectangular cross-section. The critical Reynolds numbers are found to be significantly smaller than previously reported, and different instability modes are identified, with the dominant mechanism being based on the local lift-up process. As the yaw angle varies, the instability and critical Reynolds number also change, showing the importance of the yaw angle in the flow dynamics.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Energy & Fuels
Jianlong Chang, Qingui Zhang, Liujing He, Yi Zhou
Summary: This paper numerically simulates the vortex shedding characteristics caused by the flow separation of the NACA0012 airfoil at Re = 1 x 10(4) using computational fluid dynamics (CFD). The study investigates the variation of vortex shedding structure and frequency characteristics at different angles of attack. The results show that the flow state transitions from steady to unsteady with increasing angle of attack, leading to a more complex vortex structure on the suction surface. The frequency spectrum corresponding to the lift coefficient can be analyzed to understand the vortex shedding characteristics. As the angle of attack increases, the stability of the flow field decreases and the Strouhal number of the vortex shedding frequency decreases as well.
Article
Mechanics
David C. Fritts, L. Wang, T. S. Lund, S. A. Thorpe
Summary: The study shows that the interaction of Kelvin-Helmholtz billows leads to more rapid and intense instabilities and turbulence than individual billows. These findings are significant for understanding Kelvin-Helmholtz instabilities in geophysical environments.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
H. M. Aravind, Thomas Dubos, Manikandan Mathur
Summary: This study investigates the stability of two-dimensional Kelvin-Helmholtz vortices using numerical simulations. The results show that different types of instabilities occur at the core and the edge of the vortices, and stratification strongly influences the instability at the vortex edge. The dependence of the dominant instability characteristics on the Richardson number is systematically studied. The local stability approach is able to predict the orientation of flow structures resulting from different instabilities, consistent with previous three-dimensional numerical simulations.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Mouad Boudina, Frederick P. Gosselin, Stephane etienne
Summary: Soft corals, such as Antillogorgia bipinnata, are colony building animals that feed by catching food particles brought by currents. Vibrations induced by VIVs can significantly enhance their ability to capture food particles, leading to up to 40% more particles being captured compared to fixed state.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Shuai Shuai, Darish Jeswin Dhas, Anubhab Roy, M. Houssem Kasbaoui
Summary: We investigate the effect of inertial particles dispersed in a circular patch of finite radius on the stability of a two-dimensional Rankine vortex in semi-dilute dusty flows. The feedback force from the particles triggers a novel instability, and even non-inertial particles can destabilize the vortex. A critical mass loading is identified, above which a specific eigenmode becomes unstable. Inertial particles have different impacts on stability compared to non-inertial particles. High-wavenumber modes emerge after the linear stage, causing the breakdown of the initial Rankine structure. This novel instability highlights how the feedback force from the disperse phase can induce the breakdown of an otherwise resilient vortical structure.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Multidisciplinary
Adam Kadlecsik, Akos Szeidemann, Miklos Vincze
Summary: We conducted laboratory experiments to study the dynamics of a free fluid surface in a cylindrical tank with a rotating bottom plate. The shear instability in the system generated polygonal structures that propagated along the fixed vertical sidewalls. By analyzing the wavelengths and drift rates of these patterns, we found that the drift rates of the polygonal vortices can be well approximated by a simple formula derived from the dispersion relation of linear gravity waves using easily observable parameters, with an empirical correction factor.
EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS
(2023)
Article
Mechanics
Sanjay Mittal, Jawahar Sivabharathy Samuthira Pandi, Mainak Hore
Summary: The study investigates the flow past a cylinder with side walls at various Reynolds numbers and aspect ratios, finding that the complexity of wake transitions increases with aspect ratio. The vortex structures and shedding characteristics change with Reynolds number and aspect ratio, showcasing different flow patterns and shedding modes.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Engineering, Chemical
Jos J. Derksen
Summary: Simulations of interactions between flexible cylinders and laminar flow resolved geometrical details using lattice-Boltzmann method and immersed boundary method. Flexibility of cylinders significantly affects the temporal behavior of flow systems, as demonstrated in Poiseuille flow exhibiting vortex shedding.
Article
Energy & Fuels
Anan Garzozi, David Greenblatt
Summary: This research investigates the effects of alternating slot blowing (ASB) on wind energy generation in oscillating wind energy conversion systems. It was found that ASB significantly improves energetic efficiency by exceeding natural vortex shedding amplitudes and producing higher net peak power coefficients compared to conventional VIV energy harvesters. Further research is needed to improve slot design, flow excitation and forcing, and mathematical modeling of the system.
