Pub Date : 2024-08-05DOI: 10.1103/physrevfluids.9.l082601
Sergio Hoyas, Ricardo Vinuesa, Peter Schmid, Hassan Nagib
Direct numerical simulations (DNSs) are among the most powerful tools for studying turbulent flows. Even though the achievable Reynolds numbers are lower than those obtained through experimental means, DNS offers a clear advantage: The entire velocity field is known, allowing for the evaluation of any desired quantity. This capability includes the computation of derivatives of all relevant terms. One such derivative provides the indicator function, which is the product of the wall distance and the wall-normal derivative of the mean streamwise velocity. This derivative may depend on mesh spacing and distribution, but it is extremely affected by the convergence of the simulation. The indicator function is crucial for understanding inner and outer interactions in wall-bounded flows and describing the overlap region between them. We find a clear dependence of this indicator function on the mesh distributions we examine, raising questions about classical mesh and convergence requirements for DNS and achievable accuracy. Within the framework of the logarithmic plus linear overlap region, coupled with a parametric study of channel flows and some pipe flows, sensitivities of extracted overlap parameters are examined. This study reveals a path to establishing their high- or nearly asymptotic values at modest Reynolds numbers, but larger than the ones used in this work, accessible by high-quality DNS with reasonable cost.
直接数值模拟（DNS）是研究湍流的最强大工具之一。尽管可实现的雷诺数低于通过实验获得的雷诺数，但 DNS 仍具有明显的优势：整个速度场是已知的，因此可以评估任何所需的量。这种能力包括计算所有相关项的导数。其中一个导数就是指示函数，它是壁面距离与平均流向速度的壁面法向导数的乘积。该导数可能取决于网格间距和分布，但受模拟收敛性的影响极大。指标函数对于理解壁面流的内外相互作用以及描述它们之间的重叠区域至关重要。我们发现该指标函数与我们研究的网格分布有明显的依赖关系，这就提出了有关 DNS 的经典网格和收敛要求以及可实现精度的问题。在对数加线性重叠区域的框架内，结合对通道流和一些管道流的参数研究，对提取的重叠参数的敏感性进行了检验。这项研究揭示了在雷诺数不大但大于本研究中使用的雷诺数的情况下，通过高质量 DNS 以合理的成本建立高雷诺数或近似值的途径。
{"title":"Sensitivity study of resolution and convergence requirements for the extended overlap region in wall-bounded turbulence","authors":"Sergio Hoyas, Ricardo Vinuesa, Peter Schmid, Hassan Nagib","doi":"10.1103/physrevfluids.9.l082601","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.l082601","url":null,"abstract":"Direct numerical simulations (DNSs) are among the most powerful tools for studying turbulent flows. Even though the achievable Reynolds numbers are lower than those obtained through experimental means, DNS offers a clear advantage: The entire velocity field is known, allowing for the evaluation of any desired quantity. This capability includes the computation of derivatives of all relevant terms. One such derivative provides the indicator function, which is the product of the wall distance and the wall-normal derivative of the mean streamwise velocity. This derivative may depend on mesh spacing and distribution, but it is extremely affected by the convergence of the simulation. The indicator function is crucial for understanding inner and outer interactions in wall-bounded flows and describing the overlap region between them. We find a clear dependence of this indicator function on the mesh distributions we examine, raising questions about classical mesh and convergence requirements for DNS and achievable accuracy. Within the framework of the logarithmic plus linear overlap region, coupled with a parametric study of channel flows and some pipe flows, sensitivities of extracted overlap parameters are examined. This study reveals a path to establishing their high-<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mtext>Re</mtext><mi>τ</mi></msub></math> or nearly asymptotic values at modest Reynolds numbers, but larger than the ones used in this work, accessible by high-quality DNS with reasonable cost.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-02DOI: 10.1103/physrevfluids.9.084801
S. Frei, E. Burman, E. Johnson
This article discusses the effect of rotation on the boundary layer in high Reynolds number flow over a ridge using a numerical method based on stabilized finite elements that captures steady solutions up to a Reynolds number of order . The results are validated against boundary layer computations in shallow flows and for deep flows against experimental observations reported in Machicoane et al. [Phys. Rev. Fluids3, 034801 (2018)]. In all cases considered the boundary layer remains attached, even at arbitrarily large Reynolds numbers, provided the Rossby number of the flow is less than some critical Rossby number of order unity. At any fixed Rossby number larger than this critical value, the flow detaches at sufficiently high Reynolds number to form a steady recirculating region in the lee of the ridge. At even higher Reynolds numbers no steady flow is found. This disappearance of steady solutions closely reproduces the transition to unsteadiness seen in the laboratory.
