arXiv - PHYS - Fluid Dynamics最新文献_第10页

A revisit of the development of viscoplastic flow in pipes and channels 管道和渠道中粘塑性流动的发展回顾

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-09-01 DOI: arxiv-2409.00842

Alexandros Syrakos, Evgenios Gryparis, Georgios C. Georgiou

引用次数: 0

Viscoelastic Worthington jets & droplets produced by bursting bubbles 由气泡破裂产生的粘弹性沃辛顿射流（&&液滴

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-08-09 DOI: arxiv-2408.05089

Ayush K. Dixit, Alexandros Oratis, Konstantinos Zinelis, Detlef Lohse, Vatsal Sanjay

{"title":"Viscoelastic Worthington jets & droplets produced by bursting bubbles","authors":"Ayush K. Dixit, Alexandros Oratis, Konstantinos Zinelis, Detlef Lohse, Vatsal Sanjay","doi":"arxiv-2408.05089","DOIUrl":"https://doi.org/arxiv-2408.05089","url":null,"abstract":"Bubble bursting and subsequent collapse of the open cavity at free surfaces\u0000of contaminated liquids can generate aerosol droplets, facilitating pathogen\u0000transport. After film rupture, capillary waves focus at the cavity base,\u0000potentially generating fast Worthington jets that are responsible for ejecting\u0000the droplets away from the source. While extensively studied for Newtonian\u0000fluids, the influence of non-Newtonian rheology on this process remains poorly\u0000understood. Here, we employ direct numerical simulations to investigate the\u0000bubble cavity collapse in viscoelastic media, such as polymeric liquids,\u0000examining how their elastic modulus $G$ and their relaxation time $lambda$\u0000affect jet and droplet formation. We show that the viscoelastic liquids yield\u0000Newtonian-like behavior as either parameter $G$ or $lambda$ approaches zero,\u0000while increasing them suppresses jet formation due to elastic resistance to\u0000elongational flows. Intriguingly, for some cases with intermediate values of\u0000$G$ and $lambda$, smaller droplets are produced compared to Newtonian fluids,\u0000potentially enhancing aerosol dispersal. By mapping the phase space spanned by\u0000the elastocapillary number (dimensionless $G$) and the Deborah number\u0000(dimensionless $lambda$), we reveal three distinct flow regimes: (i) jets\u0000forming droplets, (ii) jets without droplet formation, and (iii) absence of jet\u0000formation. Our results elucidate the mechanisms underlying aerosol suppression\u0000versus fine spray formation in polymeric liquids, with implications for\u0000pathogen transmission and industrial processes involving viscoelastic fluids.","PeriodicalId":501125,"journal":{"name":"arXiv - PHYS - Fluid Dynamics","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141942731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Mode-to-mode nonlinear energy transfer in turbulent channel flows 湍流通道流中模式间的非线性能量传递

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-08-09 DOI: arxiv-2408.05062

Jitong Ding, Daniel Chung, Simon J. Illingworth

{"title":"Mode-to-mode nonlinear energy transfer in turbulent channel flows","authors":"Jitong Ding, Daniel Chung, Simon J. Illingworth","doi":"arxiv-2408.05062","DOIUrl":"https://doi.org/arxiv-2408.05062","url":null,"abstract":"We investigate nonlinear energy transfer for channel flows at friction\u0000Reynolds numbers of $Re_{tau}=180$ and $590$. The key feature of the analysis\u0000is that we introduce a new variable, which quantifies the energy transferred\u0000from a source mode to a recipient mode through explicit examination of\u0000nonlinear triadic interactions in streamwise-spanwise wavenumber space. First,\u0000we use this variable to quantify the nonlinear energy transfer gain and loss\u0000for individual Fourier modes. The nonlinear energy transfer gain and loss\u0000cannot be directly obtained from the turbulent kinetic energy (TKE) equation.\u0000Second, we quantify the nonlinear energy transfer budgets for three types of\u0000structures: streamwise streaks, oblique waves and Tollmien-Schlichting waves.\u0000We found that a transverse cascade from streamwise-elongated modes to\u0000spanwise-elongated modes exists in all three structures. Third, we quantify the\u0000forward and inverse cascades between resolved scales and subgrid scales in the\u0000spirit of large-eddy simulation. For the cutoff wavelength range we consider,\u0000the forward and inverse cascades between the resolved scales and subgrid scales\u0000result in a net forward cascade from the resolved scales to the subgrid scales.\u0000The shape of the net forward cascade curve with respect to the cutoff\u0000wavelength resembles the net forward cascade predicted by the Smagorinsky eddy\u0000viscosity.","PeriodicalId":501125,"journal":{"name":"arXiv - PHYS - Fluid Dynamics","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141942645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Dynamically relevant recurrent flows obtained via a nonlinear recurrence function from two-dimensional turbulence 通过二维湍流的非线性递推函数获得动态相关的递推流