Article
Orthopedics
Pierre Laumonerie, Meagan E. Tibbo, Gregoire Laumond, Dominique Barbier, Pauline Assemat, Pascal Swider, Franck Accadbled
Summary: The study aimed to compare the biomechanical properties of tibial fixation in hamstring-graft ACL reconstruction using different fixation methods. Results showed that the screw and dowel construct provided significantly improved fixation properties compared to interference screws alone in a porcine model. Larger screw diameter and 4-strand ACL grafts also led to better load-to-failure performance of the construct. More research is needed to confirm if these results are reproducible in vivo.
EUROPEAN JOURNAL OF ORTHOPAEDIC SURGERY AND TRAUMATOLOGY
(2022)
Article
Computer Science, Interdisciplinary Applications
J-L Estivalezes, W. Aniszewski, F. Auguste, Y. Ling, L. Osmar, J-P Caltagirone, L. Chirco, A. Pedrono, S. Popinet, A. Berlemont, J. Magnaudet, T. Menard, S. Vincent, S. Zaleski
Summary: A series of benchmarks based on the physical situation of phase inversion between two immiscible liquids is presented, aiming at progressing towards the direct numerical simulation of two-phase flows. Several CFD codes developed in French laboratories are used to provide physical solutions, convergence studies, and code comparisons to probe the physics of the problem and validate the physical relevance of the simulations.
JOURNAL OF COMPUTATIONAL PHYSICS
(2022)
Article
Physics, Applied
J. Lemetayer, C. Marion, D. Fabre, F. Plouraboue
Summary: This contribution investigates the phenomenon of "multiple emitters un-scalability" in multiple emitters systems and finds that the corona discharge inception is affected by electro-static interactions between emitters, which can be balanced by adjusting the interactions between emitters and collectors. The study also reveals that the electrostatic interactions among emitters can be balanced by the interactions between emitters and collectors, resulting in the generation of various multi-inception patterns.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2022)
Article
Mechanics
J. Sierra-Ausin, M. Lorite-Diez, J. I. Jimenez-Gonzalez, V. Citro, D. Fabre
Summary: This study examines the spatio-temporal pattern formation of wake flow past a streamwise rotating sphere from a dynamical system perspective. It reveals the connection between rotating waves and helical patterns within the wake. The research finds that, for low rotation rates, the flow field undergoes a transition similar to that of flow past a static sphere, but with a rapid variation in flow frequencies due to rotation. The transition from a single helix pattern to a double helix structure within the wake displays hysteric behavior in several regions. Eventually, the interaction between single and double helix structures leads to temporal chaos.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Clinical Neurology
Roxane Compagnon, Baptiste Brun-Cottan, Pauline Assemat, Julie Vial, Jerome Sales de Gauzy, Pascal Swider
Summary: This prospective study explored the apparent diffusion coefficients of asymptomatic intervertebral discs in a pediatric cohort. The results showed that the hydration of these discs was normal, and the values of apparent diffusion coefficients varied and were correlated with lordosis concavity. This study provides valuable information for the study of pediatric spinal pathologies.
EUROPEAN SPINE JOURNAL
(2022)
Article
Chemistry, Physical
Remi Gonin, Pierre Horgue, Romain Guibert, David Fabre, Remi Bourguet, Fouad Ammouri, Elena Vyazmina
Summary: The filling process of a horizontal hydrogen tank for light duty vehicles was investigated using multi-physics numerical simulations. The simulations, conducted in OpenFOAM, included modeling of fluid flow and heat transfer, and showed good agreement with experimental data. The study found that in the absence of thermal stratification, the 2D and 3D simulation results closely matched the experimental results. In the presence of thermal stratification, the 3D simulation captured the average temperature and timing of thermal gradients, as well as the deflection of the jet.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2022)
Article
Mechanics
Jie Zhang, Ming-Jiu Ni, Jacques Magnaudet
Summary: This study numerically investigates the dynamics of gas bubbles released in line under highly inertial conditions. Depending on the ratios of buoyancy, viscous and capillary forces, the bubbles can either rise independently or continue to interact and possibly collide. The shape of the bubbles and the initial distance between them play a crucial role in determining their trajectories.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
J. Sierra-Ausin, D. Fabre, V. Citro, F. Giannetti
Summary: The mechanisms leading to acoustic whistling for a jet passing through a circular hole in a thick plate connecting two domains are investigated. Two generic situations are considered: one with a closed upstream cavity and an open downstream domain, and the other with both upstream and downstream regions considered open. A low Mach asymptotic model is used to derive a global impedance of the system, and the knowledge of this impedance provides an instability criterion and eigenvalue predictions. The method is validated against linearized fully compressible solutions and used to characterize the range of instabilities.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Chemistry, Physical
Dolachai Boniface, Julien Sebilleau, Jacques Magnaudet, Veronique Pimienta
Summary: In this study, a series of experiments were conducted to investigate the dynamic behavior of a dichloromethane drop deposited on a water solution containing a surfactant. The results showed that the drop exhibited an induction stage, oscillations along the contact line, and a spontaneous spinning motion, with a stable spinning rate. These phenomena were attributed to the Marangoni effect induced by the dissolution of dichloromethane.