{"title":"Attached and separated rotating flow over a finite height ridge","authors":"S. Frei, E. Burman, E. Johnson","doi":"10.1103/physrevfluids.9.084801","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.084801","url":null,"abstract":"This article discusses the effect of rotation on the boundary layer in high Reynolds number flow over a ridge using a numerical method based on stabilized finite elements that captures steady solutions up to a Reynolds number of order <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mn>10</mn><mn>6</mn></msup></math>. The results are validated against boundary layer computations in shallow flows and for deep flows against experimental observations reported in Machicoane <i>et al.</i> [<span>Phys. Rev. Fluids</span> <b>3</b>, 034801 (2018)]. In all cases considered the boundary layer remains attached, even at arbitrarily large Reynolds numbers, provided the Rossby number of the flow is less than some critical Rossby number of order unity. At any fixed Rossby number larger than this critical value, the flow detaches at sufficiently high Reynolds number to form a steady recirculating region in the lee of the ridge. At even higher Reynolds numbers no steady flow is found. This disappearance of steady solutions closely reproduces the transition to unsteadiness seen in the laboratory.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-02DOI: 10.1103/physrevfluids.9.084301
Anna Ipatova, Alexis Duchesne, H. N. Yoshikawa, Pascal Mariot, Corenthin Leroy, Christine Faille, Ichiro Ueno, Georg F. Dietze, Farzam Zoueshtiagh
We explore the potential for air bubble entrapment beneath micrometer-sized particles following immersion. This investigation employs theoretical, numerical, and experimental methodologies, with a focus on the wetting characteristics of both the particle and its substrate. These properties are crucial in determining the likelihood of entrapment and its impact on the particle's adhesion force to the substrate. The theoretical model provides the mathematical framework to account for the additional force exerted on the particle due to the entrapped bubble, while numerical calculations yield corresponding force values. The results underscore the significant influence of the wettability of both the particle and the substrate on this force. In support of findings of the numerical model, companion experiments were performed. The results demonstrate that the bubbles can indeed be entrapped at microscales underneath micrometric particles. Experimental measurements of detachment force reveal the substantial impact of these entrapped bubbles on the force required to detach particles from a surface. Specifically, the force appears notably higher when either the particle or the substrate, or both, exhibit hydrophobic characteristics. We highlight the alignment observed between numerical calculations and experimental results, while also examining and discussing any identified disparities and their root causes. Lastly, we propose an energy model that predicts the post-detachment configuration of the bubble, determining whether it remains attached to the particle, adheres to the substrate, or splits into daughter bubbles distributed across both surfaces. These findings hold significance for a wide range of industrial applications where the immersion of micrometer-sized entities, such as dirt or bacteria, is common during liquid-based cleaning processes.