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-08-09 DOI: arxiv-2408.05079

Edward M. Redfern, Andrei L. Lazer, Dan Lucas

{"title":"Dynamically relevant recurrent flows obtained via a nonlinear recurrence function from two-dimensional turbulence","authors":"Edward M. Redfern, Andrei L. Lazer, Dan Lucas","doi":"arxiv-2408.05079","DOIUrl":"https://doi.org/arxiv-2408.05079","url":null,"abstract":"This paper demonstrates the efficient extraction of unstable recurrent flows\u0000from two-dimensional turbulence by using nonlinear triads to diagnose\u0000recurrence in direct numerical simulations. Nearly recurrent episodes are\u0000identified from simulations and then converged using a standard Newton-\u0000GMRES-hookstep method, however with much greater diversity than previous\u0000studies which performed this 'recurrent flow analysis'. Unstable periodic and\u0000relative periodic orbits are able to be identified which span larger values of\u0000dissipation rate, i.e. corresponding to extreme bursting events. The triad\u0000variables are found to provide a more natural way to weight the greater variety\u0000of spatial modes active in such orbits than a standard Euclidian norm of\u0000complex Fourier amplitudes. Moreover the triad variables build in a reduction\u0000of the continuous symmetry of the system which avoids the need to search over\u0000translations when obtaining relative periodic orbits. Armed with these orbits\u0000we investigate optimal weightings when reconstructing the statistics of\u0000turbulence and suggest that, in fact, a simple heuristic weighting based on the\u0000solution instability provides a very good prediction, provided enough\u0000dynamically relevant orbits are included in the expansion.","PeriodicalId":501125,"journal":{"name":"arXiv - PHYS - Fluid Dynamics","volume":"58 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141942732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Receding contact line dynamics on superhydrophobic surfaces 超疏水性表面上的后退接触线动力学

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-08-09 DOI: arxiv-2408.04992

Lorenzo Betti, Jordy Queiros Campos, Amandine Lechantre, Lea Cailly-Brandstater, Sarra Nouma, Jérôme Fresnais, Etienne Barthel adn Yann Bouret, Xavier Noblin, Céline Cohen

{"title":"Receding contact line dynamics on superhydrophobic surfaces","authors":"Lorenzo Betti, Jordy Queiros Campos, Amandine Lechantre, Lea Cailly-Brandstater, Sarra Nouma, Jérôme Fresnais, Etienne Barthel adn Yann Bouret, Xavier Noblin, Céline Cohen","doi":"arxiv-2408.04992","DOIUrl":"https://doi.org/arxiv-2408.04992","url":null,"abstract":"We have explored receding contact line dynamics on superhydrophobic surfaces,\u0000composed of micropillars arrays. We present here dynamic receding contact angle\u0000measurements of water on such surfaces, covering contact line speeds spanning\u0000over five decades. We have studied the effect of pillars fraction on dynamical\u0000receding contact angles. We compared these measurements to those on smooth\u0000surfaces with the same chemical nature and also with similar systems reported\u0000in the literature. We show that superhydrophobic surfaces exhibit a significantly lower\u0000dependence of contact angle on contact line speed compared to smooth surfaces.\u0000Additionally, we observed that a higher surface fraction of pillars leads to a\u0000greater dependence of the contact angle on contact line speed, approaching the\u0000dependence of the angle on smooth surface. Interestingly, we show that the\u0000exact texuration of the surface does not play a fundamental role in the\u0000angle-velocity relationships as long as microtextures present the same type of\u0000periodic pattern (pillar arrays or microgrid). These results are interpreted in\u0000terms of viscous friction reduction on superhydrophobic surfaces, shedding\u0000light on the underlying mechanisms governing their unique dynamic behavior. In\u0000addition we show that contact angles follow same laws for two different\u0000geometries (milimetric sessile drop and a centimetric capillary bridge).","PeriodicalId":501125,"journal":{"name":"arXiv - PHYS - Fluid Dynamics","volume":"167 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141942663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Weak-inertial effects on destabilized receding contact lines 失稳后退接触线的弱惯性效应

