European Journal of Mechanics B-fluids最新文献

{"title":"Study on mechanism of VIV causing limited amplitude vibration through LES for a 4:1 rectangular cylinder","authors":"Yuanyan Tang,&nbsp;Yi Hui,&nbsp;Ke Li","doi":"10.1016/j.euromechflu.2024.01.011","DOIUrl":"10.1016/j.euromechflu.2024.01.011","url":null,"abstract":"<div><p><span>Vortex-induced vibration (VIV) is characterized as a phenomenon of limited amplitude vibration. Understanding the basic nature and underlying mechanism of VIV is necessary for predicting the vibration amplitude. In this study, using Large Eddy Simulation<span> (LES) of forced vibration, a detailed investigation of the flow pattern and wind load during VIV of a 4:1 rectangular cylinder is conducted. The results indicate that both vibration amplitude (</span></span><em>y</em>₀<em>/D</em>) and wind speed (<em>U</em>_<em>R</em><span>) significantly influence the flow pattern and wind load. Notably, an increase in vibration amplitude leads to a predominance of motion-induced force and a corresponding amplification of the fluctuating lift coefficient. Additionally, a decrease in the phase difference between lift force and displacement is observed, establishing this phase difference as a critical parameter for predicting vibration amplitude. Regarding wind speed, it is observed that as </span><em>U</em>_<em>R</em> increases, the predominance of motion-induced force diminishes, resulting in a concurrent decrease in the fluctuating lift coefficient. Upon further investigation into the work performed by various forces within a single vibration cycle, it has been determined that as the vibration amplitude escalates, the work of the lift force (energy input <em>W</em>_<em>I</em><span>) initially increases, then diminishes, whereas the work of the damping force (energy dissipation </span><em>W</em>_<em>O</em>) continuously rises. The intersection of these two trajectories signifies the point of energy equilibrium between input and output, thereby establishing the vibration amplitude of VIV. The predicted vibration amplitudes, grounded in this principle, have been corroborated by experimental results.</p></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139585379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study on the steady-oscillatory transition of three-dimensional (3D) natural convection via Hopf bifurcation","authors":"Jingkui Zhang ,&nbsp;Jiapeng Chang ,&nbsp;Miao Cui ,&nbsp;Yi Fan ,&nbsp;Qifen Li ,&nbsp;Cheng Peng","doi":"10.1016/j.euromechflu.2024.01.009","DOIUrl":"10.1016/j.euromechflu.2024.01.009","url":null,"abstract":"<div><p><span><span>The transition from steady-state flow to periodic oscillatory flow<span> for the natural convection by </span></span>Hopf bifurcation<span> is investigated in a three-dimensional (3D) cavity. The spectral collocation method (SCM) in combination with the artificial compressibility<span> method (ACM), which is developed by ourselves as a numerical method SCM-ACM with high accuracy, is employed to solve the governing equations directly instead of linear stability analysis<span> method that is commonly used for the research on flow instability. The results show that the amplitude decays exponentially with time and the decay rate is linear with the Grashof number (</span></span></span></span><em>Gr</em>). The critical Grashof number for steady-oscillatory transition is obtained as <em>Gr</em>_<em>cr</em> = 3.423 × 10⁶. The dimensionless angular frequency <em>ω</em>_<em>cr</em><span> = 0.24 is also determined by Fourier analysis. In this work, we also examine the heat-momentum interactions within the boundary layers, visualize the periodic oscillations of temperature and velocity amplitudes, and analyze the origin of instability from multiple angles. The results show that large oscillations of velocity and temperature are observed near the isothermal<span> walls. The oscillation is enhanced by the increase of thermal boundary layer thickness and flow velocity at both ends of isothermal walls. The maximum velocity and temperature amplitudes appear at the lower left and upper right corners of the mid-plane (</span></span><em>Z</em><span> = 0.5), where are the origin of instability, and the spanwise walls are almost independent of oscillations. The oscillatory flow of natural convection in three-dimensional cavity originates from the continuously increasing buoyancy force, and its transition occurs by Hopf bifurcation. Moreover, the temperature amplitude exhibits a wavy distribution on the mid-plane (</span><em>X</em> = 0.5) and strongly depends on the depth <em>Z</em><span>. These results provide benchmark data for future numerical studies and engineering application.