{"title":"Retention or repulsion forces induced by bubbles trapped at the base of an immersed microparticle on a substrate","authors":"Anna Ipatova, Alexis Duchesne, H. N. Yoshikawa, Pascal Mariot, Corenthin Leroy, Christine Faille, Ichiro Ueno, Georg F. Dietze, Farzam Zoueshtiagh","doi":"10.1103/physrevfluids.9.084301","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.084301","url":null,"abstract":"We explore the potential for air bubble entrapment beneath micrometer-sized particles following immersion. This investigation employs theoretical, numerical, and experimental methodologies, with a focus on the wetting characteristics of both the particle and its substrate. These properties are crucial in determining the likelihood of entrapment and its impact on the particle's adhesion force to the substrate. The theoretical model provides the mathematical framework to account for the additional force exerted on the particle due to the entrapped bubble, while numerical calculations yield corresponding force values. The results underscore the significant influence of the wettability of both the particle and the substrate on this force. In support of findings of the numerical model, companion experiments were performed. The results demonstrate that the bubbles can indeed be entrapped at microscales underneath micrometric particles. Experimental measurements of detachment force reveal the substantial impact of these entrapped bubbles on the force required to detach particles from a surface. Specifically, the force appears notably higher when either the particle or the substrate, or both, exhibit hydrophobic characteristics. We highlight the alignment observed between numerical calculations and experimental results, while also examining and discussing any identified disparities and their root causes. Lastly, we propose an energy model that predicts the post-detachment configuration of the bubble, determining whether it remains attached to the particle, adheres to the substrate, or splits into daughter bubbles distributed across both surfaces. These findings hold significance for a wide range of industrial applications where the immersion of micrometer-sized entities, such as dirt or bacteria, is common during liquid-based cleaning processes.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-02DOI: 10.1103/physrevfluids.9.083901
Pietro Carlo Boldini, Benjamin Bugeat, Jurriaan W. R. Peeters, Markus Kloker, Rene Pecnik
In the region close to the thermodynamic critical point and in the proximity of the pseudoboiling (Widom) line, strong property variations substantially alter the growth of modal instabilities, as revealed in Ren et al. [J. Fluid Mech.871, 831 (2019)]. Here, we study nonmodal disturbances in the spatial framework using an eigenvector decomposition of the linearized Navier-Stokes equations under the assumption of locally parallel flow. To account for nonideality, a new energy norm is derived. Several heat transfer scenarios at supercritical pressure are investigated, which are of practical relevance in technical applications. The boundary layers with the fluid at supercritical pressure are heated or cooled by prescribing the wall and free-stream temperatures so that the temperature profile is either entirely subcritical (liquidlike), supercritical (gaslike), or transcritical (across the Widom line). The free-stream Mach number is set to . In the nontranscritical regimes, the resulting streamwise-independent streaks originate from the lift-up effect. Wall cooling enhances the energy amplification for both subcritical and supercritical regimes. When the temperature profile is increased beyond the Widom line, a strong suboptimal growth is observed over very short streamwise distances due to the Orr mechanism. Due to the additional presence of transcritical Mode II, the optimal energy growth at large distances is found to arise from an interplay between lift-up and Orr mechanism. As a result, optimal disturbances are streamwise-modulated streaks with strong thermal components and with a propagation angle inversely proportional to the local Reynolds number. The nonmodal growth is put in perspective with modal growth by means of an -factor comparison. In the nontranscritical regimes, modal stability dominates regardless of a wall-temperature variation. In contrast, in the transcritical regime, nonmodal factors are found to resemble the imposition of an adverse pressure gradient in the ideal-gas regime. When cooling beyond the Widom line, optimal growth is greatly enhanced, yet strong inviscid instability prevails. When heating beyond the Widom line, optimal growth could be sufficiently large to favor transition, particularly with a high free-stream turbulence level.