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-08-09 DOI: arxiv-2408.05045

Akhil Varma

引用次数: 0

Numerical simulation and analysis of mixing enhancement due to chaotic advection using an adaptive approach for approximating the dilution index 使用近似稀释指数的自适应方法对混沌平流引起的混合增强进行数值模拟和分析

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-08-09 DOI: arxiv-2408.05055

Carla Feistner, Mónica Basilio Hazas, Barbara Wohlmuth, Gabriele Chiogna

{"title":"Numerical simulation and analysis of mixing enhancement due to chaotic advection using an adaptive approach for approximating the dilution index","authors":"Carla Feistner, Mónica Basilio Hazas, Barbara Wohlmuth, Gabriele Chiogna","doi":"arxiv-2408.05055","DOIUrl":"https://doi.org/arxiv-2408.05055","url":null,"abstract":"A velocity field characterized by chaotic advection induces stretching and\u0000folding processes that increase the solute-solvent interface available for\u0000diffusion. Identifying chaotic flow fields with optimized mixing enhancement is\u0000relevant for applications like groundwater remediation, microfluidics, and many\u0000more. This work uses the dilution index to quantify the temporal increase in\u0000mixing of a solute within its solvent. We introduce a new approach to select a\u0000suitable grid size for each time step in the dilution index approximation,\u0000motivated by the theory of representative elementary volumes. It preserves the\u0000central feature of the dilution index, which is monotonically increasing in\u0000time and hence leads to reliable results. Our analysis highlights the\u0000importance of a suitable choice for the grid size in the dilution index\u0000approximation. We use this approach to demonstrate the mixing enhancement for\u0000two chaotic injection-extraction systems that exhibit chaotic structures: a\u0000source-sink dipole and a rotated potential mixing. By analyzing the chaotic\u0000flow fields, we identify Kolmogorov--Arnold--Moser (KAM) islands, non-mixing\u0000regions that limit the chaotic area in the domain and, thereby, the mixing\u0000enhancement. Using our new approach, we assess the choice of design parameters\u0000of the injection-extraction systems to effectively engineer chaotic mixing. We\u0000demonstrate the important role of diffusion in filling the KAM islands and\u0000reaching complete mixing in the systems.","PeriodicalId":501125,"journal":{"name":"arXiv - PHYS - Fluid Dynamics","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141942646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Pressure-Velocity Coupling in Transpiration Cooling 蒸腾冷却中的压力-速度耦合

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-08-09 DOI: arxiv-2408.05166

Sophie Hillcoat, Jean-Pierre Hickey

{"title":"Pressure-Velocity Coupling in Transpiration Cooling","authors":"Sophie Hillcoat, Jean-Pierre Hickey","doi":"arxiv-2408.05166","DOIUrl":"https://doi.org/arxiv-2408.05166","url":null,"abstract":"Transpiration cooling is an active thermal protection system of increasing\u0000interest in aerospace applications wherein a coolant is effused through a\u0000porous wall into a hot external flow. The present work focuses on the\u0000interaction between the high-temperature turbulent boundary layer and the\u0000pressure-driven coolant flow through the porous wall. Coupling functions were\u0000obtained from pore-network simulations to characterize the flow through the\u0000porous medium. These were then coupled to direct numerical simulations of a\u0000turbulent boundary layer over a massively-cooled flat plate. Two different\u0000types of coupling function were used: linear expressions, which do not account\u0000for flow interactions between neighbouring pores, and shallow convolutional\u0000neural networks (CNN) which incorporate spatial correlations. All coupled cases\u0000demonstrated a significant variation in blowing due to the streamwise variation\u0000in mean pressure associated with the onset of coolant injection. This trend was\u0000reflected in the cooling effectiveness, and was mitigated in the CNN-coupled\u0000cases due to the incorporation of lateral flow between neighbouring pores. The\u0000distribution of turbulent kinetic energy (TKE) in the coupled cases was also\u0000modified by the coupling due to the competing effects of near-wall turbulence\u0000attenuation and increased shear due to increasing blowing ratio. Finally, the\u0000coupling was shown to impact the power spectral density of the pressure\u0000fluctuations at the wall within the transpiration region, attenuating the\u0000largest scales of the turbulence whilst leaving the smaller scales relatively\u0000unaffected.","PeriodicalId":501125,"journal":{"name":"arXiv - PHYS - Fluid Dynamics","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141942730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The effect of Reynolds number on the separated flow over a low-aspect-ratio wing 雷诺数对低宽比机翼上分离流的影响