</span></p></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139517176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Wakes and secondary structures past stator wheel in test turbine VT-400 observed by PIV","authors":"Daniel Duda ,&nbsp;Marek Klimko ,&nbsp;Petr Milčák ,&nbsp;Matěj Jeřábek ,&nbsp;Václav Uruba ,&nbsp;Vitalii Yanovych ,&nbsp;Pavel Žitek","doi":"10.1016/j.euromechflu.2024.01.008","DOIUrl":"10.1016/j.euromechflu.2024.01.008","url":null,"abstract":"<div><p>Flow inside the axial test turbine VT-400 is measured by using a standard methodology of Particle Image Velocimetry (PIV). The studied area lies between the stator and rotor wheel in meridional plane. This area covers both: the regular flow near hub and the endwall secondary structures as well. Regular structure of wakes and jets past stator blades is observed in terms of mean velocities and turbulence intensity. The fluctuations are close to isotropy and the energy distribution across length-scales exhibits almost Kolmogorov scaling. Near the hub, we observe secondary vortices. Despite the positive radial ejections in that regions, these secondary vortices drift towards the hub, they dissipate energy and circulation and their core grows in size.</p></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0997754624000165/pdfft?md5=6b98ca5af03b5c4c8231c7e848eb9db1&pid=1-s2.0-S0997754624000165-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139483556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Corrigendum to “The role of Brinkmann ratio on non-Newtonian fluid flow due to a porous shrinking/stretching sheet with heat transfer” [Eur. J. Mech. B Fluids 92 (2022) 153–165]","authors":"U.S. Mahabaleshwar ,&nbsp;A.B. Vishalakshi ,&nbsp;Martin Ndi Azese","doi":"10.1016/j.euromechflu.2024.01.005","DOIUrl":"10.1016/j.euromechflu.2024.01.005","url":null,"abstract":"","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0997754624000050/pdfft?md5=23b2b44c5bc50a89e4017f3ebd2cfadf&pid=1-s2.0-S0997754624000050-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139500050","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Direct numerical simulation of laminar, transitional and turbulent radially inward flow between closely spaced corotating disks","authors":"S. Klingl ,&nbsp;S. Lecheler ,&nbsp;M. Pfitzner","doi":"10.1016/j.euromechflu.2024.01.007","DOIUrl":"10.1016/j.euromechflu.2024.01.007","url":null,"abstract":"<div><p>This study describes direct numerical simulation (DNS) of radially inward spiralling corotating disk flow with a narrow disk spacing, using the open source solver Nek5000 and the supercomputer SuperMUC-NG at Leibniz Supercomputing Centre. Knowledge about laminar and turbulent regime boundaries in this flow scenario is important for modelling and performance prediction of friction turbines. Simulations are performed in differently sized sections of the flat annulus that is formed by two opposing corotating disk surfaces. Three sets of operating conditions are covered, from the laminar, transitional and turbulent region of a previously determined stability chart respectively. Directly downstream of the inlet boundary, the flow is artificially perturbed with a random body force acting normal to the disk surfaces. Fourier analysis of the DNS flow field reveals that the artificial perturbation is dampened across all wavenumbers for the laminar conditions, while at the transitional conditions a small range of modes is weakly amplified towards the outlet. The identified unstable modes were previously correctly predicted by linear stability analysis. Comparison to experimental velocity profile measurements from a previous study at the same transitional operating conditions suggests strongly perturbed flow during the experiment. For inflow conditions leading to turbulent flow, average velocity profiles from DNS coincide with those from experiment and from commercial fluid simulation software with turbulence modelling (ANSYS CFX). Close to the walls, turbulent dissipation and turbulent kinetic energy distributions do not agree with the ANSYS CFX results. Friction Reynolds number settles at about 118 after turbulent flow has developed from the initial perturbation. Two point correlations and corresponding energy spectra are presented.</p></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0997754624000153/pdfft?md5=aef2fe8bfc9a77b9fedc4bbe2bbd8b5e&pid=1-s2.0-S0997754624000153-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139470993","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact process of a droplet on solid surfaces: Influence of surface wettability using lattice Boltzmann method","authors":"Salaheddine Channouf,&nbsp;Mohammed Jami,&nbsp;Ahmed Mezrhab","doi":"10.1016/j.euromechflu.2024.01.006","DOIUrl":"10.1016/j.euromechflu.2024.01.006","url":null,"abstract":"<div><p><span>This research employed the pseudopotential multi-relaxation times lattice Boltzmann method<span> to investigate the impact process of a droplet on solid surfaces, focusing on the influence of surface wettability<span> for three different Reynolds