正如 Ren 等人[J. Fluid Mech. 871, 831 (2019)]所揭示的那样，在接近热力学临界点的区域和伪沸（Widom）线附近，强烈的性质变化会大大改变模态不稳定性的增长。在此，我们在局部平行流假设下，使用线性化纳维-斯托克斯方程的特征向量分解来研究空间框架中的非模态扰动。为了考虑非理想性，我们导出了一种新的能量规范。研究了超临界压力下的几种传热情况，这些情况在技术应用中具有实际意义。通过预设壁面温度和自由流温度，对超临界压力下的流体边界层进行加热或冷却，使温度曲线完全为亚临界（液态）、超临界（气态）或跨临界（跨越维多姆线）。自由流马赫数设定为 10-3。在非跨临界状态下，产生的与流无关的条纹源于抬升效应。壁面冷却增强了亚临界和超临界状态下的能量放大。当温度曲线上升到超过维多姆线时，由于奥尔机制的作用，在很短的流向距离上观察到强烈的次优增长。由于跨临界模式 II 的额外存在，发现大距离的最佳能量增长来自于升力和奥尔机制之间的相互作用。因此，最佳扰动是具有强热成分的流调制条纹，其传播角度与局部雷诺数成反比。通过 N 因子比较，我们将非模态增长与模态增长进行了比较。在非跨临界状态下，无论壁面温度如何变化，模态稳定性都占主导地位。相反，在跨临界状态下，非模态 N 因子与理想气体状态下施加的不利压力梯度相似。当冷却超过维多姆线时，最佳增长会大大增强，但会出现强烈的不粘性不稳定性。当加热超过维多姆线时，最佳增长可能大到有利于过渡，特别是在自由流湍流水平较高的情况下。
{"title":"Transient growth in diabatic boundary layers with fluids at supercritical pressure","authors":"Pietro Carlo Boldini, Benjamin Bugeat, Jurriaan W. R. Peeters, Markus Kloker, Rene Pecnik","doi":"10.1103/physrevfluids.9.083901","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.083901","url":null,"abstract":"In the region close to the thermodynamic critical point and in the proximity of the pseudoboiling (Widom) line, strong property variations substantially alter the growth of modal instabilities, as revealed in Ren <i>et al.</i> [<span>J. Fluid Mech.</span> <b>871</b>, 831 (2019)]. Here, we study nonmodal disturbances in the spatial framework using an eigenvector decomposition of the linearized Navier-Stokes equations under the assumption of locally parallel flow. To account for nonideality, a new energy norm is derived. Several heat transfer scenarios at supercritical pressure are investigated, which are of practical relevance in technical applications. The boundary layers with the fluid at supercritical pressure are heated or cooled by prescribing the wall and free-stream temperatures so that the temperature profile is either entirely subcritical (liquidlike), supercritical (gaslike), or transcritical (across the Widom line). The free-stream Mach number is set to <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mn>10</mn><mrow><mo>−</mo><mn>3</mn></mrow></msup></math>. In the nontranscritical regimes, the resulting streamwise-independent streaks originate from the lift-up effect. Wall cooling enhances the energy amplification for both subcritical and supercritical regimes. When the temperature profile is increased beyond the Widom line, a strong suboptimal growth is observed over very short streamwise distances due to the Orr mechanism. Due to the additional presence of transcritical Mode II, the optimal energy growth at large distances is found to arise from an interplay between lift-up and Orr mechanism. As a result, optimal disturbances are streamwise-modulated streaks with strong thermal components and with a propagation angle inversely proportional to the local Reynolds number. The nonmodal growth is put in perspective with modal growth by means of an <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>N</mi></math>-factor comparison. In the nontranscritical regimes, modal stability dominates regardless of a wall-temperature variation. In contrast, in the transcritical regime, nonmodal <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>N</mi></math> factors are found to resemble the imposition of an adverse pressure gradient in the ideal-gas regime. When cooling beyond the Widom line, optimal growth is greatly enhanced, yet strong inviscid instability prevails. When heating beyond the Widom line, optimal growth could be sufficiently large to favor transition, particularly with a high free-stream turbulence level.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883701","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-02DOI: 10.1103/physrevfluids.9.083301
Li-Xin Shi (石理新), Song-Chuan Zhao (赵松川)
We investigate the dynamic evolution of heterogeneity in shear-thickening suspensions subjected to swirling excitation with a free surface. The uniform state of such a system may lose its stability when the oscillation frequency is above a threshold, and density waves spontaneously form [Shi et al., J. Fluid Mech.984, A69 (2024)]. Here, we report a state where jammed clusters emerge in high-density regions of the density waves. The jammed cluster exhibits unique motion, creating downstream high-density regions distinct from the previously reported state of density waves. Additionally, theoretical calculations show that reducing suspension thickness lowers the frequency and global concentration threshold for the heterogeneity onset. Notably, the minimal for instability can be lower than the onset of discontinuous shear thickening transition. We also highlight the role of the free surface in cluster growth and persistence.