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-08-09 DOI: arxiv-2408.04801

Luke Smith, Kunihiko Taira

{"title":"The effect of Reynolds number on the separated flow over a low-aspect-ratio wing","authors":"Luke Smith, Kunihiko Taira","doi":"arxiv-2408.04801","DOIUrl":"https://doi.org/arxiv-2408.04801","url":null,"abstract":"At high incidence, low-aspect-ratio wings present a unique set of aerodynamic\u0000characteristics, including flow separation, vortex shedding, and unsteady force\u0000production. Furthermore, low-aspect ratio wings exhibit a highly impactful tip\u0000vortex, which introduces strong spanwise gradients into an already complex\u0000flow. In this work, we explore the interaction between leading edge flow\u0000separation and a strong, persistent tip vortex over a Reynolds number range of\u0000$600 leq Re leq 10,000$. In performing this study, we aim to bridge the\u0000insight gained from existing low Reynolds number studies of separated flow on\u0000finite wings ($Re approx 10^2$) and turbulent flows at higher Reynolds numbers\u0000($Re approx 10^4$). Our study suggests two primary effects of Reynolds number.\u0000First, we observe a break from periodicity, along with a dramatic increase in\u0000the intensity and concentration of small-scale eddies, as we shift from $Re =\u0000600$ to $Re = 2,500$. Second, we observe that many of our flow diagnostics,\u0000including the time-averaged aerodynamic force, exhibit reduced sensitivity to\u0000Reynolds number beyond $Re = 2,500$, an observation attributed to the\u0000stabilizing impact of the wing tip vortex. This latter point illustrates the\u0000manner by which the tip vortex drives flow over low-aspect-ratio wings, and\u0000provides insight into how our existing understanding of this flowfield may be\u0000adjusted for higher Reynolds number applications.","PeriodicalId":501125,"journal":{"name":"arXiv - PHYS - Fluid Dynamics","volume":"44 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141942648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Computational Realization of Popping Impinging Sprays of Hypergolic Bipropellants by a Eulerian-Lagrangian Approach 用欧拉-拉格朗日方法计算实现超醇双推进剂的爆裂冲击喷流

arXiv - PHYS - Fluid Dynamics Pub Date : 2024-08-09 DOI: arxiv-2408.04880

Jinyang Wang, Kai Sun, Tianyou Wang, Peng Zhang

{"title":"Computational Realization of Popping Impinging Sprays of Hypergolic Bipropellants by a Eulerian-Lagrangian Approach","authors":"Jinyang Wang, Kai Sun, Tianyou Wang, Peng Zhang","doi":"arxiv-2408.04880","DOIUrl":"https://doi.org/arxiv-2408.04880","url":null,"abstract":"This work adopts a Eulerian-Lagrangian approach to numerically simulate the\u0000spray impingement of MMH (Monomethyl hydrazine)/NTO (nitrogen tetroxide), which\u0000are prevalent rocket engine bipropellants for deep space missions and satellite\u0000orbital maneuvers. The emphasis of the work is to computationally realize the\u0000popping phenomenon and to study its parametric dependence on liquid and\u0000gas-phase reaction rates. The liquid-phase reaction of MMH/NTO is realized\u0000based on the extended spray equation, incorporating the additional independent\u0000variable, propellant mass fraction, to account for the mixing of droplets. The\u0000spray popping can be computationally reproduced over wide ranges of Damk\"ohler\u0000numbers for both liquid- and gas-phase reactions. Furthermore, the\u0000computational results have been validated through qualitative comparison with\u0000experimental images and quantitative comparison with experimental frequencies.\u0000The present results verify our hypothesis that the heat release from the\u0000liquid-phase reaction enhances the evaporation of MMH and NTO so that the\u0000intense gas-phase reaction zone around the spray impingement point periodically\u0000separates the MMH and NTO impinging sprays to cause the popping phenomenon.\u0000Furthermore, it was found that the popping phenomenon can be suppressed by\u0000reducing the Damk\"ohler numbers of liquid-phase reaction and therefore to\u0000suppress the evaporation of the propellants. This work is believed to provide\u0000valuable understanding for avoiding the off-design popping phenomenon that may\u0000reduce combustion efficiency and increase the risk of combustion instability in\u0000rocket engines.","PeriodicalId":501125,"journal":{"name":"arXiv - PHYS - Fluid Dynamics","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141942665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0