numbers<span> Re = 100, 200, and 500). Initially, the impact process is studied on both hydrophobic and hydrophilic surfaces<span>, revealing distinct behaviors characterized by spreading and recoiling stages. Subsequently, the investigation extends to a mixed wettability wall, offering insights into the droplet's density behaviors. Through this study, we demonstrate that the wettability of the surface plays a crucial role in determining the contact dynamics with the impacting droplet. Notably, the average velocity of the droplet exhibits a monotonic increase with higher wettability. Furthermore, the droplet profile responds to variations in the Reynolds number, though droplet deformation remains relatively limited even when the interaction with the wetting surface intensifies. Our findings shed light on the complex </span></span></span></span></span>interplay between wettability, droplet dynamics, and surface interactions during impact processes.</p></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139462018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unsteady double-diffusive Brinkman–Bénard convection in cylindrical enclosure saturated with hybrid bi-viscous Bingham nanoliquid","authors":"Sanjalee,&nbsp;Y.D. Sharma,&nbsp;O.P. Yadav","doi":"10.1016/j.euromechflu.2024.01.004","DOIUrl":"10.1016/j.euromechflu.2024.01.004","url":null,"abstract":"<div><p><span><span>This paper aims to present an analytical as well as a comparative study to investigate the effect of the Brinkman porous medium<span><span><span> on the onset of regular and chaotic motion in cylindrical enclosures of different heights. The hybrid bi-viscous Bingham nanoliquid is considered as the working fluid. Modified Brinkman–Buongiorno and bi-viscous Bingham fluid models are incorporated to obtain the flow governing dynamics. The thermophysical properties of the hybrid nanoliquid are calculated using phenomenological laws<span> and the mixture theory. The study is carried out for the axisymmetric mode, and the </span></span>Bessel functions<span> are taken as the eigenfunctions of the problem. Double Fourier–Bessel series expansions are used for weakly non-linear stability analysis. The limiting cases of the study are obtained, and the results on the onset of convection, heat, and mass transport are discussed graphically. The behavior of the dynamical system is analyzed using the maximum </span></span>Lyapunov exponent plot, the </span></span>bifurcation diagram, and phase plots. Outcomes suggest that convection sets in earlier in the water-based hybrid nanoliquid than in the bi-viscous Bingham hybrid nanoliquid. The use of Single-walled </span>carbon nanotubes<span> enhances the heat transfer rate by approximately 17%. Further, it is concluded that a tall cylindrical enclosure is the most favorable geometry for achieving a higher heat transfer rate among the others.</span></p></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139422322","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Time-resolved characteristics of oscillatory particle-laden air flow in a realistic human airway model","authors":"J. Jedelsky,&nbsp;F. Lizal,&nbsp;M. Jicha","doi":"10.1016/j.euromechflu.2024.01.003","DOIUrl":"10.1016/j.euromechflu.2024.01.003","url":null,"abstract":"<div><p>Human airways represent a complex flow system with a spatially and temporally variable character of air flow during respiration. In this paper, we experimentally studied the oscillatory flow<span> of air with monodispersed micron-sized liquid particles in a transparent, anatomically realistic model of human upper airways and several bronchi generations using phase-Doppler anemometry (PDA). The PDA provided point-wise high-frequency measurements of axial velocities of individual aerosol particles in multiple positions of the airways (in the trachea and the upper bronchi) for three breathing regimes with a sinusoidal course. Typical time-resolved velocity plots at several positions within the model were documented and analysed using dimensionless criteria. Local mean air velocity and turbulence time-lines disclosed specific flow dynamic features in the multiple bifurcation system, namely the transit of vortical structures, oscillations induced by flow reversals, and inspiratory flow separations behind bifurcations. The results elucidated the laminar, transitional and turbulent flows during inspiratory and expiratory breathing phases. The character of the flow varies significantly with position in the airways, while the breathing regime has a generally low effect on the flow character. Inspection of the flow in the terminal branches indicated the need to add further branches for more realistic results there.