{"title":"Localized jammed clusters persist in shear-thickening suspension subjected to swirling excitation","authors":"Li-Xin Shi (石理新), Song-Chuan Zhao (赵松川)","doi":"10.1103/physrevfluids.9.083301","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.083301","url":null,"abstract":"We investigate the dynamic evolution of heterogeneity in shear-thickening suspensions subjected to swirling excitation with a free surface. The uniform state of such a system may lose its stability when the oscillation frequency is above a threshold, and density waves spontaneously form [Shi <i>et al.</i>, <span>J. Fluid Mech.</span> <b>984</b>, A69 (2024)]. Here, we report a state where jammed clusters emerge in high-density regions of the density waves. The jammed cluster exhibits unique motion, creating downstream high-density regions distinct from the previously reported state of density waves. Additionally, theoretical calculations show that reducing suspension thickness lowers the frequency and global concentration <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi mathvariant=\"normal\">Φ</mi></math> threshold for the heterogeneity onset. Notably, the minimal <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi mathvariant=\"normal\">Φ</mi></math> for instability can be lower than the onset of discontinuous shear thickening transition. We also highlight the role of the free surface in cluster growth and persistence.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Miscible multiphase flow in porous media is a key phenomenon in various industrial and natural processes, such as hydrogen storage and geological carbon sequestration. However, the parameters controlling the patterns of displacement and mixing in these flows are not completely resolved. This study delves into the effects of heterogeneity and inlet pressure on mixing and displacement patterns of low-viscosity miscible phase invasion into a high-viscosity resident phase, that is saturating a porous medium. The findings highlight the substantial influence of inlet pressures and heterogeneity levels in transitioning from uniform to fingering patterns at the pore scale. These phenomena are detectable at the Darcy scale, and their transition from a uniform front to finger formation is effectively marked through a modified Sherwood number. This modified Sherwood number links microscale patterns to physical properties such as velocity distribution, diffusion, and viscosity contrasts. Additionally, the study employs breakthrough curve (BTC) analysis to illustrate the role of higher heterogeneity and inlet pressure in broadening the fluid velocity distribution, leading to the fingering pattern. These research insights provide a nondimensional approach that scales the BTCs, and can serve future models of miscible phase flow in porous media, linking pore-scale dynamics with macroscale Darcy-scale observations.
{"title":"From mixing to displacement of miscible phases in porous media: The role of heterogeneity and inlet pressures","authors":"Yahel Eliyahu-Yakir, Ludmila Abezgauz, Yaniv Edery","doi":"10.1103/physrevfluids.9.084501","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.084501","url":null,"abstract":"Miscible multiphase flow in porous media is a key phenomenon in various industrial and natural processes, such as hydrogen storage and geological carbon sequestration. However, the parameters controlling the patterns of displacement and mixing in these flows are not completely resolved. This study delves into the effects of heterogeneity and inlet pressure on mixing and displacement patterns of low-viscosity miscible phase invasion into a high-viscosity resident phase, that is saturating a porous medium. The findings highlight the substantial influence of inlet pressures and heterogeneity levels in transitioning from uniform to fingering patterns at the pore scale. These phenomena are detectable at the Darcy scale, and their transition from a uniform front to finger formation is effectively marked through a modified Sherwood number. This modified Sherwood number links microscale patterns to physical properties such as velocity distribution, diffusion, and viscosity contrasts. Additionally, the study employs breakthrough curve (BTC) analysis to illustrate the role of higher heterogeneity and inlet pressure in broadening the fluid velocity distribution, leading to the fingering pattern. These research insights provide a nondimensional approach that scales the BTCs, and can serve future models of miscible phase flow in porous media, linking pore-scale dynamics with macroscale Darcy-scale observations.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141887219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-01DOI: 10.1103/physrevfluids.9.083601
L. Jørgensen
Drop impact experiments are performed with very viscous fluids to propose a description of the drop deformation at low Reynolds number. We focus on a specific case where dimensionless parameters other than the Reynolds number play no role, which means that only kinetic energy and viscous dissipation determine the final deformation. The same situation in the case of a Reynolds number larger than ten has been clarified years ago. The maximum diameter of the spread drop is well described by a 1/5 power law of the Reynolds number only. Here the deformation of the drop, defined as the contact diameter rescaled by the drop size, is also a power law of the Reynolds number. From experimental data and scaling arguments, the exponent of the power law is shown to be 1/3.
