Article
Mechanics
Xiaobo Chen
Summary: This paper formulates and analyzes the fundamental solution of the ship-motion problem, taking into account the weakly damped free-surface flows. The inclusion of viscous effects leads to the existence of three wavenumbers instead of two. Novel formulations of Havelock's type are developed and numerical issues are addressed. The article also examines the benefits of introducing viscous effects in the fundamental solution and emphasizes their importance.
Article
Mechanics
Saswata Basak, Palas Kumar Farsoiya, Ratul Dasgupta
Summary: The study focuses on the mechanics of jet formation from capillary-gravity waves on a liquid pool surface in a cylindrical container, showing that linear theory is inadequate in describing the process. Nonlinear theory predicts energy transfer and numerical simulations reveal the jet originates from a small dimple at the wave trough. The theory qualitatively describes jet overshoot and liquid velocity/pressure fields, but does not capture the evolution of the dimple or the thinning of the jet neck leading to pinchoff.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Engineering, Marine
Dianyong Liu, Fuzhen Li, Xiao Liang
Summary: The simulation of shipping of green water and prediction of slamming loads are fundamental issues in the field of naval architecture. This study applied a numerical method to simulate green water and slamming on ships in freaking waves. The results showed that the second green water had a longer duration and more violent intensity compared to the first. The analysis of motions and slamming loads indicated that different areas were affected by different frequency components.
Article
Engineering, Marine
Haitong Xu, C. Guedes Soares
Summary: This paper introduces an effective method for estimating the hydrodynamic coefficients of a manoeuvring model, and conducts stability and convergence analysis. The proposed method overcomes the common ill-conditioned issues in parameter estimation and demonstrates high robustness to noise. Experimental data from free-running ship model tests are used for parameter estimation, and the effectiveness of the proposed method is validated.
Article
Mathematics, Applied
K. R. Khusnutdinova, M. R. Tranter
Summary: Coupled Boussinesq equations are used to describe long weakly nonlinear longitudinal strain waves in a bi-layer with significant differences in linear long-wave speeds, known as high-contrast case. By constructing solutions for deviations from evolving mean values, the Ostrovsky equations within this derivation are solved for initial conditions with zero mean, bypassing the zero-mass constraint limitation. The models are applied to various wave generation scenarios and interactions, with numerical simulations controlled by derived conservation laws.
Article
Engineering, Multidisciplinary
K. Tang, J. X. Wang, X. Chen, D. P. Jiang, Y. L. Li
Summary: This research solves the time-domain nonlinear problem of ship motion in waves with forward speed using a 3D hybrid Green function method. By conducting numerical simulations and comparing with experimental results, it has been proven to have good predictive accuracy under complex conditions.
ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS
(2021)
Article
Engineering, Marine
Byung-Soo Kim, Shuguang Wang, Zhang Zhu, Yonghwan Kim
Summary: This study investigates the turning abilities of a KVLCC2 vessel in calm water and waves using free-running simulations based on an open-source computational fluid dynamics (CFD) library. The results show that the wavelength and wave direction have significant effects on the turning ability, but the turning characteristics remain unchanged over time.
Article
Engineering, Marine
Yuyi Hu, Weizeng Shao, Jun Li, Chunling Zhang, Lingqiao Cheng, Qiyan Ji
Summary: This study investigates short-term variations in the water temperature of Antarctic surface water and reveals that the sea surface temperatures of the Pacific and Atlantic Ocean is greater than the Indian Ocean. It is also found that El Nino and La Nina events can rapidly increase the sea surface temperature in the Pacific Ocean. Additionally, the depth of cool water in the Indian Ocean has decreased since 2008.
JOURNAL OF MARINE SCIENCE AND ENGINEERING
(2022)
Article
Engineering, Marine
Khang Minh Phan, Hamid Sadat
Summary: This paper investigates the hydrodynamic performance of KCS in the presence of a non-uniform shear current using high-fidelity CFD simulations. Results show that the shear current significantly affects the ship's resistance, free surface elevation, pressure distribution, vortex structures, boundary layer, and wake field. The direction and strength of the shear current have varied effects on the ship's performance, with the largest changes observed for the strongest shear current. The predicted Kelvin angles and transverse wavelengths confirm the findings of simplified theories on ship-shear current interaction.
Article
Engineering, Marine
Young-Myung Choi, Benjamin Bouscasse, Alain H. Clement, Lionel Gentaz, Pierre Ferrant, Young Jun Kim, Sime Malenica
Summary: An alternative expression for the time domain free surface Green's function is proposed, which satisfies the homogeneous Neumann condition on the mean free surface. This new expression can be beneficial for the boundary element method based on the double-body flow linearization. It is also shown to be a solution to Clement's 4th order Ordinary Differential Equation, and the Frobenius method with time step movement is used for accurate and efficient evaluation.