</span></p></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139422442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of turbulent coherent structures on the performance and wake of a wind turbine","authors":"Yan Wang,&nbsp;Ronghu Guan,&nbsp;Liang Wang,&nbsp;Pan Lu","doi":"10.1016/j.euromechflu.2024.01.002","DOIUrl":"10.1016/j.euromechflu.2024.01.002","url":null,"abstract":"<div><p><span>Wind energy in the atmospheric boundary layer serves as the primary source for energy absorption and structural load on wind turbines<span><span>. However, the impact of turbulent coherent structures on the aerodynamic performance and wake characteristics of wind turbines has not been comprehensively evaluated. In this study, the </span>proper orthogonal decomposition<span> (POD) method is employed to assess the influence of turbulent coherent structures of varying scales on the aerodynamic performance and wake characteristics of wind turbines in the neutral atmospheric boundary layer. The results show that turbulent coherent structures are the main factor that determines the wind velocity fluctuation<span>, aerodynamic performance and wake characteristics of wind turbine in the atmospheric boundary layer. When considering the 13th or lower order POD mode, the wind velocity fluctuation increases with the increase of energy content (more POD modes) of the turbulent coherent structures. When considering the first 19 POD modes, the dynamic loads and power of wind turbine fluctuate with high frequencies, the thrust fluctuates in an amplitude range between 2.4 % and 13.9 % around the mean value, and the power fluctuates from 4.5 % to 28.6 % of the mean value. When considering the first 40 POD modes, the average power generation of the wind turbine increases by 26 % compared to the case with no turbulent structures considered. The study of turbine wake shows that turbulent coherent structures can expand the wind turbine wake approximately to a width of 2.5</span></span></span></span><em>D</em> and a height of 3<em>D</em> (<em>D</em> is the diameter of the wind turbine), offset the wake approximately to 2<em>D</em>, and move forward the position of the wake vortex beginning to dissipation approximately to 7<em>D</em> behind the wind turbine. In addition, turbulent coherent structures can accelerate the wake velocity recovery by increasing the momentum exchange between the atmospheric boundary layer and wind turbine wake.</p></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139374106","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessment of the effectiveness of stall delay and tip loss corrections for the simulation of small propeller performance with Virtual Blade Model","authors":"Lorenzo Stabeli Diehl,&nbsp;José Gustavo Coelho","doi":"10.1016/j.euromechflu.2023.12.013","DOIUrl":"10.1016/j.euromechflu.2023.12.013","url":null,"abstract":"<div><p><span><span>The powertrain<span><span> efficiency of most small unmanned air vehicles (SUAVs) depend on the aerodynamic performance<span> of multiple propellers, which must be modelled before its optimisation. To predict propeller performance while capturing interaction effects not accountable for by momentum theories, the Virtual Blade Model (VBM) can be used at much lower costs than conventional Computational Fluid Dynamics (CFD). However, the accuracy of VBM depends on </span></span>aerofoil polar data that often misrepresent rotational and three-dimensional effects that influence small propellers. In an attempt to expand the capabilities of VBM, it is a common practice to introduce correction models for aerofoil coefficients in its formulation, but the actual effectiveness of such approach for small </span></span>propeller analysis<span><span> remains unassessed. In this paper, VBM in OpenFOAM was extended with stall delay and tip loss models, while aerodynamic databases at low Reynolds numbers were built with XFOIL and extrapolated to the full </span>angle of attack range. The accuracy of three VBM versions was validated against wind </span></span>tunnel<span> measurements of two off-the-shelf small propellers. For the lower-pitch propeller, thrust and power at low advance ratios and efficiency at high advance ratios were significantly improved by the stall delay model. But for the higher-pitch propeller, thrust and power were overpredicted with extended versions of VBM under most operating conditions, which is attributable to an excessive shift of effective angles of attack<span> to the post-stall region by the stall delay model and to uncertainties in extrapolated polar data. The results suggest that without reliable procedures for obtaining polar data, correction models should be implemented in VBM only for the simulation of low-pitch propellers operating at low advance ratios, given their avoidance of the effective angle of attack range where XFOIL and extrapolation methods are mainly expected to fail in predicting lift behaviour.</span></span></p></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139374148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}