{"title":"Deformation of drops at low Reynolds number impact","authors":"L. Jørgensen","doi":"10.1103/physrevfluids.9.083601","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.083601","url":null,"abstract":"Drop impact experiments are performed with very viscous fluids to propose a description of the drop deformation at low Reynolds number. We focus on a specific case where dimensionless parameters other than the Reynolds number play no role, which means that only kinetic energy and viscous dissipation determine the final deformation. The same situation in the case of a Reynolds number larger than ten has been clarified years ago. The maximum diameter of the spread drop is well described by a 1/5 power law of the Reynolds number only. Here the deformation of the drop, defined as the contact diameter rescaled by the drop size, is also a power law of the Reynolds number. From experimental data and scaling arguments, the exponent of the power law is shown to be 1/3.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141873093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-01DOI: 10.1103/physrevfluids.9.084001
Konstantinos Papatryfonos, Louis Vervoort, André Nachbin, Matthieu Labousse, John W. M. Bush
Since its discovery in 2005, the hydrodynamic pilot-wave system has provided a concrete macroscopic realization of wave-particle duality and concomitant classical analogs of a growing number of quantum effects. The question naturally arises as to how closely particle-particle correlations achieved with this classical system can mimic those arising on the quantum scale. We here introduce a new platform for addressing this question, a numerical model of cooperative tunneling in a bipartite pilot-wave hydrodynamic system. We execute a static Bell test, in which the system geometry is fixed and the two subsystems are coupled through the intervening wave field. This wave-mediated coupling is not congruent with the assumptions made in deriving Bell's inequality, and so allows one to rationalize the reported violations. Nevertheless, these violations are elusive, and arise only in a limited corner of parameter space.
{"title":"Static Bell test in pilot-wave hydrodynamics","authors":"Konstantinos Papatryfonos, Louis Vervoort, André Nachbin, Matthieu Labousse, John W. M. Bush","doi":"10.1103/physrevfluids.9.084001","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.084001","url":null,"abstract":"Since its discovery in 2005, the hydrodynamic pilot-wave system has provided a concrete macroscopic realization of wave-particle duality and concomitant classical analogs of a growing number of quantum effects. The question naturally arises as to how closely particle-particle correlations achieved with this classical system can mimic those arising on the quantum scale. We here introduce a new platform for addressing this question, a numerical model of cooperative tunneling in a bipartite pilot-wave hydrodynamic system. We execute a static Bell test, in which the system geometry is fixed and the two subsystems are coupled through the intervening wave field. This wave-mediated coupling is not congruent with the assumptions made in deriving Bell's inequality, and so allows one to rationalize the reported violations. Nevertheless, these violations are elusive, and arise only in a limited corner of parameter space.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-01DOI: 10.1103/physrevfluids.9.083701
Gunnar G. Peng, Rodolfo Brandão, Ehud Yariv, Ory Schnitzer
We illuminate effects of surface-charge convection intrinsic to leaky-dielectric electrohydrodynamics by analyzing the symmetric steady state of a circular drop in an external field at arbitrary electric Reynolds number . In formulating the problem, we identify an exact factorization that reduces the number of dimensionless parameters from four— and the conductivity, permittivity and viscosity ratios—to two: a modified electric Reynolds number and a charging parameter . In the case , where charge relaxation in the drop phase is slower than in the suspending phase, and, as a consequence, the interface polarizes antiparallel to the external field, we find that above a critical value the solution exhibits a blowup singularity such that the surface-charge density diverges antisymmetrically with the power of distance from the equator. We use local analysis to uncover the structure of that blowup singularity, wherein surface charges are convected by a locally induced flow towards the equator where they annihilate. To study the blowup regime, we devise a numerical scheme encoding that local structure where the blowup prefactor is determined by a global charging-annihilation balance. We also employ asymptotic analysis to construct a universal problem governing the blowup solutions in the regime , far beyond the blowup threshold. In the case , where charge relaxation is faster in the drop phase and the interface polarizes parallel to the external field, we numerically observe and asymptotically characterize the formation at large of stagnant, perfectly conducting surface-charge caps about the drop poles. The cap size grows and the cap voltage decreases monotonically with increasing conductivity or decreasing permittivity of the drop phase relative to the suspending phase. The flow in this scenario is nonlinearly driven by electrical shear stresses at the complement of the caps. In both polarization scenarios, the flow at large