Article
Astronomy & Astrophysics
Carles Batlle, Victor Campello, Joaquim Gomis
Summary: We express the nonlocal BMS charges of a free massless Klein-Gordon scalar field in 2 thorn 1 in terms of the Green functions of the polyharmonic operators. Using these Green functions, we discuss the asymptotic behavior of the fields that ensures the existence of the charges and prove the realization of the 2 thorn 1 BMS algebra in canonical phase space. We also show that the algebra closes only up to skew-symmetric combinations of the equations of motion in configuration space. The formulation of charges in terms of Green functions allows for generalization to other dimensions and systems.
Article
Mechanics
L. F. Chen, P. H. Taylor, D. Z. Ning, P. W. Cong, H. Wolgamot, S. Draper, L. Cheng
Summary: This study investigates extreme wave runup around a simplified representative floating production, storage and offloading vessel hull with a vertical bow using computational fluid dynamics, experimental and diffraction analysis. The research finds that the key factor for the excitation of nonlinear extreme runup is the nonlinearity in the local wave field rather than vessel motion.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
A. I. Dyachenko, S. A. Dyachenko, V. E. Zakharov
Summary: In this study, we investigate a two-dimensional potential flow of an ideal fluid with a free surface. By utilizing conformal variables and analytic continuation, we find that the fluid complex potential and conformal map define a flow throughout the entire complex plane. This work offers a new perspective on fluid dynamics with a free surface by unifying the motion of vortex sheets and 2-D water waves.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Josh Shelton, Philippe H. H. Trinh
Summary: There has been significant interest in studying water waves coupled with non-zero vorticity. In this study, we derive analytical approximations for free-surface waves generated by submerged point vortices at low Froude numbers. Our findings show that the presence of Stokes lines originating from a vortex leads to the formation of waves. Trapped waves can occur when multiple point vortices are present, and this phenomenon is observed for a countably infinite set of Froude numbers in the two-vortex problem.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Jiyang Li, Zeng Liu, Shijun Liao, Alistair G. L. Borthwick
Summary: The study reveals the existence of two independent 'external' and 'internal' modes in a two-layer fluid, where exact harmonic resonance occurs when they share the same phase speed. The singularity or small divisor caused by resonant components is successfully eliminated using the homotopy analysis method, leading to convergent series solutions for steady-state interfacial wave groups with harmonic resonance. As the water depth varies, the energy carried by surface waves mirrors that carried by interface waves, showing a transfer of energy from shorter resonant components to longer primary ones as the upper layer depth increases.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Essam Nabil Ahmed, Alessandro Bottaro
Summary: This study focuses on the fully developed, steady, incompressible, laminar flow in a channel with rough and/or permeable walls. The influence of micro-structured boundary surfaces on the flow behavior is simulated using high-order effective boundary conditions derived from homogenization theory without empirical parameters. A closed-form solution of the Navier-Stokes equations is obtained for the flow in the channel, incorporating slip velocities, shear stress, and streamwise pressure gradient at each virtual boundary. The accuracy and applicability of the model are validated against full feature-resolving simulations for different textures. The Stokes-based model used to identify slip and interface permeability coefficients in the effective boundary conditions is reliable and accurate up to a certain threshold, beyond which advective effects need to be considered.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2024)
Article
Mechanics
Mustafa Turkyilmazoglu, Faisal Z. Duraihem
Summary: Thermally-driven natural convection in a porous layer is explored theoretically in this work based on Darcy's law. The study focuses on the non-circulating basic cellular flow between two infinitely long horizontal plates and its instability onset. The results show that a circulatory flow and temperature variation along the horizontal axis govern the motion, and the instability can be determined through linear stability analysis and numerical calculations.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2024)
Article
Mechanics
P. Roca Ramis de Ayreflor, A. Viudez
Summary: In this study, the inelastic interactions between a small, intense dipole and a weak, neutral monopole in two-dimensional flows are examined. It is found that dipoles with small size but large amplitude can cross and scatter off the neutral vortex, while leaving the vortex stable.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2024)
Article
Mechanics
Nilanjan Mondal, Chirodeep Bakli
Summary: This study presents a micro-nanochannel junction with directional flow achieved by a combination of junction geometry and wall functionalization. The system acts as a fluid diode with asymmetric pressure drop and flow rate in the nanochannel. The directional junction transport can be tuned with slip length, providing a key parameter for engineering various applications. The findings contribute to the understanding of flow rectification systems in nanochannels and have implications for capillary blood flow, desalination systems, and energy storage devices.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2024)
Article
Mechanics
Ussama Ali, Anas Ghannam, Md Islam, Isam Janajreh
Summary: This study utilizes a passive flow control technique involving a slit through a circular structure to dampen flow-induced vibration. The results demonstrate that the presence of a slit can decrease lift and drag coefficients and suppress flow-induced vibration.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2024)
Article
Mechanics
Sebastian A. Altmeyer