JOURNAL OF COLLOID AND INTERFACE SCIENCE
(2022)
Article
Mechanics
Paul Bonnefis, David Fabre, Christophe Airiau
Summary: The flow past a bullet-shaped blunt body moving in a pipe is investigated using global linear stability analysis (LSA) and direct numerical simulation. The results show that the confinement ratio and length-to-diameter ratio have an influence on the flow stability, with a destabilization and restabilization phenomenon observed for the strongly confined cases. The direct numerical simulation confirms the predictions made by LSA and reveals different dynamic states for weakly and strongly confined cases.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
F. Candelier, R. Mehaddi, B. Mehlig, J. Magnaudet
Summary: We compute the second-order inertial corrections to the force and torque acting on a small rigid particle moving in a steady linear flow. This is achieved by employing asymptotic expansions and formulating the problem in a coordinate system co-moving with the flow. The results are relevant to weakly buoyant particles and provide a rational extension of the classical Basset-Boussinesq-Oseen equation by incorporating the effects of unsteadiness and velocity gradients of the carrying flow.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Physics, Fluids & Plasmas
Javier Sierra-Ausin, Paul Bonnefis, Antonia Tirri, David Fabre, Jacques Magnaudet
Summary: In this paper, the deformation problem of a gas bubble suspended in an axisymmetric uniaxial straining flow is revisited from a dynamical perspective. By utilizing a newly developed Linearized Arbitrary Lagrangian-Eulerian approach, the steady equilibrium states and bubble shapes are computed. Perturbations respecting the symmetries of the imposed carrying flow are considered, revealing the bifurcation diagram consisting of a stable and an unstable branch of steady states separated by a saddle-node bifurcation. The location of this bifurcation is tracked in the parameter space. The most relevant global mode along each branch is characterized, including an oscillatory mode that becomes neutrally stable in the inviscid limit along the stable branch, and an unstable nonoscillating mode eventually leading to the breakup of the bubble along the unstable branch. Additional unstable nonoscillating modes associated with the possible drift of the bubble centroid away from the stagnation point of the undisturbed flow are identified when perturbations breaking the symmetries of the carrying flow are considered. The existence and characteristics of these modes are confirmed analytically in the inviscid limit, and a qualitative explanation is provided for the observed dynamics through a specific self-propulsion mechanism.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Multidisciplinary Sciences
Paul Bonnefis, David Fabre, Jacques Magnaudet
Summary: Recently, a study published in Proceedings of the National Academy of Sciences reported predictions and a physical scenario explaining the path instability of an air bubble rising in water. However, in this Brief Report, the authors review previously established results and show that the suggested scenario is invalidated. The actual instability mechanism is due to the hydrodynamic fluid-body coupling facilitated by the unconstrained motion of the bubble, which behaves as a rigid, nearly spheroidal body on the water's surface.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2023)
Article
Mechanics
Tristan Auregan, Thomas Bonometti, Jacques Magnaudet
Summary: We investigated the flow induced by a rigid sphere moving along the axis of a rotating cylindrical container filled with a low-viscosity fluid. The simulations revealed the formation of Taylor columns and inertial wave pattern, as well as the drag and torque acting on the sphere. The drag followed a semi-empirical law proposed for inertialess regimes, and the torque variations depended on the rotation speed.
JOURNAL OF FLUID MECHANICS
(2023)