{"title":"Equatorial blowup and polar caps in drop electrohydrodynamics","authors":"Gunnar G. Peng, Rodolfo Brandão, Ehud Yariv, Ory Schnitzer","doi":"10.1103/physrevfluids.9.083701","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.083701","url":null,"abstract":"We illuminate effects of surface-charge convection intrinsic to leaky-dielectric electrohydrodynamics by analyzing the symmetric steady state of a circular drop in an external field at arbitrary electric Reynolds number <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>Re</mi><mi>E</mi></msub></math>. In formulating the problem, we identify an exact factorization that reduces the number of dimensionless parameters from four—<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>Re</mi><mi>E</mi></msub></math> and the conductivity, permittivity and viscosity ratios—to two: a modified electric Reynolds number <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mover accent=\"true\"><mi>Re</mi><mo>̃</mo></mover></math> and a charging parameter <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>ϖ</mi></math>. In the case <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>ϖ</mi><mo><</mo><mn>0</mn></mrow></math>, where charge relaxation in the drop phase is slower than in the suspending phase, and, as a consequence, the interface polarizes antiparallel to the external field, we find that above a critical <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mover accent=\"true\"><mi>Re</mi><mo>̃</mo></mover></math> value the solution exhibits a blowup singularity such that the surface-charge density diverges antisymmetrically with the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>−</mo><mn>1</mn><mo>/</mo><mn>3</mn></mrow></math> power of distance from the equator. We use local analysis to uncover the structure of that blowup singularity, wherein surface charges are convected by a locally induced flow towards the equator where they annihilate. To study the blowup regime, we devise a numerical scheme encoding that local structure where the blowup prefactor is determined by a global charging-annihilation balance. We also employ asymptotic analysis to construct a universal problem governing the blowup solutions in the regime <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mover accent=\"true\"><mi>Re</mi><mo>̃</mo></mover><mo>≫</mo><mn>1</mn></mrow></math>, far beyond the blowup threshold. In the case <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>ϖ</mi><mo>></mo><mn>0</mn></mrow></math>, where charge relaxation is faster in the drop phase and the interface polarizes parallel to the external field, we numerically observe and asymptotically characterize the formation at large <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mover accent=\"true\"><mi>Re</mi><mo>̃</mo></mover></math> of stagnant, perfectly conducting surface-charge caps about the drop poles. The cap size grows and the cap voltage decreases monotonically with increasing conductivity or decreasing permittivity of the drop phase relative to the suspending phase. The flow in this scenario is nonlinearly driven by electrical shear stresses at the complement of the caps. In both polarization scenarios, the flow at large <math xmlns=\"http://www.w3.o","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-01DOI: 10.1103/physrevfluids.9.084002
Arnab Choudhury, Arghya Samanta
We examine the linear thermocapillary instability of a two-dimensional gravity-driven shear-imposed incompressible viscous film flowing over a uniformly heated inclined wall when the film surface is covered by an insoluble surfactant. The aim is to expand the prior research [Wei, Phys. Fluids17, 012103 (2005)] to the case of a nonisothermal viscous film. As a result, the energy equation is incorporated into the governing equations along with the mass conservation and momentum equations. In the present study, we have found two additional thermocapillary S- and P-modes in the low to moderate Reynolds number regime, along with the known H-mode (surface mode) and surfactant mode. The long-wave analysis predicts that the surfactant Marangoni number, which measures the surface tension gradient due to a change in insoluble surfactant concentration, has a stabilizing impact on the H-mode, but the thermal Marangoni number, which measures the surface tension gradient due to a change in temperature, has a destabilizing impact. These opposing effects produce an analytical relationship between them for which the critical Reynolds number for the H-mode instability of the nonisothermal film flow coincides with that of the isothermal film flow. On the other hand, the numerical result exhibits that the surfactant Marangoni number has a stabilizing influence on the thermocapillary S-mode and P-mode. More specifically, these thermocapillary instabilities diminish with an increase in the value of the surfactant Marangoni number. However, these thermocapillary instabilities can be made stronger by increasing the value of the thermal Marangoni number. Furthermore, the thermal Marangoni number destabilizes the surfactant mode instability, but the onset of instability is not affected in the presence of the thermal Marangoni number, which is in contrast to the influence of the surfactant Marangoni number on the onset of surfactant mode instability. Interestingly, the Biot number, which measures the ratio of heat convection and heat conduction, shows a dual role in the surfactant mode instability, even though the threshold of instability remains the same. In the high Reynolds number regime, the shear mode appears and is stabilized by the surfactant Marangoni number but destabilized by the thermal Marangoni number. Moreover, the comparison of results with inertia and without inertia exhibits a stabilizing role of inertia in the surfactant mode.