Summary: This article investigates how an alternating magnetic field can restrict and suppress the generation of vortices in ferrofluidic Couette flow. It finds that when the initially rotating outer cylinder is suddenly stopped, more complex vortex dynamics are generated in the system, and the presence of an alternating magnetic field can modify these dynamics, mainly depending on the modulation amplitude of the field.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2024)
Article
Mechanics
Pradeep, L. P. Singh
Summary: This study focuses on the analytical solution to the Riemann problem for a 1-D non-ideal flow of dusty gas with external force. The elementary wave curves, including rarefaction wave, shock wave, and contact discontinuity, were obtained and their implications on density, velocity of flow, and shock speed were examined. The addition of external force results in non-self-similar solutions.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2024)
Article
Mechanics
Meng Fan, Antoine Dazin, Gerard Bois, Francesco Romano
Summary: This study investigates the prominent features of the primary instabilities of a turbulent source flow between finite-span parallel rings with spatially modulated inflow conditions rotating at angular rate n. Two different two-dimensional instabilities that occur at large and low flow rates have been traced back to two different physical mechanisms related to jet-wake and mean-core flow, respectively. The effect of the radial aspect ratios on the instability characteristics of the flow between parallel rings is also considered.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2024)
Article
Mechanics
Yasmin Hengster, Martin Lellep, Julian Weigel, Matthew Bross, Johannes Bosbach, Daniel Schanz, Andreas Schroder, Florian Huhn, Matteo Novara, Daniel Garaboa Paz, Christian J. Kahler, Moritz Linkmann
Summary: Using curvature and torsion to describe Lagrangian trajectories provides insights into small and large time scales. Probability density functions (PDFs) of curvature and torsion were calculated for experimental Lagrangian trajectories in different flows, and were compared with experimental and numerical simulation results. The effect of anisotropy on geometry or tracer particle trajectories was quantified using the curvature vector, which was found to be related to velocity fluctuations.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2024)
Article
Mechanics
Nang X. Ho, Truong V. Vu
Summary: The present paper reports numerical results on the solidification process of a hollow drop on an inclined surface. The drop undergoes deformation and forms an asymmetric tip as the surface angle increases. The solidification time, however, is not affected by the surface angle. The fluid accumulates at the bottom of the drop and the bubble moves upwards before being trapped by solidification. A larger bubble reduces the tip shift. The effect of Bond number and Stefan number on solidification is also considered.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2024)
Article
Mechanics
Idalia Jagodzinska, Bartosz Olszanski, Konrad Gumowski, Slawomir Kubacki
Summary: This study investigates the characteristics of high subsonic and transonic flows through a linear cascade using experimental investigations and numerical simulations. The experiments measured static pressure, flow field, and turbulent intensity, and provided inlet conditions for the numerical simulations. The simulations validated the experimental data and tested the applicability of the turbulence models.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2024)
Article
Mechanics
Kun Sung Park, Ali Zamiri, Minsuk Choi, Byung Ju Lee, Jin Taek Chung
Summary: In this study, the stator geometry of a single-stage transonic fan was optimized to improve its aerodynamic performance and stall margin. Steady and unsteady simulations were conducted to analyze the impact of shock waves generated by the rotor blade on the stator inlet flow. Using a design of experiment and response surface method, an optimal geometry of the stator blade was obtained to increase the fan's efficiency and stall margin.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2024)
Article
Mechanics
Yuanzhao Zhang, Bo Li
Summary: This study investigated the effects of longitudinal and lateral spacing on the aerodynamic drag characteristics of the whole team and each member in speed skating team pursuit competition. The results showed that decreasing the longitudinal spacing resulted in greater drag reduction for the whole team and individual skaters. Furthermore, lateral movement of the leading skater also led to additional drag reduction for the team. Computational fluid dynamics simulations revealed differences in drag distribution between the leading skater and the middle and last skaters.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2024)
Article
Mechanics
Sichang Xu, Chris Peirone, Eugene Ryzer, Gary W. Rankin
Summary: This paper presents a study of a special bistable load-type supersonic fluidic oscillator capable of producing self-sustained oscillations in two gas pressure chambers. The experimental portion verifies the robust nature of the device performance and shows distinct differences compared to a similar prototype. A three-dimensional computational fluid dynamics model is required to accurately simulate the transient filling process, leading to an unaffordable computational cost. To address this issue, a low-order fluid circuit model is developed, which provides an accurate and rapid prediction of the transient performance.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2024)
Article
Mechanics
Sampson Davis, Eli Shellabarger, James Miller, Thomas Ward
Summary: The present work focuses on studying the effects of shock wave - boundary layer interaction in 2D hypersonic flow at the sharp leading edge of a flat plate and a flat plate followed by a compression ramp. A key parameter, the hypersonic interaction parameter x, is defined and analyzed using a semi-analytic reduced-order model. The study aims to improve on existing methods by characterizing the viscous boundary layer and investigating the upstream influence resulting from the compression ramp.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2024)