我们研究了当薄膜表面被不溶表面活性剂覆盖时，二维重力驱动剪切不可压缩粘性薄膜流过均匀加热斜壁时的线性热毛细管不稳定性。目的是将先前的研究[Wei，Phys. Fluids 17, 012103 (2005)]扩展到非等温粘性薄膜的情况。因此，能量方程与质量守恒和动量方程一起被纳入了控制方程。在本研究中，除了已知的 H 模式（表面模式）和表面活性剂模式之外，我们还发现了在低到中等雷诺数条件下的两种额外的热毛细管 S 模式和 P 模式。长波分析预测，表面活性剂马兰戈尼数（用于测量因不溶性表面活性剂浓度变化而产生的表面张力梯度）对 H 模式有稳定作用，而热马兰戈尼数（用于测量因温度变化而产生的表面张力梯度）则有破坏作用。这些相反的影响在它们之间产生了一种分析关系，即非等温膜流 H 模式不稳定的临界雷诺数与等温膜流的临界雷诺数相吻合。另一方面，数值结果表明，表面活性剂马兰戈尼数对热毛细管 S 模式和 P 模式具有稳定影响。更具体地说，这些热毛细管不稳定性随着表面活性剂马兰戈尼数的增加而减弱。然而，这些热毛细管不稳定性会随着热马兰戈尼数的增加而增强。此外，热马兰戈尼数会破坏表面活性剂模式不稳定性，但在存在热马兰戈尼数的情况下，不稳定性的发生并不受影响，这与表面活性剂马兰戈尼数对表面活性剂模式不稳定性发生的影响形成了鲜明对比。有趣的是，衡量热对流和热传导比率的比奥特数在表面活化剂模式不稳定性中显示出双重作用，尽管不稳定性阈值保持不变。在高雷诺数条件下，剪切模式出现，并通过表面活性剂马兰戈尼数而稳定，但通过热马兰戈尼数而失稳。此外，有惯性和无惯性结果的比较表明，惯性对表面活性剂模式起稳定作用。
{"title":"Thermocapillary instability of a surfactant-laden shear-imposed film flow","authors":"Arnab Choudhury, Arghya Samanta","doi":"10.1103/physrevfluids.9.084002","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.084002","url":null,"abstract":"We examine the linear thermocapillary instability of a two-dimensional gravity-driven shear-imposed incompressible viscous film flowing over a uniformly heated inclined wall when the film surface is covered by an insoluble surfactant. The aim is to expand the prior research [Wei, <span>Phys. Fluids</span> <b>17</b>, 012103 (2005)] to the case of a nonisothermal viscous film. As a result, the energy equation is incorporated into the governing equations along with the mass conservation and momentum equations. In the present study, we have found two additional thermocapillary S- and P-modes in the low to moderate Reynolds number regime, along with the known H-mode (surface mode) and surfactant mode. The long-wave analysis predicts that the surfactant Marangoni number, which measures the surface tension gradient due to a change in insoluble surfactant concentration, has a stabilizing impact on the H-mode, but the thermal Marangoni number, which measures the surface tension gradient due to a change in temperature, has a destabilizing impact. These opposing effects produce an analytical relationship between them for which the critical Reynolds number for the H-mode instability of the nonisothermal film flow coincides with that of the isothermal film flow. On the other hand, the numerical result exhibits that the surfactant Marangoni number has a stabilizing influence on the thermocapillary S-mode and P-mode. More specifically, these thermocapillary instabilities diminish with an increase in the value of the surfactant Marangoni number. However, these thermocapillary instabilities can be made stronger by increasing the value of the thermal Marangoni number. Furthermore, the thermal Marangoni number destabilizes the surfactant mode instability, but the onset of instability is not affected in the presence of the thermal Marangoni number, which is in contrast to the influence of the surfactant Marangoni number on the onset of surfactant mode instability. Interestingly, the Biot number, which measures the ratio of heat convection and heat conduction, shows a dual role in the surfactant mode instability, even though the threshold of instability remains the same. In the high Reynolds number regime, the shear mode appears and is stabilized by the surfactant Marangoni number but destabilized by the thermal Marangoni number. Moreover, the comparison of results with inertia and without inertia exhibits a stabilizing role of inertia in the surfactant mode.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：